Regioselectivity of Intermolecular Pauson鈥揔hand Reaction of Aliphatic Alkynes: Experimental and Theoretical Study of the Effect of Alkyne Polarization

详细信息    查看全文

• 作者：Erika Fager-Jokela ; Mikko Muuronen ; H茅l茅a Khaizourane ; Ana V谩zquez-Romero ; Xavier Verdaguer ; Antoni Riera ; Juho Helaja
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：November 21, 2014
• 年：2014
• 卷：79
• 期：22
• 页码：10999-11010
• 全文大小：578K
• ISSN：1520-6904

文摘

Generally judged poor electronic regioselectivity of alkyne insertion in intermolecular Pauson鈥揔hand reaction (PKR) has severely restricted its synthetic applications. In our previous rational study concerning diarylalkynes (Fager-Jokela, E.; Muuronen, M.; Patzschke, M.; Helaja, J. J. Org. Chem. 2012, 77, 9134鈥?147), both experimental and theoretical results indicated that purely electronic factors, i.e., alkyne polarization via resonance effect, induced the observed modest regioselectivity. In the present work, we substantiate that the alkyne polarization via inductive effect can result notable, synthetically valuable regioselectivity. Computational study at DFT level was performed to disclose the electronic origin of the selectivity. Overall, the NBO charges of alkynes correlated qualitatively with regioisomer outcome. In a detailed computational PKR case study, the obtained Boltzmann distributions of the transition state (TS) populations correlate closely with experimental regioselectivity. Analysis of the TS-structures revealed that weak interactions, e.g., hydrogen bonding and steric repulsion, affect the regioselectivity and can easily override the electronic guidance.