1
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Kothavale S, Iqbal SA, Hanover EL, Gupta AK, Zysman-Colman E, Ingleson MJ. Borylation-Reduction-Borylation for the Formation of 1,4-Azaborines. Org Lett 2023; 25:8912-8916. [PMID: 38055858 PMCID: PMC10729022 DOI: 10.1021/acs.orglett.3c03731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 11/28/2023] [Accepted: 11/30/2023] [Indexed: 12/08/2023]
Abstract
Given the current interest in materials containing 1,4-azaborine units, the development of new routes to these structures is important. Carbonyl directed electrophilic borylation using BBr3 is a facile method for the ortho-borylation of N,N-diaryl-amide derivatives. Subsequent addition of Et3SiH results in carbonyl reduction and then formation of 1,4-azaborines that can be protected in situ using a Grignard reagent. Overall, borylation-reduction-borylation is a one-pot methodology to access 1,4-azaborines from simple precursors.
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Affiliation(s)
- Shantaram
S. Kothavale
- EaStCHEM
School of Chemistry, The University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
| | - Saqib A. Iqbal
- EaStCHEM
School of Chemistry, The University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
| | - Emily L. Hanover
- EaStCHEM
School of Chemistry, The University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
- Organic
Semiconductor Centre and EaStCHEM School of Chemistry, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Abhishek K. Gupta
- Organic
Semiconductor Centre and EaStCHEM School of Chemistry, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Eli Zysman-Colman
- Organic
Semiconductor Centre and EaStCHEM School of Chemistry, University of St Andrews, St Andrews KY16 9ST, United Kingdom
| | - Michael J. Ingleson
- EaStCHEM
School of Chemistry, The University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom
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2
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Nad P, Mukherjee A. A Lewis Acid-Base Pair Catalyzed Dearomative Transformation of Unprotected Indoles via B-H Bond Activation. Chem Asian J 2023; 18:e202300714. [PMID: 37811913 DOI: 10.1002/asia.202300714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/29/2023] [Accepted: 10/09/2023] [Indexed: 10/10/2023]
Abstract
A sustainable and metal-free protocol has been described for the reduction of unprotected indoles. The catalytic system consists of B(C6 F5 )3 and THF as a Lewis acid-base pair that can activate the B-H bond of pincolborane (HBpin). The catalytic system encompasses a broad substrate scope. Control experiments were conducted to understand the possible catalytic intermediates involved during the present protocol.
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Affiliation(s)
- Pinaki Nad
- Department of Chemistry, Indian Institute of Technology Bhilai GEC Campus, Sejbahar, Raipur, 492015, Chhattisgarh (India
| | - Arup Mukherjee
- Department of Chemistry, Indian Institute of Technology Bhilai GEC Campus, Sejbahar, Raipur, 492015, Chhattisgarh (India
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3
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Millet CRP, Noone E, Schellbach AV, Pahl J, Łosiewicz J, Nichol GS, Ingleson MJ. Borylation directed borylation of N-alkyl anilines using iodine activated pyrazaboles. Chem Sci 2023; 14:12041-12048. [PMID: 37969579 PMCID: PMC10631245 DOI: 10.1039/d3sc04269c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 10/02/2023] [Indexed: 11/17/2023] Open
Abstract
Doubly electrophilic pyrazabole derivatives (pyrazabole = [H2B(μ-C3N2H3)]2) combined with one equiv. of base effect the ortho-borylation of N-alkyl anilines. Initial studies found that the bis(trifluoromethane)sulfonimide ([NTf2]-) pyrazabole derivative, [H(NTf2)B(μ-C3N2H3)]2, is highly effective for ortho-borylation, with this process proceeding through N-H borylation and then ortho C-H borylation. The activation of pyrazabole by I2 was developed as a cheaper and simpler alternative to using HNTf2 as the activator. The addition of I2 forms mono or ditopic pyrazabole electrophiles dependent on stoichiometry. The ditopic electrophile [H(I)B(μ-C3N2H3)]2 was also effective for the ortho-borylation of N-alkyl-anilines, with the primary C-H borylation products readily transformed into pinacol boronate esters (BPin) derivatives. Comparison of borylation reactions using the di-NTf2-and the diiodo-pyrazabole congeners revealed that more forcing conditions are required with the latter. Furthermore, the presence of iodide leads to competitive formation of side products, including [HB(μ-C3N2H3)3BH]+, which are not active for C-H borylation. Using [H(I)B(μ-C3N2H3)]2 and 0.2 equiv. of [Et3NH][NTf2] combines the higher yields of the NTf2 system with the ease of handling and lower cost of the iodide system generating an attractive process applicable to a range of N-alkyl-anilines. This methodology represents a metal free and transiently directed C-H borylation approach to form N-alkyl-2-BPin-aniline derivatives.
