Letteratura scientifica selezionata sul tema "P-Stereogenic catalysts"
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Articoli di riviste sul tema "P-Stereogenic catalysts":
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Błaszczyk, Jarosław, Bogdan Bujnicki, Patrycja Pokora-Sobczak, Grażyna Mielniczak, Lesław Sieroń, Piotr Kiełbasiński e Józef Drabowicz. "New Optically Active tert-Butylarylthiophosphinic Acids and Their Selenium Analogues as the Potential Synthons of Supramolecular Organometallic Complexes: Syntheses and Crystallographic Structure Determination". Molecules 28, n. 11 (24 maggio 2023): 4298. http://dx.doi.org/10.3390/molecules28114298.
Abstract (sommario):
The aim of the research described in this publication is two-fold. The first is a detailed description of the synthesis of a series of compounds containing a stereogenic heteroatom, namely the optically active P-stereogenic derivatives of tert-butylarylphoshinic acids bearing sulfur or selenium. The second is a detailed discussion dedicated to the determination of their structures by an X-ray analysis. Such a determination is needed when considering optically active hetero-oxophosphoric acids as new chiral solvating agents, precursors of new chiral ionic liquids, or ligands in complexes serving as novel organometallic catalysts.
2
Han, Zhengxu S., Hao Wu, Bo Qu, Yuwen Wang, Ling Wu, Li Zhang, Yibo Xu et al. "New class of P-stereogenic chiral Brønsted acid catalysts derived from chiral phosphinamides". Tetrahedron Letters 60, n. 28 (luglio 2019): 1834–37. http://dx.doi.org/10.1016/j.tetlet.2019.06.013.
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von Münchow, Tristan, Suman Dana, Yang Xu, Binbin Yuan e Lutz Ackermann. "Enantioselective electrochemical cobalt-catalyzed aryl C–H activation reactions". Science 379, n. 6636 (10 marzo 2023): 1036–42. http://dx.doi.org/10.1126/science.adg2866.
Abstract (sommario):
Enantioselective redox transformations typically rely on costly transition metals as catalysts and often stoichiometric amounts of chemical redox agents as well. Electrocatalysis represents a more sustainable alternative, in particular through the use of the hydrogen evolution reaction (HER) in place of a chemical oxidant. In this work, we describe strategies for HER-coupled enantioselective aryl carbon-hydrogen bond (C–H) activation reactions using cobalt in place of a precious metal catalyst for the asymmetric oxidation. Thus, highly enantioselective carbon-hydrogen and nitrogen-hydrogen (C–H and N–H) annulations of carboxylic amides were achieved, which gave access to point and axially chiral compounds. Furthermore, the cobalt-mediated electrocatalysis enabled the preparation of various phosphorus (P)–stereogenic compounds by selective desymmetrization through dehydrogenative C–H activation reactions.
4
Chan, Vincent S., Melanie Chiu, Robert G. Bergman e F. Dean Toste. "Development of Ruthenium Catalysts for the Enantioselective Synthesis of P-Stereogenic Phosphines via Nucleophilic Phosphido Intermediates". Journal of the American Chemical Society 131, n. 16 (29 aprile 2009): 6021–32. http://dx.doi.org/10.1021/ja9014887.
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Gladiali, Serafino, Serenella Medici, Giovanna Pirri, Sonia Pulacchini e Davide Fabbri. "BINAPS - An axially chiral P,S-heterodonor ligand for asymmetric catalysis based on binaphthalene backbone". Canadian Journal of Chemistry 79, n. 5-6 (1 maggio 2001): 670–78. http://dx.doi.org/10.1139/v01-041.
Abstract (sommario):
The chelating P,S-heterodonor ligand 2-diphenylphosphanyl-1,1'-binaphthalene-2'-thiol (11) (BINAPS), which features a chiral axis as the unique stereogenic element, has been prepared in both racemic and enantiopure form through a multistep reaction sequence using 2,2'-dihydroxy-1,1'-binaphthalene (BINOL) as the starting material. The reaction sequence is completely stereoconservative and (S)-11 is obtained with no loss of enantiopurity from pure (S)-BINOL. (R)-11 can be alternatively obtained by resolution of racemic 11 using the chiral (S)-benzylaminato Pd(II)-complex 19 as the resolving agent. The S-methyl or the S-i-propyl derivatives 14 have been used as chiral ligands in the Rh(I)-catalyzed asymmetric hydroformylation of styrene and in the hydrogen transfer reduction of acetophenone with modest success (up to 20% ee). In the presence of suitable Pd-complexes the same ligands provide higher ees in the hydrosilylation of styrene (50% ee) and in the allylic alkylation of 1,3-diphenylprop-2-enyl acetate (60% ee).Key words: heterodonor ligands, binaphthalene derivatives, enantioselective catalysis, transition metal catalysts, allylic alkylation.
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Biosca, Maria, Ernest Salomó, Pol de la Cruz-Sánchez, Antoni Riera, Xavier Verdaguer, Oscar Pàmies e Montserrat Diéguez. "Extending the Substrate Scope in the Hydrogenation of Unfunctionalized Tetrasubstituted Olefins with Ir-P Stereogenic Aminophosphine–Oxazoline Catalysts". Organic Letters 21, n. 3 (16 gennaio 2019): 807–11. http://dx.doi.org/10.1021/acs.orglett.8b04084.
7
Bagi, Péter, Réka Herbay, Gábor Györke, Péter Pongrácz, László Kollár, István Timári, László Drahos e György Keglevich. "Preparation of Palladium(II) Complexes of 1-substituted-3-phospholene Ligands and their Evaluation as Catalysts in Hydroalkoxycarbonylation". Current Organic Chemistry 23, n. 25 (14 gennaio 2020): 2873–79. http://dx.doi.org/10.2174/1385272823666191204151311.
Abstract (sommario):
: A series of palladium(II) complexes incorporating 1-substituted-3-methyl-3- phospholenes as the P-ligands were prepared from phospholene oxides by deoxygenation followed by complexation with PdCl2(PhCN)2. The two 1-substituted-3-methyl-3- phospholene ligands were trans position to each other in the Pd(II)-complexes. As the ligands contain a P-stereogenic center, the Pd-complexes were obtained as a 1:1 mixture of two stereoisomers, the homochiral (R,R and S,S) and the meso (R,S) forms, when racemic starting materials were used. An optically active Pd-complex containing (R)-1-propyl- 3-phospholene ligand was also prepared. Catalytic activity of an aryl- and an alkyl-3- phospholene-palladium(II)-complex was evaluated in hydroalkoxycarbonylation of styrene. The alkyl-derivative showed higher activity and selectivity towards the formation of the esters of 3-phenylpropionic acid. However, the overall activity of these PdCl2(phospholene)2-type complexes was low.
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Huber, Raffael, Alessandro Passera, Erik Gubler e Antonio Mezzetti. "P-Stereogenic PN(H)P Iron(II) Catalysts for the Asymmetric Hydrogenation of Ketones: The Importance of Non-Covalent Interactions in Rational Ligand Design by Computation". Advanced Synthesis & Catalysis 360, n. 15 (22 giugno 2018): 2900–2913. http://dx.doi.org/10.1002/adsc.201800433.
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Numan, Ahmed, e Matthew Brichacek. "Asymmetric Synthesis of Stereogenic Phosphorus P(V) Centers Using Chiral Nucleophilic Catalysis". Molecules 26, n. 12 (15 giugno 2021): 3661. http://dx.doi.org/10.3390/molecules26123661.
