The BC bond: some recent developments

Abstract

The negatively charged borataalkenes and the neutral boraalkenes are isolable organoelement compounds that contain BC double bonds. The use of strongly electron withdrawing fluoroaryl substituents at boron greatly facilitates the preparation of these systems. The (C₆F₅)₂B containing boranes show greatly enhanced α-CH acidicties. This favours the formation of the corresponding borataalkenes by deprotonation. Several synthetic routes to reactive boraalkenes have been developed that make use of fluoroaryl containing B–H borenium cations. The borataalkenes serve as active borata-Wittig olefination reagents. Many boraalkenes undergo [2 + 2] cycloaddition reactions at the BC double bond with various unsaturated organic reagents. Both the borataalkenes and boraalkenes may serve as π-ligands in organometallic and coordination chemistry.