Newly utilized low-valent titanium reductant, titanium(II) bromide, was conveniently prepared by treating titanium(IV) bromide with hexamethyldisilane. The pinacol reaction of aromatic and aliphatic aldehydes including primary aldehydes proceeded smoothly in dichloromethane-pivalonitrile at temperatures ranging from -23 to 0 degrees C by the combined use of soluble titanium(II) bromide and copper to give 1,2-diols in good to high yields with good to high dl-selectivities.