boron trichloride in dichloromethane 1.) -78 deg C, 3 h; 2.) r.t., 1 h;

1: 69 percent / triethylamine / dimethylformamide / 1.) 2 h; 2.) r.t. 18 h 2: 70 percent / 1N BCl3 / CH2Cl2 / 1.) -78 deg C, 3 h; 2.) r.t., 1 h View Scheme