Synthesis of Derivatives of 6H-1,2-Oxazine by Cyclization of Ketoximes With Derivatives of Terminal Acetylene Compounds

Abstract

A new series of 6H-1,2-oxazines were synthesized by the reaction of ketones with hydroxylamine hydrochloride in the presence of sodium acetate to give ketoximes 1(a-e). Chloramine-T was used as an effective reagent for the generation of α-nitrosolefins from ketoximes 1(a-e) which subsequently underwent hetero Diels-Alder reaction with terminal acetylenes 4(a-d), to give 6H-1,2-Oxazine derivatives 5(a-t).

Recent Advances in the Chemistry of Conjugated Nitrosoalkenes and Azoalkenes

“…6H-1,2-Oxazine derivatives 85 have been prepared in yields ranging from 51% to 68% through [4 + 2] cycloaddition reaction of aryl NSA 84, generated under basic conditions from the corresponding ketoximes 83 by reaction with chloramine T, and terminal acetylenes (Scheme 17). 57 This method is tolerant to acetylenes bearing several substituents such as propyl, hydroxymethyl, ester, and phenyl groups.…”