Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*)

Jiping Fu, Shinji Fujimori, Scott E Denmark

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

This chapter focuses on the mechanistic studies and preparative aspects of reactions catalyzed by chiral phosphoramides. The modest reactivity and selectivity observed with chiral Lewis bases as well as the dependence of enantioselectivity on the promoter loading has been addressed in a detailed mechanistic investigation. In a kinetic study, the reaction was found to be of first order in benzaldehyde and allylsilane, however the reaction order in phosphoramide was determined. Although mechanistically intriguing, the dual pathways have opposing effects on the rate and selectivity of the process. First, since the reaction is second order in the catalyst, the rate falls off as the square of catalyst concentration. Second, at lower concentration, a competing, less selective pathway can compromise the overall reaction selectivity. The solution to these challenges involved the introduction of dimeric analogs of phosphoramide with the expectation that the covalent tether would increase the effective concentration of the second catalyst molecule through proximity.

Original languageEnglish (US)
Title of host publicationLewis Base Catalysis in Organic Synthesis
PublisherWiley-VCH Verlag
Pages281-338
Number of pages58
Volume1
ISBN (Electronic)9783527675142
ISBN (Print)9783527336180
DOIs
StatePublished - Aug 17 2016

Fingerprint

Lewis Bases
Catalysis
Chemical activation
Phosphoramides
Catalysts
Enantioselectivity
Molecules
Kinetics
phosphoramide

Keywords

  • Aldol reaction
  • Allylation reaction
  • Allyltrichlorosilane
  • Bisphosphoramide
  • Catalysis
  • Chiral ethyl ketones
  • Chiral methyl ketones
  • Diastereoselectivity
  • Directed aldol addition
  • Donor-acceptor interactions
  • Electrophilic
  • Enantioselectivity
  • Hexacoordinate silicon
  • Hypercoordinate silicon
  • Internal stereoselection
  • Lewis base
  • Nucleophilic
  • Pentacoordinate silicon
  • Phosphine oxides
  • Phosphoramides
  • Relative stereoselection
  • Silanes
  • Silicenium ions
  • Stereoselective
  • Synthetic methods
  • Trichlorosilyl chlorohydrin
  • Trichlorosilyl enol ethers
  • Trichlorosilyl ketene acetals
  • Trigonal bipyramidal silicon

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Fu, J., Fujimori, S., & Denmark, S. E. (2016). Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*). In Lewis Base Catalysis in Organic Synthesis (Vol. 1, pp. 281-338). Wiley-VCH Verlag. https://doi.org/10.1002/9783527675142.ch9

Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*). / Fu, Jiping; Fujimori, Shinji; Denmark, Scott E.

Lewis Base Catalysis in Organic Synthesis. Vol. 1 Wiley-VCH Verlag, 2016. p. 281-338.

Research output: Chapter in Book/Report/Conference proceedingChapter

Fu, J, Fujimori, S & Denmark, SE 2016, Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*). in Lewis Base Catalysis in Organic Synthesis. vol. 1, Wiley-VCH Verlag, pp. 281-338. https://doi.org/10.1002/9783527675142.ch9
Fu J, Fujimori S, Denmark SE. Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*). In Lewis Base Catalysis in Organic Synthesis. Vol. 1. Wiley-VCH Verlag. 2016. p. 281-338 https://doi.org/10.1002/9783527675142.ch9
Fu, Jiping ; Fujimori, Shinji ; Denmark, Scott E. / Bifunctional Lewis Base Catalysis With Dual Activation of X3Si Nu and C=O(n → σ*). Lewis Base Catalysis in Organic Synthesis. Vol. 1 Wiley-VCH Verlag, 2016. pp. 281-338
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AB - This chapter focuses on the mechanistic studies and preparative aspects of reactions catalyzed by chiral phosphoramides. The modest reactivity and selectivity observed with chiral Lewis bases as well as the dependence of enantioselectivity on the promoter loading has been addressed in a detailed mechanistic investigation. In a kinetic study, the reaction was found to be of first order in benzaldehyde and allylsilane, however the reaction order in phosphoramide was determined. Although mechanistically intriguing, the dual pathways have opposing effects on the rate and selectivity of the process. First, since the reaction is second order in the catalyst, the rate falls off as the square of catalyst concentration. Second, at lower concentration, a competing, less selective pathway can compromise the overall reaction selectivity. The solution to these challenges involved the introduction of dimeric analogs of phosphoramide with the expectation that the covalent tether would increase the effective concentration of the second catalyst molecule through proximity.

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KW - Trichlorosilyl enol ethers

KW - Trichlorosilyl ketene acetals

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