1
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Braddock DC, Rowley BC, Lickiss PD, Fussell SJ, Qamar R, Pugh D, Rzepa HS, White AJP. On the Use of Triarylsilanols as Catalysts for Direct Amidation of Carboxylic Acids. J Org Chem 2023. [PMID: 37432502 PMCID: PMC10367078 DOI: 10.1021/acs.joc.3c00585] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Triarylsilanols have been reported as the first silicon-centered molecular catalysts for direct amidation of carboxylic acids with amines as identified after a screen of silanols, silanediols, disiloxanediols, and incompletely condensed silsesquioxanes as potential homogeneous catalysts. Subsequent synthesis and testing of various electronically differentiated triarylsilanols have identified tris(p-haloaryl)silanols as more active than the parent triarylsilanol, where the bromide congener is found to be the most active. Catalyst decomposition can be observed by NMR methods, but RPKA methods reveal that product inhibition is operative, where tertiary amides are more inhibitory than secondary amides. Studies using an authentically synthesized triaryl silylester as a putative intermediate in the catalytic system enable a plausible mechanism to be proposed as supported by computationals.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Ben C Rowley
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Paul D Lickiss
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | | | - Rabia Qamar
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - David Pugh
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, U.K
| | - Henry S Rzepa
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Andrew J P White
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
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2
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Braddock DC, Lancaster BMJ, Tighe CJ, White AJP. Surmounting Byproduct Inhibition in an Intermolecular Catalytic Asymmetric Alkene Bromoesterification Reaction as Revealed by Kinetic Profiling. J Org Chem 2023. [PMID: 37327488 DOI: 10.1021/acs.joc.3c00672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Kinetic profiling has shown that a (DHQD)2PHAL-catalyzed intermolecular asymmetric alkene bromoesterification reaction is inhibited by primary amides, imides, hydantoins, and secondary cyclic amides, which are byproducts of common stoichiometric bromenium ion sources. Two approaches to resolving the inhibition are presented, enabling the (DHQD)2PHAL loading to be dropped from 10 to 1 mol % while maintaining high bromoester conversions in 8 h or less. Iterative post-reaction recrystallizations enabled a homochiral bromonaphthoate ester to be synthesized using only 1 mol % (DHQD)2PHAL.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Ben M J Lancaster
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Christopher J Tighe
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, Imperial College Road, London SW7 2AZ, U.K
| | - Andrew J P White
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
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3
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Ciccarelli D, Christopher Braddock D, Surman AJ, Arenas BIV, Salal T, Marczylo T, Vineis P, Barron LP. Enhanced selectivity for acidic contaminants in drinking water: From suspect screening to toxicity prediction. J Hazard Mater 2023; 448:130906. [PMID: 36764252 DOI: 10.1016/j.jhazmat.2023.130906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/27/2023] [Accepted: 01/28/2023] [Indexed: 06/18/2023]
Abstract
A novel analytical workflow for suspect screening of organic acidic contaminants in drinking water is presented, featuring selective extraction by silica-based strong anion-exchange solid-phase extraction, mixed-mode liquid chromatography-high resolution accurate mass spectrometry (LC-HRMS), peak detection, feature reduction and compound identification. The novel use of an ammonium bicarbonate-based elution solvent extended strong anion-exchange solid-phase extraction applicability to LC-HRMS of strong acids. This approach performed with consistently higher recovery and repeatability (88 ± 7 % at 500 ng L-1), improved selectivity and lower matrix interference (mean = 12 %) over a generic mixed-mode weak anion exchange SPE method. In addition, a novel filter for reducing full-scan features from fulvic and humic acids was successfully introduced, reducing workload and potential for false positives. The workflow was then applied to 10 London municipal drinking water samples, revealing the presence of 22 confirmed and 37 tentatively identified substances. Several poorly investigated and potentially harmful compounds were found which included halogenated hydroxy-cyclopentene-diones and dibromomethanesulfonic acid. Some of these compounds have been reported as mutagenic in test systems and thus their presence here requires further investigation. Overall, this approach demonstrated that employing selective extraction improved detection and helped shortlist suspects and potentially toxic chemical contaminants with higher confidence.
