1
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Iqbal SA, Millet CRP, Pahl J, Yuan K, Ingleson MJ. Two Directing Groups Used for Metal Catalysed Meta-C-H Functionalisation Only Effect Ortho Electrophilic C-H Borylation. European J Org Chem 2022; 2022:e202200901. [PMID: 36636663 PMCID: PMC9828458 DOI: 10.1002/ejoc.202200901] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 10/20/2022] [Indexed: 01/16/2023]
Abstract
Two templates used in meta-directed C-H functionalisation under metal catalysis do not direct meta-C-H borylation under electrophilic borylation conditions. Using BCl3 only Lewis adduct formation with Lewis basic sites in the template is observed. While combining BBr3 and the template containing an amide linker only led to amide directed ortho C-H borylation, with no pyridyl directed meta borylation. The amide directed borylation is selective for the ortho borylation of the aniline derived unit in the template, with no ortho borylation of the phenylacetyl ring - which would also form a six membered boracycle - observed. In the absence of other aromatics amide directed ortho borylation on to phenylacetyl rings can be achieved. The absence of meta-borylation using two templates indicates a higher barrier to pyridyl directed meta borylation relative to amide directed ortho borylation and suggests that bespoke templates for enabling meta-directed electrophilic borylation may be required.
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Affiliation(s)
- Saqib A Iqbal
- EaStCHEM School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Clement R P Millet
- EaStCHEM School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Jürgen Pahl
- EaStCHEM School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Kang Yuan
- EaStCHEM School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Michael J Ingleson
- EaStCHEM School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
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2
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Rej S, Chatani N. Regioselective Transition‐Metal‐Free C(sp
2
)−H Borylation: A Subject of Practical and Ongoing Interest in Synthetic Organic Chemistry. Angew Chem Int Ed Engl 2022; 61:e202209539. [DOI: 10.1002/anie.202209539] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Indexed: 12/22/2022]
Affiliation(s)
- Supriya Rej
- Department of Applied Chemistry Faculty of Engineering and Research Center for Environmental Preservation Osaka University Suita, Osaka 565-0871 Japan
- Institut für Chemie Technische Universität Berlin Strasse des 17. Juni 115 10623 Berlin Germany
| | - Naoto Chatani
- Department of Applied Chemistry Faculty of Engineering and Research Center for Environmental Preservation Osaka University Suita, Osaka 565-0871 Japan
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3
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Rej S, Chatani N. Regio‐Selective Transition‐Metal‐Free C(sp2)‒H Borylation: A Subject of Practical and Ongoing Interest in Synthetic Organic Chemistry. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202209539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Supriya Rej
- Osaka University School of Engineering Graduate School of Engineering: Osaka Daigaku Kogakubu Daigakuin Kogaku Kenkyuka Applied Chemistry JAPAN
| | - Naoto Chatani
- Osaka University School of Engineering Graduate School of Engineering: Osaka Daigaku Kogakubu Daigakuin Kogaku Kenkyuka Applied Chemistry 2-1 Yamadaoka 566-0871 Suita, Osaka JAPAN
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4
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Wu G, Yang Z, Xu X, Hao L, Chen L, Wang Y, Ji Y. Metal-Free Boron-Mediated ortho-C-H Hydroxylation of N-Benzyl-3,4,5-tribromopyrazoles. Org Lett 2022; 24:3570-3575. [PMID: 35512319 DOI: 10.1021/acs.orglett.2c01347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel route has been reported for C-H hydroxylation of benzyl compounds directed by a 3,4,5-tribromopyrazole auxiliary via boronation/oxidation using BBr3 and NaBO3·4H2O. The strategy exhibits outstanding site selectivity and affords the corresponding phenols in moderate to excellent yields under metal-free conditions. Besides, this protocol can be achieved in one pot, which is highly promising as a practical method for use in a multistep organic synthetic process.
