Phosphine-catalyzed chemoselective acylesterification, tandem addition and Michael type reaction between alkynoates and acid anhydrides have been developed, which lead to efficient synthesis of either the polysubstituted olefins or the multifunctional dienes in moderate to excellent yields with high stereoselectivity. Mechanistic investigation indicates that the tandem addition proceeds via a Michael–umpolung addition cascade. This study unveils the divergent and unprecedented reactivity of alkynoates toward C–O bond of electrophiles under the organophosphine catalysis.