Direct Enantio- and Diastereoselective Vinylogous Addition of Butenolides to Chromones Catalyzed by Zn-ProPhenol

We report the first enantio- and diaster-eoselective 1,4-addition of butenolides to chromones. Both alpha,beta- and beta,gamma-butenolide nucleophiles are compatible with the Zn-ProPhenol catalyst, and preactivation as the siloxyfurans is not required. The scope of electrophiles includes a variety of substituted chromones, as well as a thiochromone and a quinolone, and the resulting vinylogous addition products are generated in good yield (31 to 98%), diastereo- (3:1 to >30:1), and enantioselectivity (90:10 to 99:1 er). These Michael adducts allow rapid access to several natural product analogs, and can be easily transformed into a variety of other interesting scaffolds as well.