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Affiliation(s)
- Gaorong Wu
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Zhaoziyuan Yang
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Xiaobo Xu
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Liqiang Hao
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Lu Chen
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Yangyang Wang
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
| | - Yafei Ji
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
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5
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Yuan K, Volland D, Kirschner S, Uzelac M, Nichol GS, Nowak-Król A, Ingleson MJ. Enhanced N-directed electrophilic C-H borylation generates BN-[5]- and [6]helicenes with improved photophysical properties. Chem Sci 2022; 13:1136-1145. [PMID: 35211280 PMCID: PMC8790800 DOI: 10.1039/d1sc06513k] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 12/31/2021] [Indexed: 12/11/2022] Open
Abstract
Helicenes are chiral polycyclic aromatic hydrocarbons (PAHs) of significant interest, e.g. in supramolecular chemistry, materials science and asymmetric catalysis. Herein an enhanced N-directed electrophilic C-H borylation methodology has been developed that provides access to azaborine containing helicenes (BN-helicenes). This borylation process proceeds via protonation of an aminoborane with bistriflimidic acid. DFT calculations reveal the borenium cation formed by protonation to be more electrophilic than the product derived from aminoborane activation with BBr3. The synthesised helicenes include BN-analogues of archetypal all carbon [5]- and [6]helicenes. The replacement of a CC with a BN unit (that has a longer bond) on the outer helix increases the strain in the BN congeners and the racemization half-life for a BN-[5]helicene relative to the all carbon [5]helicene. BN incorporation also increases the fluorescence efficiency of the helicenes, a direct effect of BN incorporation altering the distribution of the key frontier orbitals across the helical backbone relative to carbo-helicenes.
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Affiliation(s)
- Kang Yuan
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Daniel Volland
- Institut für Anorganische Chemie, Institute for Sustainable Chemistry and Catalysis with Boron Universität Würzburg Am Hubland 97074 Würzburg Germany
- Institut für Organische Chemie & Center for Nanosystems Chemistry, Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Sven Kirschner
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Marina Uzelac
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Gary S Nichol
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Agnieszka Nowak-Król
- Institut für Anorganische Chemie, Institute for Sustainable Chemistry and Catalysis with Boron Universität Würzburg Am Hubland 97074 Würzburg Germany
- Institut für Organische Chemie & Center for Nanosystems Chemistry, Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Michael J Ingleson
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
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6
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Yamazaki K, Rej S, Ano Y, Chatani N. Origin of the Enhanced Reactivity in the ortho C-H Borylation of Benzaldehydes with BBr 3. Org Lett 2021; 24:213-217. [PMID: 34939820 DOI: 10.1021/acs.orglett.1c03829] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The metal-free ortho C-H borylation of benzaldehyde derivatives using a transient imine directing group was recently developed by our group, providing an efficient strategy for the synthesis of organoboron reagents. Herein, we report on an extensive investigation of the reaction mechanism using density functional theory (DFT) calculations. Computations for the reaction pathway with various imine substrates, as well as the effect of an added base were examined, and the experimentally observed reactivity enhancement is proposed to originate from the tunability of the destabilizing strain energies that results in a reversible complexation process with BBr3.
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Affiliation(s)
- Ken Yamazaki
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Supriya Rej
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yusuke Ano
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Naoto Chatani
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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7
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Lv J, Zhang XJ, Wang M, Zhao Y, Shi Z. BBr 3 -Mediated P(III)-Directed C-H Borylation of Phosphines. Chemistry 2021; 28:e202104100. [PMID: 34878200 DOI: 10.1002/chem.202104100] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Indexed: 01/09/2023]
Abstract
Transition-metal-catalyzed C-H borylation has been widely used in the preparation of organoboron compounds. Here, we developed a general protocol on metal-free P(III)-directed C-H borylation of phosphines mediated by BBr3 , resulting in the formation of products bearing both phosphorus and boron. The development of the metal-free strategy to mimic previous metallic processes has shown low cost, superior practicality, and environmental friendliness. Density functional theory (DFT) calculations demonstrate the preferred pathway for this metal-free directed C-H borylation process.
