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.