1: activated Mg / tetrahydrofuran / Ambient temperature 2: tetrahydrofuran / 1.) -78 deg C, 1 h, 2.) r.t., 10 h; other magnesium complexes, other bis-electrophiles; reaction with dichlorodiphenylsilane View Scheme

magnesium 1) THF, r.t., 2) a) -78 deg C, 1 h, b) up to r.t.; Yield given. Multistep reaction;

in tetrahydrofuran 1.) -78 deg C, 1 h, 2.) r.t., 10 h; Yield given;