Dissertations / Theses on the topic 'Cyclopropanation reaction'
To see the other types of publications on this topic, follow the link: Cyclopropanation reaction.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 36 dissertations / theses for your research on the topic 'Cyclopropanation reaction.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
SARKAR, ABHIJNAN. "HETEROGENEOUS IRON CATALYZED CYCLOPROPANATION REACTION." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/698432.
Full textAbstract:
Until now, NGR (nitrogen-enriched graphene) catalysts have mostly been employed for hydrogenation/oxidation reactions. In this piece of work, we expand the field of applicability of an iron NGR catalyst to cyclopropanation reactions. In this work, a heterogeneous Fe-based nitrogen-doped carbon supported catalyst has been successfully employed for the cyclopropanation reaction of alkenes. According to best of our knowledge, this is the first example of a heterogeneous Fe-catalyzed cyclopropanation reaction in today's date. These kinds of materials, generally employed for reduction or oxidation reaction, are now indeed effective catalyst also for carbene transfer reactions. The activity of Fe/Phen@C-800in the reaction was initially explored by using ethyl diazoacetate and α-methylstyrene as substrates as the model transformation. Various parameters such as solvent, temperature, time and catalyst support etc. were changed. The nature of the solvent has a minimal influence both on the reaction yield and diasteroselectivity making this reaction versatile from the media profile. The variation of the reaction temperature furnished the product in slightly lower yield. When a 5-fold amount of the olefin with respect to the diazo compound was used, homocoupling products (diethyl fumarate and diethyl maleate) deriving from EDA were detected in very low amount (<5 %). Even when the amount of olefin was decreased (1.5 eq) homocoupling side products increased, although a very good yield of the cyclopropane was maintained, demonstrating the applicability of the procedure even to more expensive olefins. Interestingly, the catalyst is water tolerant and only a slight decreased yield was obtained using a “wet” solvent. A change in the catalyst support from carbon to inorganic oxides (MgO or SiO2) does not significantly affect the yield and the diastero selectivity. Furthermore control experiments effected by employing catalysts prepared by the same procedure employed for Fe/Phen@C-800, but omitting either Fe(OAc)2 or Phen, resulted in no detectable formation of cyclopropane. Fe/Phen@C-800-catalysts showed good results in dimethoxyethane at 60 °C for 4 h, affording high yields of the desired cyclopropanes (mixture of cis and trans isomers) and only <5 % ethyl maleate and fumarate. The model reaction has been successfully scaled-up to 15-fold without significant variations of yield and diasteroisomeric ratio. The developed protocol allows obtaining several cyclopropanes from aromatic and aliphatic olefins and different diazocompounds. High to excellent yields were obtained for terminal olefins, including geminally substituted ones. Aliphatic olefins require longer reaction times. A moderate trans diastereoselectivity was observed in all cases. The catalysts do not show any activity towards internal olefins and can be used to selectively cyclopropanate a terminal olefin in a substrate containing both internal and terminal olefinic groups. The selectivity for the terminal double bond can be explained by the lack of activity of the catalyst in the case of internal olefins, most likely due to a hindered approach of the substrate to the carbene formed on the surface of the catalyst. Mono substituted diazo compounds (ester or ketone) afforded the corresponding cyclopropanes in excellent yields. More sterically demanding diazocompounds such as t-BDA has a dramatic effect on the diasteroselection, furnishing the cis- isomer only in traces. Disubstituted diazomethanes proved to be more challenging. Mono substituted diazo compounds such as diphenyldiazomethane failed to afford corresponding cyclopropanes under standard conditions, although it yielded the product in moderate yield at a higher temperature and longer reaction time (100 °C for 8h in toluene), while the more stable diazomalonate did not react even under these conditions. The catalysts was recycled several times, but a gradual deactivation is immediately observed since the first recycle. In principle, the loss of activity can be attributed either to metal leaching or to deactivation of the catalyst. After the first recycle, ICP analysis of the solution showed that only 0.1% of the initial iron had been lost in solution. This result indicates that the loss of recycling ability is not due to metal leaching. In order to make the whole process both efficient and effective, two routes of reactivation were explored. Attempted reactivation of the catalyst at 300 °C seems to have a slightly positive effect but that at 400 °C is not effective. The initial catalyst activity was effectively restored using an oxidative reactivation protocol under mild conditions (H2O2, 3 v/v% aqueous solution), which may be of more general use even for other reactions if olefins or other polymerizable compounds are employed as substrates. Oxidative regeneration is typical for catalyst that suffer of physicochemical deactivation (e.g. fouling or poisoning). Indeed, we verified that complete deactivation of the catalyst occurs even by treating the material only with styrene under the reaction conditions and the activity is restored by oxidative treatment. This result indicates the polymerization of the olefin on the catalytic surface as a possible cause for the deactivation rather than a mechanical or thermal modification of the catalyst.
2
Bremeyer, Nadine. "An enantioselective organocatalytic intramolecular cyclopropanation reaction." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614801.
Full text
3
TACHON, CHRISTINE. "Diphosphirannes : nouvelle reaction de cyclopropanation en chimie du phosphore." Toulouse 3, 1989. http://www.theses.fr/1989TOU30094.
Full textAbstract:
Le memoire presente concerne une nouvelle reaction de cyclopropanation en serie phosphoree conduisant a la formation de diphosphiranes. La structure de ces nouveaux synthons a ete determinee par rmn et par diffraction rx. Une premiere approche de la reactivite de ces synthons est presentee
4
Solorio, Alvarado César Rogelio. "Gold (i)-catalyzed Retro-Cyclopropanation Reaction and Development of Trindane-Based Approach Toward c60." Doctoral thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/51876.
Full textAbstract:
La cicloisomerización de 1,5-, 1,6- y 1,7-eninos catalizada por Au(I) y Au(III) ha
sido desarrollada con un enfoque sintético y mecanístico. Los aportes hechos
hasta el momento nos han permitido elucidar de modo general la reactividad de
los complejos catiónicos de oro(I) (Esquema R1).
Se demostró que en la ciclación de 1,6-eninos B1, la migración propargílica 1,5
del éter metílico tenía lugar originando la estructura base de los globuloles, una
familia de productos naturales. Sin embargo al explorar la reactividad de 1,7-
eninos C1, tuvo lugar una migración propargílica 1,6, dando lugar a la formación
de benzo[C]fluorenos.
Alternativamente con una sustitución similar en los eninos de partida utilizando
los 1,6-eninos D1 (esquema R2) tuvo lugar una nueva reacción catalizada por oro.
En este caso, un nuevo proceso de anulación catalizado por complejos catiónicos
de oro(I) nos condujo a la formación de naftalenos 1,3-disustituidos E1 (esquema R2)
Los naftalenos 1,3-disustituidos son una clase de compuestos no accesibles de
manera convencional mediante acoplamiento cruzado o por sustitución electrófila
aromática.
Durante el estudio de anulación con D1, determinamos el mecanismo de esta
reacción. Encontramos que este proceso tiene lugar vía cicloisomerización 6-
endo-dig generando un dihidronaftaleno D2 (esquema R2), que tras migración
[1,2] de hidógeno genera D3. Tras protodemetalación, genera el enol eter D4.
Retro-ciclopropanación sobre D4 origina un naftaleno 1,3-bisustituido E1, junto
con la formación de un carbeno libre de oro(I) G1 para dar lugar a un
bisciclopropano tetracíclico F1.
Esta es la primera vez que se observa el proceso de reto-ciclopropanación en
química de oro.
5
Hillier, Michael Campion. "The intramolecular cyclopropanation reaction and its application towards the synthesis of pseudopeptides and natural products /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
6
Aldajaei, Jamal. "Determination of the factors that affect the gas-phase reactivity of metal-centered cyclopropanation catalysts and examination of the properties of their reaction products." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3393.