Abstract (sommario):
Organophosphates have been widely used in agrochemistry, as reagents for organic synthesis, and in biochemistry. Phosphate mimics possessing four unique substituents, and thereby a chirality center, are useful in transition metal catalysis and as nucleotide therapeutics. The catalytic, stereocontrolled synthesis of phosphorus-stereogenic centers is challenging and traditionally depends on a resolution or use of stochiometric auxiliaries. Herein, enantioenriched phosphorus centers have been synthesized using chiral nucleophilic catalysis. Racemic H-phosphinate species were coupled with nucleophilic alcohols under halogenating conditions. Chiral phosphonate products were synthesized in acceptable yields (33–95%) and modest enantioselectivity (up to 62% ee) was observed after identification of an appropriate chiral catalyst and optimization of the solvent, base, and temperature. Nucleophilic catalysis has a tremendous potential to produce enantioenriched phosphate mimics that could be used as prodrugs or chemical biology probes.
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Funk, Michael A. "A P catalyst for stereogenic P(III)". Science 371, n. 6530 (11 febbraio 2021): 687.5–687. http://dx.doi.org/10.1126/science.371.6530.687-e.
Tesi sul tema "P-Stereogenic catalysts":
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Salomó, i. Prat Ernest. "P-Stereogenic Intermediates and MaxPHOX ligands. Iridium Catalyzed Asymmetric Hydrogenations". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663829.
Abstract (sommario):
Asymmetric hydrogenation of double bonds by means of organometallic catalysis is a powerful tool for organic synthesis; it is an efficient and simple method to produce valued chiral compounds. Among the many different existing ligands, phosphorous ones have proven very useful for these procedures. The ligand plays a vital role in the catalysis, as the ligand’s chirality can transferred to the product. There is a wide range of P-based chiral ligands and can be classified in 3 groups depending on where the chirality lies; on the P unit, on the C-backbone or on both the P unit and the C-backbone.
In the first section of the present PhD thesis we have studied new methodologies for the synthesis of compounds with chiral phosphorous. We developed the reduction of an important chiral phosphinous acid developed in our group to the corresponding secondary phosphine borane by means of a completely enantioselective SN2@P. This phosphine is a known compound, useful to access important P-stereogenic ligands. We have also designed a derivative of the aforementioned phosphinous acid, which is much more stable. This derivative maintains all the reactivity of the phosphinous acid in the SN2@P reaction with nucleophiles.
In the second section of the present PhD thesis we were able to produce a small family of P-stereogenic Ir-MaxPHOX catalysts. We have applied this library to the reduction of different interesting substrates from a pharmaceutical or agrochemical point of view. We hydrogenated different challenging imines (N-aryl imines and N-alkyl imines) to the corresponding amines with excellent enantioselectivities. We also reduced cyclic enamides (α- and β-enamides) to the corresponding amides. In this later case, the control over the ee was complete. These are the best results reported in the literature so far.La hidrogenación asimétrica de dobles enlaces mediante catálisis es un método eficiente y simple para producir valiosos compuestos quirales. De entre los distintos ligandos existentes, los de fósforo han demostrado ser muy útiles en estos procesos. El ligando juega un rol vital en la catálisis debido a que la quiralidad en este se puede transmitir al al producto. Hay un amplio rango de ligandos que contienen fósforo y se pueden clasificar básicamente en 3 grupos según donde reside la quiralidad; en el esqueleto de carbono, en el átomo de P o bien en ambos. En la primera parte de la presente tesis doctoral hemos estudiado nuevas metodologías para la síntesis de moléculas con P* (fósforo quiral). Desarrollamos la reducción de un importante ácido fosfinoso quiral desarrollado por nuestro grupo a la correspondiente fosfina secundaria boronada mediante una reacción SN2@P completamente enantioselectiva. La fosfina obtenida es un compuesto conocido que se usa para sintetizar diferentes ligandos P-stereogenicos. También sintetizamos un derivado del ya antes mencionado ácido fosfinoso, el cual es mucho más estable. Demostramos que este derivado mantiene toda la reactividad en la reacción SN2@P con nucleófilos respeto al ácido fosfinoso. Durante la segunda parte de esta tesis sintetizamos una pequeña familia de catalizadores Ir-MaxPHOX y los usamos para hidrogenar asimétricamente distintos compuestos de interés para la industria farmacéutica y agroquímica. Hemos hidrogenado distintas iminas (N-aril y N-alquil iminas) a las correspondientes aminas con excelentes enantioselectividades. Conseguimos también reducir enamidas cíclicas (α- y β-enamidas) a las correspondientes amidas. Para este último caso, el control sobre el ee fue completo, consiguiendo así los mejores resultados para estos sustratos hasta la fecha.
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Doran, Seán. "The synthesis and application of bulky S-stereogenic and P- stereogenic chiral ligands". Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/96997.
Abstract (sommario):
This doctoral thesis was focused on the design and synthesis of novel chiral ligands for application in asymmetric catalysis. One of the best examples of asymmetric catalysis is the asymmetric hydrogenation reaction for its atom economy, ease of access to both S and R enantiomers and almost ultimate enantiomeric excess obtainable in a multitude of substrates. There has been much investigation into this reaction and there has been a plethora of chiral ligands designed which catalyze this reaction in high enantiomeric excess using metals such as rhodium, iridium and ruthenium. The vast majority of these ligands are diphosphines with their chirality lying either on the backbone of the ligand or on the coordinating phosphorus atom itself.
In the beginning of this work investigation was undertook to explore the possibility of successfully employing a new type of ligand class in the asymmetric hydrogenation reaction, namely the N-phosphino sulfinamide or PNSO ligands. PNSO ligands had been successfully applied to the asymmetric Pauson-Khand reaction in the Riera group yielding cyclopentenone Pauson-Khand adducts in high yield and very high enantioselectivity. The family of PNSO ligands prepared in the Riera group was attractive because apart from the high yields and enantioselectivities obtained from the reactions in which they were used, they proved to be easily prepared in short syntheses from commercially available starting materials. It was believed if they could be successfully applied in asymmetric hydrogenation for their ease of preparation they would be an attractive alternative to the diphosphine ligand class. Unfortunately the first two PNSO-Rh complexes successfully prepared provided low enantioselectivities and difficulties were encountered while trying to prepare further analogues.
After some time trying to achieve PNSO-Rh complex analogues unsuccessfully the direction of the project was shifted away from the N-phosphino sulfinamide ligand class in asymmetric hydrogenation. The MaxPhos ligand had recently been developed in the group and had proven highly promising. A study was demanded of its substrate scope as applied in rhodium catalyzed asymmetric hydrogenation. Substrates already described in the literature were prepared and the asymmetric hydrogenation of them catalyzed by the MaxPhos-Rh precatalyst was performed and conditions to do so were optimized. Of seven substrates prepared the MaxPhos-Rh proved to hydrogenate five of those with high enantioselectivity.
