Mechanism of the gold-catalyzed cyclopropanation of alkenes with 1,6-enynes

The gold(I)-catalyzed intermolecular cyclopropanation of alkenes with 1,6-enynes is an electrophilic process, which is mechanistically related to the well-known Simmons-Smith reaction proceeding through zinc carbenoids. This cyclopropanation is stereospecific, even in cases where the reaction was found to proceed stepwise.