Full textAbstract:
Gas phase studies of organometallic systems have provided deep insight into reaction mechanisms and reaction intermediates. In this thesis, several metal/ligand systems were examined in an effort to form metal carbenes in the gas phase. With cobalt and iron porphyrins, the carbene undergoes metal-ligand insertion. With copper bis-oxazolines, metal carbenes tend to undergo metal-ligand insertion and a Wolff rearrangement. To avoid insertions, we turned to a rigid ligand, 1, 10-phenanthroline. Under ESI conditions, a copper (I) complex with phenanthroline can be formed. When treated with diazoacetate esters, the dominant product results from addition with loss of nitrogen followed by loss of CO. This appears to be the result of a Wolff rearrangement of the metal carbene to give a metal ketene complex that spontaneously loses CO. There is no evidence of any stable metal carbenes in this reaction system. Trimethylsilyldiazomethane was also used as a carbene precursor, and its reaction with the copper phenanthroline complex gives addition with loss of nitrogen; but the product exhibits no carbene reactivity with alkenes. Here computational modeling suggests that the metal carbene undergoes a 1, 2 methyl migration, giving an exceptionally stable sila-alkene complex with the copper. As an alternative path to a metal carbene, we have used ESI to form a complex between the copper (I) phenanthroline and betaine (N, N, N-trimethylglycine). Under CID, this complex wills decarboxylates to give a copper ylide complex. Further CID leads to loss of trimethylamine and the formation of a complex between methylene and the copper phenanthroline. Depending on the CID conditions, two isobaric products are formed. One exhibits no carbene reactivity and the other readily gives carbene behavior with alkenes. The former is likely a metal-ligand insertion product, and the latter is the true metal carbene species. We explored the reactions of the carbene with electron-rich alkenes, such as ethyl vinyl ether and 3, 4-dihydro-2H-pyran, and electron-deficient alkenes, such as trichloroethylene.
7
Herlé, Bart. "Stereoselective Cyclopropanations via Gold(I)-Catalyzed Retro-Buchner Reactions." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/454770.
Full textAbstract:
La formació de carbens bencílics d’or(I) a partir de cicloheptatriens substituïts en la posició 7, a través de la reacció de retro-Buchner, ha aparegut recentment com una alternativa segura i versàtil a la descomposició de diazocompostos. No obstant, la formació de dits carbens requereix altes temperatures, limitant la seva aplicació. El treball d’aquest tesi doctoral s’ha dedicat a superar aquesta desavantatge i millorar la versatilitat de la transformació.
Els derivats de 1H-ciclopropa[l]fenantrè, que s’assemblen al tautòmer norcaradiè del cicloheptatriè, es descomponen per donar lloc a carbens lliures mitjançant la irradiació amb llum. Es va investigar la formació de carbens d’or(I) amb derivats de fenantrè mitjançant la reacció de retro-Buchner. No obstant, no es va trobar cap millora significativa amb respecte l’ús de derivats de cicloheptatriè.
Per altre banda, la generació de carbens al·lílics d’or(I) a partir de 7-alquenilcicloheptatriens, té lloc a temperatures significativament més baixes. Tenint en compte aquest fet, es va desenvolupar una reacció de ciclopropanació d’olefines per donar vinil-ciclopropans i vinil-aminociclopropans amb bons rendiments i elevada selectivitat per donar l’isòmer cis. Els derivats de 7-alquenil-cicloheptatriè es formen en un sol pas a partir d’aldehids i cetones emprant un nou reactiu del tipus Julia-Kocienski.
Addicionalment, utilitzant tècniques experimentals i computacionals, es van estudiar els mecanismes mediats per or(I) de la reacció de retro-Buchner, de la ciclopropanació i de la reacció de epimerització dels vinil-ciclopropans. Això va permetre el desenvolupament d’un model esteroquímic avançat per a les reaccions de ciclopropanació catalitzades per or(I).
El coneixement aportat per els estudis mecanístics i la síntesi millorada de derivats de cicloheptatriè van permetre la síntesi de derivats de cicloheptatriè més congestionats estèricament, què donen lloc a carbens d’or(I) a temperatura ambient i són el punt de partida per al desenvolupament d’una ciclopropanació enantioselectiva de gran aplicació.La formación de carbenos bencílicos de oro(I) a partir de cicloheptatrienos sustituídos en la posición 7, a través de la reacción de retro-Buchner, ha surgido recientemente como una alternativa segura y versátil a la descomposición de diazocompuestos. Sin embargo, la formación de dichos carbenos tiene lugar a altas temperaturas, limitando su aplicación. El trabajo de esta tesis doctoral se dedicó a superar esta desventaja y a mejorar la versatilidad de la transformación. Los derivados de 1H-ciclopropa[l]fenantreno, que se asemejan al tautómero norcaradieno del cicloheptatrieno, se descomponen para dar lugar a carbenos libres mediante irradiación con luz. Se investigó la formación de carbenos de oro(I) con derivados de fenantreno, a través de la reacción de retro-Buchner. No obstante, no se encontró ninguna mejora significativa con respecto al uso de derivados de cicloheptatrieno. Por otro lado, la generación de carbenos alílicos de oro(I) a partir de 7-alquenil-cicloheptatrienos, tiene lugar a temperaturas significativamente más bajas. Dada esta observación, se desarrolló una reacción de ciclopropanación de olefinas para dar vinil-ciclopropanos y vinil-aminociclopropanos en buenos rendimientos y con elevada selectividad para el isómero cis. Los derivados de 7-alquenil-cicloheptatrieno son formados en un sólo paso a partir de aldehídos y cetonas utilizando un nuevo reactivo de tipo Julia-Kocienski. Adicionalmente, utilizando técnicas experimentales y computacionales, se estudiaron los mecanismos mediados por oro(I) de la reacción de retro-Buchner, de la ciclopropanación y de la reacción de epimerización de los vinilciclopropanos. Esto permitió el desarrollo de un modelo estereoquímico avanzado para las reacciones de ciclopropanación catalizadas por oro(I). El conocimiento aportado por los estudios mecanísticos y la síntesis mejorada de derivados de cicloheptatrieno, permitieron la síntesis de derivados de cicloheptatrieno más estéricamente congestionados, que dan lugar a carbenos de oro(I) a temperatura ambiente y son el punto de partida para el desarrollo de una ciclopropanción enantioselectiva de gran aplicación.
The formation of benzylic gold(I) carbenes from 7-substituted cycloheptatrienes via a retro-Buchner reaction has recently emerged as a safe and versatile alternative to decomposition of diazo compounds. However, the carbene formation takes places at high temperatures, which puts a limit on its application. The work in this thesis is dedicated to overcome this drawback and enhance the versatility of this transformation. Free carbenes can be generated from light-induced decomposition of 1H-cyclopropa[l]phenanthrenes, which bear great resemblance to the norcaradiene tautomer of cycloheptatriene. Therefore, the propensity to form gold(I) carbenes via the retro-Buchner reaction of phenanthrene derivatives was investigated, albeit without finding significant improvements over the cycloheptatriene derivatives. The formation of allylic gold(I) carbenes from 7-alkenyl cycloheptatrienes takes place at significantly lower temperatures. Based on this observation, a highly cis-selective olefin cyclopropanation reaction has been developed, affording vinylcyclopropanes and vinyl-aminocyclopropanes in moderate to good yield. The 7-alkenyl cycloheptatriene derivatives can be formed in a single step from aldehydes and ketones by a novel Julia-Kocienski reagent. The mechanisms of the gold(I)-mediated retro-Buchner, cyclopropanation, and epimerization reactions for vinylcyclopropanes have been studied experimentally and computationally, which led to the development of an advanced stereomodel for gold(I)-catalyzed cyclopropanation reactions. Owing to the mechanistic insights, and the improved strategy for the synthesis of cycloheptatriene reagents, a sterically encumbered cycloheptatriene derivative was developed, which allows the formation of gold(I) carbenes at room temperature, paving the way for a broad-scope enantioselective cyclopropanation reaction.
8
Hartikka, Antti. "Towards Rational Design of Asymmetric Catalyst for Organometallic and Organocatalytic Reactions." Doctoral thesis, Uppsala : University Library / Universitetsbiblioteket, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7905.
Full text
9
Castano, B. "SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY OF CHIRAL TETRAAZAMACROCYCLE - PC-L* -CU(I) AND AG (I) COMPLEXES." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/229590.
Full textAbstract:
Homogeneous catalysis is a constantly growing and evolving area of study: in the last forty years many discoveries have been reported in both industrial and academic fields. Thanks to the use of organometallic catalysts, many inorganic and organic reactions of great importance have been revolutionized, so that homogeneous catalysis is now essential in many aspects of organic chemistry and for several industrial processes. On the other hand, heterogeneous catalysis is important because of its easier application in industry. Heterogeneous single site catalysts in many cases show superior performances in terms of activity, selectivity and recyclability coupling together the advantages of heterogeneous and homogeneous systems. It is important to note that the most commonly used ligands to form catalytic complexes often need really complicated synthesis so that the cost of the catalyst becomes excessive. In our research group we are focusing on the synthesis of molecules obtainable in few synthetic steps and easy to modify in order to be used as asymmetric ligands for transition metals.
