Catalytic Enantioselective
Electrophilic Aminations of Acyclic α-Alkyl β-Carbonyl
Nucleophiles
作者:Li Deng、Xiaofeng Liu、Bingfeng Sun
DOI:10.1055/s-0029-1217334
日期:——
Highly enantioselective aminations of acyclic α-alkyl β-keto thioesters and trifluoroethyl α-methyl α-cyanoacetate (12) with as low as 0.05 mol% of a bifunctional cinchona alkaloid catalyst were established. This ability to afford high enantioselectivity for the amination of α-alkyl β-carbonyl compounds renders the 6′-OH cinchona alkaloid-catalyzed amination applicable for the enantioselective synthesis of acyclic chiral compounds bearing N-substituted quaternary stereocenters. The synthetic application of this reaction is illustrated in a concise asymmetric synthesis of α-methylserine, a key intermediate previously utilized in the total synthesis of a small molecule immunomodulator, conagenin.
Enantioselective Electrophilic Amination of α-Cyanothioacetates with Azodicarboxylates Catalyzed by an Axially Chiral Guanidine Base
作者:Masahiro Terada、Daisuke Tsushima、Megumi Nakano
DOI:10.1002/adsc.200900594
日期:2009.11
An enantioselectiveelectrophilicamination of α-substituted cyanothioacetates with azodicarboxylate is demonstrated using an axiallychiralguanidine as a chiral Brønsted base catalyst. The corresponding product, having a quaternary stereogenic center at the α-carbon atom, is formed in excellent enantioselectivity.