magnesium in tetrahydrofuran (N2); to suspn. of Mg at -10°C added over 40 min BrMg(CH2)5Cl soln., stirred for 30 min at 25°C and 60 min at 0°C, dilutedwith THF, added over 1.5 h soln. of Sn compd. at 0°C, warmed slowly, reacted for 7 h at 25°C; quenched with satd. aq. NH4Cl, aq. layer extd. (ether), combined org. layers washed (satd. aq. NaCl), dried (MgSO4), concd. (vac.), chromd. (MeCN/THF);