In particular we have prepared and fully characterised a small library of non-chiral and chiral pyridine containing macrocyclic ligands (Pc-L) possessing the same donor properties but with either C1, C2 or C2v symmetry. The strategy adopted for the synthesis of these macrocyclic ligands is very flexible and allows for structural modifications. Relative basicity of the four nitrogens atoms and metal complexation of Pc-L ligands with different copper(I) salts were studied.
The use of [Cu(I)(Pc-L)] complexes was investigated at first in Henry catalytic reaction under mild conditions. The remarkable diastereoselectivity observed when isatine was reacted with nitroethane under the optimised catalytic conditions is worth to note, considering the easy access to a highly functionalized isatine skeleton. However, further studies on the ligand steric requirements in order to achieve significant enantioselectivities are required.
Then [Cu(I)(Pc-L)] complexes were tested as competent catalysts in asymmetric cyclopropanation reactions, at first under homogenous conditions in 1,2-dichloroethane. Cyclopropanes were obtained in good to excellent yields and enantiomeric excesses up to 99%. Thanks to the collaboration with Dr. Dal Santo, we have developed supported hydrogen-bonded (SHB) chiral copper(I) complexes. These supported catalysts showed good performances in cyclopropanation reactions under heterogeneous conditions in batch. The heterogeneised systems showed higher or comparable activities than the homogeneous counterpart and a good recyclability, allowing the use of more environmentally friendly n-hexane as solvent in place of 1,2-dichloroethane. Cyclopropanes were obtained in good to excellent yields and enantiomeric excesses up to 67%. We did not observe any significant Cu leaching when employing n-hexane as a reaction medium and the catalytic system is of truly heterogeneous nature, since the filtered solution is not catalytically active. The observed confinement effects are more dependent on the employed solvent (non-polar vs halogenated) than to the kind of support (ordered or non-ordered). Worth to note is the fact that even commercial silica can be used as a support, without any need of structural modification of the ligand in order to strongly graft the complex.
Thanks to the three month collaboration with Prof. David J. Cole-Hamilton from the University of St. Andrews (UK), these catalytic system based on SHB chiral copper(I) complexes were also tested as competent catalysts for asymmetric cyclopropanation reactions under flow conditions allowing the use of more eco-sustainable CO2 as a vector instead of solvents normally used for these reactions. The heterogeneised systems under flowing CO2 showed comparable or even higher chemoselectivities than the homogeneous counterpart. In terms of enantioselection excellent results were obtained also with non-activated alkenes like 1-octene where ees are comparable to those observed in the homogenous phase. Interestingly, all the data in CO2 were obtained at 40°C, while the best temperature for the cyclopropanation reaction in the homogenous phase was 0°C. Moreover supported catalysts showed a good recyclability and the TON number has been increased (up to 440). The catalysts system remained active up to 25 h without any loss in catalytic activity and chemoselectivity improved upon prolonged reaction times. Catalyst were stable and robust with a negligible copper leaching (0.007% of total copper). Future studies will be devoted to optimise the ligand design in order to improve the stereo-selective outcome of the reaction.
Collaborating with Dr. Giorgio Abbiati, we next extend our studied on metal complexes testing our ligands with other metal ions in order to explore the coinage group. We have prepared silver(I) complexes of Pc-L* with different silver(I) salts. The [Ag(I)(Pc-L)] complexes demonstrated to be suitable catalysts for the synthesis of 1-alkoxyisocromenes starting from various 2-alkynylbenzaldehydes and different primary and secondary alcohols. Best results were obtained with BF4-complex. The approach is characterised by absolute regioselectivity, mild reaction condition, good to excellent reaction yields, cleanness of the reaction, reduced purification steps. The [Ag(I)(Pc-L)] complexes are quite stable, versatile and can be used under open-air atmosphere. The reaction mechanism was investigated by in depth NMR studies and an aimed intramolecular trapping experiment. Our efforts are now devoted to the development of an enantioselective version of this transformation.
Finally the synthesis of several tiosemicarbazide derived Schiff base copper complexes has been reported. They have been fully characterised with spectral and analytical experiments. All synthesised complexes showed excellent catalytic activities in cyclopropanation reactions and TON up to 18,400 could be obtained. In contrast to the prolonged EDA addition time generally required to reduce the formation of homo-coupling products in cyclopropanation, we found those complexes very selective. Furthermore, a single addition of EDA is required to yield the desired cyclopropanes in excellent yields. Moreover, the catalysts are very robust and no decrease in yield was observed even after three catalytic runs. Several cyclopropanes have been obtained in good to excellent yields even from non-activated olefins. In the case of the cyclopropanation of (-)b-pinene, out of four possible diastereoisomers, only one product was formed that could be isolated pure in 84% yield.
10
Jubault, Philippe. "Génération électrochimique de carbanions α-phosphorés α, α-dihalogénés : électrosynthèse de gem-dihalogénoalcènes et de cycloalkylphosphonates. Mise en évidence d'un phénomène d'activation électrochimique du magnésium." Rouen, 1996. http://www.theses.fr/1996ROUES018.
Full textAbstract:
La première partie de ce travail concerne la génération électrochimique d'ylures de phosphore α,α-dihalogénés à partir de sels de phosphonium polyhalogénés et leur utilisation pour la synthèse de gem-dihalogénoalcènes selon une réaction de Wittig. Au cours de l'électrosynthèse de gem-difluoroalcènes, nous observons un phénomène particulier d'activation électrochimique de l'anode de magnésium que nous appelons activation électrochimique du magnésium. Ce phénomène permet la synthèse rapide et efficace de nombreux gem-dihalogénoalcènes. Nous proposons une interprétation pour ce mécanisme d'activation, étayée par la caractérisation des intermédiaires réactionnels. Dans la seconde partie de ce travail, ce phénomène d'activation électrochimique de l'anode de magnésium est utilisé pour la génération électrochimique du carbanion du trichlorométhylphosphonate de diisopropyle qui est engagé dans des réactions d'alkylation, de cyclopropanation et de cycloalkylation. De plus, des électrosynthèses en un seul réacteur de cyclopropylphosphonates β-substitués, de cyclopropylphosphonates α,β-substitués et de cycloalkylphosphonates sont développées.
11
Adesina, Olumide, Cassandra T. Eagle, Ayobami Olukanni, and Reza Mohseni. "Purification of Cyclohexene for Cyclopropanation Reactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/143.
Full textAbstract:
Environmentally friendly reactions yielding cis-cyclopropanes are desired in the insecticide industry as these are most effective at reducing the population of insects while remaining benign to the environment. We are exploring the best parameters for the most effective cis-cyclopropanation reactions. An alkene and a diazo compound react together in the presence of a dirhodium catalyst to produce cyclopropanes. First however, the starting materials must be pure. Alfa Aesar supplies cyclohexene which is reported to be 99% pure, however, Gas column chromatography/Mass spectroscopy reveals that the sample is only 3% cyclohexene. Using an adopted published procedure, we discovered that distillation under nitrogen produces cyclohexene in greater than 95% pure. This is suitable for use in cyclopropanation reactions.
12
Parlier, Andrée. "Application des complexes carbeniques du tungstene a la synthese organique et organometallique." Paris 6, 1987. http://www.theses.fr/1987PA066570.
Full text
13
Grange, Emma. "Stereochemical control in cyclopropanation reactions mediated by sulfonium ylides." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432748.
Full text
14
Nomura, Kenichi. "Studies on a Nucleophilic Cyclopropanation Reactions with Bis(iodozincio)methane." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120873.
Full text
15
Saha, Chandreyee. "Synthesis and application of chiral sulfides in asymmetric cyclopropanation and epoxidation reactions." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573155.
