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Kumar R, Meher RK, Karmakar H, Panda TK. Hydrosilylation of nitriles and tertiary amides using a zinc precursor. Org Biomol Chem 2024; 22:3053-3058. [PMID: 38545870 DOI: 10.1039/d4ob00161c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/18/2024]
Abstract
We report a competent and selective hydrosilylation of nitriles and tertiary amides catalyzed by the readily available zinc bis(hexamethyldisilazide) under solvent-free and mild conditions, making it a sustainable and desirable alternative to existing methods. Both protocols afforded high conversion, superior selectivity, and a broad substrate scope, from electron-withdrawing to electron-donating and heterocyclic substitutions.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
| | - Rohan Kumar Meher
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
| | - Himadri Karmakar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
| | - Tarun K Panda
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
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2
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Bhandari M, Kaur M, Rawat S, Singh S. Highly Electrophilic Mononuclear Cationic Aluminium Alkoxide Complexes: Syntheses, Reactivity and Catalytic Applications. Chemistry 2023; 29:e202301229. [PMID: 37294029 DOI: 10.1002/chem.202301229] [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: 04/19/2023] [Revised: 06/08/2023] [Accepted: 06/09/2023] [Indexed: 06/10/2023]
Abstract
Herein, we report the synthesis of β-diketiminate-supported aluminium complexes bearing terminal alkoxide and mono-thiol functional groups: LAlOMe(Et) (2), LAlOtBu(Et) (3), and LAlSH(Et) (4), (L=[HC{C(Me)N-(2,6-iPr2 C6 H3 )}2 ]). Complexes 2 and 3 are further used as synthons to generate the fascinating cationic aluminium alkoxide complexes, [LAlOMe(μ-OMe)-Al(Et)L][EtB(C6 F5 )3 ] (5), [LAlOMe(OEt2 )][EtB(C6 F5 )3 ] (6), and [LAlOtBu(OEt2 )][EtB(C6 F5 )3 ] (8). These electrophilic cationic species are well characterized by spectroscopic and crystallographic techniques. The assessment of Lewis acidity by the Gutmann-Beckett method revealed superior Lewis acidity of the cations substituted with electron-demanding alkoxy groups in comparison to the known methyl analogue [LAlMe][B(C6 F5 )4 ]. This has been further endorsed by computational calculations to determine the NBO charges and hydride ion affinity for complexes 6 and 8. These complexes are also capable of activating triethylsilane in stoichiometric reactions. The applicability of these complexes has been realized in the hydrosilylation of ethers, carbonyls, and olefines. Additionally, the solid-state structure of a new THF stabilized aluminium halide cation [LAlCl(THF)][B(C6 F5 )4 ] (11) has also been reported.
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Affiliation(s)
- Mamta Bhandari
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, SAS Nagar, Mohali, 140306, Punjab, India
| | - Mandeep Kaur
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, SAS Nagar, Mohali, 140306, Punjab, India
| | - Sandeep Rawat
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, SAS Nagar, Mohali, 140306, Punjab, India
| | - Sanjay Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, SAS Nagar, Mohali, 140306, Punjab, India
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Mayer RJ, Hampel N, Ofial AR, Mayr H. Resolving the Mechanistic Complexity in Triarylborane-Induced Conjugate Additions. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- Robert J. Mayer
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377München, Germany
| | - Nathalie Hampel
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377München, Germany
| | - Armin R. Ofial
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377München, Germany
| | - Herbert Mayr
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377München, Germany
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Milinkovic A, Dupé A, Belaj F, Mösch-Zanetti NC. Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations. Chemistry 2022; 28:e202201867. [PMID: 35775999 DOI: 10.1002/chem.202201867] [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: 06/17/2022] [Indexed: 01/07/2023]
Abstract
Molybdenum(VI) bis(imido) complexes [Mo(NtBu)2 (LR )2 ] (R=H 1 a; R=CF3 1 b) combined with B(C6 F5 )3 (1 a/B(C6 F5 )3 , 1 b/B(C6 F5 )3 ) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H-H, Si-H and O-H bonds. Cleavage of H2 and Et3 SiH affords ion pairs [Mo(NtBu)(NHtBu)(LR )2 ][HB(C6 F5 )3 ] (R=H 2 a; R=CF3 2 b) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H2 O leads to [Mo(NtBu)(NHtBu)(LR )2 ][(HO)B(C6 F5 )3 ] (R=H 3 a; R=CF3 3 b). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a. Mechanistic elucidation revealed insertion of the aldehyde into the B-H bond of [HB(C6 F5 )3 ]- . We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(LR )2 ][{PhCH2 O}B(C6 F5 )3 ] (R=H 4 a; R=CF3 4 b). Catalysis occurs at [HB(C6 F5 )3 ]- while [Mo(NtBu)(NHtBu)(LR )2 ]+ (R=H or CF3 ) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).
