Generation and Trapping of Cyclopentenylidene Gold Species: Four Pathways to Polycyclic Compounds

Cyclopentenylidene gold complexes can easily be formed from vinyl allenes through a Nazarov-like mechanism. Such carbenes may transform in four different ways into polycyclic frameworks: electrophilic cyclopropanation, C−H insertion, C−C migration, or proton shift. We have studied the selectivity of these different pathways and used our findings for the expedient preparation of valuable complex molecules. An application to the total synthesis of a natural product, Δ9(12)-capnellene, is presented. DFT computations were carried out to shed light on the mechanisms.