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Artykuły w czasopismach na temat "Polymerization Reaction - C-N Bond"
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Gillon, Bronwyn H., Kevin JT Noonan, Bastian Feldscher, Jennifer M. Wissenz, Zhi Ming Kam, Tom Hsieh, Justin J. Kingsley, Joshua I. Bates i Derek P. Gates. "Molecular studies of the initiation and termination steps of the anionic polymerization of P=C bonds". Canadian Journal of Chemistry 85, nr 12 (1.12.2007): 1045–52. http://dx.doi.org/10.1139/v07-121.
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The initiation and termination steps of the anionic polymerization of P=C bonds have been modeled. The initiation step was investigated through the stoichiometric reaction of MesP=CPh2 (1) with RLi (R = Me or n-Bu). In each case, the addition was highly regioselective with the formal attack of R– at phosphorus to give the carbanion Li[Mes(R)P–CPh2] (3a, R = Me; 3b, R = n-Bu). To simulate the termination step in the anionic polymerization of 1, carbanions 3a and 3b were quenched in situ with various electrophiles. Through these reactions, several new tertiary phosphines have been prepared, namely, Mes(Me)P–CPh2H (4a), Mes(n-Bu)P–CPh2H (4b), Mes(Me)P–CPh2Me (6a), Mes(Me)P–CPh2–P(NEt2)2 (7a), Mes(Me)P–CPh2–SiMe2H (8a), and Mes(Me)P–CPh2–SiMe3 (9a). In addition, compounds 4a, 7a, 8a, and 9a were characterized by X-ray crystallography. Most of the metrical parameters are typical of tertiary phosphines; however, the P–CPh2H bonds were elongated in all cases reflecting the considerable steric bulk surrounding this bond. Unexpectedly, an unusually large 31P–31P coupling constant (2JPP > 200 Hz) was observed for 7a both in solution and the solid state. This observation may be rationalized by a through space P···P interaction. This rationale is further supported by the short P···P distance [P(1)—P(2) = 2.966(1) Å; cf. Σ rvdw = 3.7 Å] and a small P–C–P bond angle for 7a [P(1)–C(11)–P(1) = 99.17(9)°].Key words: phosphaalkenes, phosphorus polymers, phosphines, anionic polymerization.
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Verebélyi, Klára, Ákos Szabó, Zsombor Réti, Györgyi Szarka, Ákos Villányi i Béla Iván. "Highly Efficient Cationic Polymerization of β-Pinene, a Bio-Based, Renewable Olefin, with TiCl4 Catalyst from Cryogenic to Energy-Saving Room Temperature Conditions". International Journal of Molecular Sciences 24, nr 6 (8.03.2023): 5170. http://dx.doi.org/10.3390/ijms24065170.
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Polymers based on renewable monomers are projected to have a significant role in the sustainable economy, even in the near future. Undoubtedly, the cationically polymerizable β-pinene, available in considerable quantities, is one of the most promising bio-based monomers for such purposes. In the course of our systematic investigations related to the catalytic activity of TiCl4 on the cationic polymerization of this natural olefin, it was found that the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4/N,N,N′,N′-tetramethylethylenediamine (TMEDA) initiating system induced efficient polymerization in dichloromethane (DCM)/hexane (Hx) mixture at both −78 °C and room temperature. At −78 °C, 100% monomer conversion was observed within 40 min, resulting in poly(β-pinene) with relatively high Mn (5500 g/mol). The molecular weight distributions (MWD) were uniformly shifted towards higher molecular weights (MW) in these polymerizations as long as monomer was present in the reaction mixture. However, chain–chain coupling took place after reaching 100% conversion, i.e., under monomer-starved conditions, resulting in considerable molecular weight increase and MWD broadening at −78 °C. At room temperature, the polymerization rate was lower, but chain coupling did not occur. The addition of a second feed of monomer in the polymerization system led to increasing conversion and polymers with higher MWs at both temperatures. 1H NMR spectra of the formed polymers indicated high in-chain double-bond contents. To overcome the polarity decrease by raising the temperature, polymerizations were also carried out in pure DCM at room temperature and at −20 °C. In both cases, rapid polymerization occurred with nearly quantitative yields, leading to poly(β-pinene)s with Mns in the range of 2000 g/mol. Strikingly, polymerization by TiCl4 alone, i.e., without any additive, also occurred with near complete conversion at room temperature within a few minutes, attributed to initiation by adventitious protic impurities. These results convincingly prove that highly efficient carbocationic polymerization of the renewable β-pinene can be accomplished with TiCl4 as catalyst under both cryogenic conditions, applied widely for carbocationic polymerizations, and the environmentally benign, energy-saving room temperature, i.e., without any additive and cooling or heating. These findings enable TiCl4-catalyzed eco-friendly manufacturing of poly(β-pinene)s, which can be utilized in various applications, and in addition, subsequent derivatizations could result in a range of high-added-value products.
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Zhao, Yaqi, Banglei Liang, Zhenxin Zhao i Qiao Feng. "Property and Structure Characterization of High Molecular Weight Polyacrylonitrile Polymers Initiated by 2,2'-Azobis (2-methyl propionamide) Dihydrochloride Using Aqueous Deposited Polymerization Technique". MATEC Web of Conferences 358 (2022): 01028. http://dx.doi.org/10.1051/matecconf/202235801028.
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Powdery high molecular weight polyacrylonitrile (HMW-PAN) polymers were successfully synthesized by aqueous deposited polymerization (ADP) method with 2,2'-azobis (2-methyl propionamide) dihydrochloride (AIBA) as the initiator and itaconic acid (IA) as comonomer. The utilization of IA into the ADP system was conducive to relax the proceeding of thermo-oxidation process. Differential scanning calorimeter (DSC) curves of obtained PAN copolymers showed the doublet peaks character under air atmosphere, attributing to the exothermic cyclization and oxidative reactions during heat-treatment process. With the utilization of IA in the reaction system, crystallinity and grain sizes of the PAN polymers decreased. The stretching vibration of nitrile group (C≡N) at 2240cm-1 was the strongest peak in both Fourier transform infrared spectra (FTIR). And the stretching vibration and bending of CH2 were the stronger peaks in FTIR. Amido group (NH2), carbonyl group (C=O) and C-O single bond existed in FTIR of PAN homopolymer and copolymers, indicating occurrence of C≡N hydrolysis during polymerization process except carboxyl group (COOH) introduced by IA.
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Aprilian, Rafly, Mas Ayu Elita Hafizah, Azwar Manaf i Andreas. "Conversion Enhancement of Vinyl Acetate Monomer to Polyvinyl Acetate Emulsion through Emulsion Polymerization Method". Materials Science Forum 1028 (kwiecień 2021): 263–68. http://dx.doi.org/10.4028/www.scientific.net/msf.1028.263.
