sulfur; hydridotetrakis(triphenylphosphine)rhodium (Ph3P)4RhH; tri(n-butyl)silane; bis(1,2-diphenylphosphino)benzene in N,N-dimethyl-formamide T=20°C; 6 h; Inert atmosphere;

in N,N-dimethyl-formamide 20°C, 1 h;

in ethylene glycol 50°C, 1 h;

in dichloromethane addn. of S-comp. to small portions of (CF3CO)2O and 90 to 99percent H2O2, after an hour addn. of (CF3CO)2O and 90percent H2O2, mild reflux 10 h;