Full textAbstract:
Application of two different chiral sulfides m asymmetric cyclopropanation and epoxidation reactions have been studied. Cyclopropanation reactions of chiral stabilised sulfonium ylides derived from chiral sulfide 13 with acyclic enones have been studied. The surprisingly low enantioselectivity obtained in such reactions was proposed to be due to a rapid and reversible intramolecular proton transfer process occurring within the betaine intermediate prior to ring-closure. The hypothesis was verified by carrying out the reactions of stabilised sulfonium ylides with methyl vinyl ketone. Variation in enantioselectivities were observed when the ylide substituent was varied from ketone to ester to amide. Isotope effects were also studied to further support the hypothesis. Improvement in enantioselectivities were observed in deuterium incorporated cyclopropanes. The study was further extended to ammonium ylide cyclopropanation reactions to study the cause of erosion in enantioselectivity in certain ammonium ylide- mediated cyclopropanation reactions. Chiral sulfide isothiocineole 59, has been recently reported by the Aggarwal group. The sulfide was easily prepared in one step from limonene 75 and y-terpinene 76 although in low yield. The one-step reaction was investigated further. Stoichiometry, time and order of addition of reagents were varied and a substantial improvement in the synthesis of 59 was achieved. Isothiocineole 59 was applied in asymmetric epoxidation reactions and the scope of ylide reactions in terms of ylide substituents (aryl, alkenyl) and aldehydes (aromatic and aliphatic) was explored.
16
Olukanni, Ayobami, Cassandra T. Eagle, olumide Adesina, and Reza M. Mohseni. "Purification of Ethyl Diazoacetate by Vacuum Distillation for use in Cyclopropanation Reactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/135.
Full textAbstract:
Environmentally friendly insecticides have long been desired in the production of food. Pyrethiod compounds not only decompose under light and heat, but they are highly toxic to insects while having effectively no toxicity to mammals. The cis-cyclopropane ring in pyrethiod insecticides is the most challenging component to synthesize. We are exploring the best parameters for the most effective cis-Cyclopropanation reactions. An alkene and a diazo compound react together in the presence of a dirhodium catalyst to produce cyclopropanes. First however, the starting materials must be pure. My part of the project is to purify ethyl diazoacetate(EDA). Column chromatography has been used, but yielded no fraction containing EDA as determined by Gas chromatography/Mass spectrometry. Extraction of EDA with sodium carbonate solution yielded similar results. Thus, I turned to distillation at reduced pressure. This method produced EDA in high enough purity to be used in cyclopropanation reactions. The purity of EDA was determined by H-1 nuclear magnetic resonance spectroscopy.
17
Ruppel, Joshua V. "Cobalt(II)-Catalyzed Atom/Group Transfer Reactions: Stereoselective Carbene and Nitrene Transfer Reactions." Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/484.
Full textAbstract:
Metalloporphyrins have been shown to catalyze many fundamental and practically important chemical transformations, some of which represent the first demonstrations of these catalytic processes. The most notable examples include an assortment of atom/group transfer reactions, such as oxene, nitrene, and carbene transfers. Atom/group transfer reactions allow for the direct conversion of abundant and inexpensive alkenes and alkanes into value-added functional molecules. Previous reports from our group have shown that cobalt-porphyrin based carbene and nitrene transfer reactions are some of the most selective and practical catalytic systems developed for cyclopropanation and aziridination. Backed by a family of D2-symmetric chiral cobalt porphyrins our group continues the development of stereoselective carbene and nitrene transfer reactions.
Metal-catalyzed cyclopropanation of olefins with diazo reagents has attracted great research interest because of its fundamental and practical importance. The resulting cyclopropyl units are recurrent motifs in biologically important molecules and can serve as versatile precursors in organic synthesis. Supported by a family of D2-symmetric chiral cobalt porphyrins, we have demonstrated the use of succimidyl diazoacetate as carbene source for a highly diastereo- and enantioselective cyclopropanation process. The resulting cyclopropyl succinimdyl esters are highly reactive and serve as valuable synthons for generating cyclopropylcarboxamides. We have also developed the first cobalt-porphyrin based intramolecular cyclopropanation, which is able to produce the resulting bicyclic lactones in high yields and enantioselectivity.
Nitrene transfer reactions are also an attractive route to produce biologically and synthetically important molecules such as amines and aziridines. Although much progress has been made in nitrene transfer reactions utilizing [N-(p-toluenesulfonyl) imino]phenyliodinane (PhI=NTs) the nitrene source suffers from several drawbacks. Consequently, there has been growing interest in developing catalytic nitrene transfer reactions using alternate nitrene sources. To this end, we have utilized arylsulfonyl azides as nitrene source to explore their use in the development of a cobalt-porphyrin catalyzed enantioselective aziridination system. The cobalt catalyzed process can proceed under mild and neutral conditions in low catalyst loading without the need of other reagents, while generating nitrogen gas as the only byproduct. We have also explored the use of arylsulfonyl azides as nitrene source in a cobalt-catalyzed intramolecular C-H amination process.
18
Ni, Zhenjie. "Synthesis of Cyclobutenes and Bicyclo (2.1.0) pentanes Through Platinum and Ruthenium- catalyzed Reactions." Thesis, Ecole centrale de Marseille, 2014. http://www.theses.fr/2014ECDM0004/document.
Full textAbstract:
Dans ce manuscrit, nous avons décrit l'accès aux dérivés bicyclo[2.1.0]pentanes via deux réactions métalo-Catalysées, à savoir une cycloisomérisation d’énynes-1,6 catalysée par le platine et la cyclopropanation de cyclobutènes catalysée par le ruthénium à l’aide carboxylates propargyliques tertiaires. Tout d'abord, nous avons développé la formation, catalysée par Pt(II), de cyclobutènes à partir d’énynes-1,6 reliés par un hétéroatome (azote ou oxygène) pour former les aza- et oxa-Bicyclo[3.2.0]hept-6-Ènes respectivement. Il est montré que la présence de substituant(s) alkyle(s) en position propargylique et l'utilisation de solvants faiblement coordonnés, tels que le DMA sont les caractéristiques principales favorisant la formation de cyclobutènes. Ensuite, la disponibilité de cyclobutènes issus de la cycloisomérisation des 1,6-Énynes a permis leur utilisation pour la construction de systèmes bicyclo[2.1.0]pentanes par la mise en œuvre d’une cyclopropanation catalysée par le ruthénium utilisant les carboxylates propargyliques tertiaires. Ces composés sont obtenus sous la forme d’un diastéréomère unique avec des rendements bons à excellents. Cette réaction fournit une alternative sûre aux méthodes utilisant les dangereux composés diazo précurseurs de carbène pour générer les bicyclo[2.1.0]pentanes fonctionnalisés dans des conditions douces et avec des rendements élevésIn this manuscript, we have described an access to bicyclo[2.1.0]pentanes via two metal-Catalyzed reactions, namely a platinum-Catalyzed cycloisomerization of heteroatom-Tethered 1,6-Enynes and the subsequent ruthenium-Catalyzed cyclopropanation of cyclobutenes with tertiary propargyl carboxylates.First, we have developed the Pt(II)-Catalyzed formation of cyclobutenes from nitrogen and oxygen-Tethered 1,6-Enynes to form aza- and oxabicyclo[3.2.0]hept-6-Enes respectively. It is shown that the presence of alkyl substituent(s) at propargyl position and the use of weakly coordinating solvents such as DMA are the key elements favoring the formation of cyclobutenes.Second, the availability of cyclobutenes from the cycloisomerization of 1,6-Enynes has allowed their utilization for the construction of strained bicyclo[2.1.0]pentane structures as single diastereomers in good to excellent yield through a ruthenium-Catalyzed cyclopropanation. It provides a safe method which avoid the use of the hazardous diazo compounds precursors of carbenes to generate functionalized bicyclo[2.1.0]pentane frameworks in high yields under mild conditions
19
Herrero, Gómez Elena. "Gold (i)-catalyzed cyclizations of 1,6- and 1,7-enynes: new gold complexes and cyclopropanation reactions." Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/9035.
Full textAbstract:
Esta tesis doctoral se ha dedicado al estudio tanto experimental como teórico de diferentes aspectos relacionados con la ciclación de eninos catalizada por oro(I). La memoria se ha dividido en dos partes, el primero de ellos recoge el estudio de complejos de oro(I) mientras que el segundo se ha dedicado a las aplicaciones de dichos complejos en reacciones de activación de alquinos, en concreto para la reacción de ciclación de eninos. En el primer capítulo se exponen los resultados obtenidos en un estudio teórico comparativo de complejos con metales del grupo 11 así como la síntesis y caracterización estructural de complejos de oro que contienen interacciones π oro-anillo aromático sencillo. Por otra parte, se describe la síntesis de un nuevo complejo de oro con un ligando fosfito voluminoso, que es un excelente catalizador para reacciones de cicloisomerización de eninos.
