REACTION OF 5-SUBSTITUTED-2-MERCAPTO-1,3,4-THIADIAZOLES WITH ALPHA-HALOKETONES AND ALPHA-HALOESTERS

The 2-mercapto-5-p-(arylsulphonyl) phenyl-1,3,4-thiadiazoles 1a-c reac t with chloroacetone, bromoacetophenone, methyl chloroacetate and ethy l chloroacetate affording either mercapto-substituted derivatives 4 or mixtures of 4 and N-3 - substituted derivatives 5. The new compounds 4 were characterized by their IR-, UV-, H-1-NMR and C-13-NMR-spectra. The results were explained on the basis of ambident reactivity of nucl eophiles 6 (derived from 1) using the principle of hard and soft acids and bases (HSAB).