ELECTROCHEMICAL REDUCTION OF 4H-1,3-THIAZINES - SYNTHESIS OF SUBSTITUTED PYRROLES AND (OR) 6H-1,3-THIAZINES

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.