Luo Yongrui, Li Yuli, Wu Jian, Xue Xiao-Song, Hartwig John F, Shen Qilong
Key Laboratory of Organofluorine Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, PR China.
Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.
Science. 2023 Sep 8;381(6662):1072-1079. doi: 10.1126/science.adg9232. Epub 2023 Sep 7.
The step that cleaves the carbon-halogen bond in copper-catalyzed cross-coupling reactions remains ill defined because of the multiple redox manifolds available to copper and the instability of the high-valent copper product formed. We report the oxidative addition of α-haloacetonitrile to ionic and neutral copper(I) complexes to form previously elusive but here fully characterized copper(III) complexes. The stability of these complexes stems from the strong Cu-CF bond and the high barrier for C()-C() bond-forming reductive elimination. The mechanistic studies we performed suggest that oxidative addition to ionic and neutral copper(I) complexes proceeds by means of two different pathways: an S2-type substitution to the ionic complex and a halogen-atom transfer to the neutral complex. We observed a pronounced ligand acceleration of the oxidative addition, which correlates with that observed in the copper-catalyzed couplings of azoles, amines, or alkynes with alkyl electrophiles.
在铜催化的交叉偶联反应中，切断碳-卤键的步骤仍不明确，这是因为铜有多种氧化还原态，且所形成的高价铜产物不稳定。我们报道了α-卤代乙腈与离子型和中性铜（I）配合物的氧化加成反应，以形成之前难以捉摸但在此已得到充分表征的铜（III）配合物。这些配合物的稳定性源于较强的Cu-C键以及形成C（）-C（）键的还原消除反应的高势垒。我们进行的机理研究表明，离子型和中性铜（I）配合物的氧化加成反应通过两种不同途径进行：对离子型配合物的S2型取代以及对中性配合物的卤原子转移。我们观察到氧化加成反应有明显的配体加速作用，这与在铜催化的唑类、胺类或炔类与烷基亲电试剂的偶联反应中观察到的情况相关。
