Structural Elucidation of the Reaction Products of Benzoxazole Derivatives with Dimethyl Acetylenedicarboxylate. V

Abstract

Benzoxazole and o-aminophenol each reacted with dimethyl acetylenedicarboxylate (DMAD) to give the same product, which was previously suggested to be a [1, 4] benzoxazine [2, 3-b] pyran derivative (2). An X-ray crystallographic analysis has now shown the structure of this compound to be trimethyl 2, 3-dihydro-2-oxo-4H-1, 4-benzoxazine-△^3.7-aconitate. A similar treatment of o-aminophenols and β-aminoalcohols with an excess of DMAD afforded new 1, 4-benzoxazines and 1, 4-oxazines, respectively.