The reaction between trialkylboranes and copper(II) salts. An unusual electron-transfer oxidation-reduction

Organoboranes as a Source of Radicals

“…239 Similar results are obtained with 2-furanboronic acid, ferroceneboronic acid, and triphenylboroxine . This reaction is also suitable for the preparation of alkyl halides from trialkylboranes and copper(II) salts (2 equiv per alkyl group) . The formation of alkyl radicals by electron-transfer oxidation of trialkylboranes is the key step of this process.…”

“…242 This reaction is also suitable for the preparation of alkyl halides from trialkylboranes and copper(II) salts (2 equiv per alkyl group). 243 The formation of alkyl radicals by electron-transfer oxidation of trialkylboranes is the key step of this process. The radicals then react with a second equivalent of copper(II) halide to give the corresponding alkyl halides.…”

Oxidation of Alkyl Trifluoroborates: An Opportunity for Tin‐Free Radical Chemistry

“…[8] Moreover, their oxidation chemistry has remained largely unexplored. [9,10] To initially probe our design, we examined the behavior of benzyl trifluoroborate 1 a, bearing in mind that the benzyl radical should be an easy one to generate and that trapping with TEMPO [11] would give strong evidence for the radical intermediate formation (adduct 2 a; Table 1). A preliminary screening of the reaction conditions provided valuable information.…”

Cu‐Catalyzed Coupling of Aliphatic Amines with Alkylboronic Esters

“…[40] The voltammogram of CuBr 2 does not change in the presence of the boronic ester, suggesting there is not a direct interaction between 1 and the Cu salt. [41,42] However, cyclic voltammetry of a mixture of morpholine and 1 does show the formation of a new peak (oxidation potential of E pc = 1.25 V; figure 1b). Given that this is greater than the oxidation potential of morpholine (E pc = 0.81 V), we suggest this could arise from a new species generated upon interaction of 1 and a morpholine radical, which can be oxidised at a lower potential than the boronic ester without activation.…”