zinc(II) chloride in tetrahydrofuran Ar atmosphere; addn. of LDA to soln. of B-compd. and CH2Br2 in THF (-78°C), stirring (15 min), addn. of ZnCl2, slow warming (20°C) stirring (8 h); addn. of petroleum ether, addn. of satd. soln. of aq. NH4Cl, sepn. of aq. layer, washing (Et2O/petroleum ether), drying of combined org. phases on filtration (MgSO4), removal of solvent (vac.), chromy. (silica gel, 3percent Et2O/petroleum ether);