中国科学院化学研究所万立骏团队报道了银表面辅助芳基溴间的脱氢溴交偶联。相关研究成果于2024年4月10日发表在国际知名学术期刊《美国化学会杂志》。

交叉偶联反应是化学合成中不可或缺的工具。该领域的一个有趣挑战是在具有相似反应性的两种前体之间实现选择性交叉偶联，或者在极限范围内实现相同分子之间的选择性交叉偶联。

该文中，研究人员报道了银表面1，3，5-三（2-溴苯基）苯分子之间出乎意料的脱溴交叉偶联。使用扫描隧道显微镜在单分子水平上检测了反应过程，量化了脱溴交叉偶联的选择性，并揭示了底物晶格相关催化活性或分子组装效应对选择性的调节。

理论计算表明，脱溴交叉偶联是通过脱溴TBPB的区域选择性C–H键活化，和随后的自由基中间体的高度选择性C–C偶联进行的。反应动力学对交叉偶联的选择性起着重要作用。

该项工作不仅扩展了化学合成的工具箱，而且为表面偶联反应的选择性提供了重要的机制见解。

附：英文原文

Title: Silver Surface-Assisted Dehydrobrominative Cross-Coupling between Identical Aryl Bromides

Author: Zhen-Yu Yi, Zi-Cong Wang, Ruo-Ning Li, Zhi-Hao Li, Jun-Jie Duan, Xue-Qing Yang, Yu-Qi Wang, Ting Chen, Dong Wang, Li-Jun Wan

Issue&Volume: April 10, 2024

Abstract: Cross-coupling reactions represent an indispensable tool in chemical synthesis. An intriguing challenge in this field is to achieve selective cross-coupling between two precursors with similar reactivity or, to the limit, the identical molecules. Here we report an unexpected dehydrobrominative cross-coupling between 1,3,5-tris(2-bromophenyl)benzene molecules on silver surfaces. Using scanning tunneling microscopy, we examine the reaction process at the single-molecular level, quantify the selectivity of the dehydrobrominative cross-coupling, and reveal the modulation of selectivity by substrate lattice-related catalytic activity or molecular assembly effect. Theoretical calculations indicate that the dehydrobrominative cross-coupling proceeds via regioselective C–H bond activation of debrominated TBPB and subsequent highly selective C–C coupling of the radical-based intermediates. The reaction kinetics plays an important role in the selectivity for the cross-coupling. This work not only expands the toolbox for chemical synthesis but also provides important mechanistic insights into the selectivity of coupling reactions on the surface.

DOI: 10.1021/jacs.4c00825

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c00825