Stereoselective synthesis of tetrasubstituted alkenes via torquoselectivity-controlled olefination of carbonyl compounds with ynolates.

The efficient synthesis of tetrasubstituted alkenes by the olefination of carbonyl compounds with ynolates is described. This reaction involves the cycloaddition of ynolates with carbonyl groups, followed by electrocyclic ring-opening of the resulting β-lactone enolates. Orbital symmetry during the electrocyclic ring opening requires conrotatory motion. The direction of this rotation (inward or outward) determines the E/Z geometry to the tetrasubstituted olefin product through torquoselectivity. Theoretical calculations revealed that several secondary orbital interactions are essential for the high torquoselectivity. This methodology is a novel olefination for constructing multisubstituted olefins.