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Affiliation(s)
- Davide Ciccarelli
- Environmental Research Group, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK; NIHR-HPRU Chemical and Radiation Threats and Hazards, NIHR-HPRU Environmental Exposures and Health, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK
| | | | - Andrew J Surman
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
| | | | - Tara Salal
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
| | - Tim Marczylo
- NIHR-HPRU Chemical and Radiation Threats and Hazards, NIHR-HPRU Environmental Exposures and Health, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK; UK Health Security Agency, Harwell Science Campus, Femi Avenue, Harwell, Didcot OX11 0GD, UK
| | - Paolo Vineis
- NIHR-HPRU Chemical and Radiation Threats and Hazards, NIHR-HPRU Environmental Exposures and Health, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK; Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK
| | - Leon P Barron
- Environmental Research Group, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK; NIHR-HPRU Chemical and Radiation Threats and Hazards, NIHR-HPRU Environmental Exposures and Health, MRC Centre for Environment and Health, School of Public Health, Imperial College London, 86 Wood Lane, London W12 0BZ, UK.
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4
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McCarthy S, Desaunay O, Jie ALW, Hassatzky M, White AJP, Deplano P, Braddock DC, Serpe A, Wilton-Ely JDET. Homogeneous Gold Catalysis Using Complexes Recovered from Waste Electronic Equipment. ACS Sustain Chem Eng 2022; 10:15726-15734. [PMID: 36507095 PMCID: PMC9727779 DOI: 10.1021/acssuschemeng.2c04092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 11/02/2022] [Indexed: 06/17/2023]
Abstract
Despite the greater awareness of elemental sustainability and the benefits of the circular economy concept, much waste electrical and electronic equipment (WEEE) is still destined for landfill. Effective methods for valorizing this waste within our society are therefore imperative. In this contribution, two gold(III) complexes obtained as recovery products from WEEE and their anion metathesis products were investigated as homogenous catalysts. These four recovery products were successfully applied as catalysts for the cyclization of propargylic amides and the condensation of acetylacetone with o-iodoaniline. Impressive activity was also observed in the gold-catalyzed reaction between electron-rich arenes (2-methylfuran, 1,3-dimethoxybenzene, and azulene) and α,β-unsaturated carbonyl compounds (methyl vinyl ketone and cyclohexenone). These recovered compounds were also shown to be effective catalysts for the oxidative cross-coupling reaction of aryl silanes and arenes. When employed as Lewis acid catalysts for carbonyl-containing substrates, the WEEE-derived gold complexes could also be recovered at the end of the reaction and reused without loss in catalytic activity, enhancing still further the sustainability of the process. This is the first direct application in homogeneous catalysis of gold recovery products sourced from e-waste.
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Affiliation(s)
- Sean McCarthy
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Oriane Desaunay
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Alvin Lee Wei Jie
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Maximilian Hassatzky
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Andrew J. P. White
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Paola Deplano
- Department
of Chemical and Soil Sciences, University
of Cagliari, Monserrato, 09042 Cagliari, Italy
| | - D. Christopher Braddock
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
| | - Angela Serpe
- Department
of Civil and Environmental Engineering and Architecture (DICAAR),
INSTM Unit, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy
- Environmental
Geology and Geoengineering Institute of the National Research Council
(IGAG-CNR), Via Marengo
2, 09123 Cagliari, Italy
| | - James D. E. T. Wilton-Ely
- Department
of Chemistry, Imperial College, Molecular Sciences Research Hub,
White City Campus, London W12 0BZ, U.K.
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5
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Braddock DC, Duran-Corbera A, Nilforoushan M, Yang Z, He T, Santhakumar G, Bahou KA, Rzepa HS, Woscholski R, White AJP. (±)-Polysiphenol and Other Analogues via Symmetrical Intermolecular Dimerizations: A Synthetic, Spectroscopic, Structural, and Computational Study. J Nat Prod 2022; 85:2650-2655. [PMID: 36288514 PMCID: PMC9706781 DOI: 10.1021/acs.jnatprod.2c00749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Indexed: 06/16/2023]
Abstract
We report an improved total synthesis of 4,5-dibromo-9,10-dihydrophenanthrene-2,3,6,7-tetraol, (±)-polysiphenol, via intermolecular McMurray dimerization of 5-bromovanillin and subsequent intramolecular oxidative coupling as the key steps. The synthetic route is applicable to 4,5-dichloro- and 4,5-difluoro-halologues (as well as a 4,5-dialkyl-analogue). Distinctive AA'BB' multiplets in their 1H NMR spectra for the dimethylene bridges of the dibromo and dichloro compounds reveal them to be room-temperature stable atropisomers, while for the difluoro compound they present as a singlet. X-ray crystal structure determinations of their tetramethylated synthetic precursors show atropisomeric twist angles of 48°, 46°, and 32°, respectively, with the former representing the largest yet observed in any 4,5-disubstituted-9,10-dihydrophenanthrene. DFT computational studies reveal an unprecedented two-stage atropisomeric interconversion process involving time-independent asynchronous rotations of the dimethylene bridge and the biaryl axis for halologues containing chlorine or bromine, but a more synchronous rotation for the difluoro analogue.
