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Dachwitz S, Duwe DH, Wang YH, Gruß H, Hannappel Y, Hellweg T, Sewald N. Suzuki-Miyaura Cross-Coupling of Bromotryptophan Derivatives at Ambient Temperature. Chemistry 2020; 26:16357-16364. [PMID: 32639079 PMCID: PMC7756874 DOI: 10.1002/chem.202002454] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/23/2020] [Indexed: 02/06/2023]
Abstract
Mild reaction conditions are highly desirable for bio‐orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross‐couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand‐free solvent‐stabilised Pd‐nanoparticles represent an efficient and sustainable alternative to conventional phosphine‐based catalysts, because the cross‐coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross‐coupling of brominated tryptophan derivatives. The solvent‐stabilised Pd‐nanoparticles are even more efficient than the literature‐known ADHP‐Pd precatalyst. Interestingly, the latter also leads to the formation of quasi‐homogeneous Pd‐nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near‐ambient temperatures and short reaction times of only 2 h. The influence of different Nα‐protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan‐containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium‐coordinating side chains were present in proximal positions.
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Affiliation(s)
- Steffen Dachwitz
- Department of Chemistry, Organic and Bioorganic Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Dario H Duwe
- Department of Chemistry, Organic and Bioorganic Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Yating Hong Wang
- Department of Chemistry, Organic and Bioorganic Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Hendrik Gruß
- Department of Chemistry, Organic and Bioorganic Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Yvonne Hannappel
- Department of Chemistry, Physical Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Thomas Hellweg
- Department of Chemistry, Physical Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Norbert Sewald
- Department of Chemistry, Organic and Bioorganic Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
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Allen JE, Kassel WS, Piro NA. Synthesis, structures and characterization of complexes containing a 2,6-bis(guanidinyl)pyridine ligand on iron(II), cobalt(II), nickel(II), copper(I), copper(II) and zinc(II). Polyhedron 2018. [DOI: 10.1016/j.poly.2018.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Elumalai P, Ujjval R, Nethaji M, Thirupathi N. Syntheses, characterization, solution behavior and catalytic activity of trans-[(guanidine)2PdX2] (X = Cl and OC(O)R; R = Me, Ph and Bu) in Heck–Mizoroki coupling reactions involving chloroarenes/methyl acrylate. Polyhedron 2018. [DOI: 10.1016/j.poly.2018.05.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Lee S, Gabidullin B, Richeson D. Distinct Palladium(II) Carbene Complexes Supported by Six-Membered 1,3-Disubstituted Permidin-2-ylidene, Six-Membered N-Heterocyclic Carbenes. ACS OMEGA 2018; 3:6587-6594. [PMID: 31458835 PMCID: PMC6644826 DOI: 10.1021/acsomega.8b00437] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 06/06/2018] [Indexed: 06/10/2023]
Abstract
The first synthesis, isolation, and characterization of permidin-2-ylidene complexes of Pd(II) is reported with entry resulting from either a direct reaction with isolable six-membered N-heterocyclic carbene or from the enetetramine, arising from dimerization of the carbene. Furthermore, a simplified method to prepare N,N'-disubstituted perimidinium bromide salts, precursors to 1,3-disubstituted perimidin-2-ylidene, was achieved using ammonium bromide as a source of weak acid. Through synthesis and nuclear magnetic resonance spectroscopic analysis of a carbene-phosphinidine adduct, an interrogation of the fundamental π-bonding ability of 1,3-diisopropylperimidin-2-ylidene revealed this interaction to be weak and of a similar order to unsaturated imidazol-2-ylidenes.
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Schwamm RJ, Vianello R, Maršavelski A, García MÁ, Claramunt RM, Alkorta I, Saame J, Leito I, Fitchett CM, Edwards AJ, Coles MP. (15)N NMR Spectroscopy, X-ray and Neutron Diffraction, Quantum-Chemical Calculations, and UV/vis-Spectrophotometric Titrations as Complementary Techniques for the Analysis of Pyridine-Supported Bicyclic Guanidine Superbases. J Org Chem 2016; 81:7612-25. [PMID: 27494395 DOI: 10.1021/acs.joc.6b01330] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Pyridine substituted with one and two bicyclic guanidine groups has been studied as a potential source of superbases. 2-{hpp}C5H4N (I) and 2,6-{hpp}2C5H3N (II) (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) were protonated using [HNEt3][BPh4] to afford [I-H][BPh4] (1a), [II-H][BPh4] (2), and [II-H2][BPh4]2 (3). Solution-state (1)H and (15)N NMR spectroscopy shows a symmetrical cation in 2, indicating a facile proton-exchange process in solution. Solid-state (15)N NMR data differentiates between the two groups, indicating a mixed guanidine/guanidinium. X-ray diffraction data are consistent with protonation at the imine nitrogen, confirmed for 1a by single-crystal neutron diffraction. The crystal structure of 1a shows association of two [I-H](+) cations within a cage of [BPh4](-) anions. Computational analysis performed in the gas phase and in MeCN solution shows that the free energy barrier to transfer a proton between imino centers in [II-H](+) is 1 order of magnitude lower in MeCN than in the gas phase. The results provide evidence that linking hpp groups with the pyridyl group stabilizes the protonation center, thereby increasing the intrinsic basicity in the gas phase, while the bulk prevents efficient cation solvation, resulting in diminished pKa(MeCN) values. Spectrophotometrically measured pKa values are in excellent agreement with calculated values and confirm that I and II are superbases in solution.
