1
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Xie F, Mao Z, Curran DP, Liang H, Dai W. Facile Borylation of Alkenes, Alkynes, Imines, Arenes and Heteroarenes with N-Heterocyclic Carbene-Boranes and a Heterogeneous Semiconductor Photocatalyst. Angew Chem Int Ed Engl 2023; 62:e202306846. [PMID: 37555790 DOI: 10.1002/anie.202306846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 08/08/2023] [Accepted: 08/09/2023] [Indexed: 08/10/2023]
Abstract
Although the development of radical chain and photocatalytic borylation reactions using N-heterocyclic carbene (NHC)-borane as boron source is remarkable, the persistent problems, including the use of hazardous and high-energy radical initiators or the recyclability and photostability issues of soluble homogeneous photocatalysts, still leave great room for further development in a sustainable manner. Herein, we report a conceptually different approach toward highly functionalized organoborane synthesis by using recoverable ultrathin cadmium sulfide (CdS) nanosheets as a heterogeneous photocatalyst, and a general and mild borylation platform that enables regioselective borylation of a wide variety of alkenes (arylethenes, trifluoromethylalkenes, α,β-unsaturated carbonyl compounds and nitriles), alkynes, imines and electron-poor aromatic rings with NHC-borane as boryl radical precursor. Mechanistic studies and density functional theory (DFT) calculations reveal that both photogenerated electrons and holes on the CdS fully perform their own roles, thereby resulting in enhancement of photocatalytic activity and stability of CdS.
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Affiliation(s)
- Fukai Xie
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Zhan Mao
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15208, USA
| | - Hongliang Liang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Wen Dai
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
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2
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Li G, Huang G, Sun R, Curran DP, Dai W. Regioselective Radical Borylation of α,β-Unsaturated Esters and Related Compounds by Visible Light Irradiation with an Organic Photocatalyst. Org Lett 2021; 23:4353-4357. [PMID: 34003657 DOI: 10.1021/acs.orglett.1c01270] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Radical hydroboration reactions have only recently been reported and are still rare. Here we describe a photoredox radical hydroboration of α,β-unsaturated esters, amides, ketones, and nitriles with NHC-boranes that uses only an organocatalyst and visible light. The conditions are mild, the substrate scope is broad, and the α/β regioselectivity is high. The reaction requires only the organocatalyst; there is no costly metal, and there are no other additives (base, cocatalyst, initiator).
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Affiliation(s)
- Guosong Li
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Guanwang Huang
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Ruixia Sun
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
| | - Wen Dai
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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3
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Kawamoto T, Morioka T, Noguchi K, Curran DP, Kamimura A. Inverse Hydroboration of Imines with NHC-Boranes Is Promoted by Diphenyl Disulfide and Visible Light. Org Lett 2021; 23:1825-1828. [PMID: 33621108 DOI: 10.1021/acs.orglett.1c00230] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We describe a simple and efficient procedure for nucleophilic borylation of imines in the absence of a photoredox catalyst. Visible light irradiation of an acetonitrile solution of an imine, an NHC-borane, and diphenyl disulfide (10 mol %) provides various stable α-amino NHC-boranes in good yields. The reaction proceeds via addition of a nucleophilic boryl radical to an imine, followed by hydrogen abstraction from thiophenol, which is generated from NHC-borane and diphenyl disulfide.
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Affiliation(s)
- Takuji Kawamoto
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Tsubasa Morioka
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Kohki Noguchi
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Akio Kamimura
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
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4
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Takahashi K, Geib SJ, Maeda K, Curran DP, Taniguchi T. Radical trans-Hydroboration of Substituted 1,3-Diynes with an N-Heterocyclic Carbene Borane. Org Lett 2021; 23:1071-1075. [PMID: 33481616 DOI: 10.1021/acs.orglett.0c04284] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Monohydroboration of substituted 1,3-diynes with an N-heterocyclic carbene borane (NHC-borane) occurs under radical conditions using an azo initiator, such as ACCN and AIBN, and a thiol as a polarity-reversal catalyst. The reaction is highly regio- and stereoselective and provides stable NHC-(E)-alkynylalkenylboranes.
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Affiliation(s)
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | | | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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5
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Shimoi M, Watanabe T, Maeda K, Curran DP, Taniguchi T. Berichtigung: Radical
trans
‐Hydroboration of Alkynes with N‐Heterocyclic Carbene Boranes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202014353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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6
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Shimoi M, Watanabe T, Maeda K, Curran DP, Taniguchi T. Corrigendum: Radical
trans
‐Hydroboration of Alkynes with N‐Heterocyclic Carbene Boranes. Angew Chem Int Ed Engl 2020; 59:22824. [DOI: 10.1002/anie.202014353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Affiliation(s)
- Daniel A. Bolt
- Department of ChemistryUniversity of Pittsburgh Pittsburgh PA USA 15208
| | - Dennis P. Curran
- Department of ChemistryUniversity of Pittsburgh Pittsburgh PA USA 15208
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8
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Studer A, Curran DP. Happy Birthday to Bernd Giese. Adv Synth Catal 2020. [DOI: 10.1002/adsc.202000065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Armido Studer
- Organisch-Chemisches InstitutWestfälische Wilhelms-Universität orrensstrasse 40 48149 Münster Germany
| | - Dennis P. Curran
- Department of ChemistryUniversity of Pittsburgh Pittsburgh PA 15260 USA
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9
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Abstract
Reactions of N-heterocyclic carbene boranes (NHC-boranes) with electron-poor aromatic rings under photoredox conditions provide dearomatized 3-NHC-boryl-1,5-cycohexadienes, which are formally products of 1,4-hydroboration reactions. When regioisomers are possible, the more crowded (doubly ortho-substituted) product is formed preferably or exclusively. The mechanism may involve oxidation of the NHC-borane to an NHC-boryl radical, reduction of the electron-poor aromatic ring to a radical anion, coupling of the radical and the radical anion to give a cyclohexadienyl anion, and finally regioselective protonation.
