One-pot synthesis and chemistry of bis[1,2]dithiolopyrroles

Hunig's base and S2Cl2 give the fused 1,4-thiazines 1 and (in the presence of formic acid) 2 and 3, each of which readily extrudes sulfur, selectively and quantitatively, to give the fused pyrroles 4, 5 and 6 respectively; at higher temperatures Hunig's base and S2Cl2 can be converted into the pyrroles in one pot, and the cycloadducts 8 and 10 are thus readily available in two steps.