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Mechanistic insight into the rhodium-catalyzed O-H insertion reaction : a DFT study

(2014) ORGANOMETALLICS. 33(10). p.2448-2456
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Abstract
A DFT study on the reaction of diazoacetate with primary allyl alcohol mediated by dirhodium catalyst has been carried out in detail. Calculations indicate that the major O-H insertion product can be obtained via either a [1,3]-proton shift of the free enol or a [1,2]-proton shift of the free oxonium ylide, which are regulated by the orientation of the ester group. In the case of a [1,3]-proton shift the reaction begins with the nucleophilic attack of the alcohol at the carbenoid, generating a metal-associated oxonium ylide followed by a [1,4] -proton shift to the adjacent carbonyl oxygen atom of the ester group, resulting in a metal-associated enol. Subsequently, its decomposition liberates a free enol intermediate. The whole process requires an overall barrier of 4.2 kcal/mol and is exergonic by 6.4 kcal/mol. The [1,3]-proton shift of the enol also readily provides the final O-H insertion product, which has a barrier of 11.7 kcal/mol using a three-alcohol cluster as catalyst. For the free oxonium ylide pathway, formation of an alternative metal-associated oxonium ylide is also straightforward, having an overall barrier of 4.5 kcal/mol. In the presence of extra alcohol molecules, the decomposition of the metal-associated oxonium ylide can generate an alcohol-stabilized free oxonium ylide (endergonic by only 4.1 kcal/mol). Afterward, it undergoes a [1,2]-proton shift, resulting in the O-H insertion product, which requires an energy barrier of 4.7 kcal/mol. In comparison, the competitive [2,3]-sigmatropic rearrangement for the metal-associated oxonium ylides is not sensitive to the orientation of the ester, which has a similar activation free energy around 14.0 kcal/mol. Accordingly, it is always disfavored over the O-H insertion, which kinetically agrees well with the experimental observations, in which traces of [2,3]-sigmatropic rearrangement product were obtained for the primary allyl alcohol.
Keywords
DIAZO-COMPOUNDS, MOLECULAR CALCULATIONS, TANDEM YLIDE, ALCOHOLS, DENSITY, DONOR/ACCEPTOR CARBENOIDS, ENANTIOSELECTIVE INSERTION, C BOND FORMATION, 3+2 CYCLOADDITION REACTIONS, INITIATED CLAISEN REARRANGEMENT

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MLA
Xie, Zhi-Zhong, et al. “Mechanistic Insight into the Rhodium-Catalyzed O-H Insertion Reaction : A DFT Study.” ORGANOMETALLICS, vol. 33, no. 10, 2014, pp. 2448–56.
APA
Xie, Z.-Z., Liao, W.-J., Cao, J., Guo, L.-P., Verpoort, F., & Fang, W. (2014). Mechanistic insight into the rhodium-catalyzed O-H insertion reaction : a DFT study. ORGANOMETALLICS, 33(10), 2448–2456.
Chicago author-date
Xie, Zhi-Zhong, Wen-Juan Liao, Jun Cao, Li-Ping Guo, Francis Verpoort, and Weihai Fang. 2014. “Mechanistic Insight into the Rhodium-Catalyzed O-H Insertion Reaction : A DFT Study.” ORGANOMETALLICS 33 (10): 2448–56.
Chicago author-date (all authors)
Xie, Zhi-Zhong, Wen-Juan Liao, Jun Cao, Li-Ping Guo, Francis Verpoort, and Weihai Fang. 2014. “Mechanistic Insight into the Rhodium-Catalyzed O-H Insertion Reaction : A DFT Study.” ORGANOMETALLICS 33 (10): 2448–2456.
Vancouver
1.
Xie Z-Z, Liao W-J, Cao J, Guo L-P, Verpoort F, Fang W. Mechanistic insight into the rhodium-catalyzed O-H insertion reaction : a DFT study. ORGANOMETALLICS. 2014;33(10):2448–56.
IEEE
[1]
Z.-Z. Xie, W.-J. Liao, J. Cao, L.-P. Guo, F. Verpoort, and W. Fang, “Mechanistic insight into the rhodium-catalyzed O-H insertion reaction : a DFT study,” ORGANOMETALLICS, vol. 33, no. 10, pp. 2448–2456, 2014.
@article{5758566,
  abstract     = {A DFT study on the reaction of diazoacetate with primary allyl alcohol mediated by dirhodium catalyst has been carried out in detail. Calculations indicate that the major O-H insertion product can be obtained via either a [1,3]-proton shift of the free enol or a [1,2]-proton shift of the free oxonium ylide, which are regulated by the orientation of the ester group. In the case of a [1,3]-proton shift the reaction begins with the nucleophilic attack of the alcohol at the carbenoid, generating a metal-associated oxonium ylide followed by a [1,4] -proton shift to the adjacent carbonyl oxygen atom of the ester group, resulting in a metal-associated enol. Subsequently, its decomposition liberates a free enol intermediate. The whole process requires an overall barrier of 4.2 kcal/mol and is exergonic by 6.4 kcal/mol. The [1,3]-proton shift of the enol also readily provides the final O-H insertion product, which has a barrier of 11.7 kcal/mol using a three-alcohol cluster as catalyst. For the free oxonium ylide pathway, formation of an alternative metal-associated oxonium ylide is also straightforward, having an overall barrier of 4.5 kcal/mol. In the presence of extra alcohol molecules, the decomposition of the metal-associated oxonium ylide can generate an alcohol-stabilized free oxonium ylide (endergonic by only 4.1 kcal/mol). Afterward, it undergoes a [1,2]-proton shift, resulting in the O-H insertion product, which requires an energy barrier of 4.7 kcal/mol. In comparison, the competitive [2,3]-sigmatropic rearrangement for the metal-associated oxonium ylides is not sensitive to the orientation of the ester, which has a similar activation free energy around 14.0 kcal/mol. Accordingly, it is always disfavored over the O-H insertion, which kinetically agrees well with the experimental observations, in which traces of [2,3]-sigmatropic rearrangement product were obtained for the primary allyl alcohol.},
  author       = {Xie, Zhi-Zhong and Liao, Wen-Juan and Cao, Jun and Guo, Li-Ping and Verpoort, Francis and Fang, Weihai},
  issn         = {0276-7333},
  journal      = {ORGANOMETALLICS},
  keywords     = {DIAZO-COMPOUNDS,MOLECULAR CALCULATIONS,TANDEM YLIDE,ALCOHOLS,DENSITY,DONOR/ACCEPTOR CARBENOIDS,ENANTIOSELECTIVE INSERTION,C BOND FORMATION,3+2 CYCLOADDITION REACTIONS,INITIATED CLAISEN REARRANGEMENT},
  language     = {eng},
  number       = {10},
  pages        = {2448--2456},
  title        = {Mechanistic insight into the rhodium-catalyzed O-H insertion reaction : a DFT study},
  url          = {http://dx.doi.org/10.1021/om401092h},
  volume       = {33},
  year         = {2014},
}

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