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Synthesis of Polyvinyl Acetate (PVAc) through the conversion of Vinyl Acetate Monomer (VAM) was carried out by emulsion polymerization method assisted by thermal initiator Ammonium persulfate (APS) under reaction temperature was kept at 70 °C – 80 °C with 5 hours of reaction time and agitation speed at 300 rpm. The polymerization reaction was running used batch process technique where is all components were mixed all together simultaneously. A set of polymerization reactions was conducted when the absence of surfactant and cationic and amphoteric surfactant presence. The monomer chain's double bond was found at 1645 cm-1 was measured by FTIR Spectrophotometer did not disappear after polymerization reaction was utterly done. The spectrum FTIR of Polyvinyl acetate did not explicitly found at 1644 cm-1. During the reaction, characterization was conducted by measuring the solid content value where the maximum solid content was achieved was 6,1 % when using Amphoteric surfactant while the lowest solid content was obtained when the absence of surfactant. Other parameters were conducted to observe the acidity value by pH Meter.
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Veselý, Ivan, i Václav Dědek. "Reactivity of 2,2-difluoro-3-methyl-3-butenal toward some O-, N- and C-nucleophiles". Collection of Czechoslovak Chemical Communications 50, nr 12 (1985): 2730–42. http://dx.doi.org/10.1135/cccc19852730.
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Addition of nucleophiles to 2,2-difluoro-3-methyl-3-butenal (I) is complicated by its spontaneous polymerization. Compound I afforded neither hydrate nor dimethyl acetal but reacted with ethylene glycol to give the cyclic acetal II. Reaction with acetyl chloride and acetic anhydride led to the respective acetate III and diacetate IV. Satisfactory reaction with N-nucleophiles was observed only in the case of hydroxylamine and dinitrophenylhydrazine. Diethylamine reacted with I only at 150 °C to give the reduction product VI and the ethylaldimine VII. The compound I added nitromethane and sodium cyanide (giving X and XI, respectively); the adducts or products of their reduction with lithium aluminium hydride were hydroxylated at the double bond to give analogues of alcoholic sugars with difluoromethylene group in position 3. Hydroxylation of the butenal I or the acetate III afforded 3,3-difluoro-2,4-dihydroxy-4-methyloxolane (XIX) which was prepared also by cleavage of the acetal XVIII obtained from II by hydroxylation. Addition of bromine to the double bond in III and IV gave the dibromo derivatives XV and XVI; the attempted replacement of bromine in XV and XVI by acetate anion failed. Bromination of I in aqueous medium afforded 3-bromo-2,2-difluoro-3-methyl-4-butanolide (XIV).
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Sari, R. N., i E. Hastarini. "Functional groups of bio-lubricants from crude catfish oil (Pangasius hypothalamus)". IOP Conference Series: Earth and Environmental Science 919, nr 1 (1.11.2021): 012044. http://dx.doi.org/10.1088/1755-1315/919/1/012044.
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Abstract Bio-lubricants have great potential in the production of lubricating in the future. Several studies have developed animal oils as lubricants, which come from a by-product of fish processing. Fish oil extracted from the material and processed into bio-lubricants reached the highest yield of 94%. This research aimed to study the bio-lubricants functional groups. The research steps extracted crude fish oil as raw material, hydrolysis using HCl catalyst, polymerization using benzoyl peroxide, and polyesterification using ethylene glycol. The extraction process used the wet rendering method with a ratio of catfish waste (viscera) to the water of 1:2 (w/v) at 70 °C for 30 minutes. The best bio-lubricants were analyzed for functional groups using an FT-IR instrument with a wave range of 4000-450 cm−1. The results obtained were the absorption wavelength peak of 3472 cm−1, indicating O-H bonds with the sloping peak and the weak bond. The absorption wave peak of 3006-2852 cm−1 indicated a strong C-H bond (alkane). The absorption wave peaks of 1743 cm−1 indicated the presence of a C=O double bond. The adsorption wave peaks at 1465 cm−1 indicated carbon chain bonds between C-C, while the absorption wave peaks at 1115 and 1174 cm−1 indicated C-O bonds. The three spectral indicated that the ester groups formed in bio-lubricants. In the polymerization reaction, there was no absorption wave of 1600-1500 cm−1 which indicated that all C=C groups had been polymerized by benzoyl peroxide. Meanwhile, a sloping absorption wave of 3472 cm−1 was found in the polyesterification reaction due to the weak O-H bond. The analysis obtained above showed the differences in wave peak between bio-lubricant and crude fish oil as raw material but had the same group shape.
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Yu, Ke, Yan Lin, Jinchen Fan, Qiaoxia Li, Penghui Shi, Qunjie Xu i Yulin Min. "Ternary N, S, and P-Doped Hollow Carbon Spheres Derived from Polyphosphazene as Pd Supports for Ethanol Oxidation Reaction". Catalysts 9, nr 2 (26.01.2019): 114. http://dx.doi.org/10.3390/catal9020114.
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Ethanol oxidation reaction (EOR) is an important electrode reaction in ethanol fuel cells. However, there are many problems with commercial ethanol oxidation electrocatalysts today, such as poor durability, poor anti-CO poisoning ability, and low selectivity for C–C bond cleavage. Therefore, it is very meaningful to develop a high-performance EOR catalyst. Herein, we designed ternary N, S, and P-doped hollow carbon spheres (C–N,P,S) from polyphosphazene (PCCP) as Pd supports for EOR. Using SiO2 spheres as the templates, the PCCP was first coated on the surfaces of SiO2 spheres by in situ polymerization. Through high-temperature pyrolysis and hydrofluoric acid-etching, the hollow PCCP has a large surface area and porous structure. After loading Pd nanoparticles (NPs), the Pd/C–N, P, S catalysts with Pd NPs decorated on the surfaces of C–N, P, S can achieve a high mass peak current density of 1686 mA mgPd−1, which was 2.8 times greater than that of Pd/C. Meanwhile, the Pd/C–N, P, S catalyst also shows a better stability than that of Pd/C after a durability test of 3600s.
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Sujono, Sujono, i Zainal A. Mas’ud. "UREA CORE COATING WITH CROSSLINKED HYDROPHILIC POLIMERS FOR CONTROLLED RELEASE FERTILIZER APPLICATION". Helium: Journal of Science and Applied Chemistry 1, nr 2 (31.12.2021): 51–56. http://dx.doi.org/10.33751/helium.v1i2.4539.
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Controlled release fertilizer (CRF) can be made by coating the fertilizer core with a polymer layer. The simultaneous coating reaction of the polymerization needs to be controlled in the reactor. A controlled reactor system was developed for the polymerization of granular fertilizer coating using integrated electronic control of the 8-bit ATTiny 2313 AVR microcontroller chip. Urea granule fertilizer is coated with hydrophilic polymer polyacrylamide and crosslinked polyacrylate with N,N'-methylene-bis acrylamide (MBA). The reaction was initiated by benzoyl peroxide (BPO) at 61 oC. The coating was successfully formed in 45 minutes reaction. The coating process in the control reactor was more effective than without control, thereby reducing the deposition of polymer deposits that did not coat the fertilizer. The characterization of the fertilizer coating layer based on infrared spectroscopy (FTIR) showed that polymerization synthesis had occurred based on the presence of C=C bonds. The IR spectrum showed a reduced absorption of the C=C stretching vibration medium in the acrylamide monomer compared with the polymer (crosslinked polyacrylamide), namely the wavenumbers of 1614 cm-1 in acrylamide and 1601 cm-1 in polyacrylamide spectrum. Similarly, the loss of C=C absorption in the crosslinked polyacrylate spectrum but appeared in the acrylic monomer spectrum at 1636 cm-1 wave. This group is reduced or lost after polymerization due to an addition reaction.
