1.11 Generation of Radicals from Organoboranes

Abstract

Radicals can be generated by the cleavage of the C—B bond of alkylboranes or boronic acid derivatives. The fragmentation process may result from a nucleohomolytic substitution process or from a redox process. The nucleohomolytic substitution is ideal for the generation of alkyl radicals and is usually part of a chain-reaction process. Redox processes (mainly oxidative reactions) have been used to generate both alkyl and aryl radicals. The use of stoichiometric oxidizing agents can be avoided by employing photoredox catalysis. A broad range of synthetic applications such as radical cascade processes, multicomponent reactions, and cross-coupling reactions in the presence of suitable metal catalysts are now possible. In their diversity, organoboron compounds represent one of the most general sources of radicals. The merging of radical chemistry with the classical chemistry of organoboron derivatives opens tremendous opportunities for applications in organic synthesis.