Polycondensed heterocycles. II. A new preparative route to 11-Oxo-5H,11H-pyrrolo[2,1-c][1,4]benzothiazepine

6-Methylthio-10-oxo-5H,10H-pyrrolo1,2-b]isoquinoline 11 was isolated in an attempted synthesis of 11-oxo-5H,11H-pyrrolo2,1-c]1,4]benzothiazepine 1 from 1-(2-methylthiobenzyl)pyrrole-2-carboxylic acid chloride 9 , obtained using as starting material o-methylthiobenzyl bromide 3 and passing through 1-(2-methylthiobenzyl)pyrrole-2-carbonitrile 5 , by cyclization with aluminum chloride. However the successful demethylation with sodium in dimethylacetamide of 1-(2-methylthiobenzyl)pyrrole-2-carboxyamide 12 , formed by hydrolysis of nitrile 5 , allowed us to prepare by another way the corresponding thiol 13 and consequently the 1-(2-mercaptobenzyl)pyrrole-2-carboxylic acid 14 , which when subjected to intramolecular ring closure by CDI in place of DCC gave 1 in higher yield, 69% instead of 43%. Finally, the direct cyanation of 1-(2-ethoxycarbonylthiobenzyl)pyrrole 16 , prepared utilizing the 1-(2-mercaptobenzyl)pyrrole 15 obtained by demethylation of the corresponding thioanisol 4 which was carried out as above, afforded the unexpected 1-(2-ethylthio-benzyl)pyrrole-2-carbonitrile 17 .