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Mori, Atsunori, Sonoka Yamamoto, Yushin Shibuya, Toyoko Suzuki, Kentaro Okano i Masaki Horie. "One-Shot Deprotonative Metalation/Transmetalation/Polymerization of Halothiophenes Catalyzed by Nickel Complex for Polythiophene Synthesis". Synthesis 53, nr 17 (21.01.2021): 3081–84. http://dx.doi.org/10.1055/a-1368-7072.
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AbstractEffect of divalent metals was studied in the cross-coupling polymerization of thiophenes leading to head-to-tail-type poly-3-hexylthiophene. Deprotonation of the C–H bond at the 5-position of 2-halo-3-hexylthiophene by LDA followed by metal exchange was carried out in one pot and following addition of nickel catalyst underwent polymerization. One-shot reaction involving deprotonation/transmetalation/ cross coupling polymerization was also examined with manganese(II) chloride and nickel(II) catalyst.
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Wappel, Julia, Roland C. Fischer, Luigi Cavallo, Christian Slugovc i Albert Poater. "Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands". Beilstein Journal of Organic Chemistry 12 (28.01.2016): 154–65. http://dx.doi.org/10.3762/bjoc.12.17.
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A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations.
Rozprawy doktorskie na temat "Polymerization Reaction - C-N Bond"
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Mudarra, Alonso Ángel Luis. "Coinage complexes in C-C and C-N bond-forming reactions". Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670357.
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Els complexos organometàl·lics de coure, plata i or juguen un paper fonamental com espècies reactives
en diverses transformacions químiques. Aquesta tesi aporta coneixement sobre el comportament
d’aquests complexos en la formació d’enllaços C-C i/o C-N. En concret, estudiem: i) el mecanisme de
reacció a través del qual els complexos de coure co-catalitzen un acoblament oxidant en el context de
sistemes bimetàl·lics de rodi i coure; ii) el potencial de nucleòfils de plata com a agents transmetal·lants
en reaccions de trifluorometilació catalitzades per pal·ladi; iii) el mecanisme de reacció de sistemes
bimetàl·lics de Pd/Ag emprant un sistema model; i iv) el comportament de complexos bis(trifluorometil)
cuprat, argentat i aurat com a nucleòfils. En aquesta tesi, on s´han combinat estudis experimentals i
computacionals, s’ha adquirit nou coneixement sobre els processos estudiats, i s’ha contribuït al camp de
la recerca química basada en el coneixement.Los complejos organometálicos de cobre, plata y oro juegan un papel fundamental como especies reactivas en diversas transformaciones químicas. Esta tesis aporta conocimiento sobre el comportamiento de estos complejos en la formación de enlaces C-C y/o C-N. En concreto, estudiamos: i) el mecanismo de reacción por el cual complejos de cobre co-catalizan un acoplamiento oxidante en el contexto de sistemas bimetálicos de rodio y cobre; ii) el potencial de nucleófilos de plata como agentes transmetalantes en reacciones de trifluorometilación catalizadas por paladio; iii) el mecanismo de reacción de sistemas bimetálicos de Pd/Ag usando un sistema modelo; y iv) el comportamiento de complejos bis(trifluorometil) cuprato, argentato y aurato como nucleófilos. En esta tesis, donde se han combinado estudios experimentales y computacionales, se ha adquirido nuevo conocimiento sobre los procesos estudiados, y se ha contribuido al campo de la investigación química basada en el conocimiento.
Organometallic coinage metal complexes are be key reactive species for promoting a wide variety of chemical transformations. This thesis improves the understanding the behavior of these complexes in relevant C-C and/or C-N bond-forming reactions. Specifically, we have explored: i) the mechanistic intricacies of copper species as co-catalyst in the context of rhodium/copper-catalyzed oxidative coupling reactions; ii) the capability of silver nucleophiles as transmetalating agents in palladium-catalyzed trifluoromethylation reactions; iii) the reaction mechanism of Pd/Ag bimetallic reactions using a model system as probe; and, iv) the study of bis(trifluoromethyl) coinage metallates as nucleophiles. The fundamental insights gathered in this Thesis, encompassing both experimental and computational approaches, improve our understanding of the processes under study and make a contribution to the general field of knowledge-driven research in Chemistry.
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Lin, Xufeng. "Density functional theory studies of selected transition metals catalyzed C-C and C-N bond formation reactions". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39359645.
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Lee, Yunmi. "Site- and Enantioselective C-C and C-B Bond Forming Reactions Catalyzed by Cu-, Mg-, Zn-, or Al-based N-Heterocyclic Carbene Complexes". Thesis, Boston College, 2010. http://hdl.handle.net/2345/1165.
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Thesis advisor: Amir H. HoveydaChapter 1. In this chapter, the ability of chiral bidentate N-heterocyclic carbenes (NHCs) to activate alkylmetal reagents directly in order to promote C‒C bond forming reactions in the absence of a Cu salt is presented. Highly regio- and enantioselective Cu-free allylic alkylation reactions of di- and trisubstituted allylic substrates with organomagnesium, organozinc, and organoaluminum reagents are demonstrated. Chiral bidentate sulfonate-bearing NHC-Zn and NHC-Al complexes are isolated and fully characterized. Based on crystal structures of these catalytic complexes, mechanistic details regarding Cu-free allylic alkylations with alkylmetal reagents are proposed. Chapter 2. New methods for efficient and highly enantioselective Cu-catalyzed allylic alkylation reactions of a variety of trisubstituted allylic substrates with alkylmagnesium and alkyl-, aryl-, 2-furyl-, and 2-thiophenylaluminum reagents are presented. Transformations are promoted by a chiral NHC complex in the presence of commercially available, inexpensive and air stable CuCl2*H2O. Enantiomerically enriched compounds containing difficult-to-access all-carbon quaternary stereogenic centers are obtained. Chapter 3. New methods for highly site- and enantioselective Cu-catalyzed allylic alkylation reactions of allylic phosphates with vinylaluminum reagents are presented. The requisite vinylaluminums are prepared by reaction of readily accessible terminal alkynes with DIBAL-H and used directly without further purification. Vinyl additions are promoted in the presence of a chiral bidentate sulfonate-based NHC complex and a Cu salt. The desired SN2' products are obtained in >98% E selectivities, >98% SN2' selectivities, >98% group selectivities (<2% i-Bu addition) and high enantioselectivities. The enantioselective total synthesis of the natural product bakuchiol highlights the versatility of the one-pot hydroalumination/Cu-catalyzed enantioselective allylic vinylation process. Chapter 4. Efficient and highly site-selective Cu-catalyzed hydroboration reactions of 1,2-disubstituted aryl olefins with bis(pinacolato)diboron (B2(pin)2) are presented. Transformations are promoted by an NHC-Cu complex in the presence of MeOH, affording only secondary β-boronate isomers. A Cu-catalyzed method for the synthesis of enantiomerically enriched secondary alkylboronates promoted by chiral NHC complexes is disclosed. Chapter 5. A new method for efficient and site-selective tandem Cu-catalyzed copper-boron additions to terminal alkynes with B2(pin)2 in the presence of an NHC-Cu complex is demonstrated. In a one-pot process, Cu-catalyzed hydroboration of alkynes provides vinylboronates in situ, which undergo a second site-selective hydroboration to afford vicinal diboronates. Highly Enantiomerically enriched diboronates obtained through Cu-catalyzed enantioselective dihydroboration in the presence of chiral bidentate sulfonate-based NHC-Cu complex are obtained. The control of site selectivity in the first-stage hydroboration of alkynes is critical for efficient and highly enantioselective reactions in the tandem dihydroboration. Functionalizations of the vicinal diboronates described herein underline the significance of the current method
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Patil, Shradha Vasant. "Radical additions of hydrocarbons, ethers and acetals to alkenes via allyl transfer reaction: A new chain reaction for C-H bond functionalization". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50658.