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6
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Braddock DC, Limpaitoon N, Oliwa K, O'Reilly D, Rzepa HS, White AJP. A stereoselective hydride transfer reaction with contributions from attractive dispersion force control. Chem Commun (Camb) 2022; 58:4981-4984. [PMID: 35322841 DOI: 10.1039/d2cc01136k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The experimentally determined stereochemical outcome of an unprecedented hydride transfer from a lithium alkoxide to an aldehyde is reported, as deconvoluted by the combined use of a single enantiomer alkoxide in conjunction with a deuterium label. The stereoselective outcome is consistent with a computationally predicted transition state model stabilised by contributions from attractive dispersion forces.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Natnicha Limpaitoon
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Krzysztof Oliwa
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Daniel O'Reilly
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Henry S Rzepa
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Andrew J P White
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
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7
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Abstract
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Methyltrimethoxysilane [MTM, CH3Si(OMe)3]
has been demonstrated to be an effective, inexpensive, and safe reagent
for the direct amidation of carboxylic acids with amines. Two simple
workup procedures that provide the pure amide product without the
need for further purification have been developed. The first employs
an aqueous base-mediated annihilation of MTM. The second involves
simple product crystallization from the reaction mixture providing
a low process mass intensity
direct amidation protocol.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Joshua J Davies
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
| | - Paul D Lickiss
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London W12 0BZ, U.K
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8
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9
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McCarthy S, Lee Wei Jie A, Braddock DC, Serpe A, Wilton-Ely JDET. From Waste to Green Applications: The Use of Recovered Gold and Palladium in Catalysis. Molecules 2021; 26:5217. [PMID: 34500651 PMCID: PMC8434531 DOI: 10.3390/molecules26175217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 08/19/2021] [Accepted: 08/26/2021] [Indexed: 11/16/2022] Open
Abstract
The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed.
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Affiliation(s)
- Sean McCarthy
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK;
| | - Alvin Lee Wei Jie
- Department of Civil and Environmental Engineering and Architecture, INSTM Unit, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy;
| | - D. Christopher Braddock
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK;
| | - Angela Serpe
- Department of Civil and Environmental Engineering and Architecture, INSTM Unit, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy;
| | - James D. E. T. Wilton-Ely
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK;
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10
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Abstract
Despite being one of the most frequently carried out chemical reactions in industry, there is currently no amidation protocol that is regarded as safe, high yielding, environmentally friendly and inexpensive. The direct amidation of a carboxylic acid with an amine is viewed as an inherently good solution for developing such a protocol. Since the 1960s, there has been a gradual development in the use of silicon reagents for direct amidation. This review covers the methods published to April 2021 for silicon reagent mediated direct amidation of a carboxylic acid with an amine. This review also covers the use of polymeric SiO2 to promote direct amidation.
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Affiliation(s)
- Joshua J Davies
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - D Christopher Braddock
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
| | - Paul D Lickiss
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK.
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11
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Bahou KA, Braddock DC, Meyer AG, Savage GP. Relay Cross Metathesis for the Iterative Construction of Terpenoids and Synthesis of a Diterpene-Benzoate Macrolide of Biogenetic Relevance to the Bromophycolides. Org Lett 2020; 22:3176-3179. [PMID: 32227974 PMCID: PMC7171603 DOI: 10.1021/acs.orglett.0c00935] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
We report a relay
cross metathesis (ReXM) reaction for the construction
of terpenoids in an iterative protocol. The protocol features the
cross metathesis of a relay-actuated Δ6,7-functionalized
C10-monoterpenoid alcohol with C10-monoterpenoid
citral to form a C15-sesquiterpene. Subsequent functional
group manipulation allows for the method to be repeated in an iterative
fashion. The method is used for the synthesis of a diterpene-benzoate
macrolide of biogenetic relevance to the bromophycolide family of
natural products.
