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, Delta(9(12))-capnellene, is presented. DFT computations were carried out to shed light on the mechanisms.