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Affiliation(s)
- Wen Dai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
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10
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Abstract
The boron-centered radicals derived from alkenyl N-heterocyclic carbene (NHC)-boranes bearing ester substituents were recently found to ring close in 5-endo mode by addition to the oxygen atoms of the ester substituents. The inference from this was that NHC-boryl radicals might add intermolecularly to carbonyl-containing substrates. Several different NHC-boryl radicals were generated by H-atom abstraction from NHC-ligated trihydroborates. Electron paramagnetic resonance (EPR) spectroscopy proved that these did indeed add to the oxygen atoms of diaryl ketones with production of the corresponding bora-ketyl radicals. The same unusual regioselectivity of addition was observed with monoaryl ketones, but no bora-ketyls were observed with dialkyl ketones. Similarly, no bora-ketyl adduct radicals were observed with esters, even esters of benzoic acid. EPR spectroscopic evidence suggested that NHC-boryl radicals were also added to the O-atoms of aromatic aldehydes. Amine-boryl and phosphine-boryl radicals were also observed to add to the O-atom of benzophenone with production of the corresponding ketyl radicals.
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Affiliation(s)
- John C Walton
- EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
| | - Wen Dai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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11
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Takahashi K, Shimoi M, Watanabe T, Maeda K, Geib SJ, Curran DP, Taniguchi T. Revisiting Polyfluoroarenes as Radical Acceptors: Radical C–F Bond Borylation of Polyfluoroarenes with N-Heterocyclic Carbene Boranes and Synthesis of Borane-Containing Liquid Crystals. Org Lett 2020; 22:2054-2059. [DOI: 10.1021/acs.orglett.0c00481] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
| | | | | | | | - Steven J. Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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12
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Shimoi M, Kevlishvili I, Watanabe T, Maeda K, Geib SJ, Curran DP, Liu P, Taniguchi T. The Thermal Rearrangement of an NHC-Ligated 3-Benzoborepin to an NHC-Boranorcaradiene. Angew Chem Int Ed Engl 2020; 59:903-909. [PMID: 31670450 DOI: 10.1002/anie.201912234] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Indexed: 11/08/2022]
Abstract
An N-heterocyclic-carbene-ligated 3-benzoborepin with a bridged structure has been synthesized by double radical trans-hydroboration of benzo[3,4]cycloundec-3-ene-1,5-diyne with an N-heterocyclic carbene borane. The thermal reaction of the NHC-ligated borepin at 150 °C gives an isolable NHC-boranorcaradiene. Experiments and density functional theory calculations support a mechanism whereby the borepin initially rearranges to a boranorcaradiene by a thermal 6π-electrocyclic reaction. This is followed by 1,5-boron shift to give a rearranged boranorcaradiene. This shift occurs with stereoinversion at boron through a transition state with open-shell diradical character. This is the first example of the isolation of a boranorcaradiene from a thermal reaction of a borepin.