The TOF of the MaxPhos rhodium catalyst applied in the hydrogenation of the Z-MAC substrate was examined by monitoring the flux of hydrogen and was calculated at 0.065 s-1. MaxPhos complexes of cobalt and palladium were prepared to form part of the investigation into widening the reaction scope of the ligand. [(MaxPhos)Co2(CO)4(C2H2)] proved to catalyze the Pauson-Khand reaction of norbornadiene and 1-hexyne with 24 % yield and 28 %, a noteworthy enantiomeric excess for the catalytic asymmetric Pauson-Khand reaction. Chalcogenated derivatives of MaxPhos were prepared. The diselenide was used to explore the electronic nature of the ligand. The MaxPhos-rhodium carbonyl stretching was examined. MaxPhos-BH3 was used to prepare mono-chalcogenated MaxPhos derivatives. They were applied also in asymmetric hydrogenation once complexed to rhodium but enantiomeric excess of no more than 21 % was obtained in the hydrogenation of the substrate Z-MAC. The aminophosphine, a chiral building block and key intermediate in the preparation of the MaxPhos ligand, was used in the attempt to prepare bulky chiral amidine ligands and although two such species were prepared they proved inapplicable in asymmetric catalysis.Se desarrollaron los ligandos N-fosfino sulfinamida (PNSO) en el grupo de Riera para su aplicación en la reacción Pauson-Khand asimétrica. Se probaron que estos ligandos eran muy eficaces en esta reacción y daban rendimientos y enantioselectividades muy altos de los aductos Pauson-Khand. Probar la eficacia de estos ligandos PNSO en hidrogenación asimétrica formó parte de este trabajo. Se prepararon dos ligandos PNSO, se complejaron con rodio formando complejos neutros. Se protonaron los complejos neutros con ácido tetraflorobórico para formar los complejos catiónicos. Se usaron estos complejos de rodio- PNSO, tanto los complejos neutros como los catiónicos como catalizadores en la hidrogenación asimétrica del sustrato Z-MAC. Los complejos de rodio con el ligando PNSO substituido por el grupo tolilo en azufre no hidrogenaba el sustrato pero los complejos de rodio con el ligando PNSO dotado de tres grupos tert-butilos hidrogenaba el sustrato aunque con baja selectividad. Después de un tiempo intentando conseguir análogos de ligandos tipo PNSO sin éxito se cambió la dirección del proyecto. Se decidió centrarse en el ligando MaxPHOS el cual había sido desarrollado recientemente en el grupo Riera. El ligando MaxPHOS demostró gran eficacia en hidrogenación asimétrica con dos sustratos pero se deseaba un estudio mas amplio del potencial del ligando así que se sintetizaron siete sustratos y se probó el catalizador MaxPHOS en la hidrogenación asimétricas de esos sustratos. El catalizador MaxPHOS-Rh proporcionó excesos enantioméricos muy altos en cinco de los siete sustratos. Se hizo un estudio de las propiedades electrónicas del ligando MaxPHOS aprovechando los estudios de (31)P RMN y el MaxPHOS diselenuro lo cual se preparó anteriormente. También se estudió el “stretching” carbonilo del complejo MaxPHOS-Rh. Se demostró que el ligando MaxPHOS era menos rico en electronos que el ligando trichickenfootphos. Se prepararon complejos de MaxPHOS con paladio y cobalto para examinar la eficacia del ligando en reacciones mas allá de hidrogenación asimétrica como la reacción Pauson–Khand catalítica asimétrica. Se sintetizaron varios derivados del ligando MaxPHOS a partir de los intermedios clave en la preparación del ligando y se probaron en hidrogenación asimétrica proporcionando excesos enantioméricos bajos.
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Despalle, Alexis. "Développement de nouveaux outils et de nouvelles approches synthétiques pour le contrôle des chiralités centrale, axiale et hélicoïdale". Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0130.
Abstract (sommario):
Depuis les travaux pionniers d’Akiyama et Terada en 2004 sur l’utilisation d’organocatalyseurs acides phosphoriques chiraux, de nombreux efforts ont été déployés pour le développement de catalyseurs C2-symétriques à chiralité axiale avec, toutefois, un accès synthétique fastidieux. La synthèse de catalyseurs acides thiophosphi(o)niques originaux P-stéréogènes facilement accessibles et configurationnellement stables a été réalisée et leur réactivité a ensuite été évaluée dans une réaction de Pictet-Spengler énantiosélective avec des résultats préliminaires encourageants. Dans un second projet, nous avons d’abord tenté de développer une nouvelle réaction d’arylation organocatalysée énantiosélective afin d’obtenir des nouveaux atropisomères coumarine-aryle avec des résultats préliminaires prometteurs. Nous avons aussi souhaité développer une méthode de synthèse stéréosélective de furanes possédant deux axes stéréogènes par conversion de chiralité. Ainsi, nous avons d’abord réalisé la synthèse énantiosélective de dihydrofuranes par hétéroannulation avec deux types de nucléophiles et modes d'activation différents. La synthèse de (hétéro) [4]hélicènes configurationnellement stables constitue un défi synthétique car ces molécules racémisent rapidement à température ambiante. Deux hétéro [4]pseudo-hélicènes stables configurationnellement ont été obtenus par hydroarylation intramoléculaire d’alcynes catalysée à l’or. Nous avons également tenté la synthèse de composés [4]hélicéniques par double réaction de Friedel-Crafts organocatalysée par un acide de Brønsted mais les produits souhaités n’ont jamais pu être isolésSince the pioneering work of Akiyama and Terada in 2004 on the use of chiral phosphoric acid as organocatalysts, a huge amount of efforts has been devoted to the development of C2-axially chiral catalysts. Despite being successful in many transformations, the potential industrial development of this family of catalysts is hampered by a tedious multisteps synthetic access. In this context, the synthesis of easily accessible, configurationally stable P-stereogenic and original thiophosphi(o)nic acid catalysts was achieved and, as a preliminary experiment, they were engaged in an enantioselctive Pictet-Spengler reaction showing very encouraging results. In a second project, we tried to develop a new organocatalyzed enantioselective arylation reaction to obtain new coumarin-aryl atropisomers with promising results. Then, we aimed at developing a new method for the stereoselective synthesis of furans displaying two atropisomericaxis by chirality conversion strategy. We first performed the enantioselective synthesis of dihydrofurans by a heteroannulation. Very promising results were obtained with two types of arylacetyl nucleophiles activated by a bifonctionnal organocatalyst or by a catalytic complex of Ni(II) and chiral diamine.The synthesis of configurationnally stable (hetero) [4]helicenes constitutes a synthetic challenge since these molecules rapidly racemizeat room temperature. Two configurationnally stable hetero [4]pseudo-helicenes were obtained by Au-promoted alkynes intramolecular hydroarylation. We also tried to synthesize [4]helicenic compounds by Brønsted acid organocatalized double Friedel-Crafts reaction. However, the desired products could not be isolated
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Liu, Peng. "Helicoselective Synthesis of Dioxa[6]helicenes and Design of Orginal P-Stereogenic Brønsted Acid Organocatalystsx". Electronic Thesis or Diss., Ecole centrale de Marseille, 2020. http://www.theses.fr/2020ECDM0004.
Abstract (sommario):
Cette thèse est composée de deux parties principales. Premièrement, l'accès synthétique hélicosélectif à une nouvelle série de dioxa[6]hélicènes dioxa configurationnellement stables à partir de précurseurs achiraux simples a été développé. L’hélice est créée et contrôlée au cours d'une réaction domino organocatalysée comprenant une alkylation de Michael suivie d’un couplage C–O, qui fournit les 2-nitrodihydrofuranes chiraux sous forme d’uniques stéréoisomères présentant à la fois une chiralité centrale (deux atomes de carbone stéréogènes) et une chiralité hélicoïdale. Il s’agit du premier cas d'une transformation chimique dans laquelle les chiralités centrales et hélicoïdales sont contrôlées simultanément. Ceci donne accès à des molécules chirales très originales pour la synthèse d'hétérohelicènes optiquement actifs par élimination de HNO2 avec une excellente rétention la chiralité hélicoïdale dans la plupart des cas. Dans une second partie, une nouvelle classe d’organocatalyseurs de type acides de Brønsted a été développée dans laquelle la chiralité est centrée sur l'atome de phosphore. Les acides thiophosphiniques P-stéréogènes chiraux optiquement actifs ont été synthétisés., ce qui ouvre de nouvelles opportunités en l’organocatalyse énantiosélective. Ces nouveaux organocatalyseurs ont notamment été utilisés dans la réaction de Pictet-Spengler et les produits ont été obtenus avec de bons rendements et énantiosélectivité modérée (jusqu'à 47% ee). Cette première étape valide le concept initial mais une optimisation supplémentaire est nécessaire pour atteindre des excès énantiomériques plus élevés et pour rendre ces organocatalyseurs plus générauxThis PhD thesis is composed of two main parts. First, the expedient helicoselective synthetic access to a new series of configurationally stable dioxa[6]helicenes from simple achiral precursors was developed. The helicity is created and controlled during an organocatalyzed domino Michael/C–O alkylation step, which delivers chiral 2-nitrodihydrofurans as single stereoisomers featuring both central chirality (two stereogenic carbon atoms) and a helical shape. Interestingly, this represents the first case of a catalytic chemical transformation in which both central and helical chiralities are controlled simultaneously, offering unprecedented chiral platform molecules for the synthesis of enantioenriched heterohelicenes by simple base-promoted elimination of HNO2 with excellent retention of the helical information in most cases. Secondly, a new design for Brønsted acid organocatalysis was developed in which the chirality is centered on the phosphorus atom. Chiral P-stereogenic thiophosphinic acids were synthesized in high enantiomeric excess. This opens new synthetic opportunities for both hydrogen-bonding and ion-pairing enantioselective organocatalysis. These new catalysts were used notably in Pictet-Spengler reactions delivering the products in moderate enantioselectivity (up to 47% ee). This first step validate the concept but further optimization is necessary to reach higher enantiomeric excess and to make these catalysts more general
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Gallen, Ortiz Albert. "P-Stereogenic ligands with the tert-butylmethylphosphine fragment. Coordination chemistry and catalysis of their organometallic complexes". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/666577.
