1-Arylaminoimidazole-2-thiones as intermediates in the synthesis of imidazo[2,1-b][1,3,4]thiadiazines

The synthesis of the hitherto unknown imidazo[2,1-b][1,3,4]thiadiazines 7 in good to very good yields (up to 77%) by using suitable imidazole-2-thione precursors 1 has been described, while S-vinylimidazoles 8 and 9 were isolated as by-products. Moreover, the reactivity of the three possible reaction sites of the starting thiones 1 was initially examined by methylation experiments, whereupon the enhanced reactivity of sulfur was proven by the isolation of the methylated derivatives 3 and 4. By prolonged methylation the imidazolinone 6 is finally formed. Theoretical calculations support the experimental results of alkylation products.