Reactions of some 5-substituted imidazo[2,1-b]-1,3,4-thiadiazoles

The conversion of the 5-bromoimidazo2, 1-b]-1, 3, 4-thiadiazole Ib to the 5-cyano derivative Ic is firstly described. The 5-nitroimidazo2, 1-b]-1, 3, 4-thiadiazole Id is smoothly reduced by aluminium amalgam to the 5-imino-5, 6-dihydroimidazo2, 1-b]-1, 3, 4-thiadiazole II. However, reaction of Id with sodium dithionite unexpectedly gives 1, 3, 4-thiadiazoles III and V depending upon conditions.