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Functionalization of hydrocarbons via a free-radical based allyl transfer reaction using various allyl bromide substrates has been previously studied. The work described in this dissertation focuses on the replacement of Br by phthalimido-N-oxyl (PINO ) which helps make this chemistry environmentally friendly. To replace Br with PINO , replacement of previously used allyl-bromide substrates with new allyl-PINO substrates were necessary. Various allyl- PINO compounds were synthesized and the use of these allyl-phthalimido-N-oxyl (allyl-PINO) compounds for the functionalization of various alkyl aromatic hydrocarbons is demonstrated.Kinetic studies were performed to observe the efficiency of the new chain reaction compared to the previously reported studies with allyl-bromides. We recently discovered that these allyl substrates are useful for the functionalization of ethers and acetals. The functionalization of various cyclic and acyclic ethers was performed using these allyl transfer reactions. This reaction was also performed in-solution, which allowed us to perform these reactions at low reagent concentrations. Kinetic chain lengths were measured for these reactions. High chain lengths were observed for all used ethers. Kinetic studies to investigate the rate of radical addition-elimination processes were performed using laser flash photolysis and competition kinetics. These experiments helped us to measure the reactivity and selectivity of PINO as a chain carrier in comparison with Br .
Additionally, a new competition experiment was designed to study the relative rate constant for
the -fragmentation process. For this experiment a novel substrate that contains two leaving
groups, Br and PINO , was synthesized, and the relative rates of elimination of Br vs PINO
were compared.
Ph. D.
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Naber, John R. (John Robert). "Advances in the Stille reaction and new methods for continuous flow Pd-catalyzed C-N bond forming reactions". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57575.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Vita. Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Chapter 1: A highly active catalyst system based upon a biaryl monophosphine ligand, XPhos, for the palladium-catalyzed Stille reaction has been developed. This method allows for the coupling of aryl chlorides with a range of tributylarylstannanes to produce the corresponding biaryl compounds in good to excellent yields (61-98%) in short reaction times (4 h). Palladium(II) acetate [Pd(OAc)2] and XPhos in a 1:1.1 ratio were milled into a fine powder that was used as pre-catalyst for these reactions. Chapter 2: A catalyst system for the Stille cross-coupling reactions of aryl mesylates and tosylates is reported. Using the combination of Pd(OAc)2, XPhos, and CsF in t-BuOH an array of aryl and heteroaryl sulfonates were successfully employed in these reactions. Morever, heteroarylstannanes, such as furyl, thienyl, and N-methylpyrrolyl, which are often prone to decomposition, were efficiently coupled under these conditions. Ortho-substitution on the stannane coupling partner was well tolerated; however, the presence of ortho substituents on the aryl sulfonates greatly reduced the efficiency of these reactions. Chapter 3: A continuous-flow, multistep Heck synthesis was made possible by integrating microreactors, liquid-liquid extraction, and microfluidic distillation. The microfluidic distillation enabled solvent exchange from CH2Cl2 in the first reaction step to N,N-dimethylformamide (DMF) in the final reaction step. Chapter 4: A method to mitigate clogging of microsystems during Pd-catalyzed C-N bond-forming reactions under continuous flow conditions was developed. Bridging of particles across the channel and deposition of materials on the walls of the microreactor were both found to be causes that led to clogging and techniques to minimize their effects using sonication were developed. This system allows Pd-catalyzed amination reactions for the formation of a diaryl amines to proceed for extended periods of time without significant pressure increase in the reactor. Chapter 5: A highly efficient method for the Pd-catalyzed coupling of aryl chloride and anilines has been developed. Catalysts based on allyl palladium chloride dimer and BrettPhos, using biphasic reaction conditions of toluene and water with KOH as a base, provided excellent yields for these reactions. The use of a packed bed reactor allowed for these reactions to be run in a continuous flow manner.
by John R. Naber.
Ph.D.
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Golisz, Suzanne Rose. "Organometallic Reaction Mechanisms: Olefin Polymerization Catalysis and C-H Bond Activation by Early Transition Metal Bisphenolate Complexes and Protonolysis of Bipyrimidine Platinum Methyl Complexes". Thesis, 2010. https://thesis.library.caltech.edu/5925/1/Thesis_SRG.pdf.
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Mechanistic aspects of organometallic transformations such as polymerization, C H activation, and protonolysis have been examined. Relationships between catalyst geometry and polymer microstructure were defined. The mechanism of an intramolecular C H activation process was found to involve two competing pathways. The protonolysis of platinum methyl complexes was investigated for kinetic isotope effects and observation of intermediates.
Bisphenolate ligands with pyridine and benzene diyl linkers were synthesized and metalated with group 4 and 5 transition metals. The solid state structures of some of the group 4 complexes were solved. The titanium, zirconium, hafnium, and vanadium complexes were tested for propylene, 1 hexene, and ethylene/1 octene polymerization activities with methylaluminoxane as co catalyst. Titanium and zirconium (IV) precatalysts with pyridine diyl linkers provided mixtures of isotactic and atactic polypropylene while titanium (IV) precatalysts with benzene diyl linkers gave atactic polypropylene only. The hafnium (IV) precatalyst with a pyridine diyl linker generated moderately isotactic polypropylene.
A titanium dibenzyl complex featuring a ligand with two phenolates linked by a benzene diyl was found to undergo thermal decomposition to give toluene and a cyclometalated dimeric complex. The thermal decomposition followed first order kinetics and was studied at a number of temperatures to determine the activation parameters. Deuterated isotopologs were synthesized to measure the kinetic isotope effects. The complexes with deuterium in the benzyl methylene positions decomposed slower than the protio analogs. Isotopologs of toluene with multiple deuteration positions were observed in the product mixtures. These data are consistent with competing α-abstraction and σ-bond metathesis.
