455 results found
Cavalli ES, Mies T, Rzepa HS, et al., 2022, Pyrimidine nucleosides syntheses by late-stage base heterocyclization reactions, Organic Letters, Vol: 24, Pages: 8931-8935, ISSN: 1523-7052
An efficient two-step procedure for the syntheses of pyrimidine nucleosides is presented. A series of glycosyl 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives were prepared from β-anomeric isonitriles by reaction with Meldrum’s acid or by allowing aminomethylene Meldrum’s acid to react with an 1-aldofuranosyl halide or acetate. The resultant 5-(aminomethylene)-1,3-dioxane-4,6-dione derivatives underwent reaction with benzyl- or 2,4-dimethoxybenzyl isocyanate via transacylation to provide uridine-5-carboxylic acid derivatives and related nucleosides. These nucleoside carboxylic acids were converted into other C-5 derivatives by bromo-decarboxylation with N-bromosuccinimide.
Braddock D, Duran-Corbera A, Nilforoushan M, et al., 2022, (±)-Polysiphenol and other Analogues via Symmetrical Intermolecular Dimerizations: a Synthetic, Spectroscopic, Structural and Computational Study, Journal of Natural Products, Vol: 85, Pages: 2650-2655, ISSN: 0163-3864
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.
Rzepa HS, Arita M, Miyamoto K, et al., 2022, A combined DFT-predictive and experimental exploration of the sensitivity towards nucleofuge variation in zwitterionic intermediates relating to mechanistic models for unimolecular chemical generation and trapping of free C-2 and alternative bimolecular pathways involving no free C-2, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 24, Pages: 25816-25821, ISSN: 1463-9076
Dumon AS, Rzepa HS, Alamillo-Ferrer C, et al., 2022, A computational tool to accurately and quickly predict F-19 NMR chemical shifts of molecules with fluorine-carbon and fluorine-boron bonds, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 24, Pages: 20409-20425, ISSN: 1463-9076
Braddock D, Limpaitoon N, Oliwa K, et al., 2022, A stereoselective hydride transfer reaction with contributions from attractive dispersion force control, Chemical Communications, Vol: 58, Pages: 4981-4984, ISSN: 1359-7345
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.
Hanson RM, Jeannerat D, Archibald M, et al., 2022, IUPAC specification for the FAIR management of spectroscopic data in chemistry (IUPAC FAIRSpec) - guiding principles, Pure and Applied Chemistry, Vol: 94, Pages: 623-636, ISSN: 0033-4545
set of guiding principles for the development of a standard for FAIR management of spectroscopic data are outlined and discussed. The principles form the basis for future recommendations of IUPAC Project 2019-031-1-024 specifying a detailed data model and metadata schema for describing the contents of an “IUPAC FAIRData Collection” and the organization of digital objects within that collection. Foremost among the recommendations will be a specification for an “IUPAC FAIRData Finding Aid” that describes the collection in such a way as to optimize the findability, accessibility, interoperability, and reusability of its contents. Results of an analysis of data provided by an American Chemical Society Publications pilot study are discussed in relation to potential workflows that might be used in implementing the “IUPAC FAIRSpec” standard based on these principles.
