Rhodium-Catalyzed Asymmetric [2+2+2] Cycloaddition of α,ω-Diynes with Unsymmetrical 1,2-Disubstituted Alkenes

It has been established that a cationic rhodium(I)/axially chiral biaryl bisphosphine complex catalyzes the asymmetric [2 + 2 + 2] cycloaddition of alpha,omega-diynes with electron-rich and unstrained unsymmetrical 1,2-disubstituted alkenes to give chiral multicyclic compounds with good yields and ee values. Interestingly, enantioselectivity highly depends on the structures of alpha,omega-diynes used presumably due to the presence of two distinct reaction pathways.