1861-02-5Relevant academic research and scientific papers
STEREOISOTOPIC STUDY OF THE REDUCTION OF 1-PHENYLETHANOL BY ETHERATED BORON TRIFLUORIDE-TRIETHYLSILANE SYSTEM
Smonou, Ioulia,Orfanopoulos, Michael
, p. 5793 - 5796 (1988)
The kinetic hydrogen-deuterium isotope effects and the stereochemistry of the deoxygenation of 1-phenylethanol with boron trifluoride and triethylsilane have been studied.The results are consistent with a mechanism that involves of the formation of the phenethyl cation in a rate determining step and its fast reduction with triethylsilane.
Radical Anion Reactions in n-Butyl-lithium-Potassium t-Pentyl Oxide Mixtures
Wilhelm, Dieter,Clark, Timothy,Rague Schleyer, Paul von
, p. 211 - 213 (1983)
Ethyl- or isopropyl-benzenes react with n-butyl-lithium-potassium t-pentyl oxide mixtures to give coupling products characteristic of styrene radical anions which are postulated to arise from one-electron oxidation of styrene dianion intermediates.
Room-Temperature Palladium-Catalyzed Deuterogenolysis of Carbon Oxygen Bonds towards Deuterated Pharmaceuticals
Ou, Wei,Xiang, Xudong,Zou, Ru,Xu, Qing,Loh, Kian Ping,Su, Chenliang
supporting information, p. 6357 - 6361 (2021/02/16)
Site-specific incorporation of deuterium into drug molecules to study and improve their biological properties is crucial for drug discovery and development. Herein, we describe a palladium-catalyzed room-temperature deuterogenolysis of carbon–oxygen bonds
Copper-Catalyzed Direct C-H Alkylation of Polyfluoroarenes by Using Hydrocarbons as an Alkylating Source
Xie, Weilong,Heo, Joon,Kim, Dongwook,Chang, Sukbok
supporting information, p. 7487 - 7496 (2020/08/06)
Construction of carbon-carbon bonds is one of the most important tools in chemical synthesis. In the previously established cross-coupling reactions, prefunctionalized starting materials were usually employed in the form of aryl or alkyl (pseudo)halides or their metalated derivatives. However, the direct use of arenes and alkanes via a 2-fold oxidative C-H bond activation strategy to access chemoselective C(sp2)-C(sp3) cross-couplings is highly challenging due to the low reactivity of carbon-hydrogen (C-H) bonds and the difficulty in suppressing side reactions such as homocouplings. Herein, we present the new development of a copper-catalyzed cross-dehydrogenative coupling of polyfluoroarenes with alkanes under mild conditions. Relatively weak sp3 C-H bonds at the benzylic or allylic positions, and nonactivated hydrocarbons could be alkylated by the newly developed catalyst system. A moderate-to-high site selectivity was observed among various C-H bonds present in hydrocarbon reactants, including gaseous feedstocks and complex molecules. Mechanistic information was obtained by performing combined experimental and computational studies to reveal that the copper catalyst plays a dual role in activating both alkane sp3 C-H bonds and sp2 polyfluoroarene C-H bonds. It was also suggested that the noncovalent π-πinteraction and weak hydrogen bonds formed in situ between the optimal ligand and arene substrates are key to facilitating the current coupling reactions.
Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
supporting information, p. 4119 - 4129 (2020/08/10)
A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
, p. 3802 - 3808 (2020/07/09)
A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
Optically Active 1-Deuterio-1-phenylethane – Preparation and Proof of Enantiopurity
Küppers, Julian,Rabus, Ralf,Wilkes, Heinz,Christoffers, Jens
, p. 2629 - 2634 (2019/03/28)
Enantiopure (S)-(1-2H)ethylbenzene was prepared in two steps from optically active (S)-1-phenylethanol via (R)-(1-chloroethyl)benzene (two inversions of configuration). Since the value for the specific rotation [α] is very low for the enantiomers of (1-2H)ethylbenzene, the enantiopurity of the synthetic product could not be determined with certainty by polarimetry. Therefore, bis-sulfonamides were prepared by twofold chlorosulfonation (para and ortho) of (S)-(1-2H)ethylbenzene and subsequent amidation with (R)- and (S)-α-phenethylamine. For both diastereoisomers, the (R,R,S)- and the (S,S,S)-sulfonamides, 92 % de was determined by 1H NMR spectroscopy. Therefore, it could be concluded, that (S)-(1-2H)ethylbenzene had been obtained with 92 % ee.
