In(OTf)3-Catalyzed [3 + 2] Cycloaddition Reactions of Donor-Acceptor Cyclopropanes with Thioamides.

An In(OTf)3-catalyzed [3 + 2] cycloaddition reaction between donor-acceptor cyclopropanes enabled by a single keto acceptor (cyclopropyl ketones) and thioamides has been developed. The broad substrate scope has been demonstrated by synthesizing a series of new highly functionalized dihydrothiophenes with up to a 95% isolated yield. In addition, the protocol can be applied to the double [3 + 2] cycloaddition reactions of bicyclopropanes with thioamide.