ADDITION-REARRANGEMENT REACTIONS OF 5-AMINO-3-OXO-DELTA-4-1,2,4-THIADIAZOLINES

Bond-switching rearrangement via hypervalent sulfur occurs during the reactions of 5-anilino-2-benzyl-3-oxo-DELTA-4-1,2-4-thiadiazoline 5 with electrophilic nitriles, isothiocyanates, carbon disulfide and ketenes, yielding the products 6 and 7. In contrast, N,N'-ditolylcarbodiimide reacts with 5 to give the normal addition product 8, which rearranges only partially to 9 in several solvents (chloroform, acetonitrile and dimethyl sulfoxide). The equilibrium position depends on the temperature, favoring 9 at higher temperatures.