n-butyllithium in tetrahydrofuran; hexane boronic ester and ICH2Cl in rigorously dried THF cooled to -78°Cand stirred under Ar during dropwise addn. of 1.6 M n-BuLi in hexane, kept overnight at 20-25°C; concd. in vac., treated with petroleum ether and concd. aq. NH4Cl, org.phase dried over MgSO4, distilled bulb to bulb in vac.;