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Item Synthesis and reactivity of α-diazo-β-keto sulfonamides(Georg Thieme Verlag KG, 2024-06-19) Maguire, Anita R.; Judge, Evan; O'Shaughnessy, Keith A.; Lawrence, Simon E.; Collins, Stuart G.; Science Foundation Ireland; Irish Research Council; Higher Education Authority; Synthesis and Solid State Pharmaceutical Centre; European Regional Development FundCopper mediated reactions of α-diazo-β-keto sulfonamides 1 leads to a range of products including the alkyne sulfonamides 5, the enamines 6, and the α-halosulfonamides 7 and 11 with no evidence for intramolecular C–H insertion in any of the reactions, in contrast to the reactivity of the comparable α-diazo-β-keto sulfones. Use of copper(II) triflate (5 mol%) led to isolation of a series of alkyne sulfonamides 5 (up to 12%) and enamines 6 (up to 64%). Use of copper(II) chloride (5 mol%) formed, in addition, the α-halosulfonamides 7; use of stoichiometric amounts of copper(II) chloride/bromide enables facile halogenation of the β-keto sulfonamide to form the α-halosulfonamides 7 and 11 (up to 63%).Item Tetrel bonding and other non-covalent interactions assisted supramolecular aggregation in a new Pb(II) complex of an isonicotinohydrazide(MDPI, 2020-09-04) Mahmoudi, Ghodrat; Abedi, Marjan; Lawrence, Simon E.; Zangrando, Ennio; Babashkina, Maria G.; Klein, Axel; Frontera, Antonio; Safin, Damir A.; Science Foundation Ireland; Agencia Estatal de Investigación; Ministerio de Ciencia e Innovación; University of MaraghehA new supramolecular Pb(II) complex [PbL(NO2)]n was synthesized from Pb(NO3)2, N’-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide (HL) and NaNO2. [PbL(NO2)]n is constructed from discrete [PbL(NO2)] units with an almost ideal N2O3 square pyramidal coordination environment around Pb(II). The ligand L− is coordinated through the 2-pyridyl N-atom, one aza N-atom, and the carbonyl O-atom. The nitrite ligand binds in a κ2-O,O coordination mode through both O-atoms. The Pb(II) center exhibits a hemidirected coordination geometry with a pronounced coordination gap, which allows a close approach of two additional N-atoms arising from the N=C(O) N-atom of an adjacent molecule and from the 4-pyridyl N-atom from the another adjacent molecule, yielding a N4O3 coordination, constructed from two Pb–N and three Pb–O covalent bonds, and two Pb⋯N tetrel bonds. Dimeric units in the structure of [PbL(NO2)]n are formed by the Pb⋯N=C(O) tetrel bonds and intermolecular electrostatically enforced π+⋯π− stacking interactions between the 2- and 4-pyridyl rings and further stabilized by C–H⋯π intermolecular interactions, formed by one of the methyl H-atoms and the 4-pyridyl ring. These dimers are embedded in a 2D network representing a simplified uninodal 3-connected fes (Shubnikov plane net) topology defined by the point symbol (4∙82). The Hirshfeld surface analysis of [PbL(NO2)] revealed that the intermolecular H⋯X (X = H, C, N, O) contacts occupy an overwhelming majority of the molecular surface of the [PbL(NO2)] coordination unit. Furthermore, the structure is characterized by intermolecular C⋯C and C⋯N interactions, corresponding to the intermolecular π⋯π stacking interactions. Notably, intermolecular Pb⋯N and, most interestingly, Pb⋯H interactions are remarkable contributors to the molecular surface of [PbL(NO2)]. While the former contacts are due to the Pb⋯N tetrel bonds, the latter contacts are mainly due to the interaction with the methyl H-atoms in the π⋯π stacked [PbL(NO2)] molecules. Molecular electrostatic potential (MEP) surface calculations showed marked electrostatic contributions to both the Pb⋯N tetrel bonds and the dimer forming π+⋯π− stacking interactions. Quantum theory of atoms in molecules (QTAIM) analyses underlined the tetrel bonding character of the Pb⋯N interactions. The manifold non-covalent interactions found in this supramolecular assembly are the result of the proper combination of the polyfunctional multidentate pyridine-hydrazide ligand and the small nitrito auxiliary ligand.Item Generation of tosyl azide in continuous flow using an azide resin, and telescoping with diazo transfer and rhodium acetate-catalyzed O-H insertion.(American Chemical Society, 2021-11-30) O'Mahony, Rosella M.; Lynch, Denis; O'Callaghan, Katie S.; Collins, Stuart G.; Maguire, Anita R.; Science Foundation Ireland; European Regional Development FundGeneration of tosyl azide 12 in acetonitrile in flow under water-free conditions using an azide resin and its use in diazo transfer to a series of aryl acetates are described. Successful telescoping with a rhodium acetate-catalyzed O-H insertion has been achieved, thereby transforming the aryl acetate 8 to a-hydroxy ester 10, a key intermediate in the synthesis of clopidogrel 11, without requiring isolation or handling of either tosyl azide 12 or a-aryl-a-diazoacetate 9, or indeed having significant amounts of either present at any point. Significantly, the solution of a-diazo ester 9 was sufficiently clean to progress directly to the rhodium acetate-catalyzed step without any detrimental impact on the efficiency of the O-H insertion. In addition, the rhodium acetate-catalyzed O-H insertion process is cleaner in flow than under traditional batch conditions. Use of the azide resin offers clear safety advantages and, in addition, this approach complements earlier protocols for the generation of tosyl azide 12 in flow; this protocol is especially useful with less acidic substrates.Item Telescoped diazo transfer and rhodium-catalysed S-H insertion in continuous flow(Elsevier, 2021-09-29) Kearney, Aoife M.; Lynch, Dennis; Collins, Stuart G.; Maguire, Anita R.; Irish Research Council; Science Foundation Ireland; European Regional Development FundRhodium-catalysed S–H insertion of α-diazo-γ-butyrolactams has been successfully telescoped using continuous processing with in situ generated triflyl azide in flow and deacylative diazo transfer, incorporating real-time reaction monitoring of the final process outflow by IR spectroscopy. Significantly, the α-diazo-γ-butyrolactam reaction stream was sufficiently pure to progress to the rhodium-catalysed S–H insertion step without detrimental impact on the rhodium catalyst or the reaction efficiency.Item Recent advances in the transesterification of β-keto esters(Royal Society of Chemistry, 2021-07-02) Hennessy, Mary C.; O'Sullivan, Timothy P.; Irish Research CouncilThe ability to selectively transesterify β-keto esters is a useful transformation in organic synthesis. The increasing interest in transesterification for the synthesis of compounds of pharmaceutical importance, as well as for biodiesel production, has led to the development of a variety of different approaches. This article aims to summarise recent advances in the transesterifications of β-keto esters. Particular interest has been paid to methodologies with minimal environmental impact.