1: benzophenone With lithium hexamethyldisilazane in toluene T=70°C; 18 h; Inert atmosphere; 2: With chloro-trimethyl-silane in toluene T=50°C; 2 h; Inert atmosphere; 3: 2,4-dinitrobenzene-sulfenyl chloride in toluene T=20°C; 18 h; Inert atmosphere;