Metal-Catalyzed Reactions of Organoboron Compounds in Organic Syntheses

Abstract

In this review, particular attention will be given to the synthesis of organoboron compounds via the metal-catalyzed addition and coupling reactions, and their synthetic applications in organic syntheses. The traditional methods for the synthesis of organoboron compounds are based on the reaction of trialkyl borates with Grignard or lithium reagents (transmetalation) or the addition of H-B reagents to alkenes or alkynes (uncatalyzed hydroboration). Although these methods are now most common and convenient for large-scale preparations, the metal-catalyzed reactions are advantageous in terms of efficiency and selectivity of the transformations. Hydroboration of alkenes and alkynes is one of the most studied of reactions in the synthesis of organoboron compounds and their application to organic synthesis. However, the catalyzed hydroboration to be a more interesting strategy to realize the different chemo-, regio-, diastereo-, and enantioselectivities, relative to the uncatalyzed reaction. The cross-coupling reaction of metal-boryl reagents is an alternative to the transmetalation method and perhaps a more convenient and direct protocol for the synthesis of organoboron compounds from organic halides and aromatic C-H bond. Much attention has been recently focused on organoboronic acids and their esters due to their practical usefulness for synthetic organic reactions including asymmetric synthesis, combinatorial synthesis, and polymer synthesis, molecular recognition such as host-guest compounds, and neutron capture therapy in treatment of malignant melanoma and brain tumor. New synthetic procedures reviewed in this article will serve to find further applications of organoboron compounds.