Synthesis of 5,6-dihydro-4H-1,3,5-dithiazines, 2,3-dihydro-6-thioxo-6H-1,3-thiazine, and 6-amino-1,3-dithiins

Abstract

Dithiolates (1) or (2), derived from compounds containing an active methylene or a suiphonamido-group, carbon disulphide and sodium or potassium hydroxide, underwent a Mannish reaction with formaldehyde and a primary amine to form 5,6-dihydro-1,3,5-dithiazines (3) or (4). The dithiolate (12), derived from ethyl acetoacetate, cyclised under the above conditions to ethyl 2,3-dihydro-3,4-dimethyl-6-thioxo-6H-1,3-thiazine-5-carboxylate (18). The dithiolates (20), derived from cyanoacetic ester, or (10), derived from acetophenone, interacted with formaldehyde and cyanoacetic esters or with 2-cyanoacrylates to form 6-amino-1,3-dithiins (26) or iminodithians (28). Methyl 6-amino-2-[(1 -cyano-1-ethoxycarbonyl)methylene]-1,3-dithiin-5-carboxylate (26; R¹= Et, R²= Me) formed N-acyl derivatives with aliphatic acid chlorides. On oxidation the dithiin (26; R¹= Et, R²= Me) contracted to ethyl 2-cyano-2-(4-cyano-1,3-dithiolan-5-ylidene)acetate (31).