InBr3-catalyzed direct alkynylation of nitrones with terminal alkynes: an efficient synthesis of N-hydroxy-propargyl amines

An InBr₃-catalyzed direct and efficient alkynylation of nitrones with terminal alkynes was developed. The process enables practical synthesis of a wide range of synthetically useful N-hydroxy-propargyl amine derivatives in good yields under mild conditions. The application of this method to optically active propargylic N-hydroxyamines syntheses was also described. With chiral nitrones, good diastereoselectivities were obtained. Moreover, the first chiral indium(III) complex-catalyzed asymmetric alkynylation of nitrone was achieved with moderate enantioselectivity.