Synthesis with organoboranes: I. Synthesis of allylic diethylboranes and B-allylic borinanes via metalation of olefins. Contrathermodynamic isomerization of olefins

Abstract

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 were cleanly transformed into 1-pentene, 1-heptene, methylenecyclohexane and (+)-β-pinene, respectively. Stereochemistry of the addition of myrtenyldiethylborane to formaldehyde and 2-cyclohexenyldiethylborane to 4-t-butylcyclohexanone is described.