REACTION OF AMINE-BORANES AND AMINE-MONOCHLOROBORANES WITH TRIALKYLETHYLENES

At suitably elevated temperatures (usually between 80° and 180°)2-methyl-2-pentene is hydroborated quantitatively by amine-boranes and amine-monochloroboranes to yield trialkylboranes and dialkylchloroboranes respectively. Substantial migration of the boron atom from its original point of attachment often occurs subsequent to the addition at such temperatures. An amine-monochloroborane reacts less rapidly than the corresponding amine-borane and boron migration in the resulting organochloroborane occurs at a substantially slower rate. These conclusions are drawn from the ratios of the alcohols obtained by alkaline hydrogen peroxide oxidation of the organoboranes. Cis-trans-isomerization is observed in the excess of olefin in the reaction of trans-3-methyl-2-pentene with triethylamine-borane. The extent of this isomerization is more dependent on reaction temperature than time. In the equivalent reaction with triethylamine-monochloroborane the amount of cis-trans-isomerization is found to be considerably reduced. © 1969.