The Construction of 3-Methyl-4-arylpiperidines via a trans-Perhydroindolic Acid-Catalyzed Asymmetric Aza-Diels-Alder Reaction

An efficient trans-perhydroindolic acid-catalyzed asymmetric aza-Diels-Alder reaction of cyclic 1-azadienes and propanal was developed for the synthesis of chiral 3-methyl-4-aryldehydropiperidine derivatives (up to 98% yield and 99% ee). Such scaffolds are often found in bioactive compounds and medicines. A gram scale reaction was carried out with a low catalyst loading to give the desired product in high yield and with excellent enantioselectivity. The resulting dehydropiperidine derivatives can be further transformed to chiral 3-methyl-4-aryl-substituted piperidines with high efficiency.