Abstract (sommario):
The Thesis deals with the preparation, coordination chemistry and use in asymmetric homogeneous catalysis of several optically pure P-stereogenic ligands containing a tert-butylmethylphosphino fragment.
In the first part a highly stereoselective synthesis of the Secondary Phosphine Oxide (SPO) tert-butylmethylphosphine oxide is presented. Despite its simplicity, the stereoselective synthesis of this SPO had not been described in the literature. It is known that SPOs present a tautomeric equilibrium between the air-stable pentavalent form (phosphine oxide) and the trivalent form (phosphinous acid), usually completely shifted towards the pentavalent form but that can be displaced towards the phosphinous acid form by metal complexation. In the Thesis the complexation of the mentioned oxide towards Ru, Rh, Ir, Ni, Pd and Au has been explored, yielding a variety of coordination and organometallic compounds, with several coordination modes of the ligand. Some asymmetric catalytic applications of these species have also been studied, giving good conversions but low enantioselectivities.
In the second part of the Thesis, the C1-symmetric P-stereogenic ligand MaxPhos has been coordinated to [MCp*Cl] (M = Rh and Ir) and [Ru(p-cymene)Cl] fragments, yielding cationic M-stereogenic organometallic compounds as tetrafluoroborate or hexafluorophosphate salts. Interestingly, in all cases a single stereoisomer has been formed, as confirmed by NMR and X-ray crystallography. This has been rationalised by steric grounds. For Ir, the abstraction of the remaining chloride ligand by silver salts produced a diastereoselective C–H activation of a tert-butyl group of the ligand. The complexes have been used in transfer hydrogenation giving good activities but no enantioselectivities.
Finally the third part of the Thesis is devoted to the cyclometallation of [Ir(MaxPHOX)COD]BArF complexes (MaxPHOX stands for a type of P,N phosphinooxazoline ligand recently described by our group having three stereogenic centres) by several ligands under hydrogen atmosphere. It has been found that cyclometallated Ir(III)-hydrido complexes are formed, which are very stable and have been characterised thoroughly. They have been used in asymmetric hydrogenation of N-alkylimines, giving in general complete conversions and very high enantioselectivities (up to 96% ee) for these substrates, which rank among the best described to date. The mechanism of the reaction has been studied and the stereochemical outcome rationalised by means of DFT-based computational methods.La Tesi presenta la preparació, coordinació i ús en catàlisi homogènia asimètrica d’una varietat de lligands P-estereogènics òpticament purs que contenen el grup tert- butimetilfosfina. A la primera part es presenta la síntesi, altament estereoselectiva, de l’òxid de fosfina secundari (SPO) òxid de tert-butilmetilfosfina. Malgrat la simplicitat d’aquest compost, no se n’havia descrit la síntesi de forma estereoselectiva a la bibliografia. Se sap que els SPOs presenten un equilibri tautomèric entre la forma pentavalent estable a l’aire (òxid de fosfina) i la forma trivalent (àcid fosfinós). Habitualment aquest equilibri es troba totalment desplaçat envers la forma pentavalent però es pot desplaçar cap a l’àcid fosfinós per complexació amb un metall. A la Tesi, s’ha estudiat la complexació de l’òxid esmentat a Ru, Rh, Ir, Ni, Pd i Au i ha donat una gran varietat de compostos de coordinació i organometàl·lics, en els quals el lligand presenta una varietat de modes coordinació. També s’han explorat algunes aplicacions catalítiques d’aquestes espècies i s’han trobat bones conversions però baixes enantioselectivitats. A la segona part de la Tesi el lligand P-estereogènic de simetria C1 MaxPhos s’ha coordinat a fragments [MCp*Cl] (M = Rh o Ir) i [Ru(p-cimè)Cl] i ha donat compostos organometàl·lics catiònics M-estereogènics en forma de sals de tretrafluoroborat o hexafluorofosfat. És interessant destacar que estudis de RMN i cristal·lografia de raigs X han demostrat que en tots els casos s’ha format un sol estereoisòmer, fet que s’ha racionalitzat per arguments estèrics. En el cas del Ir, la abstracció del lligand cloruro amb sals de plata ha provocat l’activació de l’enllaç C–H d’un grup tert-butil de lligand en forma diastereoselectiva. Tots els compostos preparats s’han utilitzat en transferència d’hidrogen asimètrica i han donat bones activitats però enantioselectivitats baixes. Finalment, la tercera part de la Tesi està dedicada a la ciclometal·lació de complexos [Ir(MaxPHOX)COD)BArF amb diferents lligands auxiliars sota atmosfera d’hidrogen, on MaxPHOX és un lligand P,N de tipus fosfinooxazolina que el nostre grup de recerca ha descrit recentment i que conté tres centres estereogènics. S’ha observat la formació de complexos ciclometal·lats Ir(III)-hidrur molt estables, que s’han caracteritzat exhaustivament. Aquests complexos s’han usat com a catalitzadors per la reacció d’hidrogenació asimètrica d’imines alquíliques i ha donat conversions completes i enantioselectivitats de fins el 96% d’ee, que es troben entre els millors que s’han descrit mai per a aquests tipus de substrats. S’ha estudiat el mecanisme de la reacció i el curs estereoquímic, que s’ha racionalitzat mitjançant mètodes computacionals de tipus DFT.
6
Febvay, Julie. "Approches synthétiques à de nouvelles séries de phosphahélicènes". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS436.