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Affiliation(s)
- Ryan J Schwamm
- School of Chemical and Physical Sciences, Victoria University of Wellington , P.O. Box 600, Wellington 6012, New Zealand
| | - Robert Vianello
- Computational Organic Chemistry and Biochemistry Group, Ruder Bošković Institute , Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Aleksandra Maršavelski
- Computational Organic Chemistry and Biochemistry Group, Ruder Bošković Institute , Bijenička cesta 54, 10000 Zagreb, Croatia
| | - M Ángeles García
- Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED , Paseo Senda del Rey 9, 28040 Madrid, Spain
| | - Rosa M Claramunt
- Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED , Paseo Senda del Rey 9, 28040 Madrid, Spain
| | - Ibon Alkorta
- Instituto de Química Médica (IQM-CSIC) , Juan de la Cierva 3, 28006 Madrid, Spain
| | - Jaan Saame
- Institute of Chemistry, University of Tartu , 14a Ravila Street, 50411, Tartu, Estonia
| | - Ivo Leito
- Institute of Chemistry, University of Tartu , 14a Ravila Street, 50411, Tartu, Estonia
| | | | - Alison J Edwards
- Bragg Institute, Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2234, Australia
| | - Martyn P Coles
- School of Chemical and Physical Sciences, Victoria University of Wellington , P.O. Box 600, Wellington 6012, New Zealand
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Schöler S, Wahl MH, Wurster NIC, Puls A, Hättig C, Dyker G. Bidentate cycloimidate palladium complexes with aliphatic and aromatic anagostic bonds. Chem Commun (Camb) 2015; 50:5909-11. [PMID: 24764000 DOI: 10.1039/c4cc01060d] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Palladium(II) complexes of bidentate cycloimidate ligand systems with a triarylmethyl moiety exhibit exceptional downfield shifts in proton NMR spectra due to rare anagostic interactions.
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Affiliation(s)
- Stephan Schöler
- Ruhr Universität Bochum, 44801 Faculty of Chemistry, Organic Chemistry II, Universitätsstr. 150, 44801 Bochum, Germany.
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Hasan K, Pal AK, Auvray T, Zysman-Colman E, Hanan GS. Blue-green emissive cationic iridium(iii) complexes using partially saturated strongly-donating guanidyl-pyridine/-pyrazine ancillary ligands. Chem Commun (Camb) 2015; 51:14060-3. [DOI: 10.1039/c5cc04069h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A new class of cationic iridium(iii) complexes of the form [(C∧N)2Ir(N∧N)][PF6] is reported, where C∧N = cyclometallating 2-phenylpyridinato, ppy, or 2-(2,4-difluorophenyl)-5′-methylpyridinato, dFMeppy, and N∧N = guanidyl-pyridine, gpy, or -pyrazine, gpz, as the ancillary ligand.
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Affiliation(s)
- Kamrul Hasan
- Département de Chimie
- Université de Montréal
- Montréal
- Canada
| | - Amlan K. Pal
- Département de Chimie
- Université de Montréal
- Montréal
- Canada
| | - Thomas Auvray
- Département de Chimie
- Université de Montréal
- Montréal
- Canada
| | - Eli Zysman-Colman
- Organic Semiconductor Centre
- EaStCHEM School of Chemistry
- University of St Andrews
- St Andrews
- UK
| | - Garry S. Hanan
- Département de Chimie
- Université de Montréal
- Montréal
- Canada
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Pal AK, Hanan GS. Structural, electrochemical and photophysical investigations of Re(i)-complexes of κ3N-tridentate heterocyclic ligands. Dalton Trans 2014; 43:11811-4. [DOI: 10.1039/c4dt01454e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Rauws TRM, Maes BUW. Transition metal-catalyzed N-arylations of amidines and guanidines. Chem Soc Rev 2012; 41:2463-97. [DOI: 10.1039/c1cs15236j] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Sola A, Orenes RA, García MÁ, Claramunt RM, Alkorta I, Elguero J, Tárraga A, Molina P. Unprecedented 1,3-Diaza[3]ferrocenophane Scaffold as Molecular Probe for Anions. Inorg Chem 2011; 50:4212-20. [DOI: 10.1021/ic102314r] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - María Ángeles García
- Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED, Senda del Rey 9, E-28040 Madrid, Spain, and
| | - Rosa M. Claramunt
- Departamento de Química Orgánica y Bio-Orgánica, Facultad de Ciencias, UNED, Senda del Rey 9, E-28040 Madrid, Spain, and
| | - Ibon Alkorta
- Instituto de Química Médica (CSIC), Juan de la Cierva, 3, E-28006 Madrid, Spain
| | - José Elguero
- Instituto de Química Médica (CSIC), Juan de la Cierva, 3, E-28006 Madrid, Spain
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