Enantioselective intermolecular [2 + 2 + 2] cycloadditions of ene-allenes with allenoates.

An enantioselective [2 + 2 + 2] cycloaddition of ene-allenes with allenoates is described, which transforms simple π-components into stereochemically complex carbocycles in a single step. The rhodium(I)-catalyzed cycloaddition proceeds with good levels of enantioselectivity, and with high levels of regio-, chemo-, and diastereoselectivity. Our results are consistent with a mechanism involving an enantioselective intermolecular allene-allene oxidative coupling.