EFFECT OF SUBSTITUENTS IN SULFUR EXTRUSIO N REACTIONS DURING FORMATION OF THE PYRIDO[2,3-B][1,4]THIAZEPINE SKELETON

A strategy involving the reaction between an azaallylic anion linked t o a chloropyridine and different O-ethyl thiocarboxylates has shown to be effective for the synthesis of 2-aryl and 2-heteroarylpyrido[2,3-b ][1,4]thiazepine However the presence of a saturated cycle fused with the thiazepine ring results in distorsion of the parent molecule, thus weakening the conjugation, and consequently induces the sulfur extrus ion from the preliminary formed cycloadduct giving rise finally to 1,5 -naphthyridines.