Catalytic Asymmetric oxa-Michael−Michael Cascade for Facile Construction of Chiral Chromans via an Aminal Intermediate

An unprecedented highly enantioselective cascade oxa-Michael-Michael reaction has been developed. The simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, affords a powerful access to highly functionalized synthetically useful chiral chromans. Moreover, notably a new activation mode involving an aminal is disclosed for the first time.