Enantioselective Synthesis of Chromanones via a Tryptophan- Derived Bifunctional Thiourea-Catalyzed Oxa-Michael-Michael Cascade Reaction
作者:Haifei Wang、Jie Luo、Xiao Han、Yixin Lu
DOI:10.1002/adsc.201100419
日期:2011.11
Tryptophan-derived tertiary amine-thiourea catalysts were shown to promote a cascade oxa-Michael–Michael reaction between ethylene β-keto esters and nitroolefins, resulting in the formation of 3,3-disubstituted 4-chromanones bearing a quaternary center in high diastereoselectivity and enantioselectivity. The chromanone products can be readily converted to biologically important fused and spiro tricyclic