Synthesis of 4-acyl-2-(acylamino)-. DELTA. 2-1, 3, 4-thiadiazolines and 4-acyl-2-amino-. DELTA. 2-1, 3, 4-thiadiazolines by acylation of thiosemicarbazones
Proof of the structure of the 1, 3, 4-thiadiazolines (3) is based upon physical and chemical evidence. The diacetyl derivative 3a is used here as a representative. The NMR spectrum of 3a showed a C-5 proton absorption at 6 6.80 with an upfield shift of 1.24 ppm from that of the methine proton in the open-chain thiosemicarbazone 2a, in good agreement with other C-5 proton shifts reported for 1, 3, 4-thiadiazoline derivative^.^ The aromatic proton