Rzepa HS, Kuhn S, 2022, A data-oriented approach to making new molecules as a student experiment: Artificial intelligence-enabling FAIR publication of NMR data for organic esters (vol 60, 93, 2022), MAGNETIC RESONANCE IN CHEMISTRY, Vol: 60, Pages: 1032-1043, ISSN: 0749-1581
Cave-Ayland C, Bearpark M, Romain C, et al., 2022, CHAMP is a HPC Access and Metadata Portal, Journal of Open Source Software, Vol: 7, Pages: 3824-3824
Rzepa HS, Kuhn S, 2021, A data-oriented approach to making new molecules as a student experiment: artificial intelligence-enabling FAIR publication of NMR data for organic esters, MAGNETIC RESONANCE IN CHEMISTRY, Vol: 60, Pages: 93-103, ISSN: 0749-1581
- Author Web Link
- Citations: 4
Rzepa HS, 2021, The Long and Winding Road towards FAIR Data as an Integral Component of the Computational Modelling and Dissemination of Chemistry, ISRAEL JOURNAL OF CHEMISTRY, Vol: 62, ISSN: 0021-2148
Rzepa HS, 2021, Routes involving no free C-2 in a DFT-computed mechanistic model for the reported room-temperature chemical synthesis of C-2, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 12630-12636, ISSN: 1463-9076
- Author Web Link
- Citations: 4
Rzepa HS, 2021, A thermodynamic assessment of the reported room-temperature chemical synthesis of C-2, NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723
- Author Web Link
- Citations: 3
Alamillo-Ferrer C, Nielsen CD-T, Salzano A, et al., 2021, Understanding the Diastereopreference of Intermediates in Aminocatalysis: Application to the Chiral Resolution of Lactols, JOURNAL OF ORGANIC CHEMISTRY, Vol: 86, Pages: 4326-4335, ISSN: 0022-3263
Bachrach SM, Rzepa HS, 2020, Cycloparaphenylene Mobius trefoils, CHEMICAL COMMUNICATIONS, Vol: 56, Pages: 13567-13570, ISSN: 1359-7345
Yildiz CB, Leszczynska KI, Gonzalez-Gallardo S, et al., 2020, Equilibrium Formation of Stable All-Silicon Versions of 1,3-Cyclobutanediyl, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 15087-15092, ISSN: 1433-7851
- Author Web Link
- Citations: 19
Yildiz CB, Leszczyńska KI, González-Gallardo S, et al., 2020, Bildung Stabiler All-Silicium Varianten von 1,3-Cyclobutandiyl im Gleichgewicht, Angewandte Chemie, Vol: 132, Pages: 15199-15204, ISSN: 0044-8249
Sebest F, Lachhani K, Pimpasri C, et al., 2020, Cycloaddition reactions of azides and electron-deficient alkenes in deep eutectic solvents: pyrazolines, aziridines and other surprises, Advanced Synthesis & Catalysis, Vol: 362, Pages: 1877-1886, ISSN: 1615-4150
The reaction of organic azides and electron‐deficient alkenes was investigated in a deep eutectic solvent. A series of highly substituted 2‐pyrazolines was successfully isolated and their formation rationalised by DFT calculations. The critical effect of substitution was also explored; even relatively small changes in the cycloaddition partners led to completely different reaction outcomes and triazolines, triazoles or enaminones can be formed as major products depending on the alkene employed.
Klein JEMN, Knizia G, Rzepa HS, 2019, Epoxidation of Alkenes by Peracids: From Textbook Mechanisms to a Quantum Mechanically Derived Curly-Arrow Depiction, CHEMISTRYOPEN, Vol: 8, Pages: 1244-1250, ISSN: 2191-1363
- Author Web Link
- Citations: 4
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, ORGANIC & BIOMOLECULAR CHEMISTRY, Vol: 17, Pages: 3781-3789, ISSN: 1477-0520
- Author Web Link
- Citations: 6
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
- Author Web Link
- Citations: 22
Barba A, Dominguez S, Gomez C, et al., 2019, Workflows allowing creation of journal article Supporting Information and FAIR-enabled publication of Spectroscopic data, ACS Omega, Vol: 4, Pages: 3280-3286, ISSN: 2470-1343
There is an increasing focus on the part of academic institutions, funding agencies, and publishers, if not researchers themselves, on preservation and sharing of research data. Motivations for sharing include research integrity, replicability, and reuse. One of the barriers to publishing data is the extra work involved in preparing data for publication once a journal article and its supporting information have been completed. In this work, a method is described to generate both human and machine-readable supporting information directly from the primary instrumental data files and to generate the metadata to ensure it is published in accordance with findable, accessible, interoperable, and reusable (FAIR) guidelines. Using this approach, both the human readable supporting information and the primary (raw) data can be submitted simultaneously with little extra effort. Although traditionally the data package would be sent to a journal publisher for publication alongside the article, the data package could also be published independently in an institutional FAIR data repository. Workflows are described that store the data packages and generate metadata appropriate for such a repository. The methods both to generate and to publish the data packages have been implemented for NMR data, but the concept is extensible to other types of spectroscopic data as well.
