Hydrazide-catalyzed 1,3-dipolar nitrone cycloadditions

The triflate salts of cyclic hydrazides function as asymmetric catalysts for the 3+2]cycloadditions of nitrones with α,β-unsaturated aldehydes. The camphor-derived hydrazides show a preference for the exo isomers during these reactions, providing a compliment to other organically catalyzed dipolar cycloadditions. Enantiomeric excesses as high as 93% were realized for the exo isomers, while some endo products were obtained in 94% ee.