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Affiliation(s)
- Jiahang Lv
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Xue-Jun Zhang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China.,Department of Orthopedic Surgery, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, 210093, P. R. China
| | - Minyan Wang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Zhuangzhi Shi
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, P. R. China.,School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan, 453007, P. R. China
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8
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Shigeno M, Imamatsu M, Kai Y, Kiriyama M, Ishida S, Nozawa-Kumada K, Kondo Y. Construction of 1,2,3-Benzodiazaborole by Electrophilic Borylation of Azobenzene and Nucleophilic Dialkylative Cyclization. Org Lett 2021; 23:8023-8027. [PMID: 34613748 DOI: 10.1021/acs.orglett.1c03033] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
1,2,3-Benzodiazaboroles can be conveniently prepared from azobenzenes by a two-step protocol involving electrophilic ortho-borylation with BBr3 and dialkylative cyclization with the Grignard reagent. The methodology provides a diverse range of products equipped with functionalities from azobenzenes containing substituents (Me, t-Bu, F, Cl, Br, I, and OCF3) and a series of Grignard reagents (alkyl- and arylmagnesium reagents). Moreover, this study displays the moderate aromaticity of the B-N-N-containing five-membered ring and mechanistic investigations of the cyclization reaction.
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Affiliation(s)
- Masanori Shigeno
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
| | - Masaya Imamatsu
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
| | - Yusuke Kai
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
| | - Moe Kiriyama
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
| | - Shintaro Ishida
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
| | - Kanako Nozawa-Kumada
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
| | - Yoshinori Kondo
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai 980-8578, Japan
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9
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Iqbal SA, Yuan K, Cid J, Pahl J, Ingleson MJ. Controlling selectivity in N-heterocycle directed borylation of indoles. Org Biomol Chem 2021; 19:2949-2958. [PMID: 33725086 DOI: 10.1039/d1ob00018g] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Electrophilic borylation of indoles with BX3 (X = Cl or Br) using directing groups installed at N1 can proceed at the C2 or the C7 position. The six membered heterocycle directing groups utilised herein, pyridines and pyrimidine, result in indole C2 borylation being the dominant outcome (in the absence of a C2-substituent). In contrast, C7 borylation was achieved using five membered heterocycle directing groups, such as thiazole and benzoxazole. Calculations on the borylation of indole substituted with a five (thiazole) and a six (pyrimidine) membered heterocycle directing group indicated that borylation proceeds via borenium cations with arenium cation formation having the highest barrier in both cases. The C7 borylated isomer was calculated to be the thermodynamically favoured product with both five and six membered heterocycle directing groups, but for pyrimidine directed indole borylation the C2 product was calculated to be the kinetic product. This is in contrast to thiazole directed indole borylation with BCl3 where the C7 borylated isomer is the kinetic product too. Thus, heterocycle ring size is a useful way to control C2 vs. C7 selectivity in N-heterocycle directed indole C-H borylation.
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Affiliation(s)
- S A Iqbal
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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10
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Wang ZJ, Chen X, Wu L, Wong JJ, Liang Y, Zhao Y, Houk KN, Shi Z. Metal-Free Directed C-H Borylation of Pyrroles. Angew Chem Int Ed Engl 2021; 60:8500-8504. [PMID: 33449421 DOI: 10.1002/anie.202016573] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/12/2021] [Indexed: 01/08/2023]
Abstract
Robust strategies to enable the rapid construction of complex organoboronates in selective, practical, low-cost, and environmentally friendly modes remain conspicuously underdeveloped. Here, we develop a general strategy for the site-selective C-H borylation of pyrroles by using only BBr3 directed by pivaloyl groups, avoiding the use of any metal. The site-selectivity is generally dominated by chelation and electronic effects, thus forming diverse C2-borylated pyrroles against the steric effect. The formed products can readily engage in downstream transformations, enabling a step-economic process to access drugs such as Lipitor. DFT calculations (wB97X-D) demonstrate the preferred positional selectivity of this reaction.
