Radical Addition and Coupling Reactions

The ability of organoboranes to participate in free-radical reactions has been identified since the earliest investigations of their chemistry. For instance, the autoxidation of organoboranes has been proved to involve radical intermediates (Equation (184)). The reaction has led recently to the use of triethylborane as a universal radical initiator, functioning under a very wide range of reaction conditions.690-697 

Alkyl radicals stabilized with boron atom are easily generated and undergo addition and coupling reactions. Such cr-boryl radicals were generated in situ by treatment of a-chloroalkylboronic esters with CrCl2 (Equation (188))706 or with radical initiators such as AIBN (Equation (189)).707 

1-Alkenylboranes were proved to be useful traps for nucleophilic alkyl radicals, thus opening attractive routes to diversely substituted alkyl- and alkenylboronic esters (Equations (191) and (192)).457 

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