ChemInform Abstract: Heterocyclization of 2,4-Disubstituted Thiosemicarbazides with Haloketones.

ChemInform Abstract

The thiosemicarbazides (I) react with the bromoacetophenone (II) to give the anticipated dihydrothiazines (IV). Whereas the reaction of the thiosemicarbazides (V) with the chloropropiophenone (VI) yields the dihydropyrazoles (VII), the methyl analogue (VIII) of (Va) and the compound (VI) afford the unexpected dihydrothiadiazole (IX). The same product is also formed, in low yield, when the butyrophenone (X) is used. - The mechanism of the reactions leading to (IX) is discussed.