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He T, Klare HFT, Oestreich M. Catalytically Generated Meerwein's Salt-Type Oxonium Ions for Friedel-Crafts C(sp 2)-H Methylation with Methanol. J Am Chem Soc 2023; 145:3795-3801. [PMID: 36724501 DOI: 10.1021/jacs.2c13341] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A catalytic protocol for a Friedel-Crafts-type direct C(sp2)-H methylation of various arenes with methanol is disclosed. The reaction is initiated by counteranion-stabilized silylium or arenium ions, which form Meerwein's salt-like oxonium ions with methanol as the active methylating agents. The silylated methyloxonium ions are stronger electrophiles than their protonated congeners, allowing the Friedel-Crafts alkylation to proceed more efficiently and at a lower reaction temperature. The regeneration of these superelectrophiles within the catalytic cycle is accomplished by the addition of a tetraorganosilane additive, i.e., trimethyl(phenyl)silane or tetraethylsilane, that releases a silylium ion through protodesilylation by the Brønsted acidic Wheland intermediate, thereby acting as a productive "proton-into-silylium ion" generator. By this method, even the C-H methylation of electronically deactivated aryl halides with methanol is achieved. The protocol is also applicable to nonactivated primary as well as π-activated benzylic alcohols. Dialkyl ethers are also competent alkylating agents in the presence of the quaternary phenylsilane additive.
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Affiliation(s)
- Tao He
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
| | - Hendrik F T Klare
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
| | - Martin Oestreich
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
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2
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Kotsyuda S, Toraman AN, Voßnacker P, Ellwanger MA, Steinhauer S, Müller C, Riedel S. Noncovalent Interactions in Halogenated Pyridinium Salts of the Weakly Coordinating Anion [Al(OTeF 5 ) 4 ] . Chemistry 2023; 29:e202202749. [PMID: 36268910 PMCID: PMC10107151 DOI: 10.1002/chem.202202749] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/16/2022] [Accepted: 10/17/2022] [Indexed: 12/13/2022]
Abstract
The synthesis and the first structural characterization of the halogenated pyridinium salts [C5 F5 NH]+ , [C5 F4 ClNH]+ , [(C5 F5 N)2 H]+ , [(C5 Cl5 N)2 H]+ of the weakly coordinating anion (WCA) [Al(OTeF5 )4 ]- , showing noncovalent interactions in the solid state, are presented. The salts were characterized by the multinuclear NMR and IR spectroscopy as well as X-ray diffraction. Hirshfeld surface analysis and solid state structures reveal various intermolecular anion-π and σ-hole interactions between the corresponding halogenated pyridinium cations and the anion [Al(OTeF5 )4 ]- .
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Affiliation(s)
- S Kotsyuda
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - A N Toraman
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - P Voßnacker
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - M A Ellwanger
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - S Steinhauer
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - C Müller
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
| | - S Riedel
- Fachbereich Biologie, Chemie, Pharmazie, Institut für Chemie und Biochemie - Anorganische Chemie, Fabeckstraße 34/36, 14195, Berlin, Germany
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He T, Klare HFT, Oestreich M. Silylium-Ion Regeneration by Protodesilylation Enables Friedel–Crafts Alkylation with Less Isomerization and No Defunctionalization. ACS Catal 2021. [DOI: 10.1021/acscatal.1c03602] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tao He
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
| | - Hendrik F. T. Klare
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
| | - Martin Oestreich
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623 Berlin, Germany
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Riesinger C, Balázs G, Bodensteiner M, Scheer M. Stabilization of Pentaphospholes as η 5 -Coordinating Ligands. Angew Chem Int Ed Engl 2020; 59:23879-23884. [PMID: 32956573 PMCID: PMC7814675 DOI: 10.1002/anie.202011571] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Indexed: 12/15/2022]
Abstract
Electrophilic functionalisation of [Cp*Fe(η5 -P5 )] (1) yields the first transition-metal complexes of pentaphospholes (cyclo-P5 R). Silylation of 1 with [(Et3 Si)2 (μ-H)][B(C6 F5 )4 ] leads to the ionic species [Cp*Fe(η5 -P5 SiEt3 )][B(C6 F5 )4 ] (2), whose subsequent reaction with H2 O yields the parent compound [Cp*Fe(η5 -P5 H)][B(C6 F5 )4 ] (3). The synthesis of a carbon-substituted derivative [Cp*Fe(η5 -P5 Me)][X] ([X]- =[FB(C6 F5 )3 ]- (4 a), [B(C6 F5 )4 ]- (4 b)) is achieved by methylation of 1 employing [Me3 O][BF4 ] and B(C6 F5 )3 or a combination of MeOTf and [Li(OEt2 )2 ][B(C6 F5 )4 ]. The structural characterisation of these compounds reveals a slight envelope structure for the cyclo-P5 R ligand. Detailed NMR-spectroscopic studies suggest a highly dynamic behaviour and thus a distinct lability for 2 and 3 in solution. DFT calculations shed light on the electronic structure and bonding situation of this unprecedented class of compounds.
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Affiliation(s)
- Christoph Riesinger
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Gábor Balázs
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
| | | | - Manfred Scheer
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
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