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Mechanistic insight into asymmetric N-H insertion cooperatively catalyzed by a dirhodium compound and a spiro chiral phosphoric acid

(2014) ORGANOMETALLICS. 33(15). p.4042-4050
Author
Organization
Abstract
The insertion of a carbenoid into an N-H bond of an amine cooperatively catalyzed by a dirhodium catalyst and a spiro chiral phosphoric acid has been investigated in detail using density functional theory methods. Calculations indicate that the reaction begins with the nucleophilic amine attacking at the carbenoid, forming a metal-associated ammonium ylide first followed by a rapid proton transfer to afford a metal-associated enamine intermediate. Subsequently, the enamine intermediate dissociates from the metal and yield a more stable seven-membered-ring conformation via an intramolecular hydrogen-bond exchange. Formation of the enamine intermediate requires an overall barrier of 5.7 kcal/mol and is exergonic by 5.1 kcal/mol. Calculations demonstrated that, although the conversion of the achiral enamine into the N-H insertion product can be facilitated efficiently by the dirhodium catalyst through a two-step process, it can be compressed to a large extent. This is due to the more competitive decomposition of the diazoacetate catalyzed by the dirhodium catalyst, which can give a carbenoid for the next catalytic cycle. Meanwhile, formation of the carbenoid is considerably exergonic, which can promote the direct [1,3]-proton shift of enamine. However, in the presence of the Spiro chiral phosphoric acid, the asymmetric proton induction of enamine is greatly favored, requiring an activation free energy of 6.0 kcal/mol to afford the major R product. This agrees well with the experimental observation.
Keywords
RHODIUM CARBENOIDS, MOLECULAR CALCULATIONS, CINCHONA ALKALOIDS, CARBOXYLATES, DERIVATIVES, COMPLEXES, ORBITALS, DENSITY, ENANTIOSELECTIVE INSERTION, C BOND FORMATION

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Citation

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MLA
Wang, Xu-Chao, Xian-Shuang Song, Li-Ping Guo, et al. “Mechanistic Insight into Asymmetric N-H Insertion Cooperatively Catalyzed by a Dirhodium Compound and a Spiro Chiral Phosphoric Acid.” ORGANOMETALLICS 33.15 (2014): 4042–4050. Print.
APA
Wang, Xu-Chao, Song, X.-S., Guo, L.-P., Qu, D., Xie, Z.-Z., Verpoort, F., & Cao, J. (2014). Mechanistic insight into asymmetric N-H insertion cooperatively catalyzed by a dirhodium compound and a spiro chiral phosphoric acid. ORGANOMETALLICS, 33(15), 4042–4050.
Chicago author-date
Wang, Xu-Chao, Xian-Shuang Song, Li-Ping Guo, Deyu Qu, Zhi-Zhong Xie, Francis Verpoort, and Jun Cao. 2014. “Mechanistic Insight into Asymmetric N-H Insertion Cooperatively Catalyzed by a Dirhodium Compound and a Spiro Chiral Phosphoric Acid.” Organometallics 33 (15): 4042–4050.
Chicago author-date (all authors)
Wang, Xu-Chao, Xian-Shuang Song, Li-Ping Guo, Deyu Qu, Zhi-Zhong Xie, Francis Verpoort, and Jun Cao. 2014. “Mechanistic Insight into Asymmetric N-H Insertion Cooperatively Catalyzed by a Dirhodium Compound and a Spiro Chiral Phosphoric Acid.” Organometallics 33 (15): 4042–4050.
Vancouver
1.
Wang X-C, Song X-S, Guo L-P, Qu D, Xie Z-Z, Verpoort F, et al. Mechanistic insight into asymmetric N-H insertion cooperatively catalyzed by a dirhodium compound and a spiro chiral phosphoric acid. ORGANOMETALLICS. 2014;33(15):4042–50.
IEEE
[1]
X.-C. Wang et al., “Mechanistic insight into asymmetric N-H insertion cooperatively catalyzed by a dirhodium compound and a spiro chiral phosphoric acid,” ORGANOMETALLICS, vol. 33, no. 15, pp. 4042–4050, 2014.
@article{5758532,
  abstract     = {The insertion of a carbenoid into an N-H bond of an amine cooperatively catalyzed by a dirhodium catalyst and a spiro chiral phosphoric acid has been investigated in detail using density functional theory methods. Calculations indicate that the reaction begins with the nucleophilic amine attacking at the carbenoid, forming a metal-associated ammonium ylide first followed by a rapid proton transfer to afford a metal-associated enamine intermediate. Subsequently, the enamine intermediate dissociates from the metal and yield a more stable seven-membered-ring conformation via an intramolecular hydrogen-bond exchange. Formation of the enamine intermediate requires an overall barrier of 5.7 kcal/mol and is exergonic by 5.1 kcal/mol. Calculations demonstrated that, although the conversion of the achiral enamine into the N-H insertion product can be facilitated efficiently by the dirhodium catalyst through a two-step process, it can be compressed to a large extent. This is due to the more competitive decomposition of the diazoacetate catalyzed by the dirhodium catalyst, which can give a carbenoid for the next catalytic cycle. Meanwhile, formation of the carbenoid is considerably exergonic, which can promote the direct [1,3]-proton shift of enamine. However, in the presence of the Spiro chiral phosphoric acid, the asymmetric proton induction of enamine is greatly favored, requiring an activation free energy of 6.0 kcal/mol to afford the major R product. This agrees well with the experimental observation.},
  author       = {Wang, Xu-Chao and Song, Xian-Shuang and Guo, Li-Ping and Qu, Deyu and Xie, Zhi-Zhong and Verpoort, Francis and Cao, Jun},
  issn         = {0276-7333},
  journal      = {ORGANOMETALLICS},
  keywords     = {RHODIUM CARBENOIDS,MOLECULAR CALCULATIONS,CINCHONA ALKALOIDS,CARBOXYLATES,DERIVATIVES,COMPLEXES,ORBITALS,DENSITY,ENANTIOSELECTIVE INSERTION,C BOND FORMATION},
  language     = {eng},
  number       = {15},
  pages        = {4042--4050},
  title        = {Mechanistic insight into asymmetric N-H insertion cooperatively catalyzed by a dirhodium compound and a spiro chiral phosphoric acid},
  url          = {http://dx.doi.org/10.1021/om5005572},
  volume       = {33},
  year         = {2014},
}

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