Domino ring-opening cyclization (DROC) of activated aziridines and epoxides with nitrones via dual-catalysis “on water”

Abstract

An efficient and green “on water” regio- and stereoselective synthetic route to chiral 1,2,4-oxadiazinanes and 1,4,2-dioxazinanes with excellent yields (up to 99%) and de/ee (>99%) has been developed for the first time via the domino ring-opening cyclization (DROC) of N-activated aziridines and epoxides with nitrones using LiClO₄/Bu₄NBF₄ a dual catalyst system. The developed green strategy features a broader substrate scope and mild reaction conditions, and successfully overcomes the competitive oxidative ring opening of aziridines. Further synthetic significances of this green protocol are the formation of the products (i) as single diastereomers starting from a mixture of cis/trans disubstituted aziridines via dynamic kinetic epimerization (DKE) and (ii) via a multicomponent approach starting from N-methyl hydroxylamine hydrochloride, benzaldehyde and aziridine.