Reactions of 3-substituted 2-nitrosoimino-2,3-dihydrobenzothiazoles (I) with Grignard reagents gave three kinds of major products depending on the structure of Grignard reagents: the corresponding 2,2-diaryl compounds with arylmagnesium bromides by extrusion of nitrosoimino group, 2-monosubstituted compounds with bulky Grignard reagents, and 2-benzylidenehydrazono derivative with benzylmagnesium chloride