Synthesis of aryl-fused 1,4-oxazines and 1,4-oxazepines

Abstract

Simple routes for the synthesis of 1,4-benzoxazin-3-ones, 1,4-naphthoxazin-3-ones and 1,4-naphthoxazepin-3-ones are described herein. 1,4-Naphthoxazepin-3-ones were prepared by reductive amination of appropriate formyl esters. This synthesis proceeded via azines which underwent reduction with the use of aluminum amalgam and subsequent ring closure. On the other hand, derivatives of aryl-fused 1,4-oxazines were obtained from corresponding nitro esters by catalytic reduction with hydrogen and simultaneous intramolecular cyclization of amine intermediate.