The combination of a “rigid” chiral bicyclic cis-1,2-diamine skeleton with steric bulkiness and a “flexible” achiral linker was newly designed as a bifunctional organocatalyst framework and it showed excellent catalytic activity of up to 0.05 mol%, accompanied by the reversal of enantioselection depending on the position of the linker, in an amine-thiourea organocatalyzed asymmetric Michael reaction
Chiral 2-Aminobenzimidazoles as Recoverable Organocatalysts for the Addition of 1,3-Dicarbonyl Compounds to Nitroalkenes<sup>†</sup>
作者:Diana Almaşi、Diego A. Alonso、Enrique Gómez-Bengoa、Carmen Nájera
DOI:10.1021/jo9010552
日期:2009.8.21
ole organocatalysts promote the conjugate addition of a wide variety of 1,3-dicarbonyl compounds such as malonates, ketoesters, and 1,3-diketones to nitroolefins in the presence of TFA as cocatalyst in toluene as solvent at rt or 0 °C. The Michael adducts are obtained in high yield and enantioselectivity, using the chiral 2-aminobenzimidazole 7b as hydrogen-bond-mediated chiral organocatalyst. This