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Affiliation(s)
- Karim A Bahou
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, United Kingdom
| | - D Christopher Braddock
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London W12 0BZ, United Kingdom
| | - Adam G Meyer
- CSIRO Manufacturing, Jerry Price Laboratory, Research Way, Clayton, Victoria 3168, Australia
| | - G Paul Savage
- CSIRO Manufacturing, Jerry Price Laboratory, Research Way, Clayton, Victoria 3168, Australia
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12
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Bahou KA, Braddock DC, Meyer AG, Savage GP, Shi Z, He T. A Relay Strategy Actuates Pre-Existing Trisubstituted Olefins in Monoterpenoids for Cross-Metathesis with Trisubstituted Alkenes. J Org Chem 2020; 85:4906-4917. [PMID: 32191466 PMCID: PMC7145354 DOI: 10.1021/acs.joc.0c00067] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A retrosynthetic disconnection-reconnection analysis of epoxypolyenes-substrates that can undergo cyclization to podocarpane-type tricycles-reveals relay-actuated Δ6,7-functionalized monoterpenoid alcohols for ruthenium benzylidene catalyzed olefin cross-metathesis with homoprenyl benzenes. Successful implementation of this approach provided several epoxypolyenes as expected (E/Z, ca. 2-3:1). The method is further generalized for the cross-metathesis of pre-existing trisubstituted olefins in other relay-actuated Δ6,7-functionalized monoterpenoid alcohols with various other trisubstituted alkenes to form new trisubstituted olefins. Epoxypolyene cyclization of an enantiomerically pure, but geometrically impure, epoxypolyene substrate provides an enantiomerically pure, trans-fused, podocarpane-type tricycle (from the E-geometrical isomer).
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Affiliation(s)
- Karim A Bahou
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, U.K
| | - D Christopher Braddock
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, U.K
| | - Adam G Meyer
- CSIRO Manufacturing, Jerry Price Laboratory, Research Way, Clayton 3168, Victoria, Australia
| | - G Paul Savage
- CSIRO Manufacturing, Jerry Price Laboratory, Research Way, Clayton 3168, Victoria, Australia
| | - Zhensheng Shi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, U.K
| | - Tianyou He
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London W12 0BZ, U.K
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Braddock DC, Lickiss PD, Rowley BC, Pugh D, Purnomo T, Santhakumar G, Fussell SJ. Tetramethyl Orthosilicate (TMOS) as a Reagent for Direct Amidation of Carboxylic Acids. Org Lett 2018; 20:950-953. [PMID: 29394071 DOI: 10.1021/acs.orglett.7b03841] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Tetramethyl orthosilicate (TMOS) is shown to be an effective reagent for direct amidation of aliphatic and aromatic carboxylic acids with amines and anilines. The amide products are obtained in good to quantitative yields in pure form directly after workup without the need for any further purification. A silyl ester as the putative activated intermediate is observed by NMR methods. Amidations on a 1 mol scale are demonstrated with a favorable process mass intensity.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - Paul D Lickiss
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - Ben C Rowley
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - David Pugh
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - Teresa Purnomo
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - Gajan Santhakumar
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
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14
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Affiliation(s)
- Quintin A. Lo
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - David Sale
- Process
Studies Group, Jealott’s Hill Research Centre, Syngenta, Bracknell, Berkshire RG42 6EY, United Kingdom
| | - D. Christopher Braddock
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - Robert P. Davies
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
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15
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Abstract
A series of prenyl-containing malonates are kinetically benchmarked against the standard allyl-containing congeners using a ruthenium benzylidene precatalyst for ring-closing metatheses. The prenyl grouping is found to be a superior acceptor olefin compared to an allyl group in RCM processes with ruthenium alkylidenes derived from terminal alkenes. The prenyl group is also found to be a highly competent acceptor for a ruthenium alkylidene derived from a 1,1-disubstituted olefin in a RCM process.