A continuación, se presentan los resultados relacionados con el atrapamiento intermolecular mediante olefinas de los intermedios carbeno de oro implicados en la reacción de ciclación de 1,6-eninos. Por otro lado, se ha realizado un estudio teórico y computacional de la reacción de ciclación de 1,7-eninos catalizada por oro y se ha ampliado el alcance de la cicloadición [4+2] catalizada por oro(I) mediante su aplicación a 1,7-eninos substituidos.
In this PhD thesis we have studied different experimental and theoretical aspects of the gold(I)-catalyzed cyclization of enynes. The work has been divided in two chapters, one related with the study of gold(I) complexes and the second one focused on the applications of gold complexes for the activation of alkynes, more precisely on the enyne cyclization reaction.Firstly, we have performed a computational study of a family of group 11 metal complexes as well as the synthesis and structural characterization of the first gold(I) cationic complexes displaying η1−η2 gold(I)-arene interactions. We have also synthesized a phosphite gold(I) complex which is the most active catalyst for enyne cycloisomerizations.On the other hand, the intermolecular trapping of the carbene intermediates involved in the gold(I)-catalyzed cyclization of 1,6-enynes with olefins was achieved, giving rise to one of the few examples of gold(I)-catalyzed cyclopropanations. We have also performed a computacional study of the gold(I)-catalyzed cyclization of 1,7-enynes and broadened the scope of the gold(I)-catalyzed [4+2] cycloaddition by its successful application to substituted 1,7-enynes.
20
Davies, Iwan Rhydian. "Chiral auxiliaries and substrate directable reactions to access highly functionalised chiral lactones." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507750.
Full textAbstract:
This thesis describes the development of chiral auxiliary based methodologies for the asymmetric synthesis of hydroxylated !-lactones and "-lactones containing multiple contiguous stereocentres. The first chapter introduces the concept of chirality and provides a general overview of the range of strategies available for the preparation of chiral molecules in enantiomerically pure forms. The second chapter critically reviews the range of synthetic methodology that is currently available for the asymmetric synthesis of chiral #-lactones that are either natural products or useful chiral building blocks for synthesis. The third chapter describes the development of novel methodology for the epoxidation/lactonisation of a range of $-vinyl-syn-aldols to directly afford !-lactones containing up to four contiguous stereocentres in high de. These reactions were shown to proceed via a mechanism whereby hydroxyl-directed diastereoselective epoxidation is followed by intramolecular attack of their !-acyl-oxazolidin-2- one fragment, to directly afford the desired chiral !-lactone. The ‘self-cleavage’ aspect of these reactions was exploited to enable this methodology to be transferred to polymer-support using an immobilised Evans’-oxazolidin-2-one for asymmetric synthesis. Chapter 4 describes the development of a complementary methodology for the asymmetric synthesis of this type of hydroxylated !-lactone based on a strategy involving dihydroxylation of N-acyl-oxazolidin-2-one-$-vinyl-syn-aldols using catalytic amounts of osmium tetroxide. This methodology was developed as part of a reinvestigation of previously reported dihydroxylation reactions by Dias and coworkers, where we have clearly shown that the stereochemistry of thelactones reported in their paper have been incorrectly assigned. This diastereoselective dihydroxylation methodology has been successfully applied to the asymmetric synthesis of the natural product deoxyribonolactone. Finally, Chapter 5 describes the development of methodology for the asymmetric synthesis of chiral "-lactones containing four contiguous stereocentres of use as potential chiral building blocks for the synthesis of polyketide natural products. In this approach, cyclopropanation of N-acyl-oxazolidin-2-one-$-vinyl-syn-aldols occurs under the sterodirecting effect of the $- hydroxyl group to afford cyclopropyl-aldols in very high de. These cyclopropyl-aldols are then ring opened in the presence of mercuric ions, with their N-acyl-oxazolidin-2-one fragment acting as an internal nucleophile, to afford highly functionalised alkyl-mercury species that may be subsequently reduced to afford their corresponding "-lactones in high de.
21
Chagas, Rafael Pavão das. "Estudo da Aplicação de Brometo de Índio(I) em Reações para Formação de Ligações Carbono-Carbono." Universidade Federal de Santa Maria, 2011. http://repositorio.ufsm.br/handle/1/4206.
Full textAbstract:
Conselho Nacional de Desenvolvimento Científico e TecnológicoThis PhD thesis describes our results on the application of indium(I) bromide in carbon-carbon bond forming reactions. Indium enolates, generated in situ from the reaction between indium(I) bromide and α,α-dichloroketones, react with carbonyl compounds and electron-deficient alkenes. Reactions of indium enolate with α,α-dichloroketones, in presence of extra InBr, leads to the formation of 1,4-diketones. The coupling with aldehydes leads alternatively, according as the stoichiometry, to the diastereoselective synthesis of (syn+anti)-2-chloro-3-hydroxy-propan-1-ones (which can be converted to the respective trans-epoxyketones), (E)-α,β-unsaturated ketones and cyclopropanes, upon a sequenced reaction mechanism. We also have developed a methodology for the preparation of cyclopropanes through the reaction of the indium enolate and other organoindium(III) compounds, derived from the reactions between InBr and α,α-dihalo carbonyl compounds and halo-acetonitriles, with electron-deficient alkenes.
Este trabalho descreve os resultados dos estudos realizados sobre aplicações de brometo de índio(I) em reações para formação de ligações carbono-carbono. A reação entre brometo de índio(I) e α,α-diclorocetonas produz, in situ, enolatos de índio que reagem com compostos carbonílicos e alcenos deficientes em elétrons. As reações do enolato de índio com outras moléculas de α,α-diclorocetonas, na presença de InBr em excesso, leva à formação de 1,4-dicetonas. O acoplamento com aldeídos leva alternativamente, conforme a estequiometria, à formação diastereosseletiva de (syn+anti)-α-cloro-β-hidróxi-cetonas (que podem ser convertidas às respectivas trans-epóxi-cetonas), cetonas (E)-α,β-insaturadas e ciclopropanos, segundo um mecanismo de reações sequenciais. Ainda foi desenvolvida uma metodologia para preparação de ciclopropanos através da reação do enolato de índio e de outros compostos organoíndio(III), derivados da reação entre InBr e vários compostos carbonílicos α,α-di-halogenados e halogeno-acetonitrilas, com alcenos deficientes em elétrons.
22
Wang, Dongqi, and 王東琪. "Density functional theory studies of selected zinc, lithium, and samarium carbenoid species and their cyclopropanation reactions witholefins." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29486889.
Full text
23
Conyers, Ryan C. "An Investigation of Gold(I) Catalyzed Cycloaddition Reactions." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1366197923.
Full text
24
Gill, Joseph B. "Co(II) Based Metalloradical Catalysis| Carbene and Nitrene Transfer Reactions." Thesis, University of South Florida, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3666726.
Full textAbstract:
Radical chemistry has attracted a large amount of research interest over the last few decades and radical reactions have recently been recognized as powerful tools for organic synthesis. The synthetic applications of radicals have been demonstrated in many fields, including in the synthesis of complex natural products. Radical reactions have a number of inherent synthetic advantages over their ionic counterparts. For example, they typically proceed at fast reaction rates under mild and neutral conditions in a broad spectrum of solvents and show significantly greater functional group tolerance. Furthermore, radical processes have the capability of performing in a cascade fashion, allowing for the rapid construction of complex molecular structures with multiple stereogenic centers. To further enhance the synthetic applications of radical reactions, current efforts are devoted toward the development of effective approaches for the regioselective control of their reactivity as well as stereoselectivity, especially enantioselectivity, a challenging issue that is intrinsically challenged by the "free" nature of radical chemistry.
This research has identified a fundamentally new approach to radical reactions based on the concept of metalloradical catalysis (MRC) for controlling the stereoselectivity of both C- and N-centered radical reactions. Cobalt(II) porphyrins [Co(Por)], are stable metalloradicals, and have been shown to enable the activation of diazo reagents and azides to cleanly generate C- and N-centered radicals, respectively, with N2 as the only byproduct in a controlled and catalytic manner. In addition to the radical nature of [Co(Por)], the low bond dissociation energy of Co-C/Co-N bonds plays a key role in the successful turnover of the Co(II)-based catalytic carbene and nitrene transfers. Through the support of porphyrin ligands with tunable electronic, steric, and chiral environments, this general concept of Co(II)-based metalloradical catalysis (Co-MRC) has been successfully applied to the development of various radical processes that enable stereoselective carbene and nitrene transfers.
