Web Table 1. Free energy profile of the uncatalysed model cycloaddition reaction

Two complementary catalytic systems are reported for the 1,3-dipolar cycloaddition of azides and iodoalkynes. These are based on two commercially available/readily available copper complexes, [CuCl(IPr)] or [CuI(PPh3)3], which are active at low metal loadings and in the absence of any other additive (IPr system). These systems were used for the first reported mechanistic studies on this particular reaction. An experimental/computational-DFT approach allowed to establish that 1) some iodoalkynes might be prone to dehalogenation under copper catalysis conditions and, more importantly, 2) that two distinct mechanistic pathways are likely to be competitive with these catalysts; through a copper(III) metallacycle or via direct p-activation of the starting alkyne.

本研究报道了两套用于叠氮化物（azides）与碘代炔烃（iodoalkynes）间1,3-偶极环加成（1,3-dipolar cycloaddition）反应的互补催化体系。该两类体系以两种商业可得且易于制备的铜配合物（copper complexes）——[CuCl(IPr)] 或 [CuI(PPh3)3]——为核心，可在低金属负载量且无需任何额外添加剂的条件下展现催化活性（即IPr体系）。本研究首次借助该体系开展了该特定反应的机理研究。通过实验与密度泛函理论（Density Functional Theory，DFT）计算相结合的研究方法，证实了两项关键结论：其一，部分碘代炔烃在铜催化条件下可能发生脱卤反应；更为重要的是，对于此类催化剂，存在两条截然不同且可能相互竞争的反应机理路径：一条经由铜(III)金属环（copper(III) metallacycle）中间体，另一条则通过起始炔烃的直接π活化。