1
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Kelty ML, McNeece AJ, Kurutz JW, Filatov AS, Anderson JS. Electrostatic vs. inductive effects in phosphine ligand donor properties and reactivity. Chem Sci 2022; 13:4377-4387. [PMID: 35509471 PMCID: PMC9007067 DOI: 10.1039/d1sc04277g] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 03/15/2022] [Indexed: 11/21/2022] Open
Abstract
Enhanced rates and selectivity in enzymes are enabled in part by precisely tuned electric fields within active sites. Analogously, the use of charged groups to leverage electrostatics in molecular systems is a promising strategy to tune reactivity. However, separation of the through space and through bond effects of charged functional groups is a long standing challenge that limits the rational application of electric fields in molecular systems. To address this challenge we developed a method using the phosphorus selenium coupling value (J P-Se) of anionic phosphine selenides to quantify the electrostatic contribution of the borate moiety to donor strength. In this analysis we report the synthesis of a novel anionic phosphine, PPh2CH2BF3K, the corresponding tetraphenyl phosphonium and tetraethyl ammonium selenides [PPh4][SePPh2CH2BF3] and [TEA][SePPh2CH2BF3], and the Rh carbonyl complex [PPh4][Rh(acac)(CO)(PPh2(CH2BF3))]. Solvent-dependent changes in J P-Se were fit using Coulomb's law and support up to an 80% electrostatic contribution to the increase in donor strength of [PPh4][SePPh2CH2BF3] relative to SePPh2Et, while controls with [TEA][SePPh2CH2BF3] exclude convoluting ion pairing effects. Calculations using explicit solvation or point charges effectively replicate the experimental data. This J P-Se method was extended to [PPh4][SePPh2(2-BF3Ph)] and likewise estimates up to a 70% electrostatic contribution to the increase in donor strength relative to SePPh3. The use of PPh2CH2BF3K also accelerates C-F oxidative addition reactivity with Ni(COD)2 by an order of magnitude in comparison to the comparatively donating neutral phosphines PEt3 and PCy3. This enhanced reactivity prompted the investigation of catalytic fluoroarene C-F borylation, with improved yields observed for less fluorinated arenes. These results demonstrate that covalently bound charged functionalities can exert a significant electrostatic influence under common solution phase reaction conditions and experimentally validate theoretical predictions regarding electrostatic effects in reactivity.
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Affiliation(s)
- Margaret L Kelty
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Andrew J McNeece
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Josh W Kurutz
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - John S Anderson
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
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2
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Silva VB, Campos RB, Pavez P, Medeiros M, Orth ES. Nucleophilic Neutralization of Organophosphates: Lack of Selectivity or Plenty of Versatility? CHEM REC 2021; 21:2638-2665. [PMID: 34117695 DOI: 10.1002/tcr.202100123] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/17/2021] [Indexed: 12/13/2022]
Abstract
Neutralization of organophosphates is an issue of public health and safety, involving agrochemicals and chemical warfare. A promising approach is the nucleophilic neutralization, scope of this review, which focuses on the molecular nucleophiles: hydroxide, imidazole derivatives, alpha nucleophiles, amines and other nucleophiles. A reactivity mapping is given correlating the pathways and reaction efficiency with structural dependence of the nucleophile (basicity) and the organophosphate (electrophilic centers, P=O/P=S shift, leaving and non-leaving group). Reactions extremely unfavorable (>20 years) can be reduced to seconds with various nucleophiles, some which are catalytic. Although there is no universal nucleophile, a lack of selectivity in some cases accounts for plenty of versatility in other reactions. The ideal neutralization requires a solid mechanistic understanding, together with balancing factors such as milder conditions, fast process, selectivity and less toxic products.
