1,3,2-Oxazaphospholidine-2-thiones from (+)-norephedrine: stereospecific ring opening, possibly by an elimination–addition mechanism

Abstract

1,3,2-Oxazaphospholidine-2-thiones derived from (+)-norephedrine react with alkoxide to give a product of kinetic control, formed by endocyclic P–O cleavage with inversion of configuration, and one of thermodynamic control, formed by endocyclic P–N cleavage also with inversion of configuration. It is suggested that the product of kinetic control is formed by an elimination–addition process involving a metaphosphorimidate intermediate, and that of thermodynamic control by a mechanism involving nucleophilic attack opposite endocyclic nitrogen.