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Affiliation(s)
- Zheng-Jun Wang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
| | - Xiangyang Chen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Lei Wu
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
| | - Jonathan J Wong
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Yong Liang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
| | - Kendall N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Zhuangzhi Shi
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China
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11
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Wang Z, Chen X, Wu L, Wong JJ, Liang Y, Zhao Y, Houk KN, Shi Z. Metal‐Free Directed C−H Borylation of Pyrroles. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202016573] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Zheng‐Jun Wang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC) School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China
| | - Xiangyang Chen
- Department of Chemistry and Biochemistry University of California Los Angeles CA 90095 USA
| | - Lei Wu
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC) School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China
| | - Jonathan J. Wong
- Department of Chemistry and Biochemistry University of California Los Angeles CA 90095 USA
| | - Yong Liang
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC) School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC) School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China
| | - Kendall N. Houk
- Department of Chemistry and Biochemistry University of California Los Angeles CA 90095 USA
| | - Zhuangzhi Shi
- State Key Laboratory of Coordination Chemistry, Chemistry and Biomedicine Innovation Center (ChemBIC) School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China
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12
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Iashin V, Berta D, Chernichenko K, Nieger M, Moslova K, Pápai I, Repo T. Metal-Free C-H Borylation of N-Heteroarenes by Boron Trifluoride. Chemistry 2020; 26:13873-13879. [PMID: 32478432 PMCID: PMC7702085 DOI: 10.1002/chem.202001436] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 05/28/2020] [Indexed: 01/08/2023]
Abstract
Organoboron compounds are essential reagents in modern C-C coupling reactions. Their synthesis via catalytic C-H borylation by main group elements is emerging as a powerful tool alternative to transition metal based catalysis. Herein, a straightforward metal-free synthesis of aryldifluoroboranes from BF3 and heteroarenes is reported. The reaction is assisted by sterically hindered amines and catalytic amounts of thioureas. According to computational studies the reaction proceeds via frustrated Lewis pair (FLP) mechanism. The obtained aryldifluoroboranes are further stabilized against destructive protodeborylation by converting them to the corresponding air stable tetramethylammonium organotrifluoroborates.
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Affiliation(s)
- Vladimir Iashin
- Department of ChemistryUniversity of HelsinkiA. I. Virtasen aukio, 100014HelsinkiFinland
| | - Dénes Berta
- Institute of Organic ChemistryResearch Centre for Natural SciencesMagyar tudósok körútja 21117BudapestHungary
| | - Konstantin Chernichenko
- Department of ChemistryUniversity of HelsinkiA. I. Virtasen aukio, 100014HelsinkiFinland
- Present address: API Small Molecule DevelopmentJanssen Pharmaceutica N.V.Turnhoutseweg 302340BeerseBelgium
| | - Martin Nieger
- Department of ChemistryUniversity of HelsinkiA. I. Virtasen aukio, 100014HelsinkiFinland
| | - Karina Moslova
- Department of ChemistryUniversity of HelsinkiA. I. Virtasen aukio, 100014HelsinkiFinland
| | - Imre Pápai
- Institute of Organic ChemistryResearch Centre for Natural SciencesMagyar tudósok körútja 21117BudapestHungary
| | - Timo Repo
- Department of ChemistryUniversity of HelsinkiA. I. Virtasen aukio, 100014HelsinkiFinland
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13
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Iqbal SA, Pahl J, Yuan K, Ingleson MJ. Intramolecular (directed) electrophilic C-H borylation. Chem Soc Rev 2020; 49:4564-4591. [PMID: 32495755 DOI: 10.1039/c9cs00763f] [Citation(s) in RCA: 116] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
The intramolecular C-H borylation of (hetero)arenes and alkenes using electrophilic boranes is a powerful transition metal free methodology for forming C-B bonds. These C-H borylation reactions are preceded by intermolecular bond (both dative and covalent) formation, with examples proceeding via initial C-B and N-B bond formation dominating this field thus both are discussed in depth herein. Less prevalent intramolecular electrophilic C-H borylation reactions that proceed by intermolecular O-B, S-B and P-B bond formation are also summarised. Mechanistic studies are presented that reveal two mechanisms for C-H borylation, (i) electrophilic aromatic substitution (prevalent with B-X electrophiles); (ii) σ-bond metathesis mediated (prevalent with B-H and B-R electrophiles). To date, intramolecular electrophilic C-H borylation is utilised mainly for accessing boron containing conjugated organic materials, however recent developments, summarized herein alongside early studies, have highlighted the applicability of this methodology for forming synthetically versatile organo-boronate esters and boron containing bioactives. The multitude of synthetic procedures reported for intramolecular electrophilic C-H borylation contain many common features and this enables key requirements for successful C-H borylation and the factors effecting regioselectivity and substrate scope to be identified, discussed and summarized.
