INFLUENCE DE LA NATURE DES SUBSTITUANTS DANS LES REACTIONS D'EXTRUSION DE SOUFRE LORS DE L'ELABORATION DE LA CHARPENTE PYRIDO[2,3-<i>b</i>[1,4]THIAZEPINE
A strategy involving the reaction between an azaallylic anion linked to 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 extrusion from the preliminary formed cycloadduct giving rise finally to 1,5-naphthyridines.
Simple Preparation of Polyhydro-6-aryl(heteroaryl)cycloalka[<i>b</i>][1,5]naphthyridines
A variety of polyhydro-6-aryl- and heteroarylcycloalka[b][1,5] naphthyridines have been efficiently prepared by thermally induced ring contraction of pyrido[2,3-b][1,5]thiazepines obtained by reacting lithiated 2-chloro-N-cycloalkylidene-3-pyridinimines with suitable O-ethyl thiocarboxylates.