Mechanistic subtleties in the cyclopentannelation of allenolate allyl carbamates: the origin of the center-to-center chirality transfer

The stereospecific rearrangement of allene carbamates i to alkylidenecyclopentenones iii is concerted, displays charge donation from the (pi)*allenonate to the (sigma)*C-leaving group, and shows mechanistic features of both pericyclic and ionic processes, modulated in part by the degree of ionic interaction (O^–...Li^+) in the putative intermediate allenolate ii.