Highly Enantioselective Direct Vinylogous Michael Addition of γ-Butenolide to Enals
摘要:
An unprecedented and simple direct vinylogous addition of deconjugated butenolide to enals has been developed in excellent stereoselectivities (> 95% ee), with Aminal-PYrrolidine (APY) catalyst. This methodology allows for the efficient preparation of complex gamma-butenolide from readily available renewable resources. Furthermore, preliminary mechanistic investigations have allowed for the better understanding of the origin of both stereoselectivities and of the observed high reactivities.
The directvinylogousMichaeladdition of unactivated α-Angelica lactone to enones under iminium activation using 9-amino-9-deoxy-epi-quinine as catalyst along with 2-hydroxy-1-naphthoic acid as co-catalyst has led to the formation of γ,γ-disubstituted butenolides in high yields, moderate-to-good diastereoselectivities and excellent enantioselectivities. The readily available catalytic system over-rides