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Affiliation(s)
- Angela Milinkovic
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Antoine Dupé
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Ferdinand Belaj
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Nadia C Mösch-Zanetti
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
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Abstract
Borenium ions are strong Lewis acids because of the positive charge on boron. While their high reactivity had long restricted their role in organic synthesis to stoichiometric reagents, in the past ten years the introduction of suitable supporting ligands, such as N-heterocyclic carbenes, has enabled them to function as competent catalysts for various organic transformations involving the activation of strong covalent bonds, such as H-H, Si-H, B-H, C-H and C-C bonds. This review provides an overview of the recent advances in borenium-catalysed reactions with emphasis on catalyst synthesis, methodology development and mechanistic insight.
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Affiliation(s)
- Xinyue Tan
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Songhu Road 2005, Shanghai, 200438, P. R. China.
| | - Huadong Wang
- Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Songhu Road 2005, Shanghai, 200438, P. R. China.
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Guo T, Liu T, He J, Zhang Y. One‐Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles. European J Org Chem 2022. [DOI: 10.1002/ejoc.202101152] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Tao Guo
- Institution State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun Jilin 130012 China
| | - Tianwei Liu
- Institution State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun Jilin 130012 China
| | - Jianghua He
- Institution State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun Jilin 130012 China
| | - Yuetao Zhang
- Institution State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun Jilin 130012 China
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Bole LJ, Uzelac M, Hernán-Gómez A, Kennedy AR, O'Hara CT, Hevia E. Progressing the Frustrated Lewis Pair Abilities of N-Heterocyclic Carbene/GaR 3 Combinations for Catalytic Hydroboration of Aldehydes and Ketones. Inorg Chem 2021; 60:13784-13796. [PMID: 34191489 DOI: 10.1021/acs.inorgchem.1c01276] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Exploiting the steric incompatibility of the tris(alkyl)gallium GaR3 (R = CH2SiMe3) and the bulky N-heterocyclic carbene (NHC) 1,3-bis(tert-butyl)imidazol-2-ylidene (ItBu), here we report the B-H bond activation of pinacolborane (HBPin), which has led to the isolation and structural authentication of a novel ion pair, [{ItBu-BPin}+{GaR3(μ-H)GaR3}-] (2). Contrastingly, neither ItBu or GaR3 was able to react with HBPin under the conditions of this study. Combining an NHC-stabilized borenium cation, [{ItBu-BPin}+], with an anionic dinuclear gallate, [{GaR3(μ-H)GaR3}-], 2 proved to be unstable in solution at room temperature, evolving to the abnormal NHC-Ga complex [BPinC{{N(tBu)]2CHCGa(R)3}] (3). Interestingly, the structural isomer of 2, with the borenium cation residing at the C4 position of the carbene, [{aItBu-BPin}+{GaR3(μ-H)GaR3}-] (4), was obtained when the abnormal NHC complex [aItBu·GaR3] (1) was heated to 70 °C with HBPin, demonstrating that, under these forced conditions, it is possible to induce thermal frustration of the Lewis base/Lewis acid components of 1, enabling the activation of HBPin. Building on these stoichiometric studies, the frustrated Lewis pair (FLP) reactivity observed for the GaR3/ItBu combination with HBPin could then be upgraded to catalytic regimes, allowing the efficient hydroboration of a range of aldehydes and ketones under mild reaction conditions. Mechanistic insights into the possible reaction pathway involved in this process have been gained by combining kinetic investigations with a comparative study of the catalytic capabilities of several gallium and borenium species related to 2. Disclosing a new cooperative partnership, reactions are proposed to occur via the formation of a highly reactive monomeric hydride gallate, [{ItBu-BPin}+{GaR3(H)}-] (I). Each anionic and cationic component of I plays a key role for success of the hydroboration, with the nucleophilic monomeric gallate anion favoring the transfer of its hydride to the C═O bond of the organic substate, which in turn is activated by coordination to the borenium cation.
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Affiliation(s)
- Leonie J Bole
- Department für Chemie, Biochemie und Pharmazie, Universität Bern, Bern CH3012, Switzerland
| | - Marina Uzelac
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Alberto Hernán-Gómez
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Alcalá de Henares-Madrid 28805, Spain
| | - Alan R Kennedy
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Charles T O'Hara
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Eva Hevia
- Department für Chemie, Biochemie und Pharmazie, Universität Bern, Bern CH3012, Switzerland
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Bolley A, Specklin D, Dagorne S. NHC-stabilized Al(III) and Ga(III) cationic alkyls: Synthesis, structure and use in hydrosilylation catalysis. Polyhedron 2021. [DOI: 10.1016/j.poly.2020.114956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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