water in dichloromethane (N2); addn. of HBBr2(SMe2) at 0°C; filtration after 12 h into mixture of ice and ether (1:1); stirring for 30 min at room temperature; washing of organic phase with satd. NaCl-soln.; drying (MgSO4); removal of solvent in vac.; washing with hexane;

in acetonitrile T=20°C; 16 h;

Yield given. Multistep reaction;