PHOTOCHEMISTRY OF TRIVINYLBORANES - PREPARATION OF ANTI-ADDUCTS OF HYDROBORANES AND ALKYNES

Trivinylboranes, which are conveniently prepared from the addition of diborane to acetylenes, are found to readily undergo photochemical Z/E isomerization. Since the chromaphore of the E-isomer is highly twiste d by steric strain, photochemical conditions can completely convert th e Z-isomer to the E-isomer. This high yield, two step process, provide s an efficient procedure to bring about an anti-addition of hydroboran es to acetylenes.