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Affiliation(s)
- C R P Millet
- EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
| | - E Noone
- EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
| | - A V Schellbach
- EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
| | - J Pahl
- EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
| | - J Łosiewicz
- EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
| | - G S Nichol
- 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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4
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Nad P, Mukherjee A. Metal-free C-H Borylation and Hydroboration of Indoles. ACS OMEGA 2023; 8:37623-37640. [PMID: 37867714 PMCID: PMC10586279 DOI: 10.1021/acsomega.3c05071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 09/12/2023] [Indexed: 10/24/2023]
Abstract
The C-H borylation and hydroboration reactions have emerged as promising synthetic tools to construct organoboron compounds. Organoboron compounds of N-heterocycles, particularly indole derivatives, have found widespread application in a variety of fields. As a result, considerable advancement in the area of C-H borylation and hydroboration reactions of indoles was observed in the last few decades. Among the various synthetic methods applied, the metal-free approach has received special attention. This mini-review discusses the recent progress in the area of C-H borylation and hydroboration reactions of indoles under metal-free conditions, their scope, and brief mechanistic studies.
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Affiliation(s)
- Pinaki Nad
- Department
of Chemistry, Indian Institute of Technology
Bhilai, GEC Campus, Sejbahar, Raipur, Chhattisgarh 492015, India
| | - Arup Mukherjee
- Department
of Chemistry, Indian Institute of Technology
Bhilai, GEC Campus, Sejbahar, Raipur, Chhattisgarh 492015, India
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5
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Al Mamari HH, Borel J, Hickey A, Courtney E, Merz J, Zhang X, Friedrich A, Marder TB, McGlacken GP. Regioselective Iridium-Catalyzed C8-H Borylation of 4-Quinolones via Transient O-Borylated Quinolines. Chemistry 2023; 29:e202301734. [PMID: 37280155 DOI: 10.1002/chem.202301734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/04/2023] [Accepted: 06/05/2023] [Indexed: 06/08/2023]
Abstract
The quinolone-quinoline tautomerization is harnessed to effect the regioselective C8-borylation of biologically important 4-quinolones by using [Ir(OMe)(cod)]2 as the catalyst precursor, the silica-supported monodentate phosphine Si-SMAP as the ligand, and B2 pin2 as the boron source. Initially, O-borylation of the quinoline tautomer takes place. Critically, the newly formed 4-(pinBO)-quinolines then undergo N-directed selective Ir-catalyzed borylation at C8. Hydrolysis of the OBpin moiety on workup returns the system to the quinolone tautomer. The C8-borylated quinolines were converted to their corresponding potassium trifluoroborate (BF3 K) salts and to their C8-chlorinated quinolone derivatives. The two-step C-H borylation-chlorination reaction sequence resulted in various C8-Cl quinolones in good yields. Conversion to C8-OH-, C8-NH2 -, and C8-Ar-substituted quinolones was also feasible by using this methodology.