25
GAI, YONGHUA. "Activation de carbanions sulfonyles par le nickel : reactions d'homocouplage et d'elimination; application a une nouvelle methode de cyclopropanation des alcenes non-actives." Paris 6, 1991. http://www.theses.fr/1991PA066492.
Full textAbstract:
La reaction d'homocouplage des anions lithies de t-butyl alkyl sulfones primaires catalysee par l'acetylacetonate de nickel conduit aux ethyleniques 1,2-disubstitues avec de tres bons rendements. En presence du meme catalyseur, l'elimination de la t-butyl alkyl sulfones primaires peut conduire aux 1- ou 2-alcenes avec de bons rendements selon les conditions choisies. L'acetylacetonate de palladium peut egalement catalyser l'elimination des t-butyl alkyl sulfones primaires ou secondaires avec de bons rendements en olefines. La cyclopropanation de divers alcenes non-actives par les t-butyl alkyl sulfones lithies a ete realisee en presence de sels de nickel, fournissant la premiere methode generale, simple et efficace pour le transfert de groupes alkylidenes avec des chaines longues (superieure a deux carbones) sur les doubles liaisons non-activees. Divers cyclopropanes ont ete synthetises avec des rendements moyens a (tres) bons par cette methode (via transfert des groupes methylene, alkylidene, isopropylidene, benzylidene. . . ). Les alcenes terminaux, arylsubstitues et cycliques sont beaucoup plus reactifs que d'autres alcenes. La reaction se fait de facon stereospecifique vis-a-vis de la configuration de l'alcene de depart, et avec une tres bonne anti-stereoselectivite pour les alcenes cycliques ou cis-disubstitues. Les etudes de type hammett montrent clairement que la presente cyclopropanation est une reaction nucleophile. Quelques etudes sur l'aspect mecanistique des ces reactions ont ete effectees, plusieurs mecanismes possibles sont discutes
26
Fields, Kimberly Bliss. "The Design and Synthesis of Functionalized Porphyrins and Their Applications in Group Transfer Reactions, Medicine, and Materials." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3461.
Full textAbstract:
Porphyrins and their analogs are a class of chemically and biologically important compounds that have found a variety of applications in different fields such as catalysis, medicine, and materials. The physical, chemical, and biological dependence of the peripheral substituents of porphyrins on their properties has prompted great effort towards the synthesis of new porphyrins with different electronic, steric, and conformational environments. To this end, porphyrins have been prepared using a modular approach from bromo- and triflate synthons. These synthons underwent palladium-catalyzed cross-coupling with chiral amines, amides, alcohols, and boronic esters to create products that were tested for biological activity.
Metalloporphyrins were screened as catalysts for cyclopropanation and C-H amination, yielding excellent results. By changing the porphyrin catalysts’ chiral groups, all four enantiomers could be produced in the cyclopropanation of styrene derivatives with ethyl diazoacetate (or t-butyl diazoacetate). Similarly, a variety of sultams were produced from benzenesulfonyl azides in high yields and high enantioselectivities using chiral cobalt porphyrins as catalysts.
Porphyrins, metalloporphyrins, and the catalytic products generated were tested for activity in a variety of medicinal collaborations, namely as therapeutics for methicillin-resistant Staphylococcus aureus, Alzheimer’s disease, malaria, viral infections that include influenza and herpes, and cancer, as well as biological studies with ferrochelatase. They were also used in materials experiments with two different polymer groups.
27
Kan, Tze-wai Jovi. "Development of new polymer-supported reagents for organic synthesis, solvent effects in samarium promoted allylic alcohol cyclopropanation reactions and time resolved resonance studies of the photodeprotection of p-hydroxyphenacyl caged phototrigger compounds." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37925660.
Full text
28
Kadraoui, Mohammed. "Design et utilisations de complexes organométalliques intercalés dans la bentonite pour des réactions d’insertion ou de complexes organométalliques chiraux pour des réactions de cyclopropanation asymétrique." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1026.
Full textAbstract:
Cette thèse est constituée de deux parties indépendantes. La première consiste à former de nouveaux systèmes catalytiques hétérogènes par intercalation d’éthylacétonate de cuivre et de fer dans une argile : la bentonite. Pour cela, celle-ci est purifiée avant d’inclure les deux complexes. Une étude de l’activité de ces deux matériaux a été réalisée avec le diazoacétate d’éthyle afin de former le fumarate et le maléate d’éthyle. Des réactions d’insertion de carbènes ont ensuite été étudiées avec des amines et des alcools en vue de former respectivement des a-oxa et a-aza acétates d’éthyles avec des rendements de l’ordre de 60 à 95%. L’objectif de la seconde partie est d’étudier, en milieu homogène, la réaction de cyclopropanation asymétrique d’alcènes catalysée au cuivre (I) ; les motifs cyclopropaniques étant présents dans de nombreux composés possédant des activités biologiques. Pour ce faire, la synthèse de nouveaux ligands oxazolines et imines issus de l’isosorbide et l’isomannide, deux composés de la biomasse a été réalisée. Complexés au cuivre (I), ces ligands ont été évalués pour la cyclopropanation asymétrique du styrène, de l’ a-méthylstyrène, de l’indène, de l’oct-1-ène en présence de diazoacétate d’éthyle. La cyclopropanation du cyclopentène a de même été réalisée. Divers paramètres ont été examinés afin de déterminer les meilleures conditions réactionnelles. Les résultats les plus significatifs en terme de diastéréosélectivité et d’énantiosélectivité ont été obtenus lors de la cyclopropanation du styrène avec un complexe oxazoline/CuI (diastéréoselection trans/cis : 90/10, ee : 93% pour l’isomère trans). De plus, nous avons montré qu’un système diimine/Cu(CH3CN)4PF6 a donné des stéréosélectivités similaires pour la cyclopropanation du styrène et de l’ a-méthylstyrène, indiquant ainsi que ce système était moins substrat dépendantThis thesis is divided in two independent parts. The first concerns the development of new heterogeneous catalytic systems involving intercalation of ethylacetonate copper and iron complexes in a clay: the bentonite. For this purpose, the bentonite is purified prior to the inclusion of the two complexes. A study of the catalytic activity of these two materials was performed with ethyl diazoacetate to form ethyl fumarate and maleate. Carbene insertion reactions were then studied with amines and alcohols to form respectively a-oxa and a-aza ethyl acetate derivatives in 60 to 95% yields. The aim of the second part is to study, the homogeneous catalytic asymmetric cyclopropanation reaction of alkenes catalyzed by copper (I) complexes; the cyclopropane unit being present in many compounds presenting biological activities. For that purpose, the synthesis of new oxazolines and imines ligands derived from isosorbide and isomannide, two compounds of the biomass was performed. Complexed with copper (I), these ligands were evaluated for the asymmetric cyclopropanation of styrene, of a-methylstyrene, indene, of oct-1-ene in the presence of ethyl diazoacetate. Cyclopropanation of cyclopentene was similarly performed. Various parameters were examined to determine the best reaction conditions. The most significant results in terms of diastereoselectivity and enantioselectivity were obtained in the cyclopropanation of styrene with a complex oxazoline/CuI (diastereoselection trans/cis: 90/10, ee : 93% for the trans isomer). Furthermore, we showed that a catalytic system formed by a diimine and Cu(CH3CN)4PF6 gave similar stereoselectivities for the cyclopropanation of styrene and a-methyl styrene, indicating that the system is less dependent on the nature of the substrate
29
chun-han, Peng, and 彭俊翰. "Diastereoselective Cyclopropanation Reaction." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/01102121421744893720.