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Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Ilia Kevlishvili
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Takashi Watanabe
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
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13
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Shimoi M, Kevlishvili I, Watanabe T, Maeda K, Geib SJ, Curran DP, Liu P, Taniguchi T. The Thermal Rearrangement of an NHC‐Ligated 3‐Benzoborepin to an NHC‐Boranorcaradiene. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201912234] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology Kanazawa University Kakuma-machi Kanazawa 920-1192 Japan
| | - Ilia Kevlishvili
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Takashi Watanabe
- Graduate School of Natural Science and Technology Kanazawa University Kakuma-machi Kanazawa 920-1192 Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology Kanazawa University Kakuma-machi Kanazawa 920-1192 Japan
- Nano Life Science Institute (WPI-NanoLSI) Kanazawa University Kakuma-machi Kanazawa 920-1192 Japan
| | - Steven J. Geib
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Dennis P. Curran
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Peng Liu
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology Kanazawa University Kakuma-machi Kanazawa 920-1192 Japan
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14
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Dai W, Geib SJ, Curran DP. Facile Synthesis of α-N-Heterocyclic Carbene-Boryl Ketones from N-Heterocyclic Carbene-Boranes and Alkenyl Triflates. J Am Chem Soc 2019; 141:12355-12361. [DOI: 10.1021/jacs.9b05547] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Wen Dai
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
| | - Steven J. Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15208, United States
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15
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Shimoi M, Maeda K, Geib SJ, Curran DP, Taniguchi T. Esters as Radical Acceptors: β‐NHC‐Borylalkenyl Radicals Induce Lactonization by C−C Bond Formation/Cleavage on Esters. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
- Nano Life Science Institute (WPI-NanoLSI) Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Steven J. Geib
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Dennis P. Curran
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
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16
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Shimoi M, Maeda K, Geib SJ, Curran DP, Taniguchi T. Esters as Radical Acceptors: β‐NHC‐Borylalkenyl Radicals Induce Lactonization by C−C Bond Formation/Cleavage on Esters. Angew Chem Int Ed Engl 2019; 58:6357-6361. [DOI: 10.1002/anie.201902001] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Indexed: 01/22/2023]
Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
- Nano Life Science Institute (WPI-NanoLSI) Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Steven J. Geib
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Dennis P. Curran
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
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17
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Dai W, Geib SJ, Curran DP. Ring-Opening Reactions of NHC-Boriranes with In Situ Generated HCl: Synthesis of a New Class of NHC-Boralactones. J Am Chem Soc 2019; 141:3623-3629. [PMID: 30717598 DOI: 10.1021/jacs.8b13010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first ring-opening reactions of ligated boriranes (boracyclopropanes) are described. Treatment of readily available NHC-boriranes bearing ester substituents on the borirane ring with HCl provides stable γ-NHC-bora-γ-lactones in isolated yields ranging from 40% to 73%. The reactions occur through 1,3-addition of HCl across a B-C bond of the NHC-borirane to form a ring-opened NHC-boryl chloride, followed by lactonization with chloride displacement. Experimental evidence suggests that both the borirane ring-opening reaction and the boralactonization reaction occur with inversion at boron.
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Affiliation(s)
- Wen Dai
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15208 , United States
| | - Steven J Geib
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15208 , United States
| | - Dennis P Curran
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15208 , United States
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18
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Dai W, Curran DP, Walton JC. EPR and Preparative Studies of 5- endo Cyclizations of Radicals Derived from Alkenyl NHC-Boranes Bearing tert-Butyl Ester Substituents. J Org Chem 2019; 84:2102-2111. [PMID: 30663305 DOI: 10.1021/acs.joc.8b03112] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Radical H atom abstraction from a set of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two tert-butyl ester substituents was studied by EPR spectroscopy. The initial boraallyl radical intermediates rapidly ring closed onto the O atoms of their distal ester groups in 5- endo mode to yield 1,2-oxaborole radicals. Unexpectedly, two structural varieties of these radicals were identified from their EPR spectra. These proved to be two stable rotamers, in which the carbonyl group of the tert-butyl ester was oriented toward and away from the NHC ring. These rotamers were akin to the s- trans and s- cis rotamers of α,β-unsaturated carbonyl compounds. Their stability was attributed to the quasi-allylic interaction of their unpaired electrons with the carbonyl units of their adjacent ester groups. EPR spectroscopic evidence for two rotamers of the analogous methyl ester containing NHC-oxaborole radicals was also obtained. An improved synthetic procedure for preparing rare NHC-boralactones was developed involving treatment of the alkenyl NHC-boranes with AIBN and tert-dodecanethiol.
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Affiliation(s)
- Wen Dai
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Dennis P Curran
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - John C Walton
- EaStCHEM School of Chemistry , University of St. Andrews , St. Andrews , Fife KY16 9ST , United Kingdom
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19
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Bolt DA, Geib SJ, Curran DP. Synthesis and characterization of N-heterocyclic carbene complexes of 1,3,2-dioxaborolane-4,5-dione (NHC-boryl oxalates). Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.10.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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20
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Dai W, McFadden TR, Curran DP, Früchtl HA, Walton JC. 5- Endo Cyclizations of NHC-Boraallyl Radicals Bearing Ester Substituents: Characterization of Derived 1,2-Oxaborole Radicals and Boralactones. J Am Chem Soc 2018; 140:15868-15875. [PMID: 30369236 DOI: 10.1021/jacs.8b09288] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5- endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.
