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Macdonald PA, Kennedy AR, Weetman CE, Robertson SD, Mulvey RE. Synthesis, characterisation, and catalytic application of a soluble molecular carrier of sodium hydride activated by a substituted 4-(dimethylamino)pyridine. Commun Chem 2024; 7:94. [PMID: 38678145 PMCID: PMC11055874 DOI: 10.1038/s42004-024-01184-5] [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: 02/14/2024] [Accepted: 04/18/2024] [Indexed: 04/29/2024] Open
Abstract
Recently main group compounds have stepped into the territory of precious transition metal compounds with respect to utility in the homogeneous catalysis of fundamentally important organic transformations. Inspired by the need to promote more sustainability in chemistry because of their greater abundance in nature, this change of direction is surprising since main group metals generally do not possess the same breadth of reactivity as precious transition metals. Here, we introduce the dihydropyridylsodium compound, Na-1,2-tBu-DH(DMAP), and its monomeric variant [Na-1,2-tBu-DH(DMAP)]·Me6TREN, and demonstrate their effectiveness in transfer hydrogenation catalysis of the representative alkene 1,1-diphenylethylene to the alkane 1,1-diphenylethane using 1,4-cyclohexadiene as hydrogen source [DMAP = 4-dimethylaminopyridine; Me6TREN = tris(N,N-dimethyl-2-aminoethyl)amine]. Sodium is appealing because of its high abundance in the earth's crust and oceans, but organosodium compounds have been rarely used in homogeneous catalysis. The success of the dihydropyridylsodium compounds can be attributed to their high solubility and reactivity in organic solvents.
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Affiliation(s)
- Peter A Macdonald
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Alan R Kennedy
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Catherine E Weetman
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK
| | - Stuart D Robertson
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK.
| | - Robert E Mulvey
- WestCHEM, Department of Pure & Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK.
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2
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Parsons LWT, Berben LA. Metallated dihydropyridinates: prospects in hydride transfer and (electro)catalysis. Chem Sci 2023; 14:8234-8248. [PMID: 37564402 PMCID: PMC10411630 DOI: 10.1039/d3sc02080k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Accepted: 07/14/2023] [Indexed: 08/12/2023] Open
Abstract
Hydride transfer (HT) is a fundamental step in a wide range of reaction pathways, including those mediated by dihydropyridinates (DHP-s). Coordination of ions directly to the pyridine ring or functional groups stemming therefrom, provides a powerful approach for influencing the electronic structure and in turn HT chemistry. Much of the work in this area is inspired by the chemistry of bioinorganic systems including NADH. Coordination of metal ions to pyridines lowers the electron density in the pyridine ring and lowers the reduction potential: lower-energy reactions and enhanced selectivity are two outcomes from these modifications. Herein, we discuss approaches for the preparation of DHP-metal complexes and selected examples of their reactivity. We suggest further areas in which these metallated DHP-s could be developed and applied in synthesis and catalysis.
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Affiliation(s)
- Leo W T Parsons
- Department of Chemistry, University of California Davis CA 95616 USA
| | - Louise A Berben
- Department of Chemistry, University of California Davis CA 95616 USA
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3
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Macdonald PA, Banerjee S, Kennedy AR, van Teijlingen A, Robertson SD, Tuttle T, Mulvey RE. Alkali Metal Dihydropyridines in Transfer Hydrogenation Catalysis of Imines: Amide Basicity versus Hydride Surrogacy. Angew Chem Int Ed Engl 2023; 62:e202304966. [PMID: 37132607 PMCID: PMC10952797 DOI: 10.1002/anie.202304966] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/04/2023]
Abstract
Catalytic reduction of a representative set of imines, both aldimines and ketimines, to amines has been studied using transfer hydrogenation from 1,4-dicyclohexadiene. Unusually, this has been achieved using s-block pre-catalysts, namely 1-metallo-2-tert-butyl-1,2-dihydropyridines, 2-tBuC5 H5 NM, M(tBuDHP), where M=Li-Cs. Reactions have been monitored in C6 D6 and tetrahydrofuran-d8 (THF-d8 ). A definite trend is observed in catalyst efficiency with the heavier alkali metal tBuDHPs outperforming the lighter congeners. In general, Cs(tBuDHP) is the optimal pre-catalyst with, in the best cases, reactions producing quantitative yields of amines in minutes at room temperature using 5 mol % catalyst. Supporting the experimental study, Density Functional Theory (DFT) calculations have also been carried out which reveal that Cs has a pathway with a significantly lower rate determining step than the Li congener. In the postulated initiation pathways DHP can act as either a base or as a surrogate hydride.
