Reaction of Herz salts with malononitrile: a general route to (6H-1,2,3-benzodithiazol-6-ylidene)malononitriles

Abstract

6-Chloro-1,2,3-benzodithiazolium chlorides 1 (Herz salts) react with malononitrile to afford the highly coloured ylidenes 2 in low to moderate yields. The reaction is general but complex and in the case of the 6-chloro-4-methoxy-1,2,3-benzodithiazolium chloride 1e the by-products 6-chloro-4-methoxy-1,3-benzothiazole-2-carbonitrile 3, 6-chloro-4-methoxy-2,3-dihydro-1,3-benzothiazole-2,2-dicarbonitrile 4, and 4-methoxy-6-thiocyanato-1,3-benzothiazole-2-carbonitrile 5 were also isolated.