Bera Suvankar, Mondal Partha, Sarkar Debabrata, Pathi Vijay Babu, Pakrashy Sourav, Datta Ayan, Banerji Biswadip
School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India.
J Org Chem. 2021 May 21;86(10):7069-7077. doi: 10.1021/acs.joc.1c00311. Epub 2021 May 12.
A Rh(III)-catalyzed regioselective redox-neutral cascade process of carbenoid functionalization followed by dephosphonylative annulation of benzoic acids with α-diazo-β-keto phosphonate has been realized, which led to the direct synthesis of a privileged 3-substituted isocoumarin scaffold. To the best of our knowledge, this is the first report of a complete redox neutral method to synthesize isocoumarins using C-H functionalization strategy. In the catalytic cycle of this reaction, there are two possible pathways for the C-C coupling between ortho-positioned carbon atom of benzoic acid and the diazo carbon atom: (i) concerted 1,2-aryl shift and (ii) stepwise metal-carbene formation followed by migratory insertion. DFT study has predicted that the concerted pathway has lower activation energy as compared to the stepwise pathway by 1.5 kcal/mol.
实现了铑（III）催化的类卡宾官能化区域选择性氧化还原中性级联过程，随后苯甲酸与α-重氮-β-酮膦酸酯进行脱膦酰环化反应，直接合成了具有特殊结构的3-取代异香豆素骨架。据我们所知，这是首次报道使用C-H官能化策略合成异香豆素的完整氧化还原中性方法。在该反应的催化循环中，苯甲酸邻位碳原子与重氮碳原子之间的C-C偶联有两种可能的途径：（i）协同的1,2-芳基迁移和（ii）分步形成金属卡宾，随后进行迁移插入。密度泛函理论研究预测，协同途径的活化能比分步途径低1.5 kcal/mol。