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Affiliation(s)
- Peter A. Macdonald
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Sumanta Banerjee
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Alan R. Kennedy
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | | | - Stuart D. Robertson
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Tell Tuttle
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Robert E. Mulvey
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
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Structural Characterization of the 1-Metallo-2-t-Butyl-1,2-Dihydropyridyl Rubidium and Caesium Complexes. Polyhedron 2023. [DOI: 10.1016/j.poly.2023.116302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Banerjee S, Macdonald PA, Orr SA, Kennedy AR, van Teijlingen A, Robertson SD, Tuttle T, Mulvey RE. Hydrocarbon Soluble Alkali-Metal-Aluminium Hydride Surrog[ATES]. Chemistry 2022; 28:e202201085. [PMID: 35811447 PMCID: PMC9804340 DOI: 10.1002/chem.202201085] [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: 04/08/2022] [Indexed: 01/05/2023]
Abstract
A series of group 1 hydrocarbon-soluble donor free aluminates [AM(t BuDHP)(TMP)Al(i Bu)2 ] (AM=Li, Na, K, Rb) have been synthesised by combining an alkali metal dihydropyridyl unit [(2-t BuC5 H5 N)AM)] containing a surrogate hydride (sp3 C-H) with [(i Bu)2 Al(TMP)]. These aluminates have been characterised by X-ray crystallography and NMR spectroscopy. While the lithium aluminate forms a monomer, the heavier alkali metal aluminates exist as polymeric chains propagated by non-covalent interactions between the alkali metal cations and the alkyldihydropyridyl units. Solvates [(THF)Li(t BuDHP)(TMP)Al(i Bu)2 ] and [(TMEDA)Na(t BuDHP)(TMP)Al(i Bu)2 ] have also been crystallographically characterised. Theoretical calculations show how the dispersion forces tend to increase on moving from Li to Rb, as opposed to the electrostatic forces of stabilization, which are orders of magnitude more significant. Having unique structural features, these bimetallic compounds can be considered as starting points for exploring unique reactivity trends as alkali-metal-aluminium hydride surrog[ATES].
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Affiliation(s)
- Sumanta Banerjee
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Peter A. Macdonald
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Samantha A. Orr
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Alan R. Kennedy
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | | | - Stuart D. Robertson
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Tell Tuttle
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Robert E. Mulvey
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
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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
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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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He J, Rauch F, Krummenacher I, Braunschweig H, Finze M, Marder TB. Two derivatives of phenylpyridyl-fused boroles with contrasting electronic properties: decreasing and enhancing the electron accepting ability. Dalton Trans 2021; 50:355-361. [PMID: 33320139 DOI: 10.1039/d0dt03619f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Two derivatives of phenylpyridyl-fused boroles were prepared via functionalization of the pyridyl groups, namely to an electron-rich dihydropyridine moiety (compound 1) and an electron-deficient N-methylpyridinium cation (compound 2). Due to strong conjugation between the dihydropyridine moiety and the boron atom, the reduction potential of compound 1 shifts cathodically. In contrast, compound 2 exhibits three reduction processes with a first reversible reduction potential anodically shifted in comparison to its precursor (TipPBB2) or the non-borylated framework 1-methyl-2-phenylpyridin-1-ium triflate (3). The significantly anodically shifted reduction potential indicates the extreme electron deficiency of compound 2, which also leads to the reversible coordination of THF. Photophysical properties of both compounds in different solvents were investigated. Theoretical studies further support the strong conjugation in the ground state of compound 1 and the electron-deficient property of compound 2.