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Affiliation(s)
- Karim A Bahou
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - D Christopher Braddock
- Department of Chemistry, Imperial College London , South Kensington, London SW7 2AZ, U.K
| | - Adam G Meyer
- CSIRO Manufacturing, Private Bag 10, Clayton South VIC 3169, Australia
| | - G Paul Savage
- CSIRO Manufacturing, Private Bag 10, Clayton South VIC 3169, Australia
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16
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Clarke J, Bonney KJ, Yaqoob M, Solanki S, Rzepa HS, White AJP, Millan DS, Braddock DC. Epimeric Face-Selective Oxidations and Diastereodivergent Transannular Oxonium Ion Formation Fragmentations: Computational Modeling and Total Syntheses of 12-Epoxyobtusallene IV, 12-Epoxyobtusallene II, Obtusallene X, Marilzabicycloallene C, and Marilzabicycloallene D. J Org Chem 2016; 81:9539-9552. [PMID: 27704814 DOI: 10.1021/acs.joc.6b02008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The total syntheses of 12-epoxyobtusallene IV, 12-epoxyobtusallene II, obtusallene X, marilzabicycloallene C, and marilzabicycloallene D as halogenated C15-acetogenin 12-membered bicyclic and tricyclic ether bromoallene-containing marine metabolites from Laurencia species are described. Two enantiomerically pure C4-epimeric dioxabicyclo[8.2.1]tridecenes were synthesized by E-selective ring-closing metathesis where their absolute stereochemistry was previously set via catalytic asymmetric homoallylic epoxidation and elaborated via regioselective epoxide-ring opening and diastereoselective bromoetherification. Epimeric face-selective oxidation of their Δ12,13 olefins followed by bromoallene installation allowed access to the oppositely configured 12,13-epoxides of 12-epoxyobtusallene II and 12-epoxyobtusallene IV. Subsequent exploration of their putative biomimetic oxonium ion formation-fragmentations reactions revealed diastereodivergent pathways giving marilzabicycloallene C and obtusallene X, respectively. The original configurations of the substrates evidently control oxonium ion formation and their subsequent preferred mode of fragmentation by nucleophilic attack at C9 or C12. Quantum modeling of this stereoselectivity at the ωB97X-D/Def2-TZVPPD/SCRF = methanol level revealed that in addition to direction resulting from hydrogen bonding, the dipole moment of the ion-pair transition state is an important factor. Marilzabicycloallene D as a pentahalogenated 12-membered bicyclic ether bromoallene was synthesized by a face-selective chloronium ion initiated oxonium ion formation-fragmentation process followed by subsequent bromoallene installation.
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Affiliation(s)
- James Clarke
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - Karl J Bonney
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - Muhammad Yaqoob
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - Savade Solanki
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - Henry S Rzepa
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - Andrew J P White
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
| | - David S Millan
- Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - D Christopher Braddock
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, U.K
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17
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Abstract
The first stable bromoallene oxides were obtained by the DMDO epoxidation of 1-bromo-1,3-di-tert-alkylallenes, producing the first crystalline allene oxide of any kind. The epoxidations are regioselective for the bromine-bearing Δ1,2 alkene, and also face selective producing single diastereomer E-olefin products.
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Affiliation(s)
| | - Areeb Mahtey
- Department of Chemistry, Imperial College London, London, SW7 2AZ, UK.
| | - Henry S Rzepa
- Department of Chemistry, Imperial College London, London, SW7 2AZ, UK.
| | - Andrew J P White
- Department of Chemistry, Imperial College London, London, SW7 2AZ, UK.
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18
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Sung S, Sale D, Braddock DC, Armstrong A, Brennan C, Davies RP. Mechanistic Studies on the Copper-Catalyzed N-Arylation of Alkylamines Promoted by Organic Soluble Ionic Bases. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00504] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Simon Sung
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - David Sale
- Process Studies
Group, Syngenta, Jealott’s Hill Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom
| | - D. Christopher Braddock
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - Alan Armstrong
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
| | - Colin Brennan
- Process Studies
Group, Syngenta, Jealott’s Hill Research Centre, Bracknell, Berkshire RG42 6EY, United Kingdom
| | - Robert P. Davies
- Department
of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom
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19
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Campbell J, Burgal JDS, Szekely G, Davies R, Braddock DC, Livingston A. Hybrid polymer/MOF membranes for Organic Solvent Nanofiltration (OSN): Chemical modification and the quest for perfection. J Memb Sci 2016. [DOI: 10.1016/j.memsci.2016.01.024] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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20
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Kim MS, Buisson LA, Heathcote DA, Hu H, Braddock DC, Barrett AGM, Ashton-Rickardt PG, Snyder JP. Approaches to design non-covalent inhibitors for human granzyme B (hGrB). Org Biomol Chem 2015; 12:8952-65. [PMID: 25277547 DOI: 10.1039/c4ob01874e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A structure-based design campaign for non-covalent small molecule inhibitors of human granzyme B was carried out by means of a virtual screening strategy employing three constraints and probe site-mapping with FTMAP to identify ligand "hot spots". In addition, new scaffolds of diverse structures were subsequently explored with ROCS shape-based superposition methods, following by Glide SP docking, induced fit docking and analysis of QikProp molecular properties. Novel classes of moderately active small molecule blockers (≥25 μM IC50 values) from commercially available libraries were identified, and three novel scaffolds have been synthesized by multi-step procedures. Furthermore, we provide an example of a comprehensive structure-based drug discovery approach to non-covalent inhibitors that relies on the X-ray structure of a covalently bound ligand and suggest that the design path may be compromised by alternative and unknown binding poses.
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Affiliation(s)
- Mi-Sun Kim
- Department of Chemistry, 1515 Dickey Drive. and Emory University, Atlanta, GA 30322, USA.
