Réduction électrochimique de 4H-1,3-thiazines: obtention de 6H-1,3-thiazines et (ou) de pyrroles substitués

Abstract

Controlled potential electroreduction (protic medium, mercury cathode) of substituted 2-ethoxy and 2-phenyl-4H-1,3-thiazines leads to 6H-1,3-thiazines and (or) pyrroles. The nature of the isolated products appears strongly dependent on pH of the medium and type of substitution: pyrrole formation takes place in acidic medium (0.5 mol L−1 H2SO4) and is favoured by phenyl and alkoxycarbonyl groups at positions 2 and 4, respectively; formation of 6H-1,3-thiazines and their reduction products (substituted thiobenzamides, carbamates and 2-thiazoline) occurs in weakly acidic (acetate buffer) or basic (ammoniacal buffer) medium. Keywords: electrochemical reductions, substituted 4H- and 6H-1,3-thiazines, pyrroles, 2-thiazoline, cyclic regression.