[reaction: see text] A diammonium salt of chiral 1,1'-binaphthyl-2,2'-diamine and trifluoromethanesulfonimide (Tf(2)NH) shows excellent catalytic activity and enantioselectivity for the Diels-Alderreaction of alpha-acyloxyacroleins with cyclic dienes. For example, in the presence of 5 mol % of the ammonium catalyst, the Diels-Alderreaction of alpha-(cyclohexanecarbonyloxy)acrolein with cyclopentadiene