The protonolysis of bipyrimidine ligated platinum (II) complexes was explored. The bipyrimidine platinum dimethyl complex (bpm)PtMe₂ was shown to undergo protonation at the metal upon addition of trifluoroacetic acid (tfa) to give a platinum (IV) hydride intermediate which reductively eliminated methane to give (bpm)PtMe(tfa). Using a mixture of deutero and protio acid, all isotopologs of methane were observed. The protonation of (bpm)PtMe(tfa) was less straightforward as no intermediates were found, and CH₄, CH₃D, and CH₂D₂ were observed upon addition of a mixture of deutero and protio acid. The protonation of a nitrogen of the bpm ligand was also examined and determined improbable under the present conditions.
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Cheng, An-Yi, i 鄭安益. "Highly efficient copper-catalyzed system for the coupling reaction of C-O、C-N bond". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/30281727232957871420.
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碩士淡江大學
化學學系碩士班
100
The 1st Part: An efficient Cu-catalyzed O-arylation was carried out by involving phenols with iodoarenes to afford various substituted diarylether derivatives with tiny loading of Cu2O and 1H-imidazole-4-carboxylic acid as catalytic system under mild conditions, which provided good to excellent yields with good tolerance of functional groups. The 2nd Part: An efficient for a copper catalyzed domino coupling reaction has been developed,which afforded various oxindoles in good to excellent yields with tolerance of various substituents.
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Bartholoméüs, Johan. "Réactions d’amination de liens C-H : synthèse d’amines propargyliques à partir de N-mésyloxycarbamates et études mécanistiques". Thèse, 2016. http://hdl.handle.net/1866/18430.
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Les composés aminés représentent une grande part des substances actives en chimie médicinale. Les travaux rapportés dans cette thèse décrivent les efforts consacrés au développement d’une nouvelle méthode d’amination de liens C-H propargyliques. Notre groupe de recherche a développé depuis quelques années un nouveau précurseur de nitrène métallique, les N-mésyloxycarbamates, permettant d’effectuer des réactions d’amination de liaisons C-H diversement activées. Au cours du développement de notre méthodologie, la synthèse du N-mésyloxycarbamate a fait l’objet de nombreuses optimisations, notamment en améliorant l’échelle globale de la synthèse ainsi que son efficacité. De même, des efforts ont été consacrés pour diminuer le nombre d’étapes nécessaires à la synthèse du réactif en développant la synthèse d’un des intermédiaires de manière énantiosélective. Enfin, la synthèse de ce réactif a également été envisagée à l’aide de la chimie en flux continu.
Au cours du développement de la méthode de synthèse d’amines propargyliques, nous avons constaté que l’acide acétique jouait un rôle déterminant dans la conservation de bonnes sélectivités et réactivités de la réaction. Ces différentes observations ont permis de mettre au point un procédé diastéréosélectif efficace permettant d’obtenir des amines propargyliques avec des rendements allant de moyens à bons et avec d’excellentes diastéréosélectivités.
A la suite de l’étude de l’étendue de notre procédé, nous avons tenté de déterminer les mécanismes réactionnels qui régissaient la réactivité et la sélectivité de celui-ci. Nous avons ainsi montré que l’espèce réactive du système catalytique était bel et bien un nitrène métallique, et que l’étape cinétiquement déterminante était celle d’insertion. Des expériences faites en oxydant l’espèce catalytique de rhodium ont suggéré que plusieurs états d’oxydation de cette espèce peuvent être présents et actifs dans le système catalytique.The nitrogen containing compounds represent a large portion of the active substances in medicinal chemistry. The work reported in this manuscript describe the efforts devoted to the development of a new method of amination of propargylic C-H bonds. Our research group has developed recently a new metal nitrene precursor, N-mesyloxycarbamates, to perform amination reactions on various C-H bonds. During the development of our methodology, the synthesis of N-mesyloxycarbamate has undergone many improvements, including improved global scale synthesis and effectiveness. Similarly, efforts were devoted to reduce the number of steps required for the synthesis of the reagent by developing the synthesis of an intermediate enantioselectively. Finally, the synthesis of this reagent was also considered using continuous flow chemistry. During development of the method of synthesis of propargylic amines, we have found that acetic acid plays a key role in the conservation of good selectivity and reactivity of the reaction. These observations allowed to develop an efficient diastereoselective process in order to obtain propargylic amines with moderate to good yields and with excellent diastereoselectivities. Following the study of the scope of our process, we tried to determine the reaction mechanisms governing the reactivity and selectivity. We have shown that the reactive species of the catalyst system was indeed a metal nitrene, and that the rate-determining step was the insertion. Experiments made by oxidizing the rhodium catalytic species suggested that several oxidation states of this species may be present and active in the catalytic system.
Części książek na temat "Polymerization Reaction - C-N Bond"
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Atkins, Peter. "Stringing Along: Radical Polymerization". W Reactions. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199695126.003.0018.
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Perhaps the most striking observable change brought about by chemistry as applied to the everyday world is in the texture of objects. Until the early twentieth century objects were manufactured from metal, wood, and animal and plant fibres. Today, synthetic polymers, in the vernacular ‘plastics’, are ubiquitous and have changed not only the appearance of the world but also its feel. Polymers (from the Greek words for ‘many parts’) are made by stringing together small molecules, the ‘monomers’, into long chains or extensive networks. Thus, polyethylene (less formally polythene) is a chain of linked ethylene molecules, and polystyrene is a chain of linked styrene molecules. In some instances, two or more different types of monomer molecules are used to form the polymer. Thus, one form of nylon is a chain in which the alternating links are of two different compounds. There are two main ways of linking molecules together, one involving radicals (Reaction 12) and the other not. In this section I shall introduce you to radical polymerization and treat the other kind in Reaction 14. Polyethylene and its cousins are made by the radical method, and I start with them. An ethylene molecule (1, formally, ethene) is written H2C=CH2, the double bar denoting a ‘double bond’. This is the first time I have needed to introduce you to a double bond, but it will turn out to be a crucial feature of all the monomers in this section. A double bond consists of two ordinary bonds linking the same two atoms. Because each bond consists of a shared pair of electrons acting as glue between two atoms, a double bond consists of two such pairs. Although a double bond between two C atoms is stronger than a single bond between C atoms, it is not twice as strong because the two pairs of electrons struggle for the best position and tend to push each other out of the ideal location for bonding. One consequence is that a molecule can acquire lower energy by giving up one of the pairs of electrons in the double bond and forming more single bonds with other atoms.
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Hussein Mekni, Nejib Ben, i Noureddine Raouafi. "Coordination, Degrading Agent, Catalyst Property and Spectroscopy of Organocalcium Compounds". W The Synthetic Methods, Structures, and Properties of the Ca-Cσ Bond Organocalcium Containing Compounds, 56–82. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815040647122010006.