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Affiliation(s)
- S A Iqbal
- EastCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - J Pahl
- EastCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - K Yuan
- EastCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
| | - M J Ingleson
- EastCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
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14
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Iqbal SA, Cid J, Procter RJ, Uzelac M, Yuan K, Ingleson MJ. Acyl-Directed ortho-Borylation of Anilines and C7 Borylation of Indoles using just BBr 3. Angew Chem Int Ed Engl 2019; 58:15381-15385. [PMID: 31461213 PMCID: PMC6856876 DOI: 10.1002/anie.201909786] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Indexed: 01/04/2023]
Abstract
Indoles are privileged heterocycles found in many biologically active pharmaceuticals and natural products. However, the selective functionalization of the benzenoid moiety in indoles in preference to the more reactive pyrrolic unit is a significant challenge. Herein we report that N-acyl directing groups enable the C7-selective C-H borylation of indoles using just BBr3 . This transformation shows some functional-group tolerance and notably proceeds with C6 substituted indoles. The directing group can be readily removed in situ and the products isolated as the pinacol boronate esters. Acyl-directed electrophilic borylation can be extended to carbazoles and anilines with excellent ortho selectivity. 4-amino-indoles are amenable to this process, with acyl group installation and directed electrophilic C-H borylation enabling selective formation of C5-BPin-indoles.
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Affiliation(s)
- Saqib A. Iqbal
- School of ChemistryUniversity of EdinburghEdinburghEH9 3FJUK
| | - Jessica Cid
- Dept. of ChemistryUniversity of ManchesterManchesterM13 9PLUK
| | | | - Marina Uzelac
- School of ChemistryUniversity of EdinburghEdinburghEH9 3FJUK
| | - Kang Yuan
- School of ChemistryUniversity of EdinburghEdinburghEH9 3FJUK
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15
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Iqbal SA, Cid J, Procter RJ, Uzelac M, Yuan K, Ingleson MJ. Acyl‐Directed
ortho
‐Borylation of Anilines and C7 Borylation of Indoles using just BBr
3. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909786] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Saqib A. Iqbal
- School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Jessica Cid
- Dept. of Chemistry University of Manchester Manchester M13 9PL UK
| | | | - Marina Uzelac
- School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
| | - Kang Yuan
- School of Chemistry University of Edinburgh Edinburgh EH9 3FJ UK
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Yoshigoe Y, Kuninobu Y. Iron-Catalyzed ortho-Selective C–H Borylation of 2-Phenylpyridines and Their Analogs. Org Lett 2017; 19:3450-3453. [DOI: 10.1021/acs.orglett.7b01423] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Yusuke Yoshigoe
- Institute
for Materials Chemistry and Engineering, Kyushu University, 6-1
Kasugakoen, Kasuga-shi, Fukuoka 816-8580, Japan
- CREST, Japan Science
and Technology Agency (JST), 6-1 Kasugakoen, Kasuga-shi, Fukuoka 816-8580, Japan
| | - Yoichiro Kuninobu
- Institute
for Materials Chemistry and Engineering, Kyushu University, 6-1
Kasugakoen, Kasuga-shi, Fukuoka 816-8580, Japan
- CREST, Japan Science
and Technology Agency (JST), 6-1 Kasugakoen, Kasuga-shi, Fukuoka 816-8580, Japan
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