Synthesis of pyrrolo[2,1-c][1,4]benzothiazines by annellation of 3-alkoxycarbonylmethylene-4H-1,4-benzothiazines (β-enamine esters) with dimethyl acetylenedicarboxylate

Abstract

The annellation of the benzothiazines (1a–c) with DMAD affords the corresponding pyrrolo[2,1-c][1,4]benzothiazines (5a–c) rather than pyrido[2,1-c][1,4]benzothiazines. Such structural assignments are based on spectroscopic and X-ray evidence