[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[F:8].O1CCCC1.C([Li])CCC.C([O:22][B:23](OCCC)[O:24]CCC)CC>CCCCCC>[F:1][C:2]1[C:3]([F:8])=[CH:4][CH:5]=[CH:6][C:7]=1[B:23]([OH:24])[OH:22]
1,2-Difluorobenzene (40 g, 0.35 mol) and dry tetrahydrofurane (400 ml) were placed in 1 L flask equipped with mechanical stirrer, nitrogen inlet and outlet, pressure-equilibrated dropping funnel and thermometer. The reaction flask was flushed with nitrogen and minor flow was held during whole reaction time. The mixture was cooled down to −78° C. with dry ice/acetone bath and 2.5 mol/L hexane solution of n-butyllithium (140 ml; 0.35 mol) was added dropwise, keeping the reaction temperature below −70° C. After addition of all butyllithium solution the mixture was stirred at −78° C. for 2 h and then tripropylborate (66 g, 0.35 mol) was added dropwise keeping the reaction temperature below −70° C. After addition of tripropyl borate the cooling bath was removed and the reaction mixture continuously stirred to reach the room temperature then the solvents were evaporated. The thick liquid residue was acidified and then propanol was evaporated and the remaining solid was filtered off, washed out with hexane and recrystalized from water. The white crystalline product 47 g was obtained, with 85% of theor. yield.
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