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21
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Sung S, Braddock DC, Armstrong A, Brennan C, Sale D, White AJP, Davies RP. Synthesis, characterisation and reactivity of copper(I) amide complexes and studies on their role in the modified Ullmann amination reaction. Chemistry 2015; 21:7179-92. [PMID: 25788223 PMCID: PMC4471577 DOI: 10.1002/chem.201405699] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Indexed: 11/29/2022]
Abstract
A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide (1), copper(I) 2,2,6,6-tetramethylpiperidide (2), copper(I) pyrrolidide (3), copper(I) piperidide (4), and copper(I) benzylamide (5). Their solid-state structures and structures in [D6 ]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1, 2 and 4 are shown to exist as tetramers in the solid state by X-ray crystallography. In [D6 ]benzene solution, complexes 1, 2 and 5 were found by using (1) H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one-dimensional (1) H and (1) H DOSY NMR spectroscopy. Complexes 3-5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10-phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.
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Affiliation(s)
- Simon Sung
- Department of Chemistry, Imperial College LondonSouth Kensington, London, SW7 2AZ (UK)
| | | | - Alan Armstrong
- Department of Chemistry, Imperial College LondonSouth Kensington, London, SW7 2AZ (UK)
| | - Colin Brennan
- Process Studies Group, Syngenta, Jealott*s Hill Research CentreBracknell, Berkshire RG42 6EY (UK)
| | - David Sale
- Process Studies Group, Syngenta, Jealott*s Hill Research CentreBracknell, Berkshire RG42 6EY (UK)
| | - Andrew J P White
- Department of Chemistry, Imperial College LondonSouth Kensington, London, SW7 2AZ (UK)
| | - Robert P Davies
- Department of Chemistry, Imperial College LondonSouth Kensington, London, SW7 2AZ (UK)
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22
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Braddock DC, Marklew JS, Foote KM, White AJP. Note: An Enantiospecific Polyene Cyclization Initiated by an Enantiomerically Pure Bromonium Ion. Chirality 2014. [DOI: 10.1002/chir.22356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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23
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Braddock DC, Gao AX, White AJP, Whyte M. Studies towards the synthesis of halomon: asymmetric hexafunctionalisation of myrcene. Chem Commun (Camb) 2014; 50:13725-8. [DOI: 10.1039/c4cc06234e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A four-step sequence provides an enantiomerically pure hexafunctionalised myrcene as an advanced intermediate in the targeted synthesis of halomon.
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Affiliation(s)
| | - Alison X. Gao
- Department of Chemistry
- Imperial College London
- London, UK
| | | | - Mariko Whyte
- Department of Chemistry
- Imperial College London
- London, UK
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24
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Braddock DC, Sbircea DT. Proof-of-principle direct double cyclisation of a linear C15-precursor to a dibrominated bicyclic medium-ring ether relevant toLaurenciaspecies. Chem Commun (Camb) 2014; 50:12691-3. [DOI: 10.1039/c4cc06402j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Bicyclic medium ring ethers of relevance toLaurenciaspecies have been obtained by direct double brominative cyclisation of an acyclic precursor.
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25
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Armstrong A, Braddock DC, Jones AX, Clark S. Catalytic asymmetric bromolactonization reactions using (DHQD)2PHAL-benzoic acid combinations. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2013.10.043] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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26
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Braddock DC, Marklew JS, Foote KM, White AJP. An Enantiospecific Polyene Cyclization Initiated by an Enantiomerically Pure Bromonium Ion. Chirality 2013; 25:692-700. [DOI: 10.1002/chir.22194] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 05/10/2013] [Indexed: 11/08/2022]
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27
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Christopher Braddock D, Clarke J, Rzepa HS. Epoxidation of bromoallenes connects red algae metabolites by an intersecting bromoallene oxide – Favorskii manifold. Chem Commun (Camb) 2013; 49:11176-8. [DOI: 10.1039/c3cc46720a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Bonney KJ, Braddock DC. A Unifying Stereochemical Analysis for the Formation of Halogenated C15-Acetogenin Medium-Ring Ethers From Laurencia Species via Intramolecular Bromonium Ion Assisted Epoxide Ring-Opening and Experimental Corroboration with a Model Epoxide. J Org Chem 2012; 77:9574-84. [DOI: 10.1021/jo301580c] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Karl J. Bonney
- Department of Chemistry, Imperial College London, London, SW7 2AZ, U. K
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29
