Allylic organopotassium compounds prepared by metalation of olefins with trimethylsilylmethylpotassium reacted with chlorodiethylborane and B-chloroborinane to give allylic diethylboranes and B-allylic borinanes, respectively. Hydrolysis of these organoboranes proceeding with allylic rearrangement leads to isomerized olefins. In this way, (E,Z)-2-pentene, (Z)-2-heptene, 1-methylcyclohexene and (+)-α-pinene