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Affiliation(s)
- Valmir B Silva
- Department of Chemistry, Universidade Federal do Paraná, CP 19081, CEP 81531-990, Curitiba, PR, Brazil
| | - Renan B Campos
- Academic Department of Chemistry and Biology, Universidade Tecnológica Federal do Paraná, ZIP 81280-340, Curitiba, PR, Brazil
| | - Paulina Pavez
- Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Casilla 306, 6094411, Santiago, Chile
| | - Michelle Medeiros
- Department of Chemistry, Universidade Federal de Santa Catarina, CEP 88040-900, Florianópolis, SC, Brazil
| | - Elisa S Orth
- Department of Chemistry, Universidade Federal do Paraná, CP 19081, CEP 81531-990, Curitiba, PR, Brazil
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Zhou L, Li CL, Gao RT, Kang SM, Xu L, Xu XH, Liu N, Wu ZQ. Highly Regioselective and Helix-Sense Selective Living Polymerization of Phenyl and Alkoxyallene Using Chiral Nickel(II) Catalysts. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02198] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Li Zhou
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Chong-Long Li
- School of Chemistry and Chemical Engineering, North Minzu University, Yinchuan 750021 Ningxia Hui Autonomous Region, China
| | - Run-Tan Gao
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Shu-Ming Kang
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Lei Xu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Xun-Hui Xu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Na Liu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
| | - Zong-Quan Wu
- Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009 Anhui Province, China
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4
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Kennedy CR, Choi BY, Reeves MGR, Jacobsen EN. Enantioselective Catalysis of an Anionic Oxy-Cope Rearrangement Enabled by Synergistic Ion Binding. Isr J Chem 2020; 60:461-474. [PMID: 33132416 PMCID: PMC7592710 DOI: 10.1002/ijch.201900168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/20/2020] [Indexed: 01/09/2023]
Abstract
Charge-accelerated rearrangements present interesting challenges to enantioselective catalysis, due in large part to the competing requirements for maximizing reactivity (ion-pair separation) and stereochemical communication. Herein, we describe application of a synergistic ion-binding strategy to catalyze the anionic oxy-Cope rearrangement of a symmetric bis-styrenyl allyl alcohol in up to 75:25 e.r. Structure-reactivity-selectivity relationship studies, including linear free-energy-relationship analyses, with bifunctional urea catalysts indicate that H-bonding and cation-binding interactions act cooperatively to promote the chemo- and enantioselective [3,3]-rearrangement. Implications for catalyst designs applicable to other transformations involving oxyanionic intermediates are discussed.
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Affiliation(s)
- C Rose Kennedy
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Bo Young Choi
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Mary-Grace R Reeves
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Eric N Jacobsen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
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5
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Kang K, Fuller J, Reath AH, Ziller JW, Alexandrova AN, Yang JY. Installation of internal electric fields by non-redox active cations in transition metal complexes. Chem Sci 2019; 10:10135-10142. [PMID: 32015820 PMCID: PMC6968733 DOI: 10.1039/c9sc02870f] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/07/2019] [Indexed: 01/26/2023] Open
Abstract
Local electric fields contribute to the high selectivity and catalytic activity in enzyme active sites and confined reaction centers in zeolites by modifying the relative energy of transition states, intermediates and/or products. Proximal charged functionalities can generate equivalent internal electric fields in molecular systems but the magnitude of their effect and impact on electronic structure has been minimally explored. To generate quantitative insight into installing internal fields in synthetic systems, we report an experimental and computational study using transition metal (M1) Schiff base complexes functionalized with a crown ether unit containing a mono- or dicationic alkali or alkaline earth metal ion (M2). The synthesis and characterization of the complexes M1 = Ni(ii) and M2 = Na+ or Ba2+ are reported. The electronic absorption spectra and density functional theory (DFT) calculations establish that the cations generate a robust electric field at the metal, which stabilizes the Ni-based molecular orbitals without significantly changing their relative energies. The stabilization is also reflected in the experimental Ni(ii/i) reduction potentials, which are shifted 0.12 V and 0.34 V positive for M2 = Na+ and Ba2+, respectively, compared to a complex lacking a proximal cation. To compare with the cationic Ni complexes, we also synthesized a series of Ni(salen) complexes modified in the 5' position with electron-donating and -withdrawing functionalities (-CF3, -Cl, -H, -tBu, and -OCH3). Data from this series of compounds provides further evidence that the reduction potential shifts observed in the cationic complexes are not due to inductive ligand effects. DFT studies were also performed on the previously reported monocationic and dicatonic Fe(ii)(CH3CN) and Fe(iii)Cl analogues of this system to analyze the impact of an anionic chloride on the electrostatic potential and electronic structure of the Fe site.