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Affiliation(s)
- Wen Dai
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Timothy R McFadden
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Dennis P Curran
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Herbert A Früchtl
- EaStCHEM School of Chemistry , University of St. Andrews , St. Andrews , Fife KY16 9ST , United Kingdom
| | - John C Walton
- EaStCHEM School of Chemistry , University of St. Andrews , St. Andrews , Fife KY16 9ST , United Kingdom
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21
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Yuan Y, Dong W, Gao X, Xie X, Curran DP, Zhang Z. Visible-Light-Induced Radical Cascade Cyclization: Synthesis of (20S
)-Camptothecin, SN-38 and Irinotecan. CHINESE J CHEM 2018. [DOI: 10.1002/cjoc.201800358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Yao Yuan
- Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering; Shanghai Jiao Tong University; 800 Dongchuan Road, Shanghai 200240 China
| | - Wuheng Dong
- Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering; Shanghai Jiao Tong University; 800 Dongchuan Road, Shanghai 200240 China
| | - Xiaoshuang Gao
- Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering; Shanghai Jiao Tong University; 800 Dongchuan Road, Shanghai 200240 China
| | - Xiaomin Xie
- Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering; Shanghai Jiao Tong University; 800 Dongchuan Road, Shanghai 200240 China
| | - Dennis P. Curran
- Department of Chemistry; University of Pittsburgh; Pittsburgh, Pennsylvania PA 15260 USA
| | - Zhaoguo Zhang
- Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering; Shanghai Jiao Tong University; 800 Dongchuan Road, Shanghai 200240 China
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22
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Dai W, Geib SJ, Curran DP. Reactions of N-Heterocyclic Carbene Boranes with 5-Diazo-2,2-dimethyl-1,3-dioxane-4,6-dione: Synthesis of Mono- and Bis-hydrazonyl NHC-Boranes. J Org Chem 2018; 83:8775-8779. [PMID: 30004702 DOI: 10.1021/acs.joc.8b01125] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Heterocyclic carbene boranes (NHC-boranes) react with 5-diazo-2,2-dimethyl-1,3-dioxane-4,6-dione at 40 °C in dichloromethane to provide NHC-boryl hydrazone derivatives of 2,2-dimethyl-1,3-dioxane-4,6-dione. These hydrazones disproportionate to bis-hydrazones on treatment with diiodine in dichloromethane at room temperature. The mono- and bis-hydrazones are yellow solids that are stable to chromatography and storage.
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Affiliation(s)
- Wen Dai
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Steven J Geib
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Dennis P Curran
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
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23
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Subervie D, Graff B, Nerkar S, Curran DP, Lalevée J, Lacôte E. Difluorination at Boron Leads to the First Electrophilic Ligated Boryl Radical (NHC‐BF
2
.
). Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806476] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Daniel Subervie
- Univ Lyon Université Claude Bernard Lyon 1 CNRS, CNES, ArianeGroup, LHCEP Bât. Raulin, 2 rue Victor Grignard 69622 Villeurbanne France
| | - Bernadette Graff
- Institut de Science des Matériaux de Mulhouse (IS2M), UMR CNRS 7361 Université de Haute Alsace 15 rue Jean Starcky 68057 Mulhouse France
| | - Swapnil Nerkar
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Dennis P. Curran
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Jacques Lalevée
- Institut de Science des Matériaux de Mulhouse (IS2M), UMR CNRS 7361 Université de Haute Alsace 15 rue Jean Starcky 68057 Mulhouse France
| | - Emmanuel Lacôte
- Univ Lyon Université Claude Bernard Lyon 1 CNRS, CNES, ArianeGroup, LHCEP Bât. Raulin, 2 rue Victor Grignard 69622 Villeurbanne France
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24
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Subervie D, Graff B, Nerkar S, Curran DP, Lalevée J, Lacôte E. Difluorination at Boron Leads to the First Electrophilic Ligated Boryl Radical (NHC-BF 2. ). Angew Chem Int Ed Engl 2018; 57:10251-10256. [PMID: 29928777 DOI: 10.1002/anie.201806476] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Indexed: 11/10/2022]
Abstract
1,3-Dimethylimidazol-2-ylidene difluoroborane (NHC-BF2 H) was prepared in a one-pot, two-step reaction from the parent ligated borane (NHC-BH3 ). The derived difluoroboryl radical (NHC-BF2. ) was generated by laser flash photolysis experiments and characterized by UV spectroscopy and rate-constant measurements. It is transient and reacts quickly with O2 . Unusually, it also reacts more rapidly with ethyl vinyl ether than with methyl acrylate. By this measure, it is the first electrophilic ligated boryl radical. Both NHC-BH3 and NHC-BF2 H serve as co-initiators in bulk photopolymerizations, converting both electron-poor and electron-rich monomers at roughly similar rates. However, the difluorinated coinitiator provides polymers with dramatically increased chain lengths from both monomers.
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Affiliation(s)
- Daniel Subervie
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, CNES, ArianeGroup, LHCEP, Bât. Raulin, 2 rue Victor Grignard, 69622, Villeurbanne, France
| | - Bernadette Graff
- Institut de Science des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute Alsace, 15 rue Jean Starcky, 68057, Mulhouse, France
| | - Swapnil Nerkar
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Jacques Lalevée
- Institut de Science des Matériaux de Mulhouse (IS2M), UMR CNRS 7361, Université de Haute Alsace, 15 rue Jean Starcky, 68057, Mulhouse, France
| | - Emmanuel Lacôte
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, CNES, ArianeGroup, LHCEP, Bât. Raulin, 2 rue Victor Grignard, 69622, Villeurbanne, France
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25
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Shimoi M, Watanabe T, Maeda K, Curran DP, Taniguchi T. Radical trans-Hydroboration of Alkynes with N-Heterocyclic Carbene Boranes. Angew Chem Int Ed Engl 2018; 57:9485-9490. [PMID: 29845716 DOI: 10.1002/anie.201804515] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/28/2018] [Indexed: 01/06/2023]
Abstract
Hydroboration of internal alkynes with N-heterocyclic carbene boranes (NHC-boranes) occurs to provide stable NHC (E)-alkenylboranes upon thermolysis in the presence of di-tert-butyl peroxide. The E isomer results from an unusual trans-hydroboration, and the E/Z selectivity is typically high (90:10 or greater). Evidence suggests that this hydroboration occurs by a radical-chain reaction involving addition of an NHC-boryl radical to an alkyne to give a β-NHC-borylalkenyl radical. Ensuing hydrogen abstraction from the starting NHC-borane provides the product and returns the starting NHC-boryl radical. Experiments suggest that the observed trans-selectivity results from kinetic control in the hydrogen-transfer reaction.
