Asymmetric transfer hydrogenations of β-N-substituted enamino esters with ammonia borane
作者:Weiwei Zhao、Xiangqing Feng、Jing Yang、Haifeng Du
DOI:10.1016/j.tetlet.2019.03.060
日期:2019.4
β-enamino esters is one of the most efficientapproaches for their synthesis. Ammonia borane with low molecular weight, high hydrogen capacity, and good stability, is an ideal hydrogen source for the transfer hydrogenation. However, only a few successful examples have been reported for the asymmetric reduction with ammonia borane. In this work, an asymmetric metal-free transfer hydrogenation of β-N-substituted
Synthesis of chiral β-amino acid derivatives by asymmetric hydrosilylation with an imidazole derived organocatalyst
作者:Simon Jones、Xianfu Li
DOI:10.1016/j.tet.2012.04.084
日期:2012.7
hydrosilylation of a number of N-aryl and alkyl β-substituted enamino esters proceeds in generally good yield and enantioselectivity. Crucial to obtaining high yield and selectivity was the addition of benzoic acid as an additive and under these conditions, both N-alkyl and N-aryl substituents were well tolerated. β-Aryl and alkyl substituents were evaluated and a model proposed to account for the experimental
Cinchona-Derived Picolinamides: Effective Organocatalysts for Stereoselective Imine Hydrosilylation
作者:Pedro C. Barrulas、Andrea Genoni、Maurizio Benaglia、Anthony J. Burke
DOI:10.1002/ejoc.201403180
日期:2014.11
Picolinamide–cinchona organocatalysts for the successful enantioselective reduction of ketomines were developed. For the first time, a new type of chiral Lewis base, a cationic species, is reported to efficiently organocatalyze the addition of trichlorosilane to imines. Excellent yields with good to high enantioselectivities (up to 91 %) were obtained in the reduction of differently substituted substrates
Nickel-Catalyzed Asymmetric Transfer Hydrogenation of Olefins for the Synthesis of α- and β-Amino Acids
作者:Peng Yang、Haiyan Xu、Jianrong Steve Zhou
DOI:10.1002/anie.201407744
日期:2014.11.3
The field of asymmetric (transfer) hydrogenation of prochiral olefins has been dominated by noble metal catalysts based on rhodium, ruthenium, and iridium. Herein we report that a simple nickel catalyst is highly active in the transfer hydrogenation using formic acid. Chiral α‐ and β‐amino acid derivatives were obtained in good to excellent enantioselectivity. The key toward success was the use of
The mixtures of axiallychiral (aR,S)- and (aS,S)-biscarboline alcohols were firstly used as catalysts in enantioselective 1,2- and 1,4-transfer hydrogenations of ketimines and β-enamino esters, respectively. This mixed axiallychiral catalysts exhibited excellent enantioselectivity (up to 98%ee) in the transfer hydrogenations under mild reaction conditions.