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Affiliation(s)
- Hamad H Al Mamari
- Department of Chemistry, College of Science, Sultan Qaboos University, PO Box 36, Al Khoudh 123, Muscat, Sultanate of Oman
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Julie Borel
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Aobha Hickey
- School of Chemistry & Analytical and, Biological Chemistry Research Facility, University College Cork, T12 YN60, Ireland
| | - Eimear Courtney
- School of Chemistry & Analytical and, Biological Chemistry Research Facility, University College Cork, T12 YN60, Ireland
| | - Julia Merz
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Xiaolei Zhang
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Alexandra Friedrich
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Todd B Marder
- Institut für Anorganische Chemie and, Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Gerard P McGlacken
- School of Chemistry & Analytical and, Biological Chemistry Research Facility, University College Cork, T12 YN60, Ireland
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6
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Yang Z, Hao L, Xu X, Wang Y, Wu G, Ji Y. C-H Borylation of Benzophenones Using Hydrazone as the Traceless Directing Group. Org Lett 2023; 25:5875-5879. [PMID: 37498107 DOI: 10.1021/acs.orglett.3c02142] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
C-H borylation is one of the powerful C-H bond functionalization reactions. In this context, a metal-free C-H borylation of benzophenones using hydrazone as the traceless directing group has been reported. The dibromoboron intermediates can be obtained in excellent yields, and the corresponding arylboronic esters are generated in moderate to excellent yields. Furthermore, the borylated compounds can be transformed in a one-pot method, avoiding the loss of overall yield caused by the separation of the arylboronic esters.
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Affiliation(s)
- Zhaoziyuan Yang
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, and School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Liqiang Hao
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, and School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Xiaobo Xu
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, and School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Yangyang Wang
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, and School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Gaorong Wu
- School of Pharmaceutical Sciences, Gannan Medical University, Ganzhou 341000, P. R. China
| | - Yafei Ji
- Engineering Research Center of Pharmaceutical Process Chemistry, Ministry of Education, and School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
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7
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Iqbal SA, Uzelac M, Nawaz I, Wang Z, Jones TH, Yuan K, Millet CRP, Nichol GS, Chotana GA, Ingleson MJ. Amides as modifiable directing groups in electrophilic borylation. Chem Sci 2023; 14:3865-3872. [PMID: 37035693 PMCID: PMC10074396 DOI: 10.1039/d2sc06483a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 03/14/2023] [Indexed: 03/17/2023] Open
Abstract
Amide directed C-H borylation using ≥two equiv. of BBr3 forms borenium cations containing a R2N(R')C[double bond, length as m-dash]O→B(Ar)Br unit which has significant Lewis acidity at the carbonyl carbon. This enables reduction of the amide unit to an amine using hydrosilanes. This approach can be applied sequentially in a one-pot electrophilic borylation-reduction process, which for phenyl-acetylamides generates ortho borylated compounds that can be directly oxidised to the 2-(2-aminoethyl)-phenol. Other substrates amenable to the C-H borylation-reduction sequence include mono and diamino-arenes and carbazoles. This represents a simple method to make borylated molecules that would be convoluted to access otherwise (e.g. N-octyl-1-BPin-carbazole). Substituent variation is tolerated at boron as well as in the amide unit, with diarylborenium cations also amenable to reduction. This enables a double C-H borylation-reduction-hydrolysis sequence to access B,N-polycyclic aromatic hydrocarbons (PAHs), including an example where both the boron and nitrogen centres contain functionalisable handles (N-H and B-OH). This method is therefore a useful addition to the metal-free borylation toolbox for accessing useful intermediates (ArylBPin) and novel B,N-PAHs.
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Affiliation(s)
- Saqib A Iqbal
- 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
| | - Ismat Nawaz
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
- Department of Chemistry and Chemical Engineering, Lahore University of Management Sciences Lahore 54792 Pakistan
| | - Zhongxing Wang
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - T Harri Jones
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Kang Yuan
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Clement R P Millet
- 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
| | - Ghayoor Abbas Chotana
- Department of Chemistry and Chemical Engineering, Lahore University of Management Sciences Lahore 54792 Pakistan
| | - Michael J Ingleson
- EaStCHEM School of Chemistry, The University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
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8
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Luo L, Tang S, Wu J, Jin S, Zhang H. Transition Metal-Free Aromatic C-H, C-N, C-S and C-O Borylation. CHEM REC 2023; 23:e202300023. [PMID: 36850026 DOI: 10.1002/tcr.202300023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 02/10/2023] [Indexed: 03/01/2023]
Abstract
Aromatic organoboron compounds are highly valuable building blocks in organic chemistry. They were mainly synthesized through aromatic C-H and C-Het borylation, in which transition metal-catalysis dominate. In the past decade, with increasing attention to sustainable chemistry, numerous transition metal-free C-H and C-Het borylation transformations have been developed and emerged as efficient methods towards the synthesis of aromatic organoboron compounds. This account mainly focuses on recent advances in transition metal-free aromatic C-H, C-N, C-S, and C-O borylation transformations and provides insights to where further developments are required.
