P-N Cooperative Borane Activation and Catalytic Hydroboration by a Distorted Phosphorous Triamide Platform

Yi Chun Lin, Emmanuel Hatzakis, Sean M. McCarthy, Kyle D. Reichl, Ting Yi Lai, Hemant P. Yennawar, Alexander T. Radosevich

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Studies of the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across the electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second-order empirical rate law given by ν = -k[1][HBpin], where k = 4.76 × 10-5 M-1 s-1 at 25 °C. The B-H bond activation process produces P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as the catalyst and HBpin as the terminal reagent. A mechanistic proposal implicating a P-N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented, and a comparison to related phosphorus-based systems is offered.

Original languageEnglish (US)
Pages (from-to)6008-6016
Number of pages9
JournalJournal of the American Chemical Society
Volume139
Issue number16
DOIs
StatePublished - Apr 26 2017

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Boranes
Imines
Phosphorus
Chemical activation
Kinetics
Catalysis
Nuclear magnetic resonance spectroscopy
Catalysts
Regeneration
Magnetic Resonance Spectroscopy
Substrates
4,4,5,5-tetramethyl(1,3,2)dioxaborolane

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Lin, Yi Chun ; Hatzakis, Emmanuel ; McCarthy, Sean M. ; Reichl, Kyle D. ; Lai, Ting Yi ; Yennawar, Hemant P. ; Radosevich, Alexander T. / P-N Cooperative Borane Activation and Catalytic Hydroboration by a Distorted Phosphorous Triamide Platform. In: Journal of the American Chemical Society. 2017 ; Vol. 139, No. 16. pp. 6008-6016.
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abstract = "Studies of the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across the electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second-order empirical rate law given by ν = -k[1][HBpin], where k = 4.76 × 10-5 M-1 s-1 at 25 °C. The B-H bond activation process produces P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as the catalyst and HBpin as the terminal reagent. A mechanistic proposal implicating a P-N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented, and a comparison to related phosphorus-based systems is offered.",
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P-N Cooperative Borane Activation and Catalytic Hydroboration by a Distorted Phosphorous Triamide Platform. / Lin, Yi Chun; Hatzakis, Emmanuel; McCarthy, Sean M.; Reichl, Kyle D.; Lai, Ting Yi; Yennawar, Hemant P.; Radosevich, Alexander T.

In: Journal of the American Chemical Society, Vol. 139, No. 16, 26.04.2017, p. 6008-6016.

Research output: Contribution to journalArticle

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T1 - P-N Cooperative Borane Activation and Catalytic Hydroboration by a Distorted Phosphorous Triamide Platform

AU - Lin, Yi Chun

AU - Hatzakis, Emmanuel

AU - McCarthy, Sean M.

AU - Reichl, Kyle D.

AU - Lai, Ting Yi

AU - Yennawar, Hemant P.

AU - Radosevich, Alexander T.

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N2 - Studies of the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across the electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second-order empirical rate law given by ν = -k[1][HBpin], where k = 4.76 × 10-5 M-1 s-1 at 25 °C. The B-H bond activation process produces P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as the catalyst and HBpin as the terminal reagent. A mechanistic proposal implicating a P-N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented, and a comparison to related phosphorus-based systems is offered.

AB - Studies of the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across the electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second-order empirical rate law given by ν = -k[1][HBpin], where k = 4.76 × 10-5 M-1 s-1 at 25 °C. The B-H bond activation process produces P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as the catalyst and HBpin as the terminal reagent. A mechanistic proposal implicating a P-N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented, and a comparison to related phosphorus-based systems is offered.

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