1
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Zhang J, Chen Z, Chen M, Zhou Q, Zhou R, Wang W, Shao Y, Zhang F. Lanthanide/B(C 6F 5) 3-Promoted Hydroboration Reduction of Indoles and Quinolines with Pinacolborane. J Org Chem 2024. [PMID: 38178689 DOI: 10.1021/acs.joc.3c01767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
We have developed a lanthanide/B(C6F5)3-promoted hydroboration reduction of indoles and quinolines with pinacolborane (HBpin). This reaction provides streamlined access to a range of nitrogen-containing compounds in moderate to excellent yields. Large-scale synthesis and further transformations to bioactive compounds indicate that the method has potential practical applications. Preliminary mechanistic studies suggest that amine additives promote the formation of indole-borane intermediates, and the lanthanide/B(C6F5)3-promoted hydroboration reduction proceeds via hydroboration of indole-borane intermediates with HBpin and in situ-formed BH3 species, followed by the protodeborylation process.
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Affiliation(s)
- Jianping Zhang
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Ziyan Chen
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Mingxin Chen
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Qi Zhou
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Rongrong Zhou
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Wenli Wang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
| | - Yinlin Shao
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
- Institute of New Materials & Industrial Technology, Wenzhou University, Wenzhou 325035, China
| | - Fangjun Zhang
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China
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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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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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4
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Ingleson MJ. Main Group Catalyzed Arene Borylation: Challenges and Opportunities. ACS Catal 2023; 13:7691-7697. [PMID: 37288098 PMCID: PMC10242676 DOI: 10.1021/acscatal.3c01668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Indexed: 06/09/2023]
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5
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Willcox DR, Thomas SP. Group 13 exchange and transborylation in catalysis. Beilstein J Org Chem 2023; 19:325-348. [PMID: 36998308 PMCID: PMC10043741 DOI: 10.3762/bjoc.19.28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/24/2023] [Indexed: 04/01/2023] Open
Abstract
Catalysis is dominated by the use of rare and potentially toxic transition metals. The main group offers a potentially sustainable alternative for catalysis, due to the generally higher abundance and lower toxicity of these elements. Group 13 elements have a rich catalogue of stoichiometric addition reactions to unsaturated bonds but cannot undergo the redox chemistry which underpins transition-metal catalysis. Group 13 exchange reactions transfer one or more groups from one group 13 element to another, through σ-bond metathesis; where boron is both of the group 13 elements, this is termed transborylation. These redox-neutral processes are increasingly being used to render traditionally stoichiometric group 13-mediated processes catalytic and develop new catalytic processes, examples of which are the focus of this review.
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Affiliation(s)
- Dominic R Willcox
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Stephen P Thomas
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
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6
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Thomas SP, Bage AD, Nicholson K, Hunt TA, Langer T. Transborylation-Enabled Boron Catalysis. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/s-0040-1720046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
AbstractThis review highlights transborylation (controlled boron-boron exchange) and its applications as a turnover strategy in boron-catalysed methodologies. Catalytic applications of B–C, B–O, B–N, B–F, B–S, and B–Se transborylations are discussed in the context of transborylation-enabled catalysis, across a wide range of organic transformations including hydroboration, C–C bond formation, C–H borylation, chemoselective reduction, and asymmetric reduction.1 Introduction2 B–C Transborylation3 B–O Transborylation4 B–N Transborylation5 B–F Transborylation6 B–S Transborylation7 Conclusion
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Affiliation(s)
| | - Andrew D. Bage
- EaStCHEM School of Chemistry, The University of Edinburgh
| | | | | | - Thomas Langer
- Pharmaceutical Technology & Development, Chemical Development U.K., AstraZeneca
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7
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Meger F, Kwok ACW, Gilch F, Willcox DR, Hendy AJ, Nicholson K, Bage AD, Langer T, Hunt TA, Thomas SP. B–N/ B–H Transborylation: borane-catalysed nitrile hydroboration. Beilstein J Org Chem 2022; 18:1332-1337. [PMID: 36247978 PMCID: PMC9531558 DOI: 10.3762/bjoc.18.138] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/01/2022] [Indexed: 12/22/2022] Open
Abstract
The reduction of nitriles to primary amines is a useful transformation in organic synthesis, however, it often relies upon stoichiometric reagents or transition-metal catalysis. Herein, a borane-catalysed hydroboration of nitriles to give primary amines is reported. Good yields (48–95%) and chemoselectivity (e.g., ester, nitro, sulfone) were observed. DFT calculations and mechanistic studies support the proposal of a double B–N/B–H transborylation mechanism.