Full textAbstract:
碩士國立臺灣師範大學
化學研究所
92
Cyclopropane is an important building block found in many nature products. The preparation of enantiomerical pure compounds is one of the major areas in organic chemistry. The synthesis of cyclopropane and their derivaties has attracted a lot of attention in recent years, owing to their versatile roles in organic synthesis. Cyclopropanation of chiralαβ-unsaturated olefins derived from a exo-10,10-diphenyl-2,10-camphanediol 79. We find that substrates are eletrophile olefins by using sulfonium ylides as ncleophile in good chemical yield (63-96% yield). Especially, cyclopropanation of chiral auxiliary 79 derives O-acrylate Ⅱ-15 gives high diastereoselectivity(>90% de). Cyclopropanation of chiralαβ-unsaturated olefins derived from a camphor pyrazolidinone 78.Only one optical isomer(>90% de) was obtained when using α- or β- substituted chiral olefins as substrates. Cyclopropanation of chiral sulfonium ylides(107) derived from a camphor pyrazolidinone 78. We find that chiral reagents react with variousα,β-unsaturated olefins in moderate to good yield(63-90% yield).Good diastereoselectivity(76-90% de) was obtained when using non- or α-substituted unsaturated olefins as substrates.The absolute stereochemistry of the newly generated cyclopropane ring was determined to be a (1R, 2R)-configuration by single crystal X-ray analysis. The diastereoselectivity was determined by 1H-NMR analysis of the crude products.
30
Kang, Jun. "Chromium-Catalyzed Homoaldol Equivalent Reaction, Indium-Mediated Cycloisomerization, and Palladium-Catalyzed Cross-Coupling Reaction." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-08-77.
Full textAbstract:
The homoaldol reaction is one of the most powerful methods for the construction of C–C bonds as well as 1,4-oxygenated compounds yet this reaction remains in challenging tasks due to the instability of homoenolates which spontaneously cyclize to the cyclopropanolate. A regioselective catalytic homoaldol equivalent reaction of 3-bromo vinyl acetate with aldehydes under Cr(III)-Mn(0) redox condition was developed. This homoaldol equivalent reaction allows access to the 1,4-oxygenated compounds that are not possible by a conventional aldol process. Mild hydrolysis of the vinyl acetate and reduction of the homoaldol adducts generated diols and lactols in high yield (99%). Further manipulation including stereoselective epoxidation and cyclopropanation was achieved in an efficient manner.
Furans, found in many natural products and utilized in drug discovery, have been well studied but current synthetic methods toward furans have some limitations in functional group tolerance, substrate scope, and low product yield in many cases. A highly efficient and catalytic cycloisomerization reaction that transforms acetylenic α,β-epoxides to 2,3,5-tri-substituted furans under InCl3 catalysis was developed. This reaction sequence allows access to rapid construction of highly valuable, tri-substituted furan derivatives.
Cross-coupling reactions utilizing transition metals and Lewis acids are important synthetic tools for the formation of C–C and C–N bonds and a number of cross-coupling reactions between α-bromo carbonyl compounds and metal reagents such as aryl metals, alkenyl metals, and alkyl metals have been reported. Transition metal-catalyzed cross-coupling reaction for the construction of α-alkynyl carbonyl compounds has reported in a limited case. The first approach to secondary α-alkynyl carbonyl compounds from secondary α-bromo esters and amides with tributyl(phenylethynyl)stannane under palladium-catalyzed cross-coupling reaction conditions was developed. This synthetic method allows access to secondary α-alkynyl carbonyl compounds which are valuable precursors in pharmaceuticals and agricultural applications.
31
Hardee, David James. "Part 1: Lanthanum(III) Triflate-Catalyzed Cyclopropanation via Intramolecular Methylene Transfer. Part 2: Reaction Design with Aromatic Ions - Nucleophilic Acyl Substitution and Organophotoredox Catalysts." Thesis, 2011. https://doi.org/10.7916/D8RX9K2H.
Full textAbstract:
This thesis describes the development of novel synthetic methods in the areas of methylene transfer cyclopropanation and reaction design with aromatic cations. The first chapter presents a new cyclopropanation method involving intramolecular methylene transfer from an epoxide to an olefin. The lanthanum(III) triflate-catalyzed process proceeds with high stereoselectivity and a range of examples are presented to illustrate the reaction scope. An asymmetric cyclopropane synthesis combining enantioselective epoxidation and the methylene transfer protocol is also presented. The second chapter describes the application of aromatic cation activation for nucleophilic acyl substitution. The strategy is used to rapidly convert carboxylic acids to their corresponding acid chlorides with dichlorocyclopropene reagents. The effect of cyclopropene substituents and amine base additives on the rate of conversion is examined. A mild amidation protocol employing acid chloride formation is described and applied to acid-sensitive substrates and preparative peptide couplings. The final chapter discloses the development of aromatic cation photoredox catalysts. Investigations into the relationship between cyclopropenium substitution and ultraviolet/visible light absorption are presented. Cyclopropenium ions are shown to be effective photocatalysts for a variety of photoredox transformation.
32
Vanier, Sébastien F. "Synthèse formelle de l’hormaomycine et de la bélactosine A par utilisation d’une réaction de cyclopropanation intramoléculaire catalysée par un complexe de rhodium (II)." Thèse, 2009. http://hdl.handle.net/1866/3925.
Full textAbstract:
Ce mémoire présente trois approches différentes vers la synthèse du 3–(trans–2–nitrocyclopropyl)alanine, un intermédiaire synthétique de la hormaomycine. Cette molécule naturelle démontre d’intéressantes activités biologiques et pharmacologiques. Il est intéressant de souligner que ce dérivé donne facilement accès au 3–(trans–2–aminocyclopropyl)alanine, unité centrale de la bélactosine A. Ce composé naturel possédant lui aussi d’intéressantes propriétés biologiques, plusieurs études relationnelles structures-activités menant à des dérivés plus actifs de cette molécule ont été entreprises, démontrant l’intérêt toujours présent de synthétiser de façon efficace et optimale ces dérivés cyclopropaniques. Une méthodologie développée au sein de notre groupe de recherche et basée sur une réaction de cyclopropanation intramoléculaire diastéréosélective sera mise à profit afin d’élaborer une nouvelle voie de synthèse aussi élégante qu’efficace à la construction du 3–(trans–2–nitrocyclopropyl) alanine.
En utilisant un carbène de rhodium généré soit par la dégradation d’un dérivé diazoïque, soit par la formation d’un réactif de type ylure d’iodonium, une réaction de cyclopropanation diastéréosélective permettra la formation de deux autres centres contigus et ce, sans même utiliser d’auxiliaire ou de catalyseur énantioenrichis. Ensuite, un réarrangement intramoléculaire précédant deux réactions synchronisées d’ouverture de cycle et de décarboxylation permettront l’obtention du composé d’intérêt avec un rendement global convenable et en relativement peu d’étapes. De cette manière, la synthèse formelle de la bélactosine A et de l’hormaomycine a été effectuée. Cette synthèse se démarque des autres par l’utilisation d’une seule transformation catalytique énantiosélective.This master’s thesis presents three different approaches toward the synthesis of 3–(trans–2–nitrocyclopropyl)alanine, a key constituent of the natural product hormaomycin. This unusual compound demonstrates interesting biological and pharmaceutical activity. It is noteworthy that this unique amino acid can be readily converted to the corresponding 3–(trans–2–aminocyclopropyl)alanine, the central core of belactosin A, a natural compound exhibiting interesting biological properties. Efficient syntheses of these aminocyclopropane derivatives are of current interest since several structure-activity relationships in syntheses of belactosin A and hormaomycin analogues are currently under study in an effort to discover enhanced biological activity. A methodology developed in our research group based on a diastereoselective intramolecular cyclopropanation reaction will be used to elaborate a unique and elegant pathway to the synthesis of the 3–(trans–2–nitrocyclopropyl)alanine. By using a rhodium carbene generated either by the degradation of a diazoic derivative or by the formation of the corresponding iodonium ylide, a diastereoselective cyclopropanation reaction can be applied in the concerted elaboration of two chiral centers needed in the desired aminocyclopropanes, avoiding in this way the utilisation of chiral reagents. Following this key sequence, an intramolecular rearrangement followed by synchronous ring–opening/decarboxylation reactions will permit a convenient formation of the desired product in an acceptable overall yield and in few ensuing steps. In this manner, the formal synthesis of the hormaomycin and the belactosin A can be achieved. This synthesis is unique since it involves only one asymmetric step in the whole synthetic process.
33
(6847970), Jacob J. Werth. "TRANSITION METAL CATALYZED SIMMONS–SMITH TYPE CYCLOPROPANATIONS." Thesis, 2019.