Sebest F, Casarrubios L, Rzepa HS, et al., 2018, Thermal Azide-Alkene Cycloaddition Reactions: Straightforward Multi-gram Access to Δ²-1,2,3-Triazolines in Deep Eutectic Solvents, Green Chemistry, Vol: 20, Pages: 4023-4035, ISSN: 1463-9262
The multi-gram synthesis of a wide range of 1,2,3-triazolines via azide–alkene cycloaddition reactions in a Deep Eutectic Solvent (DES) is reported. The role of DES in this transformation as well as the origin of the full product distribution was studied with an experimental/computational-DFT approach.
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
The generally accepted monoacyloxyboron mechanism of boron-catalysed direct amidation is brought into question in this study, and new alternatives are proposed. We have carried out a detailed investigation of boron-catalysed amidation reactions, through study of the interaction between amines/carboxylic acids and borinic acids, boronic acids and boric acid, and have isolated and characterised by NMR/X-ray crystallography many of the likely intermediates present in catalytic amidation reactions. Rapid reaction between amines and boron compounds was observed in all cases, and it is proposed that such boron–nitrogen interactions are highly likely to take place in catalytic amidation reactions. These studies also clearly show that borinic acids are not competent catalysts for amidation, as they either form unreactive amino-carboxylate complexes, or undergo protodeboronation to give boronic acids. It therefore seems that at least three free coordination sites on the boron atom are necessary for amidation catalysis to occur. However, these observations are not consistent with the currently accepted ‘mechanism’ for boron-mediated amidation reactions involving nucleophilic attack of an amine onto a monomeric acyloxyboron intermediate, and as a result of our observations and theoretical modelling, alternative proposed mechanisms are presented for boron-mediated amidation reactions. These are likely to proceed via the formation of a dimeric B–X–B motif (X = O, NR), which is uniquely able to provide activation of the carboxylic acid, whilst orchestrating the delivery of the amine nucleophile to the carbonyl group. Quantum mechanical calculations of catalytic cycles at the B3LYP+D3/Def2-TZVPP level (solvent = CH2Cl2) support the proposal of several closely related potential pathways for amidation, all of which are likely to be lower in energy than the currently accepted mechanism.
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
An efficient two-step synthesis of symmetrical and unsymmetrical tetrahydrospirobiquinolines from o-azidobenzaldehydes is reported. A novel series of tetrahydrospirobiquinolines was prepared by sequential double-aldol condensation with acetone, cyclopentanone, and cyclohexanone to form the corresponding o,o′-diazido-dibenzylidene-acetone, -cyclopentanone, and -cyclohexanone derivatives, respectively, and hydrogenation–spirocyclization. The spirodiamines were further derivatized by electrophilic aromatic bromination, Suzuki coupling, and N-alkylation, all of which proceeded with preservation of the spirocyclic core.
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: 1523-7052
The first total synthesis of (+)-lophirone H (1) and its pentamethyl ether 29, featuring an oxonium–Prins cyclization/benzylic cation trapping reaction, is described.
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
The first catalytic kinetic resolution by N‐sulfonylation is described. 2‐Substituted indolines are resolved (s=2.6–19) using an atropisomeric 4‐dimethylaminopyridine‐N‐oxide (4‐DMAP‐N‐oxide) organocatalyst. Use of 2‐isopropyl‐4‐nitrophenylsulfonyl chloride is critical to the stereodiscrimination and enables facile deprotection of the sulfonamide products with thioglycolic acid. A qualitative model that accounts for the stereodiscrimination is proposed.
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
The first catalytic kinetic resolution by N-sulfonylation is described. 2-Substituted indolines are resolved (s=2.6–19) using an atropisomeric 4-dimethylaminopyridine-N-oxide (4-DMAP-N-oxide) organocatalyst. Use of 2-isopropyl-4-nitrophenylsulfonyl chloride is critical to the stereodiscrimination and enables facile deprotection of the sulfonamide products with thioglycolic acid. A qualitative model that accounts for the stereodiscrimination is proposed.
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