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Affiliation(s)
- Filip Meger
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Alexander C W Kwok
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Franziska Gilch
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Dominic R Willcox
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Alex J Hendy
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Kieran Nicholson
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Andrew D Bage
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
| | - Thomas Langer
- Pharmaceutical Technology & Development, Chemical Development U.K., AstraZeneca, Macclesfield, SK10 2NA, United Kingdom
| | - Thomas A Hunt
- Medicinal Chemistry, Early Oncology, AstraZeneca, Cambridge, CB4 0WG, United Kingdom
| | - Stephen P Thomas
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, United Kingdom
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8
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Moreno González A, Nicholson K, Llopis N, Nichol GS, Langer T, Baeza A, Thomas SP. Diastereoselective, Catalytic Access to Cross-Aldol Products Directly from Esters and Lactones. Angew Chem Int Ed Engl 2022; 61:e202209584. [PMID: 35916601 PMCID: PMC9804986 DOI: 10.1002/anie.202209584] [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: 06/30/2022] [Indexed: 01/09/2023]
Abstract
High oxidation-state carbonyl coupling partners including esters and lactones were reacted with enones to give aldol-type products directly using two-fold organoborane catalysis. This new retrosynthetic disconnection to aldol-type products is compatible with enolisable coupling partners, without self-condensation, and couples the high reactivity of secondary dialkylboranes with the stability of pinacolboronic esters. Excellent chemoselectivity, substrate scope (including those containing reducible functionalities and free alcohols) and diastereocontrol were achieved to access both the syn- and anti-aldol-type products. Mechanistic studies confirmed the two-fold catalytic role of the single secondary borane catalyst for boron enolate formation and formation of an aldehyde surrogate from the ester or lactone coupling partner.
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Affiliation(s)
- Adrián Moreno González
- EaStCHEM School of ChemistryUniversity of EdinburghDavid Brewster RoadEdinburghEH9 3FJUK
| | - Kieran Nicholson
- EaStCHEM School of ChemistryUniversity of EdinburghDavid Brewster RoadEdinburghEH9 3FJUK
| | - Natalia Llopis
- EaStCHEM School of ChemistryUniversity of EdinburghDavid Brewster RoadEdinburghEH9 3FJUK
| | - Gary S. Nichol
- EaStCHEM School of ChemistryUniversity of EdinburghDavid Brewster RoadEdinburghEH9 3FJUK
| | - Thomas Langer
- AstraZeneca Pharmaceutical Technology & DevelopmentChemical Development UKSilk RoadMacclesfieldSK10 2NAUK
| | - Alejandro Baeza
- Instituto de Síntesis Orgánica and Dpto. de Química OrgánicaUniversidad de AlicanteApdo. 9903080AlicanteSpain
| | - Stephen P. Thomas
- EaStCHEM School of ChemistryUniversity of EdinburghDavid Brewster RoadEdinburghEH9 3FJUK
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9
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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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10
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Nicholson K, Peng Y, Llopis N, Willcox DR, Nichol GS, Langer T, Baeza A, Thomas SP. Boron-Catalyzed, Diastereo- and Enantioselective Allylation of Ketones with Allenes. ACS Catal 2022; 12:10887-10893. [PMID: 36082052 PMCID: PMC9442582 DOI: 10.1021/acscatal.2c03158] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/11/2022] [Indexed: 01/04/2023]
Affiliation(s)
- Kieran Nicholson
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
| | - Yuxuan Peng
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
| | - Natalia Llopis
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
| | - Dominic R. Willcox
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
| | - Gary S. Nichol
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
| | - Thomas Langer
- Pharmaceutical Technology & Development, Chemical Development U.K., AstraZeneca, Silk Road, Macclesfield SK10 2NA, United Kingdom
| | - Alejandro Baeza
- Instituto de Síntesis Orgánica and Dpto. de Química Orgánica, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain
| | - Stephen P. Thomas
- EaStCHEM School of Chemistry, The University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ, United Kingdom
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11
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Pahl J, Noone E, Uzelac M, Yuan K, Ingleson MJ. Borylation Directed Borylation of Indoles Using Pyrazabole Electrophiles: A One-Pot Route to C7-Borylated-Indolines. Angew Chem Int Ed Engl 2022; 61:e202206230. [PMID: 35686751 PMCID: PMC9401042 DOI: 10.1002/anie.202206230] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Indexed: 12/23/2022]
Abstract
Pyrazabole (1) is a readily accessible diboron compound that can be transformed into ditopic electrophiles. In 1 (and derivatives), the B⋅⋅⋅B separation is ca. 3 Å, appropriate for one boron centre bonding to N and one to the C7 of indoles and indolines. This suitable B⋅⋅⋅B separation enables double E-H (E=N/C) functionalisation of indoles and indolines. Specifically, the activation of 1 with HNTf2 generates an electrophile that transforms N-H indoles and indolines into N/C7-diborylated indolines, with N-H borylation directing subsequent C7-H borylation. Indole reduction to indoline occurs before C-H borylation and our studies indicate this proceeds via hydroboration-C3-protodeboronation to produce an intermediate that then undergoes C7 borylation. The borylated products can be converted in situ into C7-BPin-N-H-indolines. Overall, this represents a transient directed C-H borylation to form useful C7-BPin-indolines.