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Affiliation(s)
- Lu Luo
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science & Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan, 430074, China
| | - Shuai Tang
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science & Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan, 430074, China
| | - Jiangyue Wu
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science & Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan, 430074, China
| | - Shiwei Jin
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science & Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan, 430074, China
| | - Hua Zhang
- Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science & Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, School of Chemistry and Materials Science, South-Central Minzu University, Wuhan, 430074, China.,Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Hangzhou, 311121, China
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9
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Nieto CI, Sanz D, Claramunt RM, Alkorta I, Elguero J. Pyrazaboles and pyrazolylboranes. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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10
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Banerjee S, Mishra M, Punniyamurthy T. Copper-Catalyzed C7-Selective C–H/N–H Cross-Dehydrogenative Coupling of Indolines with Sulfoximines. Org Lett 2022; 24:7997-8001. [DOI: 10.1021/acs.orglett.2c03190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sonbidya Banerjee
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India
| | - Manmath Mishra
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, India
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11
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Berionni G. Regioselective Transition‐Metal‐Free Arene C−H Borylations: From Directing Groups to Borylation Template Reagents. Angew Chem Int Ed Engl 2022; 61:e202210284. [DOI: 10.1002/anie.202210284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Guillaume Berionni
- Chemistry Department— Namur Institute of Structured Matter University of Namur 61 rue de Bruxelles 5000 Namur Belgium
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12
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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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13
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Millet CRP, Pahl J, Noone E, Yuan K, Nichol GS, Uzelac M, Ingleson MJ. Synthesis of Electrophiles Derived from Dimeric Aminoboranes and Assessing Their Utility in the Borylation of π Nucleophiles. Organometallics 2022; 41:2638-2647. [PMID: 36185396 PMCID: PMC9516688 DOI: 10.1021/acs.organomet.2c00393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Indexed: 11/30/2022]
Abstract
![]()
Dimeric aminoboranes,
[H2BNR2]2 (R = Me or CH2CH2) containing B2N2 cores, can
be activated by I2, HNTf2 (NTf2 =
[N(SO2CF3)2]), or [Ph3C][B(C6F5)4] to form isolable H2B(μ-NR2)2BHX (for X = I or NTf2). For X = [B(C6F5)4]− further reactivity, presumably
between [H2B(μ-NMe2)2BH][B(C6F5)4] and aminoborane, forms a B3N3-based monocation containing a three-center two
electron B-(μ-H)-B moiety. The structures of H2B(μ-NMe2)2BH(I) and [(μ-NMe2)BH(NTf2)]2 indicated a sterically crowded environment
around boron, and this leads to the less common O-bound mode of NTf2 binding. While the iodide congener reacted very slowly with
alkynes, the NTf2 analogues were more reactive, with hydroboration
of internal alkynes forming (vinyl)2BNR2 species
and R2NBH(NTf2) as the major products. Further
studies indicated that the B2N2 core is maintained
during the first hydroboration, and that it is during subsequent steps
that B2N2 dissociation occurs. In the mono-boron
systems, for example, iPr2NBH(NTf2), NTf2 is N-bound; thus, they have less steric
crowding around boron relative to the B2N2 systems.
Notably, the monoboron systems are much less reactive in alkyne hydroboration
than the B2N2-based bis-boranes, despite the
former being three coordinate at boron while the latter are four coordinate
at boron. Finally, these B2N2 electrophiles
are much more prone to dissociate into mono-borane species than pyrazabole
[H2B(μ-N2C3H3)]2 analogues, making them less useful for the directed diborylation
of a single substrate.
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Affiliation(s)
| | - Jürgen Pahl
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, U.K
| | - Emily Noone
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, U.K
| | - Kang Yuan
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, U.K
| | - Gary S. Nichol
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, U.K
| | - Marina Uzelac
- School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, U.K
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14
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Berionni G. Regioselective Transition‐Metal‐Free Arene C−H Borylations: From Directing Groups to Borylation Template Reagents. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202210284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Guillaume Berionni
- Chemistry Department— Namur Institute of Structured Matter University of Namur 61 rue de Bruxelles 5000 Namur Belgium
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15
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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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