Organocatalytic asymmetric synthesis of compounds bearing both isoxazole and pyrazole moieties via 1,6-addition of pyrazol-5-ones to 3-methyl-4-nitro-5-alkenylisoxazoles

Abstract

An efficient one-pot asymmetric synthesis of chiral compounds containing both isoxazole and pyrazole moieties has been developed. The bifunctional thiourea catalyzed asymmetric 1,6-addition of pyrazol-5-ones to 3-methyl-4-nitro-5-alkenylisoxazoles provided the corresponding acetylated chiral heterocycles after in situ treatment with AcCl/Et₃N. The corresponding products were generated in good yields (72–90%) with high enantioselectivities (83–94% ee).