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<p>Donor–acceptor cyclopropanes (DACs) serve as significant substrates for the synthesis of natural products, with Lewis acids (LAs) commonly employed as catalysts to facilitate the activation of DACs. This study investigates the [3 + 2]-cycloaddition (32CA) reaction of DAC catalyzed by the Brønsted acid TfOH, using the M06-2X/SMD/6–311 + G(d,p)//M06-2X/6-31G(d,p) computational level. The theoretical analysis reveals that the reaction mechanism comprises three critical steps: protonation, 32CA reaction and dehydration reaction, with the cycloaddition step identified as the rate-limiting step. The DAC is initiated through the protonation step to polarize the C–C bond, which enhances the electrophilicity of the carbon atom substituted by the donor group. This study elucidates the details of protonation step utilizing analytical techniques such as Laplacian bond order (LBO) and dual descriptors analysis. Furthermore, the computational analysis delineates the distinctions in the protonation progress when catalyzed by LA compared to Brønsted acid (BA), indicating a greater efficacy of LA in this context. Additionally, the influence of BA catalysts is predominantly observed during the dehydration phase, where the activation&#xa0;Gibbs free energy of the transition state structures&#xa0;(TSs) exhibits a direct correlation with the dissociation energy of BAs, achieving a fitting coefficient of 0.9871. Thus, this molecular-level investigation offers valuable insights into the DACs facilitated by BA catalysts.</p>

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Insight into [3 + 2] Cycloaddition/Dehydration Reaction of Activated Cyclopropanes Catalyzed by Brønsted Acid: A Theoretical Study

  • 期刊论文

  • 发表日期：

    2026年3月25日

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  • Yan Zhang,
  • Jia-Xing Yu,
  • Ying Xue,
  • Cui Wei,
  • Wen-Jun Zhou

摘要

Donor–acceptor cyclopropanes (DACs) serve as significant substrates for the synthesis of natural products, with Lewis acids (LAs) commonly employed as catalysts to facilitate the activation of DACs. This study investigates the [3 + 2]-cycloaddition (32CA) reaction of DAC catalyzed by the Brønsted acid TfOH, using the M06-2X/SMD/6–311 + G(d,p)//M06-2X/6-31G(d,p) computational level. The theoretical analysis reveals that the reaction mechanism comprises three critical steps: protonation, 32CA reaction and dehydration reaction, with the cycloaddition step identified as the rate-limiting step. The DAC is initiated through the protonation step to polarize the C–C bond, which enhances the electrophilicity of the carbon atom substituted by the donor group. This study elucidates the details of protonation step utilizing analytical techniques such as Laplacian bond order (LBO) and dual descriptors analysis. Furthermore, the computational analysis delineates the distinctions in the protonation progress when catalyzed by LA compared to Brønsted acid (BA), indicating a greater efficacy of LA in this context. Additionally, the influence of BA catalysts is predominantly observed during the dehydration phase, where the activation Gibbs free energy of the transition state structures (TSs) exhibits a direct correlation with the dissociation energy of BAs, achieving a fitting coefficient of 0.9871. Thus, this molecular-level investigation offers valuable insights into the DACs facilitated by BA catalysts.