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Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Takashi Watanabe
- School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.,School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
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26
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Shimoi M, Watanabe T, Maeda K, Curran DP, Taniguchi T. Radical trans
-Hydroboration of Alkynes with N-Heterocyclic Carbene Boranes. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804515] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Masaki Shimoi
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
| | - Takashi Watanabe
- School of Pharmaceutical Sciences; Institute of Medical, Pharmaceutical and Health Sciences; Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
- Nano Life Science Institute (WPI-NanoLSI); Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
| | - Dennis P. Curran
- Department of Chemistry; University of Pittsburgh; Pittsburgh PA 15260 USA
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
- School of Pharmaceutical Sciences; Institute of Medical, Pharmaceutical and Health Sciences; Kanazawa University; Kakuma-machi Kanazawa 920-1192 Japan
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27
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Kawamoto T, Shimaya Y, Curran DP, Kamimura A. Tris(trimethylsilyl)silane-mediated Reductive Decyanation and Cyano Transfer Reactions of Malononitriles. CHEM LETT 2018. [DOI: 10.1246/cl.171231] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Takuji Kawamoto
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Yudai Shimaya
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Akio Kamimura
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
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28
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Affiliation(s)
- Takuji Kawamoto
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Kyohei Oritani
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Akio Kamimura
- Department of Applied Chemistry, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
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29
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Allen TH, Horner AR, Geib SJ, Weber SG, Curran DP. Synthesis, Structure, and Acidity Constants of Ligated α-Boryl Acetic Acids. Chemistry 2018; 24:822-825. [PMID: 29207202 DOI: 10.1002/chem.201705754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Indexed: 11/09/2022]
Abstract
Basic hydrolyses of various ligated α-boryl acetic acid esters provided the first ligated derivatives of the unknown compound boroacetic acid (BH2 CH2 CO2 H). Four monoacids (L-BH2 CH2 CO2 H) and one diacid (L-BH(CH2 CO2 H)2 ) were prepared with N-heterocyclic carbene, amine, and pyridine ligands (L). The stable acids were characterized by X-ray crystallography and acidity constant (pKa ) measurements. They rank among the least acidic of all known carboxylic acids. In turn, their conjugate bases are among the strongest of all carboxylates.
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Affiliation(s)
- Thomas H Allen
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Anthony R Horner
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Stephen G Weber
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
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30
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Abstract
Three-member ring boracyclopropanes (boriranes) with N-heterocyclic carbene substituents were prepared by a recently discovered route. H atoms were selectively abstracted from the boron atoms by t-butoxyl radicals and this enabled boriranyl radicals to be detected and characterized by EPR spectroscopy for the first time. Their EPR parameters indicated they had planar π-character. From competition experiments, the rate constant for H atom abstraction was determined and found to be about 2 orders of magnitude less than for NHC-boranes. The B-H BDE of an NHC-borirane was estimated to be about 95 kcal mol-1.
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Affiliation(s)
- John C Walton
- EaStCHEM School of Chemistry, University of St. Andrews , St. Andrews, Fife KY16 9ST, United Kingdom
| | - Timothy R McFadden
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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31
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Watanabe T, Geib SJ, Curran DP, Taniguchi T. N-Heterocyclic Carbene Boranes are Hydrogen Donors in Masamune-Bergman Reactions of Benzo[3,4]cyclodec-3-ene-1,5-diynes. J Org Chem 2017; 82:13034-13042. [PMID: 29120175 DOI: 10.1021/acs.joc.7b01981] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thermal reactions of benzo[3,4]cyclodec-3-ene-1,5-diyne with N-heterocyclic carbene boranes (NHC-boranes) provided mixtures of 9-borylated 1,2,3,4-tetrahydroanthracenes along with 1,2,3,4-tetrahydroanthracene. These products indicate that NHC-boranes serve as hydrogen donors to a p-benzyne intermediate formed by the Masamune-Bergman reaction. Experimental results support a radical mechanism in nonpolar solvents, but suggest that ionic mechanisms compete in the production of 1,2,3,4-tetrahydroanthracene when the reaction is performed in a polar solvent.
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Affiliation(s)
- Takashi Watanabe
- School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Kakuma-machi, Kanazawa 920-1192, Japan
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Tsuyoshi Taniguchi
- School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Kakuma-machi, Kanazawa 920-1192, Japan
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32
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Abstract
1-Butyl-3-methylimidazol-2-ylidene borane has been synthesized directly from two inexpensive commercial reagents: 1-butyl-3-methylimidazolium bromide and sodium borohydride. This NHC-borane reagent is a stable, free-flowing liquid that shows promise for use in radical, ionic, and metal-catalyzed reactions.
