σ–π Chelation-controlled chemoselective ring openings of epoxides

The chemoselective ring opening of alkynyl epoxides in the co-existence of the corresponding alkyl epoxides is achieved in the Me3Al mediated reaction with alkynyllithium reagents. The observed interesting chemoselectivity is most probably a reflection of bidentate complexation of the Lewis acid to an n-electron of an oxygen atom of the epoxide and π-electrons of the CC triple bond.