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Affiliation(s)
- Kevin Kang
- Department of Chemistry , University of California , Irvine 92697 , USA .
| | - Jack Fuller
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , CA 90095 , USA .
| | - Alexander H Reath
- Department of Chemistry , University of California , Irvine 92697 , USA .
| | - Joseph W Ziller
- Department of Chemistry , University of California , Irvine 92697 , USA .
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , CA 90095 , USA .
- California NanoSystems Institute , Los Angeles , CA 90095 , USA
| | - Jenny Y Yang
- Department of Chemistry , University of California , Irvine 92697 , USA .
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Pupo G, Vicini AC, Ascough DMH, Ibba F, Christensen KE, Thompson AL, Brown JM, Paton RS, Gouverneur V. Hydrogen Bonding Phase-Transfer Catalysis with Potassium Fluoride: Enantioselective Synthesis of β-Fluoroamines. J Am Chem Soc 2019; 141:2878-2883. [DOI: 10.1021/jacs.8b12568] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gabriele Pupo
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Anna Chiara Vicini
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - David M. H. Ascough
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Francesco Ibba
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Kirsten E. Christensen
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Amber L. Thompson
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - John M. Brown
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Robert S. Paton
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Véronique Gouverneur
- Chemistry Research
Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
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7
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Chantarojsiri T, Ziller JW, Yang JY. Incorporation of redox-inactive cations promotes iron catalyzed aerobic C-H oxidation at mild potentials. Chem Sci 2018; 9:2567-2574. [PMID: 29732136 PMCID: PMC5911827 DOI: 10.1039/c7sc04486k] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 01/28/2018] [Indexed: 12/18/2022] Open
Abstract
The synthesis and characterization of the Schiff base complexes Fe(ii) (2M) and Fe(iii)Cl (3M), where M is a K+ or Ba2+ ion incorporated into the ligand, are reported. The Fe(iii/ii) redox potentials are positively shifted by 440 mV (2K) and 640 mV (2Ba) compared to Fe(salen) (salen = N,N'-bis(salicylidene)ethylenediamine), and by 70 mV (3K) and 230 mV (3Ba) compared to Fe(Cl)(salen), which is likely due to an electrostatic effect (electric field) from the cation. The catalytic activity of 3M towards the aerobic oxidation of allylic C-H bonds was explored. Prior studies on iron salen complexes modified through conventional electron-donating or withdrawing substituents found that only the most oxidizing derivatives were competent catalysts. In contrast, the 3M complexes, which are significantly less oxidizing, are both active. Mechanistic studies comparing 3M to Fe(salen) derivatives indicate that the proximal cation contributes to the overall reactivity in the rate determining step. The cationic charge also inhibits oxidative deactivation through formation of the corresponding Fe2-μ-oxo complexes, which were isolated and characterized. This study demonstrates how non-redox active Lewis acidic cations in the secondary coordination sphere can be used to modify redox catalysts in order to operate at milder potentials with a minimal impact on the reactivity, an effect that was unattainable by tuning the catalyst through traditional substituent effects on the ligand.
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Affiliation(s)
| | - Joseph W Ziller
- Department of Chemistry , University of California , Irvine , 92697 , USA .
| | - Jenny Y Yang
- Department of Chemistry , University of California , Irvine , 92697 , USA .
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8
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Maji R, Champagne PA, Houk KN, Wheeler SE. Activation Mode and Origin of Selectivity in Chiral Phosphoric Acid-Catalyzed Oxacycle Formation by Intramolecular Oxetane Desymmetrizations. ACS Catal 2017. [DOI: 10.1021/acscatal.7b02993] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Rajat Maji
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Pier Alexandre Champagne
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - K. N. Houk
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Steven E. Wheeler
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
- Center
for Computational Quantum Chemistry, Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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9
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Maji R, Wheeler SE. Importance of Electrostatic Effects in the Stereoselectivity of NHC-Catalyzed Kinetic Resolutions. J Am Chem Soc 2017; 139:12441-12449. [DOI: 10.1021/jacs.7b01796] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Rajat Maji
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Steven E. Wheeler
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
- Center
for Computational Quantum Chemistry, Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
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