Abstract (sommario):
Les phosphahélicènes sont des composés comportant un cycle phosphoré inclus au sein d’un squelette hélicoïdal.Ils sont efficaces en tant que ligands en catalyse organométallique asymétrique à l'or (I), et en tant que base de Lewis en organocatalyse asymétrique. Au cours de cette thèse, nous avons développé de nouvelles familles de phosphahélicènes comportant des modifications sur la partie phosphorée ainsi que sur le squelette hélicoïdal. La première synthèse d’acides de Brønsted à chiralité hélicoïdale, portant un motif benzophosphole et des fonctions P(O)OH et P(O)NH₂ a été développée. Cette étude a permis de mettre en évidence une photoréactivité [2+2] à l’état solide du cycle phosphoré. Par ailleurs, la synthèse de la première famille de phosphahélicènes à motif benzophospholène, portant les fonctions thiophosphonate P(S)OMe et acide thiophosphinique P(S)OH a été réalisée. Le motif benzophospholène induit une nouvelle régiosélectivité de la réaction de photocyclisation oxydante, ce comportement a été rationalisé par des calculs DFT. Les phosphahélicènes obtenus sont les premiers exemples d’acides de Brønsted P-stéréogènes hélicoïdaux. Par ailleurs, une voie d’accès originale à des structures hélicoïdales a été explorée. Une synthèse courte et robuste d’un thia[5]hélicène, intrinsèquement chiral mais dont la configuration est instable, a été mise au point. Des premiers essais de fonctionnalisations régiosélectives par des réactions de bromation, d’arylation C-H et par des acylations de Friedel-Crafts sont été réalisés, pour créer l’encombrement stérique nécessaire à la stabilisation de la configuration hélicoïdale. Enfin, la première version énantiosélective d’une réaction tandem cyclisation/hydratation d’ynamides N-propargyliques catalisée à l’or (I) a été réalisée. L’utilisation d’un catalyseur d’or chiral, la DM-SEGPHOS(AuCl)₂ a permis l’obtention de dix-huit pipéridinones énantioenrichies avec des excès énantiomériques allant jusqu’à 86%Phosphahelicenes are helicenic compounds embedded with a phosphole ring. Previous work of the group showed their efficiency both in asymmetric organometallic gold catalysis and organocatalysis. The aim of this work is to expand the toolbox of phosphahelicenes by modifications on the phosphorus unit and the helical backbone. The first families of helical Brønsted acids have been developed. The synthesis of the first phosphahelicenes with a phosphole ring and P(O)OH or P(O)NH₂ functions have been established. During this study we enhanced a [2+2] photocyclisation of the phosphole ring at the solid state. In addition, the first synthesis of phosphahelicene with a benzophospholene moiety and thiophosphinate P(S)OMe or thiophosphinic acid P(S)OH has been established. During the study, a new regioselectivity of the oxidative photocyclisation step induced by the benzophospholene unit has been observed and rationalized by DFT calculations. These new phosphahelicenes are the first examples of P-stereogenic and helicenic Brønsted acids. A new and original pathway to access helicenic structures has been explored. The short synthesis of a chiral but not configurationally stable thiaphospha[5]helicene has been developed. First trials to substitute it regioselectively through bromination, C-H arylation and Friedel Crafts acylations has been done to create the steric environment which could stabilize the helical chirality. Finally, the first gold-catalyzed enantioselective 6-endo-dig cyclisation of N-propargylic ynamides into dihydrobenzoquinones has been developed. The use of the chiral gold complex DM-SEGPHOS(AuCl)₂ allowed the access to eighteen dihydrobenzoquinones with enantiomeric excess up to 86%
7
Salomon, Christine. "Nouvelle synthèse stéréosélective de diphosphines à pont méthano P-stéréogéniques : applications en catalyse asymétrique et pour la préparation de clusters ou de polymères de coordination chiraux". Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS010/document.
Abstract (sommario):
Ce mémoire porte sur la synthèse asymétrique de ligands à pont méthano P-stéréogénique, ainsi que sur leurs applications en catalyse asymétrique, en chimie de coordination et pour la préparation de polymères de coordination avec des métaux de transition. Les diphosphines P-stéréogéniques sont synthétisées par création d'une liaison phosphore-carbone au niveau du pont méthano, à partir d'un anion formé en position α d'une méthylphosphines borane. Plusieurs stratégies ont été étudiées selon que l'électrophile est un complexe d’oxazaphospholidine borane, un phosphinite borane ou une chlorophosphine borane. L'utilisation de chlorophosphine borane dans cette synthèse s'est révélée la plus stéréosélective car les excès énantiomériques obtenus sont supérieurs à 99%. Les différentes stratégies étudiées montrent qu'il est possible d’accéder à des diphosphines diborane à pont méthano variées, dissymétriques ou de symétrie C2, porteuses de substituants alkyl ou aryl, tels que Me, OMe, Ph, o-An... Les diphosphines P-stéréogéniques obtenues ont été utilisées pour la synthèse des premiers clusters chiraux du palladium. Ceux-ci sont obtenus par réaction des ligands diphosphines, fraîchement décomplexées avec du DABCO, avec l’acétate de palladium en présence d’acide trifluoroacétique dans un mélange eau/acétone sous pression de CO. La structure cristallographique d'un des clusters de palladium préparés a pu être établie, confirmant la structure avec un cœur trimétallique de palladium. L'étude des propriétés électrochimiques et l'analyse RPE de ces clusters a permis de mettre en évidence la formation du premier radical dans un environnement chiral hautement structuré. Une étude de la réactivité de ces clusters chiraux dans une réaction de Friedel Craft a été réalisée, mais le produit est obtenu de façon non catalytique et sans activité optique significative. Par contre dans le cas de réactions asymétriques, tels que l’hydrogénation, l’hydrosilylation, l’allylation ou la réaction de Diels Alder, catalysées par des complexes du rhodium, du palladium ou d’argent, des inductions asymétriques de 30-38% sont obtenus. Il ressort que les synthèses stéréosélectives mises au point dans ce travail, permettent d'envisager maintenant les modifications structurales nécessaires à l'optimisation de ces catalyses asymétriques. Enfin dans une dernière partie, les diphosphines à pont méthano P-stéréogéniques ont été utilisées pour la préparation d'une nouvelle classe de polymères de coordination chiraux, dérivés du cuivre ou de l'argent. Les études photophysiques et le dichroïsme circulaire ont permis d’établir pour la première fois la structure 1-D de tels polymères et de mettre en évidence les propriétés optiques des macrocomplexes énantiomèresWe were interested in asymmetric synthesis of P-stereogenic methano bridged ligands and in their applications in asymmetric catalysis, coordination chemistry and in the preparation of coordination polymers of transition metals. P-stereogenic diphosphines were obtained highly stereoselectively by creation of a phosphorus-carbon bond on the methano bridge, starting from the anion formed in α position of methylphosphine borane. Several strategies were investigated, with the electrophiles varying from oxazaphospholidine borane complex, phosphinite borane, to chlorophosphine borane. The most stereoselective synthesis was obtained using chlorophosphine borane leading enantiomeric excesses up to 99%. Various methano bridge diphosphine diboranes, dissymmetric or C2-symmetric, bearing alkyl or aryl substituants (Me, OMe, Ph, o-An...), have been synthetised. The first chiral palladium clusters was prepared by reaction of the freshly decomplexed diphosphine with palladium acetate and trifluorocetic acid in water/acetone mixture under CO pressure. The palladium trimetallic center structure of the cluster was confirmed by X-ray analysis. Electrochemical properties and EPR analysis pointed out the formation of the first radical in highly structurated chiral environment. Preliminary studies of the chiral clusters in asymmetric Friedel Craft reaction were carried out, but lead to the product in a non-catalytic way and with no significant optical activity. The prepared chiral ligands were tested in asymmetric catalyzed hydrogenation, hydrosilylation, allylation and Diels Alder reaction using rhodium, palladium and silver derived catalysts and afforded low selectivities from 30 to 38% e.e. Nevertheless, the stereoselective syntheses of the diphosphine ligands elaborated in this work allow to pursue the optimisation of asymmetric catalysis by structural modifications. In the last chapter, P-stereogenic methano bridge diphosphines were used for the preparation of a new class of chiral coordination polymers derived from copper and silver. Photophysical studies and circular dichroism confirmed the 1-D structure and the optical properties of such polymers
8
Lemouzy, Sébastien. "Synthèse stéréospécifique et chimie de coordination de ligands hétérobifonctionnels P-stéréogènes : vers le développement de méthodologies de couplages C-C palladocatalysés". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4359.
