Chinese Journal of Organic Chemistry ›› 2021, Vol. 41 ›› Issue (8): 3272-3278.DOI: 10.6023/cjoc202103054 Previous Articles     Next Articles



徐曼, 夏远志*()   

  1. 温州大学化学与材料工程学院 浙江温州 325035
  • 收稿日期:2021-03-28 修回日期:2021-04-25 发布日期:2021-05-08
  • 通讯作者: 夏远志
  • 基金资助:
    国家自然科学基金(21572163); 国家自然科学基金(21873074)

Mechanistic Understanding of Rh(III)-Catalyzed Redox-Neutral C—H Activation/Annulation Reactions of N-Phenoxyacetamides and Methyleneoxetanones

Man Xu, Yuanzhi Xia()   

  1. College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325035
  • Received:2021-03-28 Revised:2021-04-25 Published:2021-05-08
  • Contact: Yuanzhi Xia
  • Supported by:
    National Natural Science Foundation of China(21572163); National Natural Science Foundation of China(21873074)

N-Phenoxyacetamides represent one category of typical substrates for Rh(III)-catalyzed C—H activation under external oxidant free conditions. To understand how the O-NHAc unit works as the oxidizing directing group, the mechanism for the Rh(III)-catalyzed C—H activation/annulation reactions of N-phenoxyacetamides with methyleneoxetanones was studied by density functional theory (DFT) calculations. It was uncovered that after the formation of the 7-membered rhodacycle from irreversible C—H activation and olefin insertion steps, the direct O—N bond cleavage of the internal oxidant unit to form a Rh(V)-nitrenoid species was energetically unfavorable. Instead, this intermediate underwent sequential β-H elimination/reductive elimination much more easily and formed a Rh(I) species. Once the hydrogen was transferred to the NAc moiety, the regeneration of Rh(III) occurred easily by O—N bond cleavage. From the olefination intermediate, the final product was formed by an intramolecular nucleophilic substitution reaction, in which the Cp*Rh(III) could be a catalyst. The experimental outcomes are well understood by the density functional theory (DFT)-suggested catalytic cycle of Rh(III)/Rh(I)/Rh(III).

Key words: Rh(III) catalysis, C—H activation, reaction mechanism, oxidizing directing group, density functional theory (DFT) calculation, N-phenoxyacetamide