Boron derivatives are becoming key reagents in radical chemistry. Here, we describe reactions where an organoboron derivative is used as a radical initiator, a chain-transfer reagent, and a radical precursor. For instance, B-alkylcatecholboranes, easily prepared by hydroboration of alkenes, represent a very efficient source of primary, secondary, and tertiary alkyl radicals. Their very high sensitivity toward oxygen-and heteroatom-centered radicals makes them particularly attractive for the development of radical chain processes such as conjugate addition, allylation, alkenylation, and alkynylation. Boron derivatives have also been used to develop an attractive new procedure for the reduction of radicals with alcohols and water. The selected examples presented here demonstrate that boron-containing reagents can efficiently replace tin derivatives in a wide range of radical reactions.

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Ethyl 2‐[(2,6,6‐trimethylbicyclo[3.1.1]heptyl‐3‐yl)methyl]propenoate 2‐(Ethoxycarbonyl)prop‐2‐en‐1‐yl phenyl sulfone Ethyl methacrylate Benzenesulfinic acid, sodium salt (+)‐alpha‐Pinene Catecholborane

An efficient formal anti-Markovnikov addition of HX (X = Cl, Br, I, SR and SeR) to olefins under mild reaction conditions is described. The procedure is based on the hydroboration of alkenes with catecholborane. The conversion of the intermediate B-alkylcatecholboranes to the corresponding halides, sulfides and selenides is based on a common process, i.e., generation of a radical from the alkylborane followed by abstraction of a heteroatom from an aromatic sulfonyl reagent. The efficiency of these radical reactions is remarkable. The mildness of the reaction conditions is well illustrated by the preparation of iodoalkanes. Despite the notorious reactivity of iodoalkanes under radical reaction conditions, no product degradation was observed.

Generation of radicals from B-alkylcatecholboranes represents an efficient tin-free procedure for the generation of alkyl radicals. A modified version of this method has been developed. The simple catechol is replaced by a dihydroxylated tetrahydroisoquinoline, which can be separated from the reaction products by simple extraction with an aqueous acid solution. The modified alkyl radical precursors are easily prepared from alkenes by hydroboration with BH 3 ·Me 2 S fol-