Thiophosphoramide‐Based Cooperative Catalysts for Brønsted Acid Promoted Ionic Diels–Alder Reactions

Abstract

Three's a crowd: The combination of a Brønsted acid and a hydrogen-bond donor cocatalyst was found to promote various ionic [2+4] cycloadditions under mild reaction conditions (see scheme; Ts=4-toluenesulfonyl). Thiophosphoramides are the most effective cocatalysts because of the stronger counterion activation effect resulting from three, rather than two, hydrogen bonds involved in anion binding.