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Affiliation(s)
- Daniel A Bolt
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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33
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Stone OD, Duckworth AD, Curran DP, Ballantyne JA, Brenkel IJ. Severe arthritis predicts greater improvements in function following total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2017; 25:2573-2579. [PMID: 26441252 DOI: 10.1007/s00167-015-3806-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 09/22/2015] [Indexed: 12/27/2022]
Abstract
PURPOSE Although excellent outcomes are routinely reported following total knee replacement, up to 20 % of patients remain dissatisfied. The aim of this study was to determine whether pre-operative radiographic classification was associated with functional outcomes following surgery. METHODS A retrospective review of a prospective arthroplasty database identified 256 patients that fulfilled the inclusion criteria over an 18-month period. Baseline demographic data on all patients were collected prospectively. All pre-operative radiographs were assessed using the Kellgren and Lawrence (K&L) classification system. Patients were prospectively assessed using the American Knee Society Score pre-operatively and at 1, 3 and 5 years post-surgery. RESULTS An association was found between the pre-operative radiographic severity of arthritis and the pre-operative American Knee Society Knee (AKSK) scores, with worsening radiographic grade corresponding to worsening AKSK scores (p = 0.020). There was an association between K&L classification and improvement in AKSK scores from pre-operative to 1 year (p = 0.003) and 3 years (p = 0.04), with K&L grades 3 and 4 demonstrating the most significant improvements. On multivariate regression analysis, K&L classification was the only significant predictor of improvement in AKSK at 1 year (p = 0.009). No correlation was found between K&L grade and the American Knee Society Functional Scores at any stage. CONCLUSIONS The results of this study may help to improve satisfaction rates in total knee replacement by targeting treatment. Patients can be counselled that although radiographic severity of arthritic changes can predict knee-specific functional improvement, the extent of their global functional improvement cannot. LEVEL OF EVIDENCE IV.
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Affiliation(s)
- O D Stone
- Edinburgh Royal Infirmary, Edinburgh, Scotland, UK.
| | | | - D P Curran
- Victoria Hospital Kirkcaldy, Fife, Scotland, UK
| | | | - I J Brenkel
- Victoria Hospital Kirkcaldy, Fife, Scotland, UK
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34
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Allen TH, Kawamoto T, Gardner S, Geib SJ, Curran DP. N-Heterocyclic Carbene Boryl Iodides Catalyze Insertion Reactions of N-Heterocyclic Carbene Boranes and Diazoesters. Org Lett 2017. [PMID: 28641014 DOI: 10.1021/acs.orglett.7b01777] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Boron-hydrogen bond insertion reactions of N-heterocyclic carbene (NHC) boranes and diazoesters can be catalyzed by NHC-boryl iodides and produce stable α-NHC-boryl esters. The conditions of the reaction resemble the previous rhodium-catalyzed transformations (only the catalyst is different); however, the mechanisms of the two reactions are probably very different. The new boryl iodide catalyzed method is adept at producing α-substituted-α-NHC-boryl esters, and this has led to a family of NHC-boryl esters with amino acid and amino-acid-like side chains.
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Affiliation(s)
- Thomas H Allen
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Takuji Kawamoto
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Sean Gardner
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Steven J Geib
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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35
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Watanabe T, Hirose D, Curran DP, Taniguchi T. Frontispiece: Borylative Radical Cyclizations of Benzo[3,4]cyclodec‐3‐ene‐1,5‐diynes and N‐Heterocyclic Carbene‐Boranes. Chemistry 2017. [DOI: 10.1002/chem.201782362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takashi Watanabe
- School of Pharmaceutical Sciences Institute of Medical, Pharmaceutical and Health Sciences Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Daisuke Hirose
- Graduate School of Natural Science and Technology Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
| | - Dennis P. Curran
- Department of Chemistry University of Pittsburgh Pittsburgh PA 15260 USA
| | - Tsuyoshi Taniguchi
- School of Pharmaceutical Sciences Institute of Medical, Pharmaceutical and Health Sciences Kanazawa University, Kakuma-machi Kanazawa 920-1192 Japan
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36
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Watanabe T, Hirose D, Curran DP, Taniguchi T. Borylative Radical Cyclizations of Benzo[3,4]cyclodec-3-ene-1,5-diynes and N-Heterocyclic Carbene-Boranes. Chemistry 2017; 23:5404-5409. [PMID: 28205265 DOI: 10.1002/chem.201700689] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Indexed: 11/09/2022]
Abstract
Borylative radical cyclization of benzo[3,4]cyclodec-3-ene-1,5-diynes to provide 5-borylated 6,7,8,9-tetrahydrobenzo[a]azulenes has been developed. The experimental results suggest that the reaction proceeds by a radical chain mechanism, in which di-tert-butyl hyponitrite (TBHN) works as a good radical initiator to form boryl radicals from N-heterocyclic carbene-boranes (NHC-boranes). The present reaction is a rare model that illustrates addition of boryl radicals to alkynes.
