N-methyl-2-pyrrolidonium chlorosulfonate: An efficient ionic-liquid catalyst and mild sulfonating agent for one-pot synthesis of δ-sultones

N-methyl-2-pyrrolidonium chlorosulfonate, [NMP-ClSO3H], afforded a click synthesis of δ-sultones from acetophenone derivatives. The ionic liquid plays as catalyst, mild sufonating agent, and solvent in this synthesis.