The reactions of benzyl benzene or p-toluenethiosulfonate with active methylene compounds were studied to elucidate the mechanism of anti-tumor activity of the analogous pentamethylene bismethanethiosulfonate with the expectation that any alkylation might occur. It was found that benzene or p-toluenethiosulfonate did not benzylate the active methylene compounds but one or two benzylthio groups were introduced. In the cases of less active methylene compounds, the reaction of thiosulfonates themselves occurred.