Find full textAbstract:
Cyclopropanes are commonly found throughout synthetic and natural biologically active compounds. The Simmons–Smith cyclopropanation reaction is one of the most useful methods for converting an alkene into a cyclopropane. Zinc carbenoids are the active intermediate in the reaction, capable of delivering the methylene unit to a broad variety of substrates. Significant advances have been made in the field to increase overall efficiency of the reaction including the use of diethyl zinc as a precursor and allylic alcohols as directing groups.
Despite the many notable contributions in zinc carbenoid chemistry, persistent limitations of the Simmons–Smith reaction still exist. Zinc carbenoids exhibit poor steric discrimination in the presence of a polyolefin with minimal electronic bias. Additionally, due to the electrophilic nature of zinc carbenoid intermediates, the reaction performs inefficiently with electron-deficient olefins. Finally, alkyl-substituted zinc carbenoids are known to be quite unstable, limiting the potential for substituted cyclopropanation reactions.
In this work, we demonstrate that cobalt catalysis can be utilized to access novel cyclopropane products through the activation of dihaloalkanes. The content of this thesis will focus on the limitations of Zn carbenoid chemistry and addressing them with cobalt catalyzed, reductive cyclopropanations. In addition to this reactivity, we also demonstrate the dimethylcyclopropanation of activated alkenes to furnish valuable products applicable to natural product synthesis and pharmaceutically relevant compounds. Finally, we will show the unique character of the cobalt catalyzed cyclopropanation reaction through mechanistic experiments and characterization of reaction intermediates. In whole, these studies offer a complementary method to zinc carbenoid chemistry in producing novel and diverse cyclopropane products.
34
Ricardo, Carolynne Lacar. "Synthesis of Functionalized Organic Molecules Using Copper Catalyzed Cyclopropanation, Atom Transfer Radical Reactions and Sequential Azide-Alkyne Cycloaddition." 2011. http://digital.library.duq.edu/u?/etd,154088.
Full textAbstract:
Copper-catalyzed regeneration in atom transfer radical addition (ATRA) utilizes reducing agents, which continuously regenerate the activator (CuI) from the deactivator (CuII) species. This technique was originally found for mechanistically similar atom transfer radical polymerization (ATRP) and its application in ATRA and ATRC has allowed significant reduction of catalyst loadings to ppm amounts. In order to broaden the synthetic utility of in situ catalyst regeneration technique, this was applied in copper-catalyzed atom transfer radical cascade reaction in the presence of free radical diazo initiators such as 2,2’-azobis(isobutyronitrile) (AIBN) and (2,2’-azobis(4-methoxy-2,4-dimethyl valeronitrile) (V-70), which is the first part of this dissertation. This methodology can be translated to sequential ATRA/ATRC reaction, in which the addition of CCl4 to 1,6-dienes results in the formation 5-hexenyl radical intermediate, which undergoes expedient 1,5-ring closure in the exo- mode to form 1,2-disubstituted cyclopentanes. When [CuII(TPMA)Cl][Cl] complex was used in conjunction with AIBN at 60 0C, cyclic products derived from the addition of CCl4 to 16-heptadiene, diallyl ether and N,N-diallyl-2,2,2-trifluoroacetamide were synthesized in nearly quantitative yields using as low as 0.02 mol% of the catalyst (relative to 1,6-diene). Even more impressive were the results obtained utilizing tert-butyl-N,N-diallylcarbamate and diallyl malonate using only 0.01 mol% of the catalyst. Cyclization was also found to be efficient at ambient temperature when V-70 was used as the radical initiator. High product yields (>80%) were obtained for mixtures having catalyst concentrations between 0.02 and 0.1 mol%. Similar strategy was also conducted utilizing unsymmetrical 1,6-diene esters. It was found out that dialkyl substituted substrates (dimethyl-2-propenyl acrylate and ethylmethyl-2-propenyl acrylate) underwent 5-exocyclization producing halogenated g-lactones after the addition of CCl4 in the presence of 0.2 mol% of [CuII(TPMA)Cl][Cl]. Based on calculations using density functional theory (DFT) and natural bond order (NBO) analysis, cyclization of 1,6-diene esters was governed by streoelectronic factors. <br>As a part of broadening the synthetic usefulness of in situ copper(I) regeneration, scope was further extended to sequential organic transformations. Based on previous studies, copper(I) catalyzed [3+2] azide-alkyne cycloaddition is commonly conducted via in situ reduction of CuII to CuI species by sodium ascorbate or ascorbic acid. At the same time, ATRA reactions have been reported to proceed efficiently via in situ reduction of CuII complex to the activator species or CuI complex has been fulfilled in the presence of ascorbic acid. Since the aforementioned reactions share similar catalyst in the form of copper(I), a logical step was taken in performing these reactions in one-pot sequential manner. Reactions involving azidopropyl methacrylate and 1-(azidomethyl)-4-vinylbenzene in the presence of a variety of alkynes and alkyl halides, catalyzed by as low as 0.5 mol-% of [CuII(TPMA)X][X] (X=Br-, Cl-) complex, proceeded efficiently to yield highly functionalized (poly)halogenated esters and aryl compounds containing triazolyl group in almost quantitative yields (>90%). Additional reactions that were carried out utilizing tri-, di- and monohalogenated alkyl halides in the ATRA step provided reasonable yields of functionalized trriazoles. A slightly different approach involving a ligand-free catalytic system (CuSO4 and ascorbic acid) in the first step followed by addition of the TPMA ligand in the second step was applied in the synthesis of polyhalogened polytriazoles. Sequential reactions involving vinylbenzyl azide, tripropargylamine and polyhalogenated methane (CCl4 and CBr4) provided the desired products in quantitative yield in the presence of 10 mol% of the catalyst. Modest yields of functionalized polytriazoles were obtained from the addition of less active tri- and dihalogenated alkyl halides utilizing the same catalyst loading.
<br>The last part focuses on copper(I) complexes, which were used catalysts in cyclopropanation reaction. One class represented cationic copper(I)/2,2-bipyridine complexes with p-coordinated styrene [CuI(bpy)(p-CH2CHC6H5)][A] (A = CF3SO3- (1) and PF6- (2) and ClO4- (3). Structural data suggested that the axial coordination of the counterion in these complexes observed in the solid state weak to non-coordinating (2.4297(11) Å 1, 2.9846(12) Å 2, and 2.591(4) Å 3). When utilized in cyclopropanation, complexes 1-3 provided similar product distribution suggesting that counterions have negligible effect on catalytic activity. Furthermore, the rate of decomposition of EDA in the presence of styrene catalyzed by 3 (kobs=(7.7±0.32)´10-3 min-1) was slower than the rate observed for 1 (kobs=(1.4±0.041)´10-2 min-1) or 2 (kobs=(1.0±0.025)´10-2 min-1). On the other hand, tetrahedral copper(I) complexes with bipyridine and phenanthroline based ligands have been reported to have strongly coordinated tetraphenylborate anions. CuI(bpy)(BPh4), CuI(phen)(BPh4) and CuI(3,4,7,8-Me4phen)(BPh4) complexes are the first examples in which BPh4- counterion chelates a transition metal center in bidentate fashion through h2 p-interactions with two of its phenyl rings. The product distribution revealed that the mole percent of trans and cis cyclopropanes were very similar. The observed rate constants (kobs) shown in for decomposition of EDA in the presence of externally added styrene were determined to be kobs=(1.5±0.12)´10-3 min-1, (6.8±0.30)´10-3 min-1 and (5.1±0.19)´10-3 min-1.Bayer School of Natural and Environmental Sciences
Chemistry and Biochemistry
PhD
Dissertation
35
Hornung, Nora L. "Intramolecular cyclopropanation and olefin metathesis reactions of (CO)₅W-C(OCH₂CH₂CH=CHOCH₃)C₆H₄-p̲-CH₃." 1987. http://catalog.hathitrust.org/api/volumes/oclc/15688347.html.
Full textAbstract:
Thesis (Ph. D.)--University of Wisconsin--Madison, 1987.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
36
Bahutski, Viktar. "Development of Viable Synthetic Approaches to Highly Functionalized Small Ring Systems - Synthesis of Novel Cyclopropylacrylates as Monomers for Low-Shrinkage Polymer-Composites." Doctoral thesis, 2004. http://hdl.handle.net/11858/00-1735-0000-0006-B0A8-E.
Full text