ELECTROREDUCTION OF 2-BENZYLTHIO-6H-1,3-THIAZINES

The electrochemical reduction of 2-benzylthio-6H-1,3-thiazines has been investigated in a mixture of an aqueous acetate buffer and ethanol. For the monoactivated compound (R5 = COCH3), whatever the cathode material, reduction of the imine bond occurs leading to the corresponding 3,6-dihydro-2H-1,3-thiazine. For the diactivated derivative (R4 = CO2Et, R5 = COCH3), the first reduction takes place at the ethylenic bond giving the 5,6-dihydro-4H-1,3-thiazine. Reduction of the latter depends on the cathode material: at mercury a four electron process is observed leading to the tetrahydrothiazine with elimination of benzyl mercaptan; at graphite felt, in a flow cell, a two electron reduction occurs giving a thiazine-thione with elimination of toluene. © 1990.