Recently, an approach towards bicyclo [1.1.1]pentane-containing sulfones bearing a halogen atom at the bridgehead position, Hal-[1.1.1]-SO2R, was elaborated. The reduction of the halogen atom in this system was problematic. Here, we have developed a reagent to synthesize the bridgehead non-substituted bicyclo [1.1.1]pentane sulfones: H-[1.1.1]-SO2R. An addition of [1.1.1]-propellane to methyl thioglycolate (68) followed by oxidation of the intermediate sulfide, and saponification of the ester group gave carboxylic acid 69. The Vilsmeier-Haack reaction of the latter gave the expected reagent 69a in 69% yield. Representative cyclizations of salt 69a with various bis-nucleophiles gave bicyclo [1.1.1]pentane-containing pyrazole 70, pyrimidine 71 and pyrrole 72. The structure of compound 70 was confirmed by Xray crystallographic analysis. 17 Physicochemical properties. Having developed a general and practical approach to methyl sulfones, we also decided to investigate the physicochemical properties of compounds with this substituent experimentally such as their lipophilicity, water solubility, and metabolic stability.