Dramatic Synergy in CoPt Nanocatalysts Stabilized by "click" Dendrimers for Evolution of Hydrogen from Hydrolysis of Ammonia Borane
Wang, Qi,Fu, Fangyu,Yang, Sha,Martinez Moro, Marta,Ramirez, Maria De Los Angeles,Moya, Sergio,Salmon, Lionel,Ruiz, Jaime,Astruc, Didier
, p. 1110 - 1119 (2019/01/21)
Hydrolysis of ammonia borane (AB) is a very convenient source of H2, but this reaction needs catalytic activation to become practical under ambient conditions. Here this reaction is catalyzed by bimetallic late transition-metal nanoparticles (N
Room Temperature Iron-Catalyzed Transfer Hydrogenation and Regioselective Deuteration of Carbon-Carbon Double Bonds
Espinal-Viguri, Maialen,Neale, Samuel E.,Coles, Nathan T.,MacGregor, Stuart A.,Webster, Ruth L.
supporting information, p. 572 - 582 (2019/01/08)
An iron catalyst has been developed for the transfer hydrogenation of carbon-carbon multiple bonds. Using a well-defined β-diketiminate iron(II) precatalyst, a sacrificial amine and a borane, even simple, unactivated alkenes such as 1-hexene undergo hydrogenation within 1 h at room temperature. Tuning the reagent stoichiometry allows for semi- and complete hydrogenation of terminal alkynes. It is also possible to hydrogenate aminoalkenes and aminoalkynes without poisoning the catalyst through competitive amine ligation. Furthermore, by exploiting the separate protic and hydridic nature of the reagents, it is possible to regioselectively prepare monoisotopically labeled products. DFT calculations define a mechanism for the transfer hydrogenation of propene with nBuNH2 and HBpin that involves the initial formation of an iron(II)-hydride active species, 1,2-insertion of propene, and rate-limiting protonolysis of the resultant alkyl by the amine N-H bond. This mechanism is fully consistent with the selective deuteration studies, although the calculations also highlight alkene hydroboration and amine-borane dehydrocoupling as competitive processes. This was resolved by reassessing the nature of the active transfer hydrogenation agent: experimentally, a gel is observed in catalysis, and calculations suggest this can be formulated as an oligomeric species comprising H-bonded amine-borane adducts. Gel formation serves to reduce the effective concentrations of free HBpin and nBuNH2 and so disfavors both hydroboration and dehydrocoupling while allowing alkene migratory insertion (and hence transfer hydrogenation) to dominate.
Method for constructing carbon-hydrogen bond by catalyzing alcohol dehydroxylation with palladium/platinum
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Paragraph 0114-0117, (2019/12/25)
The invention discloses a method for constructing a carbon-hydrogen (deuterium) bond. The method comprises the following step: in the presence of a palladium/platinum catalyst and aryl halide, an alcohol hydroxyl group of an alcohol and hydrogen (deuterium) gas is replaced by hydrogen (deuterium) to construct the carbon-hydrogen (deuterium) bond. According to the method, the palladium/platinum catalyst is used as a catalyst, the green hydrogen (deuterium) gas is used as a hydrogen (deuterium) source, efficient alcohol dehydroxylation is performed at room temperature to construct the carbon-hydrogen (deuterium) bond, and the method is particularly suitable for constructing the carbon-deuterium bond and can be widely applied to synthesis of deuterated drugs.
