Ynolates react with ketones at room temperature to afford α,β,β-trisubstituted acrylates (tetrasubstituted olefins) with 2:1−8:1 geometrical selectivities. This can be regarded as a new olefination reaction of ketones giving tetrasubstituted olefins in good yield, even in the case of sterically hindered substrates. The reaction mechanism involves cycloaddition of ynolates with a carbonyl group and
[GRAPHICS]A tandem [2 + 2] cycloaddition-Michael reaction using ynolate anions followed by decarboxylation produced polysubstituted five-, six-, and seven-membered cycloalkenes.