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Affiliation(s)
- Jürgen Pahl
- School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK
| | - Emily Noone
- School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, 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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12
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Thomas S, González AM, Nicholson K, Llopis N, Nichol GS, Langer T, Baeza A. Diastereoselective, Catalytic Access to Cross‐aldol Products Directly from Esters and Lactones. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202209584] [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)
- Stephen Thomas
- University of Edinburgh School of Chemistry Joseph Black Building,King's Buildings, West Mains Road EH9 3FJ Edinburgh UNITED KINGDOM
| | | | - Kieran Nicholson
- The University of Edinburgh School of Chemistry School of Chemistry UNITED KINGDOM
| | - Natalia Llopis
- The University of Edinburgh School of Chemistry School of Chemistry UNITED KINGDOM
| | - Gary S. Nichol
- The University of Edinburgh School of Chemistry School of Chemistry UNITED KINGDOM
| | - Thomas Langer
- AstraZeneca UK Ltd Macclesfield Chemical Development UK UNITED KINGDOM
| | - Alejandro Baeza
- Universidad de Alicante: Universitat d'Alacant Dpto. de Química Orgánica SPAIN
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13
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Pahl J, Noone E, Uzelac M, Yuan K, Ingleson M. Borylation Directed Borylation of Indoles Using Pyrazabole Electrophiles: A One‐Pot Route to C7‐Borylated‐Indolines. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202206230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- J. Pahl
- University of Edinburgh Chemistry UNITED KINGDOM
| | - E. Noone
- University of Edinburgh Chemistry UNITED KINGDOM
| | - M. Uzelac
- University of Edinburgh Chemistry UNITED KINGDOM
| | - K. Yuan
- University of Edinburgh Chemistry UNITED KINGDOM
| | - Michael Ingleson
- University of Edinburgh Chemistry South Bridge EH8 9YL Edinburgh UNITED KINGDOM
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14
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Légaré Lavergne J, To HM, Fontaine FG. Boric acid as a precatalyst for BH 3-catalyzed hydroboration. RSC Adv 2021; 11:31941-31949. [PMID: 35495511 PMCID: PMC9041564 DOI: 10.1039/d1ra05945a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 09/11/2021] [Indexed: 01/23/2023] Open
Abstract
We report that boric acid, BO3H3, is a good precatalyst for the BH3-catalyzed hydroboration of esters using pinacolborane as a borylation agent. Using microwave irradiation as an energy source, we demonstrated that a dozen esters were converted into the corresponding boronate ethers in good yields. It was also possible to use boric acid as a precatalyst to reduce carbonates and alkynes. Considering the hazardous and pyrophoric nature of BH3 solutions, boric acid proves to be a safe and green precatalyst for the metal-free reduction of unsaturated species. Cheap and air-stable boric acid is shown to be a good precatalyst for BH3 hydroboration of esters and carbonates.![]()
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Affiliation(s)
- Julien Légaré Lavergne
- Département de Chimie, Université Laval 1045 Avenue de la Médecine Québec G1V 0A6 Québec Canada
| | - Hoang-Minh To
- Département de Chimie, Université Laval 1045 Avenue de la Médecine Québec G1V 0A6 Québec Canada
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