9-Amino-(9-deoxy)cinchona alkaloid-derived new chiral phase-transfer catalysts
作者:Wenwen Peng、Jingwei Wan、Bing Xie、Xuebing Ma
DOI:10.1039/c4ob01648c
日期:——
9-amino-(9-deoxy)cinchona alkaloid-derived chiralphase-transfercatalysts bearing amino groups was developed by using known cinchona alkaloids as the starting materials. Due to the transformation of the 9-hydroxyl group into a 9-amino functional group, the catalytic performances were significantly improved in comparison with the corresponding first generation phase-transfercatalysts, and excellent yields (92–99%)
alkylation of the glycine imino ester 1a has been developed using a chiral quaternary ammonium salt 3d without chiral phosphine ligands. The proper choice of the achiral Pd ligand, P(OPh)3, is important to achieve high enantioselectivity. By this method with the dual catalysts, numerous enantiomerically enriched alpha-allylic amino acids 4a-h could be prepared with comparable to higher enantioselectivity
Evidence of the Electronic Factor for the Highly Enantioselective Catalytic Efficiency of <i>Cinchona</i>-Derived Phase-Transfer Catalysts
作者:Mi-Sook Yoo、Byeong-Seon Jeong、Jeong-Hee Lee、Hyeung-geun Park、Sang-sup Jew
DOI:10.1021/ol050123u
日期:2005.3.1
evaluated as phase-transfercatalysts in the enantioselective alkylation of glycine imine ester 1. The N-oxypyridine and cyanobenzene moieties might play an important role to form a rigid conformation by coordinating with H(2)O via hydrogen bonding leading to high enantioselectivity (97 approximately >99% ee), which provides evidence of an electronic factor for the high enantioselective catalytic efficiency
Counter-rotatable dual cinchona quinuclidinium salts and their phase transfer catalysis in enantioselective alkylation of glycine imines
作者:Jiin Oh、Jihyeon Park、Keepyung Nahm
DOI:10.1039/d1cc02785a
日期:——
Dual cinchona quinuclidinium salts with a diphenyl ether linker were synthesized and used as powerful asymmetric phasetransfer catalysts in the α-alkylation of imines of glycine and alanine ester with 0.01–0.1 mol% loading (17 examples, 92–99% ee). Skewed conformers of dual quinuclidiniums at TS were proposed to rationalize their high efficiency via DFT calculations.
A new asymmetric two-center phase-transfercatalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transferalkylations and Michael additions to afford the corresponding products in up to 93% ee and 82% ee, respectively.