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Christopher Braddock D, Roy D, Lenoir D, Moore E, Rzepa HS, Wu JIC, von Ragué Schleyer P. Verification of stereospecific dyotropic racemisation of enantiopure d and l-1,2-dibromo-1,2-diphenylethane in non-polar media. Chem Commun (Camb) 2012; 48:8943-5. [DOI: 10.1039/c2cc33676f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Barrett TN, Braddock DC, Monta A, Webb MR, White AJP. Total synthesis of the marine metabolite (±)-polysiphenol via highly regioselective intramolecular oxidative coupling. J Nat Prod 2011; 74:1980-1984. [PMID: 21875052 DOI: 10.1021/np200596q] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
(±)-Polysiphenol (1), an atropisomerically stable 4,5-dibrominated 9,10-dihydrophenanthrene from Polysiphonia ferulacea, was prepared by a biomimetically inspired highly regioselective intramolecular oxidative coupling of a dibrominated dihydrostilbene. The installation of the two bromine atoms prior to oxidative coupling prevents further oxidation to a planar aromatized phenanthrene. By this strategy, the synthesis of (±)-polysiphenol was achieved in four steps in 70% overall yield. Synthesis of the naturally occurring 5,5'-(ethane-1,2-diyl)bis(3-bromobenzene-1,2-diol) (2) (the likely biogenetic precursor of polysiphenol) and 5,5'-(ethane-1,2-diyl)bis(3,4,6-tribromobenzene-1,2-diol) (9) are also reported. The origins of the regioselectivity in the oxidative coupling are explored.
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Affiliation(s)
- Tim N Barrett
- Department of Chemistry, Imperial College London, London, South Kensington SW7 2AZ, UK
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31
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Braddock DC, Marklew JS, Thomas AJF. Enantiospecific bromonium ion generation and intramolecular capture: a model system for asymmetric bromonium ion-induced polyene cyclisations. Chem Commun (Camb) 2011; 47:9051-3. [DOI: 10.1039/c1cc13619d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Christopher Braddock D, Cailleau T, Cansell G, Hermitage SA, Pouwer RH, Redmond JM, White AJ. The reaction of aromatic dialdehydes with enantiopure 1,2-diamines: an expeditious route to enantiopure tricyclic amidines. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.tetasy.2010.12.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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33
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Bonney KJ, Braddock DC, White AJP, Yaqoob M. Intramolecular Bromonium Ion Assisted Epoxide Ring-Opening: Capture of the Oxonium Ion with an Added External Nucleophile. J Org Chem 2010; 76:97-104. [DOI: 10.1021/jo101617h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Karl J. Bonney
- Department of Chemistry, Imperial College London, London, United Kingdom, SW7 2AZ
| | | | - Andrew J. P. White
- Department of Chemistry, Imperial College London, London, United Kingdom, SW7 2AZ
| | - Muhammad Yaqoob
- Department of Chemistry, Imperial College London, London, United Kingdom, SW7 2AZ
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34
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Braddock DC, Pouwer RH, Burton JW, Broadwith P. Correction to Clarification of the Stereochemical Course of Nucleophilic Substitution of Arylsulfonate-Based Nucleophile Assisting Leaving Groups. J Org Chem 2009. [DOI: 10.1021/jo901785g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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35
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Braddock DC, Pouwer RH, Burton JW, Broadwith P. Clarification of the Stereochemical Course of Nucleophilic Substitution of Arylsulfonate-Based Nucleophile Assisting Leaving Groups. J Org Chem 2009; 74:6042-9. [DOI: 10.1021/jo900991z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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36
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Braddock DC, Millan DS, Pérez-Fuertes Y, Pouwer RH, Sheppard RN, Solanki S, White AJP. Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII. J Org Chem 2009; 74:1835-41. [DOI: 10.1021/jo8026577] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D. Christopher Braddock
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - David S. Millan
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - Yolanda Pérez-Fuertes
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - Rebecca H. Pouwer
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - Richard N. Sheppard
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - Savade Solanki
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
| | - Andrew J. P. White
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K., and Sandwich Laboratories, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K
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37
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Braddock DC, Hermitage SA, Kwok L, Pouwer R, Redmond JM, White AJP. The generation and trapping of enantiopure bromonium ions. Chem Commun (Camb) 2009:1082-4. [DOI: 10.1039/b816914d] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Revised structures proposed previously for obtusallenes V-VII ( 5- 7) have been confirmed on the basis of computed GIAO-DFT 13C NMR chemical shifts.