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In addition to the coordination of the calcium to the n electron pairs, some examples of coordination to the π electron pairs are observed resulting from calcium interactions with highly conjugated systems. The complex structures vary from ordinary to close to the unexpected organocalcium inverse sandwich. The organocalcium Ca-C bond containing compounds are highly reactive. They degrade and act as degrading agents on the solvent. The study of the effect of five factors: temperature, concentration, organic group, counter ion and coordinated donor solvent, shows an intramolecular degradation mechanism. Organocalcium complexes are more stable in the THP than in the THF ethereal media. Calcium and organocalcium Ca-Cσ-bond containing derivatives are described as efficient pre-catalysts for catalytic conversions of alkenes by polymerization, hydroamination, hydrosilylation, hydrogenation, and hydrophosphination. The activation process is suggested as an electrostatic interaction between the alkene and Lewis acidic calcium metallic species, leading to both vertical and horizontal polarization of the π bond electron density, resulting in an incentive for nucleophilic attack. Some researchers illustrate that the organocalcium derivatives may be described as “Trojan horses” X-ray constitutes the most efficient technique to characterize the organocalcium structures for crystalized compounds, affording interesting information about angle values and bond lengths. The 43Ca, 13C and 1H NMR spectroscopy constitutes an alternative, secondary and complementary tool for characterizing both soluble, and even insoluble compounds, monitoring the reaction progress and making specific experimental manipulations. The coupling constants 1 JCa-C, and 2 JCa-C-H are not mentioned and there is no mass spectrometry nor IR spectroscopy studies
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Deamer, David W. "Where to Next? Unsolved Questions". W Assembling Life. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190646387.003.0016.
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The first ten chapters of this book are a kind of snapshot that captures the current state of knowledge and proposes a scenario for life’s beginning that is based on the properties of RNA described by Harry Noller in the epigraph (Noller, 2012). Despite this progress, there are still enormous gaps in our understanding that remain to be filled. The purpose of this chapter is to make those gaps explicit for future investigators who might be attracted to the question of how life can begin. Because life is an interacting system of immense complexity, each component of which is essential to cellular function as a living system, the gaps have little in common. They can be presented as a set of questions related to sources and properties of organic compounds, mechanisms for capturing energy, polymerization and replication of nucleic acids, the origin of ribosomes, and the transmission of genetic information. For each question, I will discuss one or more papers that could provide clues to an answer and then add some ideas that might serve as guides to future research. A source of mononucleotides is a problem not just for the hypothesis being presented in this book but for any proposed pathway to the origin of life. Unlike amino acids, there is no obvious source of mononucleotides, for the following reasons: Three different molecular species must be present in an aqueous solution at concentrations sufficient for a reaction to occur. They must somehow, even in this mixture of organic solutes, form a specific ester bond between a phosphate and a ribose, then must form an N-glycoside bond between the ribose and a nucleobase (Fig. 11.1), and these reactions must occur spontaneously in a hydrothermal environment. Furthermore, it is not enough for one base to occur in the solution, all four (adenine, uracil, guanine, and cytosine) must be present.
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Ikariya, Takao, i Ryoji Noyori. "Advances in Homogeneous, Heterogeneous, and Biphasic Metal-Catalyzed Reactions in Dense-Phase Carbon Dioxide". W Green Chemistry Using Liquid and Supercritical Carbon Dioxide. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195154832.003.0006.
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The use of compressed carbon dioxide as a reaction medium, either as a liquid or a supercritical fluid (sc CO2), offers the opportunity not only to replace conventional hazardous organic solvents but also to optimize and potentially control the effect of solvent on chemical synthesis. Although synthetic chemists, particularly those employing catalysis, may be relative latecomers to the area of supercritical fluids, the area of catalysis in carbon dioxide has grown significantly since around 1975 to the point that a number of excellent reviews have appeared (Baiker et al., 1999; Buelow et al., 1998; Jessop and Leitner, 1999; Jessop et al., 1995c, 1999; Morgenstern et al., 1996). Developing and understanding catalytic processes in dense-phase carbon dioxide could lead to “greener” processing at three levels: (1) solvent replacement, (2) improved chemistry (e.g., higher reactivity, selectivity, less energy), and (3) new chemistry (e.g., use of CO2 as a C-1 source). In this chapter, we will highlight a number of examples from the literature in homogeneous and heterogeneous transition-metal catalysis, as well as the emerging area of biphasic catalysis in H2O/sc CO2 mixtures. The intent is to provide an illustrative rather than a comprehensive overview to four classes of catalytic transformations: acid catalysis, reduction via hydrogenation, selective oxidation catalysis, and catalytic carbon–carbon bond-forming reactions. The reader is referred to other chapters in this book and other reviews (King and Bott, 1993) for discussion of uncatalyzed reactions, phase-transfer catalysis, polymerization, and radical reactions in sc CO2. From a synthetic chemist’s viewpoint, sc CO2 has a number of potential advantages that one would like to capitalize upon. • Solvent Replacement Carbon dioxide is a nontoxic, nonflammable, inexpensive alternative to hazardous organic solvents. Simple solvent replacement will not be a sufficient driver for all chemical reactions; however, as described below, the use of carbon dioxide could lead to better chemistry for certain reactions. • Gas Miscibility Gases such as H2, O2, and CO are sparingly soluble in liquid solvents but they are highly miscible with sc CO2.
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Ukaji, Y. "5.20 Addition Reaction: Cycloaddition Involving Oxidation (N=N, N=O; No C–C Bond Formed)". W Comprehensive Chirality, 470–501. Elsevier, 2012. http://dx.doi.org/10.1016/b978-0-08-095167-6.00522-x.
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Taber, Douglass. "C-C Single Bond Construction". W Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0019.
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Several remarkable one-carbon homologations have recently appeared. André B. Charette of the Université de Montréal reported (J. Org. Chem. 2008, 73, 8097) the alkylation of diiodomethane with alkyl iodides such as 1, to give the diiodoalkane 2. Carlo Punta and the late Ombretta Porta of the Politecnico di Milano effected (Organic Lett. 2008, 10, 5063) reductive condensation of an amine 3 with an aldehyde 4 in the presence of methanol, to give the amino alcohol 5. Timothy S. Snowden of the University of Alabama showed (Organic Lett. 2008, 10, 3853) that NaBH4 reduced the carbinol 7, easily prepared from the aldehyde 6, to the acid 8. Ram N. Ram of the Indian Institute of Technology, Delhi found (J. Org. Chem. 2008, 73, 5633) that CuCl reduced 7 to the chloro ketone 9. Kálmán J. Szabó of Stockholm University extended (Chem. Commun. 2008, 3420) his elegant work on in situ borinate formation, coupling, in one pot, the allylic alcohol 10 with the acetal 11 (hydrolysed in situ) to deliver the alcohol 12 as a single diastereomer. Samir Z. Zard of the Ecole Polytechnique developed (J. Am. Chem. Soc. 2008, 130, 8898) the 6-fluoropyridyloxy ether of 13 as an effective radical leaving group, enabling efficient coupling with 14, activated by dilauroyl peroxide, to give 15. Shu Kobayashi of the University of Tokyo established (Chem. Commun. 2008, 6354) that the anion of the sulfonyl imidate 17 participated in direct Pd-mediated allylic coupling with the carbonate 16. The product sulfonyl imidate 18 is itself of medicinal interest. It is also easily converted to other functional groups, including the aldehyde 19. Jianliang Xiao of the University of Liverpool found (J. Am. Chem. Soc. 2008, 130, 10510) that Pd-mediated coupling of an aldehyde 21 in the presence of pyrrolidine led to the ketone 22. The reaction is probably proceeding via Heck coupling of the aryl halide with the in situ generated enamine. Alois Fürstner of the Max Planck Institut, Mülheim observed (J. Am. Chem. Soc. 2008, 130, 8773) that in the presence of the simple catalyst Fe(acac)3 a Grignard reagent 24 coupled smoothly with an aryl halide 23 to give 25.
