Brown Hydroboration

Abstract Brown hydroboration is the addition of boron hydrides to the less‐substituted carbon atom of alkenes (anti‐Markownikoff addition), allenes, dienes, and alkynes to form organoboranes from the less hindered side in acisfashion. These organoboranes can then be converted to a variety of compounds and show dramatically improved regioselectivity and diastereoselectivity in hydroboration. Boron hydride complexes with alkenes yield a wide variety of fully or partially substituted organoboranes. The boron hydride complexes with Lewis bases have been reported to be three categories. Different organoboranes show different chemoselectivities. Transition‐metal promoted hydroboration has been reported to improve the hydroboration.