Bromine radical release from a nickel-complex facilitates the activation of alkyl boronic acids: a boron selective Suzuki-Miyaura cross coupling

In this study, inactivated and readily available alkyl boronic acids (BAs) were successfully employed as coupling partners in a photocatalyzed Suzuki–Miyaura reaction under both batch and continuous-flow conditions, without the use of any exogenous activator or strong oxidants. Detailed mechanistic investigations were conducted, suggesting a unique BA activation pathway involving a plausible radical transfer event between a bromine radical generated in situ via photo-induced homolysis of the Ni–Br bond and the empty p-orbital on the boron atom. Consequently, the traditional requirement to tune the BA oxidation potential through hydrogen-bonding interactions with solvents or Lewis acid–base interactions was replaced by a novel halogen radical transfer (XRT) mechanism. This mechanistic hypothesis was supported by control experiments and validated through DFT calculations.

• Oliva, M
• Pillitteri, S
• Schörgenhumer, J
• Saito, R
• Van der Eycken, EV
• Sharma, UK

• Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, University of Leuven (KU Leuven) Celestijnenlaan 200F B-3001 Leuven Belgium

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