1: 1,3,5-tribromo benzene With n-butyllithium in diethyl ether; hexane T=-80°C; 0.5 h; Inert atmosphere; 2: With tri-isopropoxy-borane in tetrahydrofuran; diethyl ether; hexane T=-70°C; 0.5 h; Inert atmosphere; 3: carbon dioxide Further stages;