ON THE REACTION OF ISOTHIOSEMICARBAZIDES WITH HETEROCUMULENES .1.

Isothiosemicarbazides 2 react with acyl isothiocyanates under addition -cyclization to yield 1,3,4-thiadiazoline-2-imines 3 as well as the is omeric 2-amino-substituted 1,3,4-thiadiazolium-5-acylaminides 3'. In a similar manner the 2-hydrazino-substituted 1,3-thiazoline 4 adds etho xycarbonyl isothiocyanate to give the thiosemicarbazide 5, which under goes a rearrangement to the 1,3,4-thiadiazoline-2-imine 5'. The [2+2] cycloreversion of 3d involving ethoxycarbonyl iso(thio)cyanate and the thermal induced Dimroth rearrangement of 3'f and h are also discussed .