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Affiliation(s)
- Takashi Watanabe
- School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Daisuke Hirose
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Tsuyoshi Taniguchi
- School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan
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37
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McFadden TR, Fang C, Geib SJ, Merling E, Liu P, Curran DP. Synthesis of Boriranes by Double Hydroboration Reactions of N-Heterocyclic Carbene Boranes and Dimethyl Acetylenedicarboxylate. J Am Chem Soc 2017; 139:1726-1729. [DOI: 10.1021/jacs.6b09873] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Timothy R. McFadden
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Cheng Fang
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Steven J. Geib
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Everett Merling
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Peng Liu
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P. Curran
- Department of Chemistry and ‡Computational Modeling & Simulation Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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38
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Affiliation(s)
- Thomas H. Allen
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Steven J. Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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39
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Clark AJ, Curran DP, Fox DJ, Ghelfi F, Guy CS, Hay B, James N, Phillips JM, Roncaglia F, Sellars PB, Wilson P, Zhang H. Axially Chiral Enamides: Substituent Effects, Rotation Barriers, and Implications for their Cyclization Reactions. J Org Chem 2016; 81:5547-65. [PMID: 27267662 DOI: 10.1021/acs.joc.6b00889] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The barrier to rotation around the N-alkenyl bond of 38 N-alkenyl-N-alkylacetamide derivatives was measured (ΔG(⧧) rotation varied between <8.0 and 31.0 kcal mol(-1)). The most important factor in controlling the rate of rotation was the level of alkene substitution, followed by the size of the nitrogen substituent and, finally, the size of the acyl substituent. Tertiary enamides with four alkenyl substituents exhibited half-lives for rotation between 5.5 days and 99 years at 298 K, sufficient to isolate enantiomerically enriched atropisomers. The radical cyclizations of a subset of N-alkenyl-N-benzyl-α-haloacetamides exhibiting relatively high barriers to rotation round the N-alkenyl bond (ΔG(⧧) rotation >20 kcal mol(-1)) were studied to determine the regiochemistry of cyclization. Those with high barriers (>27 kcal mol(-1)) did not lead to cyclization, but those with lower values produced highly functionalized γ-lactams via a 5-endo-trig radical-polar crossover process that was terminated by reduction, an unusual cyclopropanation sequence, or trapping with H2O, depending upon the reaction conditions. Because elevated temperatures were necessary for cyclization, this precluded study of the asymmetric transfer in the reaction of individual atropisomers. However, enantiomerically enriched atropsiomeric enamides should be regarded as potential asymmetric building blocks for reactions that can be accomplished at room temperature.
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Affiliation(s)
- Andrew J Clark
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh Pennsylvania 15260, United States
| | - David J Fox
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Franco Ghelfi
- Dipartmento di Scienze Chimiche e Geologiche, Univerita degli Studi di Modena e Reggio Emilia , Via Campi 103, 41125 Modena, Italy
| | - Collette S Guy
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Benjamin Hay
- Department of Chemistry, University of Pittsburgh , Pittsburgh Pennsylvania 15260, United States
| | - Natalie James
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Jessica M Phillips
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Fabrizio Roncaglia
- Dipartmento di Scienze Chimiche e Geologiche, Univerita degli Studi di Modena e Reggio Emilia , Via Campi 103, 41125 Modena, Italy
| | - Philip B Sellars
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Paul Wilson
- Department of Chemistry, University of Warwick , Coventry, West Midlands CV4 7AL, U.K
| | - Hanmo Zhang
- Department of Chemistry, University of Pittsburgh , Pittsburgh Pennsylvania 15260, United States
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Curran DP, McFadden TR. Understanding Initiation with Triethylboron and Oxygen: The Differences between Low-Oxygen and High-Oxygen Regimes. J Am Chem Soc 2016; 138:7741-52. [PMID: 27243276 DOI: 10.1021/jacs.6b04014] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A unified kinetic theory for both initiation and autoxidation reactions of Et3B and O2 is put forth, and then divided into low-oxygen and high-oxygen experimental regimes for application of Et3B/O2 as an initiating system. In the low-oxygen regime, only long, efficient chains can be initiated. In the high-oxygen regime, less efficient chains can be initiated but they must compete with autoxidation. We apply the analysis along with new experimental results to show why AIBN and Et3B/O2 give different stereochemical results in hydrostannation reactions of propargyl silyl ethers. Counterintuitively, AIBN is the better initiator, initiating both the rapid chain hydrostannation and the subsequent slow E/Z isomerization. AIBN gives the thermodynamic results. Et3B/O2 is the poorer initiator, initiating only the hydrostannation and not the isomerization. Et3B gives the kinetic result. We further apply the analysis to understand recent results in Et3B/water reductions.
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Affiliation(s)
- Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Timothy R McFadden
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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41
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Allen TH, Curran DP. Relative Reactivity of Stable Ligated Boranes and a Borohydride Salt in Rhodium(II)-Catalyzed Boron-Hydrogen Insertion Reactions. J Org Chem 2016; 81:2094-8. [PMID: 26871613 DOI: 10.1021/acs.joc.6b00091] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Relative reactivities of a series of neutral ligated boranes L-BH3 (where L is NHC, amine, pyridine, or phosphine) and the cyanoborohydride anion have been assessed in Rh(II)-catalyzed B-H insertion reactions with methyl 2-phenyl-2-diazoacetate. Stable α-boryl ester products were isolated by flash chromatography in all cases except for the salt product from cyanoborohydride. All of the substrates were either comparable to or more reactive than 1,4-cyclohexadiene, which is one of the most reactive substrates in C-H insertion reactions. The range of reactivity between the most reactive pyridine-borane and the least reactive phosphine-borane is a factor of approximately 40.
