Catalytic Generation of Cationic Gold Carbene Complexes From 7‐Alkynylnorbornadienes and Their Intermolecular Cyclopropanation With Alkenes

Norbornene derivatives are commonly used in organic chemistry. The development of new norbornene derivatives is important for expanding molecular diversity. In this study, we investigated the cationic gold‐catalyzed cycloisomerization of 7‐alkynylnorbornadienes. The reaction of 7‐alkynylnorbornadienes with an excess of alkenes in the presence of a catalytic amount of [IPrAu(MeCN)]SbF 6 efficiently afforded a new class of norbornene derivatives through intermolecular cyclopropanation of cyclopropyl gold carbene complexes. This reaction exhibited a wide substrate scope, and the product was demonstrated to be applicable to polymer synthesis and click reactions. Furthermore, DFT studies suggested that the developed reaction proceeds via a mechanism involving a gold(III) metallacyclobutane intermediate, which is different from the mechanisms previously reported for cationic gold(I)‐catalyzed styrene cyclopropanation.