Quaternary ammonium zinc- or tin-containing ionic liquids: water insensitive, recyclable catalysts for Diels-Alder reactions

Synthetically important Diels-Alder reactions occur in high yield in novel Lewis acidic ambient temperature ionic liquids composed of choline chloride-MCl2 (1:2) (M = Zn or Sn), The liquids are not moisture-sensitive and after separation of the products they can be reused with no noticeable drop in activity.