The rational design of small-molecule chiral catalysts is an important subject in the development of practical organic syntheses. We have designed primary ammonium salt catalysts for enantioselective cycloaddition reactions with α- substituted acroleins such as α-(acyloxy)acroleins and α-diacylaminoacroleins. Ammonium salts of an aliphatic triamine derived from HL-Phe-L-Leu-N(CH2CH2)2 successfully promote the DielsAlder reaction of α-(acyloxy)acroleins and α-(N,N-diacylamino)acroleins, and the [2 + 2] cycloaddition reaction of α-(acyloxy)acroleins with high enantioselectivity. An ammonium salt of a C2-symmetric aromatic diamine, 1,1′-binaphthyl-2,2′- diamine, with a superacid is also an efficient catalyst and shows high activity and enantioselectivity for the DielsAlder reaction of cyclic dienes with α-(acyloxy)acroleins.
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