Wang Jingyi, Shen Xuzhong, Chen Xu, Bao Yinwei, He Jian, Lu Zhan
Department of Chemistry, Zhejiang University, Hangzhou 310058, P. R. China.
Department of Chemistry, The University of Hong Kong, Hong Kong 999077, P. R. China.
J Am Chem Soc. 2023 Oct 31. doi: 10.1021/jacs.3c09807.
Cobalt-catalyzed enantioconvergent cross-coupling of α-bromoketones with aryl zinc reagents is achieved to access chiral ketones bearing α-tertiary stereogenic centers with high enantioselectivities. The more challenging and sterically hindered α-bromoketones bearing a 2-fluorophenyl group or β-secondary and tertiary alkyl chains could also be well-tolerated. Adjusting the electronic effect of chiral unsymmetric ,,-tridentate ligands is critical for improving the reactivity and selectivity of this transformation, which is beneficial for further studies of asymmetric 3d metal catalysis via ligand modification. The control experiments and kinetic studies illustrated that the reaction involved radical intermediates and the reductive elimination was a rate-determining step.
实现了钴催化的α-溴代酮与芳基锌试剂的对映汇聚交叉偶联反应，以高对映选择性获得带有α-叔碳立体中心的手性酮。带有2-氟苯基或β-仲烷基和叔烷基链的更具挑战性且空间位阻较大的α-溴代酮也能被很好地耐受。调节手性不对称三齿配体的电子效应对于提高该转化反应的反应性和选择性至关重要，这有利于通过配体修饰对不对称3d金属催化进行进一步研究。对照实验和动力学研究表明，该反应涉及自由基中间体，且还原消除是速率决定步骤。
