Supported Ionic Liquids. New Recyclable Materials for theL-Proline-Catalyzed Aldol Reaction
作者:Michelangelo Gruttadauria、Serena Riela、Carmela Aprile、Paolo Lo Meo、Francesca D'Anna、Renato Noto
DOI:10.1002/adsc.200505227
日期:2006.1
Newmaterials for L-proline recycling have been developed. These materials have been applied to the L-proline-catalyzed aldolreaction between acetone and several aldehydes. The L-proline has been supported on the surface of modified silica gels with a monolayer of covalently attached ionicliquid with or without additional adsorbed ionicliquid. Good yields and ee values, comparable with those obtained
Unprecedented bifunctional enamine–metal Lewisacidcatalysts have been developed. In this bifunctional catalytic system, a tridentateligand tethered with a chiral secondary amine was designed to solve the acid–base self-quenching problem leading to catalyst inactivation. This new bifunctional enamine–metal Lewisacidcatalyst was found to catalyze aldol reactions of ketones efficiently in high yields
Protonated N'-benzyl-N'-l-prolyl-l-proline hydrazide has been developed as a highly enantioselective catalyst for the asymmetric directaldolreaction of aromatic aldehydes with ketones.
Rational Combination of Two Privileged Chiral Backbones: Highly Efficient Organocatalysts for Asymmetric Direct Aldol Reactions between Aromatic Aldehydes and Acylic Ketones
A new class of organocatalysts has been designed by rational combination of proline with cinchona alkaloids. The chiral amine 3a, prepared from l-proline and cinchonidine, has been found to be an efficient catalyst for the directaldolreactions of acetone or 2-butanone with a wide range of aldehydes (up to 98% ee). The cinchonidine backbone is essential to the reaction efficiency and enantioselectivity
regio- and diastereoselectivity and enantioselectivity under ambient temperature. Significantly, the reactions accommodate the synthetically important but challenging substrates, such as linear aliphaticketones, with high regioselectivity and unprecedented syn diastereoselectivity. These results are in sharp contrast with the secondary amine mediated similar reactions wherein anti diastereoselectivity