Novel one-pot synthesis of 1,3-dithiins and 1,3-thiazines under microwave irradiation

Abstract

A microwave induced expedited, high yielding three-component synthesis of 4,4'-bis[7''-aryl-5''- arylimino-2'',3'',5'',7''- tetrahydrothiazolo[4,5-d][1,3] dithiin-2''-thion-3"- yl)bibenzyls 3a-j and 4,4'-bis[4'',7''-diaryl -2'',3'',4'',5'',7''-pentahydrothiazolo [4,5-d][1,3]thiazine-2'',5''- dithion-3"-yl]bibenzyls 4a-j in one-pot involving Knoevenagel condensation followed by Michael addition is reported. The reaction is catalyzed by cheap and easily available NaCl under solvent-free conditions with excellent yield. The rate of the reaction has been found to be accelerated 213 fold as compared to the conventional method. The reaction is highly chemoselective and all the synthesized bibenzyl based 1,3-dithiins 3a-j and 1,3-thiazines 4a-j show promising antifungal activity.