Asymmetric synthesis of functionalized pyrrolizidines by an organocatalytic and pot-economy strategy
作者:Chia-Hsin Lin、Bor-Cherng Hong、Gene-Hsiang Lee
DOI:10.1039/c5ra25103f
日期:——
been developed for the enantioselective synthesis of tetrahydro-1H-pyrrolizin-3(2H)-ones starting from α,β-unsaturated aldehydes via a sequence of asymmetric Michael–oxidative esterification–Michal–reduction–reductive amination–lactamization reactions with high enantioselectivities (93–97% ee). The six-step reaction sequence can be conducted with the pot-economy synthetic strategy with only a one-step
Cinchona alkaloid-based chiral catalysts act as highly efficient multifunctional organocatalysts for the asymmetric conjugate addition of malonates to nitroolefins
作者:Veeramanoharan Ashokkumar、Ayyanar Siva
DOI:10.1039/c5ob01351h
日期:——
quaternary ammonium salts acting as organocatalysts (7a and 7b) have been prepared and used as organocatalysts for enantioselective Michael addition reactions between various nitroolefins and Michael donors (malonates) under mild reaction conditions, such as lower concentration of base and catalyst and room temperature, with very good chemical yields (up to 97%) and ee's (up to 99%).