ethylene dibromide in tetrahydrofuran Mg and (CH2Br)2 in THF were stirred for 15 min under nitrogen, THF soln. of 2-BrC6H4CH2Cl was added during 4 h, mixt. was stirred for 3 h; THF was added, soln. filtered through a coarse glass-filter to remove the residual Mg, filtrate was allowed to settle and decanted leaving magnesacycle as a ppt., soln. was derivatized with Me3SiCl and analyzed by GC-MS;