Abstract (sommario):
La première partie de ce manuscrit traite de la synthèse de phosphine-boranes P-stéréogènes énantioenrichis à partir d’un précurseur développé par notre laboratoire : le H-phénylphosphinate d’adamantyle. Grâce au développement d’une séquence monotope, une variété d’oxydes de phosphine P-stéréogènes de haute pureté optique a pu être synthétisée. Ces composés comportant une attache hydroxyle ont ensuite été réduits de façon stéréospécifique en présence de borane pour générer les précurseurs phosphine-boranes correspondants. Lors de cette étape de réduction, l’importance de la fonction hydroxyle a été mise en évidence, et un mécanisme basé sur la formation d’une espèce phosphaboracyclique intermédiaire a été proposé, sur la base de l’isolement d’intermédiaires réactionnels O-borés. Les trois rôles du borane (activation, réduction, protection de la phosphine) ont été clairement identifiés dans ce processus. Dans un second temps, nous avons pu mettre à profit la rétroaddition du groupement hydroxyalkyle en milieu basique lors de l’alkylation stéréospécifique chimiodivergente de phosphure-boranes masqués. Cette rétroaddition a permis de contourner l’instabilité chimique et configurationnelle des phosphures générés in situ, permettant l’accès à des phosphine-boranes fonctionnalisés de manière énantiospécifique. Ces ligands P,N ont été ensuite complexés au palladium et les complexes ont pu être testés comme catalyseurs de couplages C-C énantiosélectifs. Lors de ces couplages, l’angle de morsure du ligand s’est révélé crucial pour la réactivité du système catalytiqueThe first part of this manuscript deals with the synthesis of enantioenriched P-stereogenic phosphine-boranes from a chiral precursor developed in our laboratory: H-adamantyl phenylphosphinate. Through the design of a one-pot procedure, the synthesis of a wide array of highly enantioenriched phosphine oxides has been achieved. These hydroxy-functionalised compounds were reduced stereospecifically under borane conditions to yield the corresponding hydroxyalkylphosphine-boranes. During the study of this reaction, the importance of hydroxy group has been highlighted, and a mechanism relying on the formation of transient phosphaboracyclic intermediate could be proposed, on the basis of kinetic observation and isolation of O-borylated intermediates. In this transformation, borane seems to display three roles: activating, reducing and protecting agent. Next, we were able to take advantage of the retroaddition of hydroxyalkyl moiety under basic conditions to develop a new approach for the stereospecific and chemodivergent alkylation of masked secondary phosphine-boranes. This unusual reactivity allowed us to circumvent the relative chemical and configurational instability of such in situ generated phosphido-boranes intermediate, thus enabling the stereospecific synthesis of functionalised tertiary phosphine-boranes. These P-N ligands have been complexed to palladium, and the catalytic activity of these complexes in enantioselective C-C couplings has been studied. During the catalytic process, it appears that the ligand bite angle plays an important role in the catalyst activity
9
Lemouzy, Sébastien. "Synthèse stéréospécifique et chimie de coordination de ligands hétérobifonctionnels P-stéréogènes : vers le développement de méthodologies de couplages C-C palladocatalysés". Electronic Thesis or Diss., Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4359.
Abstract (sommario):
La première partie de ce manuscrit traite de la synthèse de phosphine-boranes P-stéréogènes énantioenrichis à partir d’un précurseur développé par notre laboratoire : le H-phénylphosphinate d’adamantyle. Grâce au développement d’une séquence monotope, une variété d’oxydes de phosphine P-stéréogènes de haute pureté optique a pu être synthétisée. Ces composés comportant une attache hydroxyle ont ensuite été réduits de façon stéréospécifique en présence de borane pour générer les précurseurs phosphine-boranes correspondants. Lors de cette étape de réduction, l’importance de la fonction hydroxyle a été mise en évidence, et un mécanisme basé sur la formation d’une espèce phosphaboracyclique intermédiaire a été proposé, sur la base de l’isolement d’intermédiaires réactionnels O-borés. Les trois rôles du borane (activation, réduction, protection de la phosphine) ont été clairement identifiés dans ce processus. Dans un second temps, nous avons pu mettre à profit la rétroaddition du groupement hydroxyalkyle en milieu basique lors de l’alkylation stéréospécifique chimiodivergente de phosphure-boranes masqués. Cette rétroaddition a permis de contourner l’instabilité chimique et configurationnelle des phosphures générés in situ, permettant l’accès à des phosphine-boranes fonctionnalisés de manière énantiospécifique. Ces ligands P,N ont été ensuite complexés au palladium et les complexes ont pu être testés comme catalyseurs de couplages C-C énantiosélectifs. Lors de ces couplages, l’angle de morsure du ligand s’est révélé crucial pour la réactivité du système catalytiqueThe first part of this manuscript deals with the synthesis of enantioenriched P-stereogenic phosphine-boranes from a chiral precursor developed in our laboratory: H-adamantyl phenylphosphinate. Through the design of a one-pot procedure, the synthesis of a wide array of highly enantioenriched phosphine oxides has been achieved. These hydroxy-functionalised compounds were reduced stereospecifically under borane conditions to yield the corresponding hydroxyalkylphosphine-boranes. During the study of this reaction, the importance of hydroxy group has been highlighted, and a mechanism relying on the formation of transient phosphaboracyclic intermediate could be proposed, on the basis of kinetic observation and isolation of O-borylated intermediates. In this transformation, borane seems to display three roles: activating, reducing and protecting agent. Next, we were able to take advantage of the retroaddition of hydroxyalkyl moiety under basic conditions to develop a new approach for the stereospecific and chemodivergent alkylation of masked secondary phosphine-boranes. This unusual reactivity allowed us to circumvent the relative chemical and configurational instability of such in situ generated phosphido-boranes intermediate, thus enabling the stereospecific synthesis of functionalised tertiary phosphine-boranes. These P-N ligands have been complexed to palladium, and the catalytic activity of these complexes in enantioselective C-C couplings has been studied. During the catalytic process, it appears that the ligand bite angle plays an important role in the catalyst activity
10
Vinokurov, Nikolai [Verfasser]. "Novel P-stereogenic bidentate phosphorus ligands for asymmetric catalysis / von Nikolai Vinokurov". 2007. http://d-nb.info/987044133/34.
Libri sul tema "P-Stereogenic catalysts":
1
Grabulosa, Arnald. P-stereogenic ligands in enantioselective catalysis. Cambridge: Royal Society of Chemistry, 2011.
2
P-Stereogenic Ligands in Enantioselective Catalysis. Cambridge: Royal Society of Chemistry, 2010. http://dx.doi.org/10.1039/9781849732703.
3
Spivey, James J., e Arnald Grabulosa. P-Stereogenic Ligands in Enantioselective Catalysis. Royal Society of Chemistry, The, 2010.
Capitoli di libri sul tema "P-Stereogenic catalysts":
1
Morisaki, Yasuhiro, e Yoshiki Chujo. "P-Stereogenic Oligomers, Polymers, and Related Cyclic Compounds". In Polymeric Chiral Catalyst Design and Chiral Polymer Synthesis, 457–88. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118063965.ch16.
2
Taber, Douglass. "Enantioselective Construction of Alkylated Centers". In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0039.
Abstract (sommario):
Unsaturated half acid esters such as 1 are readily prepared by Stobbe condensation between dialkyl succinate and an aldehyde. Johannes G. de Vries of DSM and Floris P. J. T. Rutjes of Radboud University Nijmegen observed (Adv. Synth. Catal. 2008, 350, 85) that these acids were excellent substrates for enantioselective hydrogenation. Kazuaki Kudo of the University of Tokyo designed (Organic Lett. 2008, 10, 2035) a resin bound peptide catalyst for the transfer reduction of unsaturated aldehydes such as 3 , using 4 as the net H2 donor. Note that 5 was produced with high enantiocontrol from 3 that was a ~ 2:1 mixture of geometric isomers. Motomu Kanai and Masakatsu Shibasaki of the University of Tokyo devised (J. Am. Chem. Soc. 2008, 130, 6072) a chiral Gd catalyst that mediated the conjugate cyanation of enones such as 6 with high ee. Eric N. Jacobsen of Harvard University prepared (Angew. Chem. Int. Ed. 2008, 47, 1762) a dimeric Al salen catalyst that showed improved activity over the monomeric catalysts. Even congested imides such as 8 could be cyanated efficiently, delivering alkylated quaternary stereogenic centers. Takahiro Nishimura and Tamio Hayashi of Kyoto University optimized (J. Am. Chem. Soc. 2008, 130, 1576) the Rh*-catalyzed enantioselective conjugate addition of silyl acetylenes to enones such as 10, to give 12. Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen devised (Angew. Chem. Int. Ed. 2008, 47, 398) conditions for the enantioselective 1,6-conjugate addition of alkyl Grignard reagents to diene esters such as the inexpensive ethyl sorbate 14. The product 16 incorporated, in addition to the newly formed stereogenic center, a geometrically defined E alkene. William S. Bechara and André B. Charette of the Université de Montréal found (Organic Lett. 2008, 10, 2315) that alkyl Grignard reagents could be induced to add with high enantioselectivity to pyridyl sulfones such as 17. In a different approach, Gregory C. Fu of MIT developed (J. Am. Chem. Soc. 2008, 130, 3302; J. Am. Chem. Soc. 2008, 130, 2756) conditions for the enantioselective alkenylation of racemic bromo esters such as 19, The latter reference is to the analogous enantioselective coupling of organozinc bromides with racemic allylic chlorides.
