434 results found
Shernyukov AV, Genaev AM, Salnikov GE, et al., 2019, Elevated reaction order of 1,3,5-tri-tert-butylbenzene bromination as evidence of a clustered polybromide transition state: a combined kinetic and computational study., Org Biomol Chem, Vol: 17, Pages: 3781-3789
The kinetics and mechanism of concurrent bromo-de-protonation and bromo-de-tert-butylation of 1,3,5-tri-tert-butylbenzene at different bromine concentrations were studied experimentally and theoretically. Both reactions have high order in bromine (experimental kinetic orders ∼5 and ∼7, respectively). According to quantum chemical DFT calculations, such high reaction orders are caused by participation of clustered polybromide anions Br2n-1- in transition states. Bromo-de-tert-butylation has a higher order due to its bigger reaction center demanding clusters of extended size. A significant primary deuterium kinetic isotope effect (KIE) for bromo-de-protonation is measured indicating proton removal is rate limiting, as confirmed by computed DFT models. The latter predict a larger value for the KIE than measured and possible explanations for this are discussed.
Du Y, Barber T, Lim SE, et al., 2019, A solid-supported arylboronic acid catalyst for direct amidation, CHEMICAL COMMUNICATIONS, Vol: 55, Pages: 2916-2919, ISSN: 1359-7345
Barba A, Dominguez S, Cobas C, et al., 2019, Workflows Allowing Creation of Journal Article Supporting Information and Findable, Accessible, Interoperable, and Reusable (FAIR)-Enabled Publication of Spectroscopic Data, ACS OMEGA, Vol: 4, Pages: 3280-3286, ISSN: 2470-1343
Nielsen CD-T, Mooij WJ, Sale D, et al., 2019, Reversibility and reactivity in an acid catalyzed cyclocondensation to give furanochromanes - a reaction at the "oxonium-Prins' vs. "ortho-quinone methide cycloaddition' mechanistic nexus, Chemical Science, Vol: 10, Pages: 406-412, ISSN: 2041-6520
Herein we report a combined experimental and computational investigation of the acid catalyzed cyclocondensation reaction between styrenyl homoallylic alcohols and salicylaldehyde to form furanochromanes. We disclose a previously unreported isomerisation of the ‘unnatural’ trans-fused products to the diastereomeric ‘natural’ cis-fused congeners. Notwithstanding the appeal of assuming this corresponds to endo to exo isomerisation of Diels–Alder (D–A) adducts via concerted retro-cycloaddition/cycloaddition reactions of an in situ generated ortho-quinone methide with the styrenyl alkene, our combined Hammett/DFT study reveals a stepwise Prins-like process via discrete benzylic carbocation intermediates for all but the most electron deficient styrenes. As these reactions fortuitously lie at the intersection of these two mechanistic manifolds, it allows us to propose an experimentally determined indicative ρ+ value of ca. −3 as marking this nexus between a stepwise Prins-type pathway and a concerted cycloaddition reaction. This value should prove useful for categorising other reactions formally involving ‘ortho-quinomethides’, without the need for the extensive computation performed here. Logical optimisation of the reaction based upon the mechanistic insight led to the use of HFIP as an additive which enables exclusive formation of ‘natural’ cis-fused products with a ∼100-fold reaction rate increase and improved scope.
Sebest F, Casarrubios L, Rzepa HS, et al., 2018, Thermal azide-alkene cycloaddition reactions: straightforward multi-gram access to (2)-1,2,3-triazolines in deep eutectic solvents, GREEN CHEMISTRY, Vol: 20, Pages: 4023-4035, ISSN: 1463-9262
Rzepa HS, Arkhipenko S, Wan E, et al., 2018, An accessible method for DFT calculation of B-11 NMR shifts of organoboron compounds, Journal of Organic Chemistry, Vol: 83, Pages: 8020-8025, ISSN: 0022-3263
The study of boron-mediated reactions in organic synthesis and reactions of organoboron compounds is greatly facilitated by the use of 11B NMR. However, the identification and characterization of reaction intermediates in often complex systems is far from trivial, as 11B NMR does not provide any detailed structural information. Greater insight into the structures present in such systems can be obtained by using DFT chemical shift calculations to support or exclude proposed reaction intermediates. In this article, we report a rapid and accessible approach to the calculation of 11B NMR shifts that is applicable to a wide range of organoboron compounds.
