boron tribromide in dichloromethane T=20°C;

1: With n-butyllithium; N,N,N',N,-tetramethylethylenediamine in diethyl ether; hexane T=20°C; 15 h; Inert atmosphere; 2: With boric acid trimethyl ester in diethyl ether; hexane T=-78 - 20°C; Inert atmosphere; 3: With hydrogenchloride in diethyl ether; hexane; water T=20°C; 2 h; Inert atmosphere;