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Lambert, Tristan H. "Asymmetric C–Heteroatom Bond Formation". W Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0036.
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Tomislav Rovis at Colorado State University developed (Angew. Chem. Int. Ed. 2012, 51, 5904) an enantioselective catalytic cross-aza-benzoin reaction of aldehydes 1 and N-Boc imines 2. The useful α-amido ketone products 4 were configurationally stable under the reaction conditions. In the realm of asymmetric synthesis, few technologies have been as widely employed as the Ellman chiral sulfonamide auxiliary. Francisco Foubelo and Miguel Yus at the Universidad de Alicante in Spain have adapted (Chem. Commun. 2012, 48, 2543) this approach for the indium-mediated asymmetric allylation of ketimines 5, which furnished amines 6 with high diastereoselectivity. There has been vigorous research in recent years into the use of NAD(P)H surrogates, especially Hantzsch esters, for biomimetic asymmetric hydrogenations. Yong-Gui Zhou at the Chinese Academy of Sciences showed (J. Am. Chem. Soc. 2012, 134, 2442) that 9,10-dihydrophenanthridine (10) can also serve as an effective “H2” donor for the asymmetric hydrogenation of imines, including 7. Notably, 10 is used catalytically, with regeneration occurring under mild conditions via Ru(II)-based hydrogenation of the phenanthridine 11. A unique approach for asymmetric catalysis has been developed (Nature Chem. 2012, 4, 473) by Takashi Ooi at Nagoya University, who found that ion-paired complexes 14 could serve as effective chiral ligands in the Pd(II)-catalyzed allylation of α-nitrocarboxylates 12. The resulting products 13 are easily reduced to furnish α-amino acid derivatives. Another novel catalytic platform has been employed (J. Am. Chem. Soc. 2012, 134, 7321) for the chiral resolution of 1,2-diols 15 by Kian L. Tan at Boston College. Using the concept of reversible covalent binding, the catalyst 16 was found to selectively silylate a secondary hydroxyl over a primary one, thus leading to the enantioenriched products 17 and 18. Scott E. Denmark at the University of Illinois has applied (Angew. Chem. Int. Ed. 2012, 51, 3236) his chiral Lewis base strategy to the enantioselective vinylogous aldol reaction of N-silyl vinylketene imines 19 to produce γ-hydroxy-α,β-unsaturated nitriles 22. For the preparation of enantioenriched homopropargylic alcohols 25, the asymmetric addition of allenyl metal nucleophiles (e.g., 24) to aldehydes 23 provides a straightforward approach.
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Nawaz Shariff, Shakeel, Supriya Saravu i Dileep Ramakrishna. "Schiff Base Complexes for Catalytic Application". W Schiff Base in Organic, Inorganic and Physical Chemistry [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107904.
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Primary amines are combined with an aldehyde group to generate Schiff base compounds, which are called condensation imine products. This class of compounds has a general structure, R-C=NR\', where R and R\' represent alkyl/aryl/cyclohexyl/heterocyclic group. These compounds contain an azomethine group that is basic in nature due to, (i) the presence of lone pair of electrons on the nitrogen and (ii) electron-donating nature of the double bond. Hence, these compounds, as ligands, participate in the formation of metal complexes. The presence of lone pair of electrons on the nitrogen atom and the hybridization involved explains the physical, chemical, and spectral properties of nitrogen-containing moieties. In the case of (sp2) hybridization (trigonal structure), the lone pair of electrons occupies either a symmetrical unhybridized 2p orbital that is perpendicular to the plane of trigonal hybrids or a symmetrical hybrid orbital, whose axis is in the plane, leaving behind only the π-electrons in the unhybridized 2p orbital. A very similar type of hybridization is experienced by the nitrogen atom in the azomethine group. Traditional phosphine complexes of nickel, palladium, and platinum, particularly those of palladium, have played an extremely important role in the development of homogeneous catalysis. Schiff base complexes as catalysts have been studied for various organic transformations such as oxidation, epoxidation, reduction, coupling reactions, polymerization reactions, hydroformylations, and many more.
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K. Patel, Bhisma, Tipu Alam i Amitava Rakshit. "Construction of C-N Bond Via Visible-Light-Mediated Difunctionalization of Alkenes". W Alkenes - Recent Advances, New Perspectives and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98949.
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In the last few years, the photo-redox process via single-electron transfer (SET) has received substantial attention for the synthesis of targeted organic compounds due to its environmental friendliness and sustainability. Of late visible-light-mediated difunctionalization of alkenes has gained much attention because of its step economy, which allows the consecutive installation of two functional groups across the C=C bond in a single operation. The construction of N-containing compounds has always been important in organic synthesis. Molecules containing C-N bonds are found in many building blocks and are important precursors to other functional groups. Meanwhile, C-N bond formation via the addition of the C=C double bond is gaining prominence. Therefore, considering the influence and synthetic potential of the C-N bond, here we provide a summary of the state of the art on visible-light-driven difunctionalizations of alkene. We hope that the construction of the C-N bond via visible-light-mediated difunctionalization of alkenes will be useful for medicinal and synthetic organic chemists and will inspire further reaction development in this interesting area.
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Kakusawa, Naoki, Kentaro Ymaguchi i Jyoji Kurita. "Remarkable Reactivity Enhancement through Sb-N Non-Bonding Interaction in Azastibocine : Palladium Catalyzed C-C Bond Forming Reaction with Organic Halides". W 19th International Congress on Heterocyclic Chemistry, 194. Elsevier, 2003. http://dx.doi.org/10.1016/b978-0-08-044304-1.50186-6.
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Hirose, Masataka, Yasutoshi Miyoshi i Seiichi Miyazaki. "Real Time Monitoring of Surface Reactions During Plasma Processing". W Microphysics of Surfaces: Nanoscale Processing. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/msnp.1995.mfb3.
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Reacting silicon surfaces in contact with the glow discharge of SiH4 or SiH4+CH4 have been studied by an FT-IR-ATR (Attenuated Total Reflection) technique. In the early stages of silicon film growth from a SiH4 plasma at a substrate temperature of 200°C, SiH2 is the major species on the surface, while at room temperature SiH3 and (SiH2)n chains are the dominant surface products. At a temperature of -95 °C, polymerization reactions among adsorbates proceeds on the surface to form polysilane. At the beginning of silicon carbide deposition on a silicon film from a SiH4+CH4 plasma, the surface hydrogen bonds are scavenged by CH3 radicals at room temperature, while they are stable at temperatures below -50°C.
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Forghani, A., L. Garber, C. Chen, R. Devireddy, J. Pojman i D. Hayes. "In Situ Polymerization of PEGDA Foam for Bone Defects". W ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51235.
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The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calcein-AM (live) and Ethidium homodimer-1 (dead) showing viability of cells inside the samples.
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Sanchez, M. A., W. Sutton, W. Rizk i J. Tompkins. "Thermal Curing and Strength of PMMA Bone Cement". W ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47067.