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39
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Christopher Braddock D, Bhuva R, Pérez-Fuertes Y, Pouwer R, Roberts CA, Ruggiero A, Stokes ESE, White AJP. The stereochemical course of bromoetherification of enynes. Chem Commun (Camb) 2008:1419-21. [PMID: 18338042 DOI: 10.1039/b800054a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Enynes undergo stereoselective syn intramolecular bromoetherification; the stereochemical course of the reaction was elucidated by X-ray crystallographic studies and by stereospecific synthesis of authentic bromoallenes.
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40
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Abstract
[Structure: see text] A hypothesis concerning the biosynthesis of the marine natural product family the obtusallenes is proposed. Multiple electrophilic bromination events are invoked.
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41
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Ahmad SM, Braddock DC, Cansell G, Hermitage SA, Redmond JM, White AJ. Amidines as potent nucleophilic organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes. Tetrahedron Lett 2007. [DOI: 10.1016/j.tetlet.2007.06.112] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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42
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Braddock DC, Tanaka K, Chadwick D, Böhm VP, Roeper M. Vacuum-driven anionic ligand exchange in Buchmeiser–Hoveyda–Grubbs ruthenium(II) benzylidenes. Tetrahedron Lett 2007. [DOI: 10.1016/j.tetlet.2007.05.108] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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43
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Ahmad SM, Braddock DC, Cansell G, Hermitage SA. Dimethylformamide, dimethylacetamide and tetramethylguanidine as nucleophilic organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes. Tetrahedron Lett 2007. [DOI: 10.1016/j.tetlet.2006.12.042] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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44
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Braddock DC, Bhuva R, Millan DS, Pérez-Fuertes Y, Roberts CA, Sheppard RN, Solanki S, Stokes ESE, White AJP. A Biosynthetically-Inspired Synthesis of the Tetrahydrofuran Core of Obtusallenes II and IV. Org Lett 2006; 9:445-8. [PMID: 17249783 DOI: 10.1021/ol062818g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] Sharpless asymmetric dihydroxylation was regioselective for the trans olefin in an E vs Z vs terminal triene substrate. To test a biosynthetic hypothesis, the resulting diol underwent diastereoselective bromoetherification to provide the des-chloro core of marine natural products obtusallenes II and IV. Alternatively, anionic chloride ring-opening of a Z-beta,gamma-unsaturated epoxide gave separable regioisomeric halohydrins. Bromoetherification gave the fully elaborated core of obtusallenes II and IV with all of the relative stereochemistry correctly set.
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Affiliation(s)
- D Christopher Braddock
- Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K.
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45
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Braddock DC, Hermitage SA, Redmond JM, White AJ. Fractional crystallisation of (±)-iso-amarine with mandelic acid: convenient access to (R,R)- and (S,S)-1,2-diamino-1,2-diphenylethanes. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2006.10.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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46
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Affiliation(s)
- Kiyotaka Tanaka
- Department of Chemistry, Imperial College London, London, SW7 2AZ U.K., Basic Chemicals Research, BASF Aktiengesellschaft, Ludwigshafen, Germany, and Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Volker P. W. Böhm
- Department of Chemistry, Imperial College London, London, SW7 2AZ U.K., Basic Chemicals Research, BASF Aktiengesellschaft, Ludwigshafen, Germany, and Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - David Chadwick
- Department of Chemistry, Imperial College London, London, SW7 2AZ U.K., Basic Chemicals Research, BASF Aktiengesellschaft, Ludwigshafen, Germany, and Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - Michael Roeper
- Department of Chemistry, Imperial College London, London, SW7 2AZ U.K., Basic Chemicals Research, BASF Aktiengesellschaft, Ludwigshafen, Germany, and Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, U.K
| | - D. Christopher Braddock
- Department of Chemistry, Imperial College London, London, SW7 2AZ U.K., Basic Chemicals Research, BASF Aktiengesellschaft, Ludwigshafen, Germany, and Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, U.K
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Abstract
Suitably ortho-substituted iodobenzenes act as organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes via the intermediacy of bromoiodinanes.
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Braddock DC, Cansell G, Hermitage SA, White AJP. Bromoiodinanes with an I(iii)–Br bond: preparation, X-ray crystallography and reactivity as electrophilic brominating agents. Chem Commun (Camb) 2006:1442-4. [PMID: 16550294 DOI: 10.1039/b600455e] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bromoiodinanes--conveniently and directly prepared from iodobenzenecarbinols and N-bromosuccinimide, and characterised for the first time crystallographically--act as electrophilic bromine donors.
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49
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Braddock DC, Cansell G, Hermitage SA, White AJ. An asymmetric synthesis of enantiopure chair and twist trans-cyclooctene isomers. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.tetasy.2004.07.036] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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