3-Substituted 2-nitrosoimino-2,3-dihydrobenzothiazole (1) reacts with primary or secondary alkyl Grignard reagents to afford bis[o-(N-substituted amino)phenyl] disulfide, 3-substituted 2-N′-alkyl- and 2-N′,N′-dialkylhydrazono-2,3-dihydrobenzothiazoles as major products. In the reactions with secondary alkyl Grignard reagents, 3-substituted 2-N′-alkylidenehydrazono-2,3-dihydrobenzothiazole was also