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Affiliation(s)
- Jiang He
- Institute for Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
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Brouillet EV, Kennedy AR, Krämer T, Mulvey RE, Robertson SD, Stewart A, Towie S. Synthesis, Structure, and DFT Analysis of the THF Solvate of 2‐Picolyllithium: A 2‐Picolyllithium Solvate with Significant Carbanionic Character. Z Anorg Allg Chem 2020. [DOI: 10.1002/zaac.202000006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Etienne V. Brouillet
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
| | - Alan R. Kennedy
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
| | - Tobias Krämer
- Department of Chemistry and Hamilton Institute Department of Pure & Applied Chemistry Maynooth University Maynooth Co. Kildare Ireland
| | - Robert E. Mulvey
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
| | - Stuart D. Robertson
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
| | - Alexander Stewart
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
| | - Stephen Towie
- WestCHEM Department of Pure & Applied Chemistry University of Strathclyde Glasgow G1 1XL UK
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9
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Stevens MA, Hashim FH, Gwee ESH, Izgorodina EI, Mulvey RE, Blair VL. Contrasting Synergistic Heterobimetallic (Na-Mg) and Homometallic (Na or Mg) Bases in Metallation Reactions of Dialkylphenylphosphines and Dialkylanilines: Lateral versus Ring Selectivities. Chemistry 2018; 24:15669-15677. [PMID: 30101451 DOI: 10.1002/chem.201803477] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Indexed: 01/01/2023]
Abstract
A series of dialkylphenylphosphines and their analogous aniline substrates have been metallated with the synergistic mixed-metal base [(TMEDA)Na(TMP)(CH2 SiMe3 )Mg(TMP)] 1. Different metallation regioselectivities for the substrates were observed, with predominately lateral or meta-magnesiated products isolated from solution. Three novel heterobimetallic complexes [(TMEDA)Na(TMP)(CH2 PCH3 Ph)Mg(TMP)] 2, [(TMEDA)Na(TMP)(m-C6 H4 PiPr2 )Mg(TMP)] 3 and [(TMEDA)Na(TMP)(m-C6 H4 NEt2 )Mg(TMP)] 4 and two homometallic complexes [{(TMEDA)Na(EtNC6 H5 )}2 ] 5 and [(TMEDA)Na2 (TMP)(C6 H5 PEt)]2 6 derived from homometallic metallation have been crystallographically characterised. Complex 6 is an unprecedented sodium-amide, sodium-phosphide hybrid with a rare (NaNNaP)2 ladder motif. These products reveal contrasting heterobimetallic deprotonation with homometallic induced ethene elimination reactivity. Solution studies of metallation mixtures and electrophilic iodine quenching reactions confirmed the metallation sites. In an attempt to rationalise the regioselectivity of the magnesiation reactions the C-H acidities of the six substrates were determined in THF solution using DFT calculations employing the M06-2X functional and cc-pVTZ Dunning's basis set.
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Affiliation(s)
- Michael A Stevens
- School of Chemistry, Monash University, Melbourne, VIC, 3800, Australia
| | - Fairuz H Hashim
- School of Chemistry, Monash University, Melbourne, VIC, 3800, Australia
| | - Eunice S H Gwee
- School of Chemistry, Monash University, Melbourne, VIC, 3800, Australia
| | | | - Robert E Mulvey
- WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK
| | - Victoria L Blair
- School of Chemistry, Monash University, Melbourne, VIC, 3800, Australia
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Lemmerz LE, Spaniol TP, Okuda J. 1,4-Dihydropyridyl complexes of magnesium: synthesis by pyridine insertion into the magnesium–silicon bond of triphenylsilyls and catalytic pyridine hydrofunctionalization. Dalton Trans 2018; 47:12553-12561. [DOI: 10.1039/c8dt01466c] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnesium triphenylsilyl complexes [Mg(SiPh3)2(THF)2] and [(Me3TACD)Mg(SiPh3)] ((Me3TACD)H = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane) serve as precursors for 1,4-dihydropyridyl complexes of magnesium which are active in the hydroboration of pyridine.
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Affiliation(s)
- L. E. Lemmerz
- Institute of Inorganic Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| | - T. P. Spaniol
- Institute of Inorganic Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| | - J. Okuda
- Institute of Inorganic Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
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McLellan R, Kennedy AR, Mulvey RE, Orr SA, Robertson SD. 1-Alkali-metal-2-alkyl-1,2-dihydropyridines: Soluble Hydride Surrogates for Catalytic Dehydrogenative Coupling and Hydroboration Applications. Chemistry 2017; 23:16853-16861. [PMID: 28940713 PMCID: PMC5820744 DOI: 10.1002/chem.201703609] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Indexed: 01/27/2023]
Abstract
Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-tert-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2 NH⋅BH3 to [NMe2 BH2 ]2 (89 % conversion) under competitive conditions (2.5 mol %, 60 h, 80 °C, toluene solvent) to that of previously reported LiN(SiMe3 )2 . Sodium and potassium dihydropyridine congeners produce similar high yields of [NMe2 BH2 ]2 but require longer times. Switching the solvent to pyridine induces a remarkable change in the dehydrocoupling product ratio, with (NMe2 )2 BH favoured over [NMe2 BH2 ]2 (e.g., 94 %:2 % for 1tLi). Demonstrating its versatility, precatalyst 1tLi was also successful in promoting hydroboration reactions between pinacolborane and a selection of aldehydes and ketones. Most reactions gave near quantitative conversion to the hydroborated products in 15 minutes, though sterically demanding carbonyl substrates require longer times. The mechanisms of these rare examples of Group 1 metal-catalysed processes are discussed.
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Affiliation(s)
- Ross McLellan
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Alan R. Kennedy
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Robert E. Mulvey
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Samantha A. Orr
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
| | - Stuart D. Robertson
- WestCHEM, Department of Pure and Applied ChemistryUniversity of StrathclydeGlasgowG1 1XLUK
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