3
Taber, Douglass. "Intermolecular and Intramolecular Diels-Alder Reactions: (-)-Oseltamivir (Fukuyama), Platensimycin (Yamamoto) and 11,12-Diacetoxydrimane (Jacobsen)". In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0078.
Abstract (sommario):
Powerful methods for catalytic, enantioselective intermolecular Diels-Alder reactions have been developed. Ben L. Feringa and Gerard Roelfes of the University of Groningen have shown (Organic Lett. 2007, 9, 3647) that a catalyst prepared by combining salmon testes DNA with a Cu complex directed the absolute sense of the addition of 1 to cyclopentadiene 2 . Mukund P. Sibi of North Dakota State University has reported (J. Am. Chem. Soc . 2007, 129 , 395) related work with achiral pyrazolidinone dienophiles and chiral Cu catalysts. Tohru Fukuyama of the University of Tokyo found (Angew. Chem. Int. Ed . 2007, 46, 5734) that the MacMillan catalyst 5 was effective at mediating the addition of acrolein 4 to the pyridine-derived diene 3, enabling an enantioselective synthesis of the prominent antiviral (-)-oseltamivir (tamiflu) 7. Hisashi Yamamoto of the University of Chicago has demonstrated (J. Am. Chem. Soc . 2007, 129, 9534 and 9536) that the novel catalyst 10 effected addition of methyl acrylate 9 to the diene 8, leading to an elegant enantioselective synthesis of the tetracycle 12, the key intermediate in the Nicolaou synthesis of platensimycin. New illustrations of the power of the intramolecular Diels-Alder reaction have been put forward. Demonstrating the influence of a single subsituent on the tether, William R. Roush of Scripps/Florida found (Organic Lett . 2007, 9, 2243) that cyclization of 13 led to the diastereomer 14, complementary to the result observed with an acyclic triene. Ryo Shintani and Tamio Hayashi of Kyoto University have extended (Angew. Chem. Int. Ed . 2007, 46, 7277) their studies of chiral diene-based Rh catalysts to the enantioselective cyclization of alkynyl dienes such as 16. Jonathan W. Burton of the University of Oxford and Andrew B. Holmes of the University of Melbourne employed (Chem. Commun . 2007, 3954) the MacMillan catalyst 5 for the cyclization of 18 to 19. It is impressive that ent- 5 catalyzed the cyclization of 18 cleanly into the diastereomer of 19 in which both of the newly-created stereogenic centers were inverted.
4
Taber, Douglass F. "Arrays of Stereogenic Centers: The Shin/Chandrasekhar Synthesis of (+)-Lactacystin". In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0042.
Abstract (sommario):
Kami L. Hull of the University of Illinois established (J. Am. Chem. Soc. 2014, 136, 11256) conditions for the diastereoselective hydroamination of 1 with 2 to give 3. Jon C. Antilla of the University of South Florida employed (Org. Lett. 2014, 16, 5548) an enantiomerically-pure Li phosphate to direct the opening of the prochiral epoxide 4 to 5. Jordi Bujons and Pere Clapés of IQAC-CSIC engineered (Chem. Eur. J. 2014, 20, 12572) an enzyme that mediated the enantioselective addition of glycolaldehyde 7 to an aldehyde 6, leading to 8. Takahiro Nishimura of Kyoto University set (J. Am. Chem. Soc. 2014, 136, 9284) the two stereogenic centers of 11 by adding 10 to the diene 9. Amir H. Hoveyda of Boston College added (J. Am. Chem. Soc. 2014, 136, 11304) the propargylic anion derived from 13 to the aldehyde 12 to give, after oxidation, the diol 14. Yujiro Hayashi of Tohoku University constructed (Adv. Synth. Catal. 2014, 356, 3106) 17 by the combination of 15 with 16. Yitzhak Apeloig and Ilan Marek of Technion-Israel Institute of Technology prepared (J. Org. Chem. 2014, 79, 12122) the bromo diol 20 by rearranging the adduct between the alkyne 19 and the acyl silane 18. James P. Morken, also of Boston College, effected (J. Am. Chem. Soc. 2014, 136, 17918) enantioselective coupling of 22 with the bis-borane 21. The product allyl borane added to benzaldehyde to give the alcohol 23. Sentaro Okamoto of Kanagawa University reduced (Org. Lett. 2014, 16, 6278) the aryl oxetane 24 to an intermediate that coupled with allyl bromide to give the alcohol 25. In the presence of catalytic CuCN, the alternative diastereomer was the major product. Erick M. Carreira of ETH Zürich used (Angew. Chem. Int. Ed. 2014, 53, 13898) a combination of an Ir catalyst and an organocatalyst to couple the aldehyde 27 with the allylic alcohol 26. The four possible combinations of enantiomerically pure catalysts worked equally well, enabling the preparation of each of the four enantiomerically pure diastereomers of 28.
5
Taber, Douglass. "Enantioselective Assembly of Oxygenated Stereogenic Centers". In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0032.
Abstract (sommario):
Reaction with an enantiomerically-pure epoxide is an efficient way to construct a molecule incorporating an enantiomerically-pure oxygenated stereogenic center. The Jacobsen hydrolytic resolution has made such enantiomerically-pure epoxides readily available from the corresponding racemates. Christopher Jones and Marcus Weck of the Georgia Institute of Technology have now (J. Am. Chem. Soc. 2007, 129, 1105) developed an oligomeric salen complex that effects the enantioselective hydrolysis at remarkably low catalyst loading. Any such approach depends on monitoring the progress of the hydrolysis, usually by chiral GC or HPLC. In a complementary approach, we (J. Org. Chem. 2007, 72, 431) have found that on exposure to NBS and the inexpensive mandelic acid 2, a terminal alkene such as 1 was converted into the two bromomandelates 3 and 4. These were readily separated by column chromatography. Individually, 3 and 4 can each be carried on the same enantiomer of the epoxide 5. As 3 and 4 are directly enantiomerically pure, epoxide 5 of high ee can be prepared reliably without intermediate monitoring by chiral GC or HPLC. Another way to incorporate an enantiomerically-pure oxygenated stereogenic center into a molecule is the enantioface-selective addition of hydride to a ketone such as 6. Alain Burgos and his team at PPG-SIPSY in France have described (Tetrahedron Lett. 2007, 48, 2123) a NaBH4 -based protocol for taking the Itsuno-Corey reduction to industrial scale. In the past, aldehydes have been efficiently α-oxygenated using two-electron chemistry. Mukund P. Sibi of North Dakota State University has recently (J. Am. Chem. Soc. 2007, 129, 4124) described a novel one-electron alternative. The organocatalyst 10 formed an imine with the aldehyde. One-electron oxidation led to an α-radical, which was trapped by the stable free radical TEMPO to give, after hydrolysis, the α-oxygenated aldehyde 11. High ee oxygenated secondary centers can also be prepared by homologation of aldehydes. Optimization of the enantioselective addition of the inexpensive acetylene surrogate 13 was recently reported (Chem. Commun. 2007, 948) by Masakatsu Shibasaki of the University of Tokyo. Note that the free alcohol of 13 does not need to be protected.