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Affiliation(s)
- Thomas H Allen
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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42
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Zhang H, Hay EB, Geib SJ, Curran DP. Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides. Beilstein J Org Chem 2015; 11:1649-55. [PMID: 26664585 PMCID: PMC4660904 DOI: 10.3762/bjoc.11.181] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 08/27/2015] [Indexed: 11/23/2022] Open
Abstract
Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration/fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3-dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles.
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Affiliation(s)
- Hanmo Zhang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - E Ben Hay
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Stephen J Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
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44
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Gardner S, Kawamoto T, Curran DP. Synthesis of 1,3-Dialkylimidazol-2-ylidene Boranes from 1,3-Dialkylimidazolium Iodides and Sodium Borohydride. J Org Chem 2015; 80:9794-7. [PMID: 26334670 DOI: 10.1021/acs.joc.5b01682] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1,3-Dialkylimidazol-2-ylidene boranes have been made in moderate yields (typically 23-53%) from the corresponding N-alkyl imidazole, an alkylating agent (usually MeI), and sodium borohydride (NaBH4). The two-step, one-pot reaction sequence takes about 1 day to perform. The reagents are inexpensive, and the reactions are easy to conduct. The synthesis of 1,3-dimethylimidazol-2-ylidene borane has been conducted on scales up to 100 mmol and is especially convenient because the pure product can be isolated by direct recrystallization from water.
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Affiliation(s)
- Sean Gardner
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Takuji Kawamoto
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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45
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Abstract
Readily available NHC-arylboranes (NHC-BH2Ar) are converted in high yield to stable NHC-difluoro(aryl)boranes (NHC-BF2Ar) by treatment with 2 equiv of 1-chloromethyl-4-fluoro-1,4-diazonia-bicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor). In turn, the NHC-difluoro(aryl)boranes participate directly in Suzuki reactions under conditions previously used for anionic trifluoroborate salts. Accordingly, NHC-difluoroboranes are a new class of stable precursors for Suzuki reactions.
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Affiliation(s)
- Swapnil Nerkar
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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46
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Watanabe T, Curran DP, Taniguchi T. Hydroboration of Arynes Formed by Hexadehydro-Diels–Alder Cyclizations with N-Heterocyclic Carbene Boranes. Org Lett 2015; 17:3450-3. [DOI: 10.1021/acs.orglett.5b01480] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Takashi Watanabe
- School of Pharmaceutical
Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Tsuyoshi Taniguchi
- School of Pharmaceutical
Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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47
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Kawamoto T, Geib SJ, Curran DP. Radical Reactions of N-Heterocyclic Carbene Boranes with Organic Nitriles: Cyanation of NHC-Boranes and Reductive Decyanation of Malononitriles. J Am Chem Soc 2015; 137:8617-22. [DOI: 10.1021/jacs.5b04677] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Takuji Kawamoto
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Steven J. Geib
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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48
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Abstract
The electron is an efficient catalyst for conducting various types of radical cascade reaction that proceed by way of radical and radical ion intermediates. But because electrons are omnipresent, catalysis by electrons often passes unnoticed. In this Review, a simple analogy between acid/base catalysis and redox catalysis is presented. Conceptually, the electron is a catalyst in much the same way that a proton is a catalyst. The 'electron is a catalyst' paradigm unifies mechanistically an assortment of synthetic transformations that otherwise have little or no apparent relationship. Diverse radical cascades, including unimolecular radical substitution reactions (SRN1-type chemistry), base-promoted homolytic aromatic substitutions (BHAS), radical Heck-type reactions, radical cross-dehydrogenative couplings (CDC), direct arene trifluoromethylations and radical alkoxycarbonylations, can all be viewed as electron-catalysed reactions.
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Affiliation(s)
- Armido Studer
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
| | - Dennis P Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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49
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Damodaran K, Li X, Pan X, Curran DP. Dynamic Behavior of N-Heterocyclic Carbene Boranes: Boron–Carbene Bonds in B,B-Disubstituted N,N-Dimethylimidazol-2-ylidene Boranes Have Substantial Rotation Barriers. J Org Chem 2015; 80:4465-9. [DOI: 10.1021/acs.joc.5b00324] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Krishnan Damodaran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Xiben Li
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Xiangcheng Pan
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Dennis P. Curran
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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Abstract
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1,1-Divinyl-2-phenylcyclopropanes
are entry points to a rich area
of rearrangement chemistry. With N,N-diallyl amide
substrates, tandem radical cyclizations can be initiated at room temperature.
Warming provides products of pure thermal rearrangements with acids,
ester, and amides. These isomerizations give vinylcyclopentenes resulting
from divinylcyclopropane rearrangements and more deeply rearranged
tricyclic spirolactams resulting from aromatic Cope rearrangements
followed by ene reactions. Conversion of the carbonyl group to an
alcohol or ether opens retro-ene pathways followed by either tautomerization
or Claisen rearrangement.
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Affiliation(s)
- E Ben Hay
- Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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