Rhodium-catalyzed highly diastereoselective intramolecular [4+2] cycloaddition of 1,3-disubstituted allene-1,3-dienes

RhCl(PPh3)(3)-catalyzed [4 + 2] intramolecular cycloaddition of allene-1,3-dienes afforded cis-fused [3.4.0]-bicyclic products with three chiral centers in good yields with excellent chemo- and diastereoselectivity. The configuration of the C?C bonds in the 1,3-diene unit controls the relative configurations of the non-bridging tertiary carbon atom in the six-membered ring. Based on the experimental results, a mechanism involving cyclometalation has been proposed.