Lu Xingkai, Li Yan, He Xinyuan, Song Pengfei, Chai Zhigang
State Key Laboratory of Chemical Resource Engineering, College of Chemistry, Beijing University of Chemical Technology, Beijing, 100029, China.
Chemistry. 2024 Jul 25;30(42):e202402003. doi: 10.1002/chem.202402003. Epub 2024 Jul 8.
Light-driven carboxylation offers a promising approach for synthesizing valuable fine chemicals under mild conditions. Here we disclose a heterogeneous photocatalytic strategy of C(sp)-H activation of formate for hydrocarboxylation of alkenes over zinc indium sulfide (ZnInS) under visible light. This protocol functions well with a variety of substituted styrenes with good to excellent yields; it also works for unactivated alkenes albeit with lower yields. Mechanistic studies confirm the existence of CO⋅ as a key intermediate. It was found that C(sp)-H activation of formate is induced by S⋅ species on the surface of ZnInS via hydrogen atom transfer (HAT) instead of a photogenerated hole oxidation mechanism. Moreover, both cleavage of the C(sp)-H of HCOO and formation of a benzylic anion were found to be involved in the rate-determining step for the hydrocarboxylation of styrene.
光驱动羧化反应为在温和条件下合成有价值的精细化学品提供了一种很有前景的方法。在此，我们揭示了一种非均相光催化策略，即在可见光下，通过硫化锌铟（ZnInS）上甲酸的C(sp)-H活化实现烯烃的氢羧化反应。该方案对多种取代苯乙烯都能很好地发挥作用，产率良好至优异；它对未活化的烯烃也有效，尽管产率较低。机理研究证实了关键中间体CO⋅的存在。研究发现，甲酸的C(sp)-H活化是由ZnInS表面的S⋅物种通过氢原子转移（HAT）诱导的，而不是通过光生空穴氧化机制。此外，还发现HCOO的C(sp)-H裂解和苄基阴离子的形成均参与了苯乙烯氢羧化反应的决速步骤。