Mandal D, Dhara D, Maiti A, et al., 2018, Mono- and Dicoordinate Germanium(0) as a Four-Electron Donor, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 24, Pages: 2873-2878, ISSN: 0947-6539
Arkhipenko S, Sabatini MT, Batsanov AS, et al., 2018, Mechanistic insights into boron-catalysed direct amidation reactions, CHEMICAL SCIENCE, Vol: 9, Pages: 1058-1072, ISSN: 2041-6520
Davies AN, Martinsen D, Rzepa HS, et al., 2017, Simplifying spectroscopic supplementary data collection, Spectroscopy Europe, Vol: 29, Pages: 6-10, ISSN: 0966-0941
Almond-Thynne J, White AJP, Polyzos A, et al., 2017, Synthesis and Reactions of Benzannulated Spiroaminals: Tetrahydrospirobiquinolines, ACS OMEGA, Vol: 2, Pages: 3241-3249, ISSN: 2470-1343
Abas H, Linsdall SM, Mamboury M, et al., 2017, Total Synthesis of (+)-Lophirone H and Its Pentamethyl Ether Utilizing an Oxonium-Prins Cyclization, ORGANIC LETTERS, Vol: 19, Pages: 2486-2489, ISSN: 1523-7060
Murray JI, Floden NJ, Bauer A, et al., 2017, Kinetic Resolution of 2-Substituted Indolines by N-Sulfonylation using an Atropisomeric 4-DMAP-N-oxide Organocatalyst, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 56, Pages: 5760-5764, ISSN: 1433-7851
Murray JI, Flodén NJ, Bauer A, et al., 2017, Kinetic Resolution of 2-Substituted Indolines by N -Sulfonylation using an Atropisomeric 4-DMAP- N -oxide Organocatalyst, Angewandte Chemie, Vol: 129, Pages: 5854-5858, ISSN: 0044-8249
May PW, Cotton SA, Harrison K, et al., 2017, The 'Molecule of the Month' Website-An Extraordinary Chemistry Educational Resource Online for over 20 Years, MOLECULES, Vol: 22, ISSN: 1420-3049
Calbo J, Weston CE, White AJP, et al., 2017, Tuning Azoheteroarene Photoswitch Performance through Heteroaryl Design, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 139, Pages: 1261-1274, ISSN: 0002-7863
Harvey MJ, McLean A, Rzepa HS, 2017, A metadata-driven approach to data repository design, JOURNAL OF CHEMINFORMATICS, Vol: 9, ISSN: 1758-2946
Clarke J, Bonney KJ, Yaqoob M, et al., 2016, 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, JOURNAL OF ORGANIC CHEMISTRY, Vol: 81, Pages: 9539-9552, ISSN: 0022-3263
Andrade MS, Silva VS, Lourenco AM, et al., 2016, Chiroptical Properties of Streptorubin B: The Synergy Between Theory and Experiment (vol 27, pg 745, 2015), CHIRALITY, Vol: 28, Pages: 663-663, ISSN: 0899-0042
Romain C, Zhu Y, Dingwall P, et al., 2016, Chemoselective Polymerizations from Mixtures of Epoxide, Lactone, Anhydride, and Carbon Dioxide, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 138, Pages: 4120-4131, ISSN: 0002-7863
Rzepa HS, 2016, Discovering More Chemical Concepts from 3D Chemical Information Searches of Crystal Structure Databases, JOURNAL OF CHEMICAL EDUCATION, Vol: 93, Pages: 550-554, ISSN: 0021-9584
Vargas-Caamal A, Luis Cabellos J, Ortiz-Chi F, et al., 2016, How Many Water Molecules Does it Take to Dissociate HCl?, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 22, Pages: 2812-2818, ISSN: 0947-6539
Shernyukov AV, Genaev AM, Salnikov GE, et al., 2016, Noncatalytic Bromination of Benzene: A Combined Computational and Experimental Study, JOURNAL OF COMPUTATIONAL CHEMISTRY, Vol: 37, Pages: 210-225, ISSN: 0192-8651
McArdle I, Fare C, Bearpark M, et al., 2015, Research Data Management 'Green Shoots' Pilot Programme, Final Reports, Research Data Management 'Green Shoots' Pilot Programme, Final Reports
This document contains the final reports of six Research Data Management "Green Shoots" projects run at Imperial College in 2014.
Plater MJ, Harrison WTA, Rzepa HS, 2015, Syntheses and structures of pseudo-mauveine picrate and 3-phenylamino-5-(2-methylphenyl)-7-amino-8-methylphenazinium picrate ethanol mono-solvate: the first crystal structures of a mauveine chromophore and a synthetic derivative, JOURNAL OF CHEMICAL RESEARCH, Pages: 711-718, ISSN: 1747-5198
Andrade MS, Silva VS, Lourenco AM, et al., 2015, Chiroptical Properties of Streptorubin B: The Synergy Between Theory and Experiment, CHIRALITY, Vol: 27, Pages: 745-751, ISSN: 0899-0042
Harvey MJ, Mason NJ, McLean A, et al., 2015, Standards-based curation of a decade-old digital repository dataset of molecular information, JOURNAL OF CHEMINFORMATICS, Vol: 7, ISSN: 1758-2946
Harvey MJ, Mason NJ, McLean A, et al., 2015, Standards-based metadata procedures for retrieving data for display or mining utilizing persistent (data-DOI) identifiers, JOURNAL OF CHEMINFORMATICS, Vol: 7, ISSN: 1758-2946
Kuok KMH, Rzepa HS, Smith EH, 2015, Asymmetric Epoxidation: A Twinned Laboratory and Molecular Modeling Experiment for Upper-Level Organic Chemistry Students, JOURNAL OF CHEMICAL EDUCATION, Vol: 92, Pages: 1385-1389, ISSN: 0021-9584
Jana A, Huch V, Rzepa HS, et al., 2015, A Molecular Complex with a Formally Neutral Iron Germanide Motif (Fe2Ge2), ORGANOMETALLICS, Vol: 34, Pages: 2130-2133, ISSN: 0276-7333
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