1: 4,4'-dibromo biphenyl With n-butyllithium in tetrahydrofuran; hexane T=-80°C; 1 h; 2: boric acid trimethyl ester in tetrahydrofuran; hexane T=20°C; 1 h; 3: With hydrogenchloride in tetrahydrofuran; hexane; water 12 h;