Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
J Am Chem Soc. 2022 Aug 31;144(34):15488-15496. doi: 10.1021/jacs.2c01229. Epub 2022 Aug 22.
A case study of catalytic carbon-carbon σ-bond homolysis is presented. The coordination of a redox-active Lewis acid catalyst reduces the bond-dissociation free energies of adjacent carbon-carbon σ-bonds, and this complexation-induced bond-weakening is used to effect reversible carbon-carbon bond homolysis. Stereochemical isomerization of 1,2-disubstituted cyclopropanes was investigated as a model reaction with a ruthenium (III/II) redox couple adopted for bond weakening. Results from our mechanistic investigation into the stereospecificity of the isomerization reaction are consistent with selective complexation-induced carbon-carbon bond homolysis. The Δ of catalyzed and uncatalyzed reactions were estimated to be 14.4 and 40.0 kcal/mol, respectively with the computational method, (U)PBE0-D3/def2-TZVPP-SMD(toluene)//(U)B3LYP-D3/def2-SVP. We report this work as the first catalytic example where the complexation-induced bond-weakening effect is quantified through transition state analysis.
呈现了一个关于催化碳-碳σ键均裂的案例研究。氧化还原活性路易斯酸催化剂的配位降低了相邻碳-碳σ键的键离解自由能，这种复合物诱导的键弱化用于实现可逆的碳-碳键均裂。采用钌（III/II）氧化还原对作为键弱化剂，研究了 1,2-二取代环丙烷的立体化学异构化作为模型反应。我们对异构化反应的立体专一性的机理研究结果与选择性的复合物诱导碳-碳键均裂一致。用计算方法（U）PBE0-D3/def2-TZVPP-SMD（甲苯）//（U）B3LYP-D3/def2-SVP 估计催化和未催化反应的Δ分别为 14.4 和 40.0 kcal/mol。我们将这项工作报告为第一个通过过渡态分析量化复合物诱导键弱化效应的催化实例。
