A bifunctional squaramide-catalysed enantioselective vinylogous Michael addition/cyclization cascade reaction of 4-unsaturated isoxazol-5-ones and α,α-dicyanoalkenes

Abstract

An effective strategy for the stereoselective synthesis of spiro isoxazolone-cyclohexenimines was developed using a bifunctional squaramide-catalysed vinylogous Michael addition/cyclization cascade reaction of 4-unsaturated isoxazol-5-ones and α,α-dicyanoalkenes. The atom-economical cascade process can proceed smoothly under extremely low catalyst loading (1 mol%) and mild conditions, and the corresponding products were obtained in moderate to good yields (45% to 90%) and enantioselectivitites (51% to 96% ee). Meanwhile, the scale-up reaction and transformation of the products were also demonstrated.