Oliva Monica, Pillitteri Serena, Schörgenhumer Johannes, Saito Riku, Van der Eycken Erik V, Sharma Upendra K
Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, University of Leuven (KU Leuven) Celestijnenlaan 200F B-3001 Leuven Belgium.
Department of Chemistry, University of Zurich Winterthurerstrasse 190 CH-8057 Zurich Switzerland.
Chem Sci. 2024 Sep 26;15(42):17490-7. doi: 10.1039/d4sc04196h.
In this study, without utilizing any exogenous activator or strong oxidants, we successfully employed inactivated and easily accessible alkyl boronic acids (BAs) as coupling partners in a photocatalyzed Suzuki-Miyaura reaction under batch and continuous-flow conditions. Detailed mechanistic studies suggest a unique BA activation pathway, a plausible radical transfer event between a bromine radical (formed a photo-induced homolysis of the Ni-Br bond) and the empty p-orbital on the boron atom. Subsequently, the necessity to tune the BA oxidation potential by means of hydrogen-bonding interaction with solvents or Lewis acid-base type interactions is replaced by a novel halogen radical transfer (XRT) mechanism. The mechanistic hypothesis has been supported by both control experiments and DFT calculations.
在本研究中,我们未使用任何外源性活化剂或强氧化剂,而是成功地将灭活且易于获取的烷基硼酸(BAs)用作在间歇和连续流动条件下光催化铃木-宫浦反应中的偶联伙伴。详细的机理研究表明了一种独特的BA活化途径,即溴自由基(由光诱导的Ni-Br键均裂形成)与硼原子上的空p轨道之间可能发生的自由基转移事件。随后,通过与溶剂的氢键相互作用或路易斯酸碱型相互作用来调节BA氧化电位的必要性被一种新型的卤素自由基转移(XRT)机制所取代。这一机理假设得到了对照实验和密度泛函理论计算的支持。