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Taber, Douglass F. "New Methods for Carbon-Carbon Bond Construction". In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0021.
Abstract (sommario):
Sunggak Kim of KAIST reported (Synlett 2009, 81) an improved protocol for the one-carbon free radical homologation of an iodide such as 1 to the nitrile. Primary, secondary, and tertiary iodides work well. We described (Tetrahedron Lett. 2009, 50, 2462) a procedure for the one-carbon homologation of a halide 4 directly to the benzyl ether 6. Bin Xu of Shanghai University showed (Chem. Commun. 2009, 3246) that conversion of a ketone 8 to the 1,1-dibromoalkene set the stage for the net one-carbon homologation to the amide 9. A. Fernández-Mateos of the Universidad de Salamanca uncovered (J. Org. Chem. 2009, 74, 3913) a powerful new branching reaction, condensing the more substituted center of an epoxide 10 with a nitrile 11 to deliver the adduct 12. Useful diastereocontrol was observed with cyclic epoxides. Uli Kazmaier of the Universität des Saarlandes optimized (Adv. Synthy. Cat. 2009, 351, 1395) a Mo catalyst for the hydrostannation of a terminal alkene 13 to the branched product 14. Dong-Mei Cui of the Zhejiang University of Technology and Chen Zhang of Zhejiang University (both in Hangzhou) developed (Chem. Commun. 2009, 1577) a complementary procedure, converting the terminal alkene 15 into the branched alkenyl tosylate 16. The Wittig reaction is notorious for racemizing sensitive aldehydes. Hélène Lebel of the Université de Montréal demonstrated (Organic Lett. 2009, 11, 41) a simple one-pot protocol for sequential oxidation and homologation of 17 that preserved the integrity of the adjacent stereogenic center. The stereocontrolled construction of trisubstituted alkenes is still a major issue in organic synthesis. Giancarlo Verardo of the University of Udine established (J. Phys. Org. Chem. 2009, 22, 24) that the α-diazo ester 19, readily prepared directly from the simple ester, was converted by I2 to the alkene 20 with high geometric control. Condensation with the Ohira reagent 22 is often the method of choice for converting an aldehyde into the homologated alkyne. Hubert Maehr and Milan Uskokovic of Bioxell and Carl P. Schaffner of the Waksman Institute described (Syn. Commun. 2009, 39, 299) an optimized, scalable procedure for the in situ preparation of 22 and the conversion of 21 to 23. Note, again, that the sensitive stereogenic center adjacent to the intermediate aldehyde was not epimerized under the reaction conditions.
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Taber, Douglass F. "Enantioselective Preparation of Alkylated Stereogenic Centers". In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0042.
Abstract (sommario):
Jon D. Stewart of the University of Florida established (Chem. Commun. 2010, 46, 8558) a scalable enzymatic reduction of geranial 1 to citronellal 2. Andreas S. Bommarius of Georgia Tech reported (Chem. Commun. 2010, 46, 8809) related studies. Isamu Shiina of the Tokyo University of Science developed (J. Am. Chem. Soc. 2010, 132, 11629) a nucleophilic catalyst for the kinetic resolution of α-chiral carboxylic acids such as 3. David W. C. MacMillan of Princeton University devised (J. Am. Chem. Soc. 2010, 132, 13600) a protocol for the enantioselective benzylation of an aldehyde 5. Kian L. Tan of Boston College (J. Am. Chem. Soc. 2010, 132, 14757) and Shannon S. Stahl and Clark R. Landis of the University of Wisconsin (J. Am. Chem. Soc. 2010, 132, 14027) developed the regioselective enantioselective hydroformylation of alkenes such as 7 with chelating substituents. Masaya Sawamura of Hokkaido University (J. Am. Chem. Soc. 2010, 132, 879) and others (Org. Lett. 2010, 12, 2438; Tetrahedron Lett. 2010, 5592, 6018) effected enantiospecific allylic coupling, as in the conversion of 9 to 10 . James P. Morken, also of Boston College, achieved (J. Am. Chem. Soc. 2010, 132, 10686) enantioselective allylation of 11. Ben L. Feringa of the University of Groningen devised (J. Am. Chem. Soc. 2010, 132, 13152) a protocol for net enantioselective conjugate addition to an α, β-unsaturated alde hyde 14. Gary A. Molander of the University of Pennsylvania found (J. Am. Chem. Soc. 2010, 132, 17108) that coupling of 16, prepared by enantioselective conjugate addition, proceeded with inversion. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry effected (J. Am. Chem. Soc. 2010, 132, 10275) enantioselective alkynylation of the thioamide 18, and Takahiro Nishimura and Tamio Hayashi of Kyoto University achieved (Chem. Commun. 2010, 46, 6837) conjugate alkynylation of the nitroalkene 20. Several other protocols (Angew. Chem. Int. Ed. 2010, 49, 5780, 7299, 8145; J. Am. Chem. Soc. 2010, 132, 14373; J. Org. Chem. 2010, 75, 7829) have been developed for the catalytic enantioselective construction of arylated stereogenic centers.
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Taber, Douglass F. "Alkaloid Synthesis: (−)-L-Batzellaside A (Toyooka), Limazepine A (Zemribo), (+)-Febrifugine (Pansare), Amathaspiramide F (Tambar), Allomatrine (Brown), Lyconadine C (Waters), Tabersonine (Andrade)". In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0057.
Abstract (sommario):
Naoki Toyooka of the University of Toyama prepared (Eur. J. Org. Chem. 2013, 2841) the lactam 1 from commercial tri-O-benzyl-D-glucal. Reduction with Dibal followed by coupling of the intermediate with allyltrimethylsilane delivered the piperidine 2, that was carried on to (−)-L-batzellaside A 3. Ronalds Zemribo of the Latvian Institute of Organic Synthesis effected (Org. Lett. 2013, 15, 4406) Ireland–Claisen rearrangement of the lactone 4 to give the pyrrolidine 5 with high geometric control. This was readily converted to limazepine E 6. Sunil V. Pansare of Memorial University used (Synthesis 2013, 45, 1863) an organocatalyst to set the relative and absolute configuration in the addition of 7 to 8 to give 9. The acyclic stereogenic center of 9 was inverted twice en route to (+)-febrifugine 10. Uttam K. Tambar of the University of Texas Southwestern Medical Center combined (Org. Lett. 2013, 15, 5138) 11 with 12 under Pd catalysis to set the relative configuration of 13. Late-stage bromination completed the synthesis of amathaspiramide F 14. Richard C. D. Brown of the University of Southampton used (Org. Lett. 2013, 15, 4596) the sulfinylimine of 15 to direct the stereochemical sense of the addition of 16. The product 17 was carried over several steps to the tetracyclic alkaloid allomatrine 18. Stephen P. Waters of the University of Vermont devised (Org. Lett. 2013, 15, 4226) what appears to be a general route to pyridones. On warming, the acyl azide derived from the acid 19 rearranged to the isocyanate, that cyclized to the pyridone 20. Deprotection led to the Lycopodium alkaloid lyconadin C 21. Among the several creative routes to indole alkaloids that have been put forward in recent months, the synthesis of tabersonine 25 (J. Am. Chem. Soc. 2013, 135, 13334) by Rodrigo B. Andrade of Temple University stands out. Deprotonation of 22 led to an anion that was condensed with 23 to give 24, with the relative and absolute configuration directed by the pendant sulfinylimine. In addition to tabersonine, the intermediate 24 was carried on to vincadifformine and to aspidospermidine.