Mechanistic Study on Gold-Catalyzed Highly Selective Hydroamination of Alkylidenecyclopropanes

摘要

Density functional theory calculations have been carried out to study the mechanism of the gold-catalyzed highly selective hydroamination of alkylidenecyclopropanes. Two main mechanisms (i.e., double-bond activation-first and three-membered-ring activation-first mechanisms) have been examined. The double-bond activation-first mechanism results in the alkene hydroamination product, and it mainly consists of three steps: C-N bond formation, C-C bond rotation, and protodeauration (rate-determining step). Meanwhile, the three-membered-ring activation-first mechanism finally produces allylic amines, and it occurs via the ring-opening (rate-determining step), C-N bond formation, and protodeauration steps. The calculation results show good agreement with the experimental outcomes on the chemo-, regio-, and diastereoselectivity. On this basis, we found that the regioselectivity is caused by the C-C bond rotation step, while the diastereoselectivity is determined by both the C-C bond rotation and the protodeauration steps in the double-bond activation-first mechanism.