N-heterocyclic carbene-catalyzed direct enantioselective synthesis of dihydroisoxazolo[5,4-b]pyridin-6-ones

A novel N-heterocyclic carbene (NHC)-catalyzed asymmetric [3 + 3] cycloaddition between alpha-bromoenals and 5-aminoisoxazoles has been developed. With this method, various dihydroisoxazolo[5,4-b]pyridin-6-ones were obtained in high yields (up to 99%) with excellent enantioselectivities (up to >99%) under mild conditions. Notably, this is the first example of direct catalytic asymmetric synthesis of dihydroisoxazolo[5,4-b]pyridin-6-ones.