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Many current bone cements have proprietary minor ingredients that affect the chemical kinetics and heat transfer modeling of the exothermic reaction during bone cement polymerization. In addition, the geometry and the method of cooling/curing the bone cement can vary by application. A method for modeling energy generation, based on temperature measurement of various geometries and conditions, expresses the exothermic reaction and the duration with respect to time. Reaction from the bone cement can yield temperatures above 110°C for the air convective cooling boundary condition. Experiments show that by using cold irrigation cooling (saline) with an initial temperature of 1.5°C, the maximum reaction temperature of the PMMA cement approaches 40°C depending upon the thickness of the cement. For bone cement cooled in air and saline at room temperature, the exothermic reaction begins around 400 seconds (8 min) after the compounds are mixed. When cold saline is applied, the time-delay of the reaction is approximately 300 additional seconds compared to the two room temperature cases. Finally, based on compression testing, the structural behavior of the PMMA cement is improved when the material is cured in a slower and wet environment.
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Lewis, J. C., M. J. Greene, R. G. Taylor i R. R. Hantgan. "THROMBASTHENIC-LIKE DEFECT IN PLATELETS OF THE AFRICAN GREEN MONKEY". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644557.
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African green monkeys, an animal model widely used in cardiovascular research, have platelets which ultrastructurally and functionally are similar to man. Through clinical screening of animals in a controlled breeding colony a congenital defect has been identified in platelets from an adolescent AG monkey, AJ403. The defect was characterized as abortive primary aggregation with ADP in the range 1.25-20.0 μM and PAF at concentrations to 5 × 10-6 M. Ultrastructurally, platelets within the aggregates had pseudopods, centralized granules and evidence of degranulation. Granule content release was verified using the luciferin-luciferase reaction in the Lumi-aggregometer. Platelet-platelet binding and close apposition, typically found with full primary and secondary aggregation, were not observed. Using a standardized in vitro assay at 37°C for 15-45 minutes, adhesion to formvar coated srufaces with AJ403 was 10-20% of control. Adherent cells had few pseudopods, minimal elaboration of the hyalomere, and limited cytoskeletal polymerization. Since the aggregation and adhesion patterns paralleled those described for Glanzmann's thrombasthenia, fibrinogen binding was quantitated using 125I fibrinogen and was ultrastructurally evaluated using fibrinogen-gold conjugates. Following ADP stimulation in the presence of fibrinogen at 0.08, 0.16 and 0.24 mg/ml, normal platelets respectively bound 64, 81 and 106 × 103 molecules fibrinogen/cell whereas platelets from AJ403 bound 28, 43 and 52 × 103 molecules/cell. This correlated with the number of gold/fibrinogen conjugates bound to the platelet surface which with AJ403 were less than 40% of control. Our observations suggest a parallel of AJ403 with Type II Thrombasthenia in man.
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Levene, Richard B., Francis M. Booyse, Juan Chediak, Therodore S. Zimmerman, David M. Livingston i Dennis C. Lynch. "ABNORMAL EXPRESSION OF VON WILLEBRAND FACTOR BY ENDOTHELIAL CELLS FROM A PATIENT WITH TYPE IIA VON WILLEBRAND’ S DISEASE". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642915.
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Studies were conducted to characterize the biosynthesis of von Willebrand factor (vWf) by cultured endothelial cells (EC) derived from the umbilical vein of a patient with type HA von Willebrand’ s disease. The patient’ s EC, compared with those from normal individuals, produced vWf which had decreased amounts of large multimers and an increase in rapidly migrating satellite species, features which are characteristic of plasma vWf from patients with type IIA von Willebrand’ s disease. The typQ IIA EC produced a full spectrum of vWf multimers in both cell lysates and post-culture medium, although the relative amounts of the larger species were decreased. The large multimers were degraded in conjunction with the appearance of rapidly migrating satellites which contained =170 kDa proteolytic fragments. Kinetic studies demonstrated that the =170 kDa species is not a primary translation product Normal metabolically labeled vWf, incubated with either the patient’ s EC or medium conditioned by these cells, was not similarly degraded. These results demonstrated that this patient’ s clinical phenotype is due to abnormal proteolysis and not to a primary failure of subunit oligomerization. Moreover, the increased degradation is attributable to increased proteolytic sensitivity of an abnormal vWf molecule rather than to pathologically elevated levels of endogenous proteases. Experiments using monoclonal antibodies which recognize either N- or C-associated epitopes have localized the defect to the N-terminal portion of the vWf molecule, which is believed to be involved in the inter-dimer polymerization reaction. The type DA EC also contained a single vWf mRNA species which comigrated with that from normal EC. However, the type HA EC contained 8-10 fold more vWf mRNA than their normal counterparts. These results suggest that the functional defect in this patient is caused by a subtle mutation in the vWf coding sequence leading to increased proteolytic sensitivity of its protein product
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Philips, M., A. G. Juul, S. Thorsen, J. Selmer i L. Thim. "PURIFICATION AND CHARACTERIZATION OF REACTIVE AND NON-REACTIVE PLASMINOGEN ACTIVATOR INHIBITOR-1 (PAI-1) FROM HUMAN PLACENTA". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642806.
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Reactive and non-reactive forms of PAI-1 have been identified in various biological materials. The structural differences between these forms remain to be determined.A monoclonal antibody specific for a non-reactive PAI-1 and a monoclonal antibody reacting with both the reactive and nonreactive form of the inhibitor were obtained by immunization with a tissue-type plasminogen activator (t-PA)-PAI-1 complex (Philips et al., Thromb Haemostas 1986; 55:213-7). These antibodies were used for the isolation of reactive and non-reactive PAI-1 by solid-phase immunoadsorption from extracts of human placenta. The inhibitor preparations were further purified by HPLC. Reactive and non-reactive PAI-1 both migrated with a Mr ∼ 52,000 when analyzed by SDS-PAGE. Furthermore, the two inhibitor forms were indistinguishable by N-terminal sequence analysis. Two N-terminal sequences were found in about equal ammounts for both the reactive and non-reactive PAI-1. They were Ser-Ala-Val-His-His-Pro-Pro- and a two residues shorter sequence (Val-His-His-Pro-Pro-). These sequences are in agreement with the published cDNA sequence of PAI-1 and shows that the inhibitor is N-terminally heterogeneously processed. The second order rate constant (ki) for the reaction between reactive PAI-1 and single-chain t-PA was about 6 106 M-1s-1. Treatment with 4 M guanidinium-HCl partially converted the non-reactive PAI-1 to a reactive form exhibiting a similar k1 for inhibition of single-chain t-PA. SDS-PAGE showed that the t-PA-PAI-1 complex could be dissociated by 1,5 M NH4OH/ 39 mM SDS resulting in the release of a PAI-1 with approximately the same Mr as native PAI-1. This indicates either that t-PA does not cleave the inhibitor or that it cleaves a peptide bond close to the C-terminus.In conclusion a non-reactive and a reactive form of PAI-1 can be purified from placenta. The two forms are distinguishable by monoclonal antibodies but they show similar Mr′ls and the same N-terminal sequences.