Department of Chemistry, Faculty of Science, Hokkaido University Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan.
Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido, 001-0021, Japan.
Chem Asian J. 2021 Dec 13;16(24):4072-4080. doi: 10.1002/asia.202100989. Epub 2021 Oct 28.
Theory-driven organic synthesis is a powerful tool for developing new organic transformations. A palladacycle(II), generated from 8-methylquinoline via C(sp )-H activation, is frequently featured in the scientific literature, albeit that the reactivity toward CO , an abundant, inexpensive, and non-toxic chemical, remains elusive. We have theoretically discovered potential carboxylation pathways using the artificial force induced reaction (AFIR) method, a density-functional-theory (DFT)-based automated reaction path search method. The thus obtained results suggest that the reduction of Pd(II) to Pd(I) is key to promote the insertion of CO . Based on these computational findings, we employed various one-electron reductants, such as Cp* Co, a photoredox catalyst under blue LED irradiation, and reductive electrolysis ((+)Mg/(-)Pt), which afforded the desired carboxylated products in high yields. After screening phosphine ligands under photoredox conditions, we discovered that bidentate ligands such as dppe promoted this carboxylation efficiently, which was rationally interpreted in terms of the redox potential of the Pd(II)-dppe complex as well as on the grounds of DFT calculations. We are convinced that these results could serve as future guidelines for the development of Pd(II)-catalyzed C(sp )-H carboxylation reactions with CO .
理论驱动的有机合成是开发新的有机转化的有力工具。通过 C(sp )-H 活化，从 8-甲基喹啉生成的钯环(II)经常出现在科学文献中，尽管其对 CO 的反应性，CO 是一种丰富、廉价且无毒的化学物质，仍然难以捉摸。我们使用人工力诱导反应 (AFIR) 方法，一种基于密度泛函理论 (DFT) 的自动反应路径搜索方法，从理论上发现了潜在的羧化途径。由此得到的结果表明，促进 CO 插入的关键是将 Pd(II)还原为 Pd(I)。基于这些计算发现，我们采用了各种单电子还原剂，如 Cp*Co，在蓝色 LED 照射下的光氧化还原催化剂，以及还原电解 ((+)Mg/(-)Pt)，这些方法以高产率得到了所需的羧化产物。在光氧化还原条件下筛选膦配体后，我们发现双齿配体如 dppe 能有效地促进这种羧化反应，这可以根据 Pd(II)-dppe 配合物的氧化还原电位以及基于 DFT 计算的结果来合理地解释。我们相信，这些结果可以为开发 Pd(II)催化的 CO 参与的 C(sp )-H 羧化反应提供未来的指导。
