Active manganese dioxide promoted cyclization of ortho-(1H-pyrrol- 1-yl)aryl and heteroaryl carboxylic acids to 5H-pyrrolo[1,2-a][3,1] benzoxazin-5-one derivatives

The hitherto unknown lactone 5H-pyrrolo[1,2-a][3,1]benzoxazin-5-one and six of its substitutedderivatives have been prepared by active manganese dioxide promoted oxidative cyclization of thecorresponding 2-(1H-pyrrol-1-yl)benzoic acids, under mild conditions, in moderate yields. The methodwas successfully extended to the cyclization of some ortho-(1H-pyrrol-1-yl)heteroaryl carboxylic acidsand 2-(1H-indol-1-yl)benzoic acids.