92 results found
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.
Sebest F, Haselgrove S, White A, et al., 2020, Metal-Free 1,2,3-triazole synthesis in deep eutectic solvents, Synlett: accounts and rapid communications in synthetic organic chemistry, Vol: 31, Pages: 605-609, ISSN: 0936-5214
The metal-free regioselective preparation of 1,5- and 1,4-disubstituted triazoles is reported through a cycloaddition-elimination sequence. Reactions were carried out in environmentally friendly DES and pure products were isolated without the need of chromatographic techniques.
Pimpasri C, White A, Diez-Gonzalez S, 2020, User-friendly copper-catalysed reduction of azides to amines, Asian Journal of Organic Chemistry, Vol: 9, Pages: 399-403, ISSN: 2193-5807
Three homoleptic copper(I) complexes have been prepared and applied to thereduction of organic azides. Under optimised conditions, complex [Cu(HPDIDMA)2]BF4 3(HPDIDMA = 2,6-bis[N-(4-dimethylaminophenyl)carbaldimino]pyridine) could reduce a rangeof electron-poor azides in a mixture of DMSO and water without the need of an additional Hsource.
Zelenay B, Munton P, Tian X, et al., 2019, A commercially available and user-friendly catalyst for hydroamination reactions under technical conditions, European Journal of Organic Chemistry, Vol: 2019, Pages: 4725-4730, ISSN: 1099-0690
The activity of a simple, commercially available copper salt, [Cu(NCMe)4](BF4) in intramolecular hydroamination reactions of alkynes and allenes is presented. Reactions were successfully carried out in technical acetonitrile in the presence of air. While attempts of alkene hydroamination failed, this catalysts was also found active in intermolecular aza‐Michael reactions.
Radtanajiravong L, Diez-Gonzalez S, 2019, Taming Brønsted acid reactivity: nucleophilic substitutions of propargylic alcohols with n-nucleophiles mediated by phosphorus-based Brønsted acid catalysts, ACS Omega, Vol: 4, Pages: 12300-12307, ISSN: 2470-1343
The activity of diethyl phosphite and diphenyl phosphate in propargylation reactionswith N-nucleophiles of varying basicity is presented. Careful choice of the reaction conditionsminimised undesired rearrangements and arylation processes, typical side reactions withBrønsted acid catalysis. These systems are compatible with technical solvents and presence ofair and they are also applicable to C-, O- and S-nucleophiles
Sapsford JS, Gates SJ, Doyle LR, et al., 2019, Cp*Fe(Me2PCH2CH2PMe2)(CHO): Hydride shuttle reactivity of a thermally stable formyl complex, Inorganica Chimica Acta, Vol: 488, Pages: 201-207, ISSN: 0020-1693
[Cp*Fe(Me2PCH2CH2PMe2)(CO)]+ [BArF24]− has been synthesised and characterised using single crystal X-ray diffraction, NMR and IR spectroscopies. Reduction of the CO ligand using Na[Et3BH] produces the corresponding neutral formyl complex Cp*Fe(Me2PCH2CH2PMe2)(CHO), that is very thermally stable, and which is attributed to the electron-releasing properties of the spectator ligands. This compound is a potent hydride donor which exists in equilibrium with [Et3BH]−, Et3B, and the structural isomer (η4-C5Me5H)Cp*Fe(Me2PCH2CH2PMe2)(CO), resulting from reversible hydride migration to the Cp* ligand.
Zelenay B, Besora M, Monasterio Z, et al., 2018, Copper-mediated reduction of azides under seemingly oxidising conditions: catalytic and computational studies, Catalysis Science and Technology, Vol: 8, Pages: 5763-5773, ISSN: 2044-4753
The reduction of aryl azides in the absence of an obvious reducing agent is reported. Careful catalyst design led to the production of anilines in the presence of water and air. The reaction medium (toluene/water) is crucial for the success of the reaction, as DFT calculations support the formation of benzyl alcohol as the oxidation product. A singular catalytic cycle is presented for this transformation based on four key steps: nitrene formation through nitrogen extrusion, formal oxidative addition of water, C(sp3)–H activation of toluene and reductive elimination.
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.
de Aguirre A, Diez-Gonzalez S, Maseras F, et al., 2018, The acetate proton shuttle between mutually trans ligands, Organometallics, Vol: 37, Pages: 2645-2651, ISSN: 0276-7333
This work addresses a counterintuitive observation in the reactivity of the well-known ruthenium complexes [Ru(X)H(CO)(PiPr3)2], according to which the 5-coordinate chloro complex (X = Cl, 1) is less reactive toward phenylacetylene than its 6-coordinate acetate analogue (X = κO2-OC(O)Me, 3), since 3 undergoes a hydride-to-alkenyl-to-alkynyl transformation, whereas the reaction of 1 stops at the alkenyl derivative. The experimental kinetics of the key alkenyl-to-alkynyl step in the acetate complex are compared to the results of DFT calculations, which disclose the ability of the acetate not only to assist the alkyne C–H activation step via a CMD mechanism but also to subsequently deliver the proton to the alkenyl ligand. Possible consequences of this mechanistic resource connecting mutually trans ligands are briefly discussed on the basis of reported chemoselectivity changes induced by carboxylate ligands in 1-alkyne hydrosilylations catalyzed by this type of ruthenium complexes.
Sebest F, Dunsford JJ, Adams M, et al., 2018, Ring-expanded N-heterocyclic carbenes for copper-mediated azide-alkyne click cycloaddition reactions, ChemCatChem, Vol: 10, Pages: 2041-2045, ISSN: 1867-3880
A series of well‐defined copper(I) complexes bearing ring‐expanded N‐heterocyclic carbene (NHC) ligands has been applied to the azide–alkyne cycloaddition reaction. The obtained results notably showed that the six‐membered NHC ligands outperform well‐established five‐membered ones. [CuI(Mes‐6)] displayed a remarkable catalytic activity while respecting the strict criteria for click reactions.
Zelenay B, Maseras F, Diez-Gonzalez S, 2017, Preparation and characterization of copper(I) diazabutadiene complexes and catalytic applications, 253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Chiang PC, Díez-González S, Bode JW, 2017, CHAPTER 14: N-Heterocyclic Carbenes as Organic Catalysts, RSC Catalysis Series, Pages: 534-566, ISBN: 9781782624233
The synthetic utility of azolium salts as catalysts was thought to be limited to the generation of acyl anion equivalents for use in benzoin and Stetter reactions. The discovery, in 2004, of new catalysts, substrates, and reaction manifolds has ignited a new generation of reactions that fall under the general rubric of N-heterocyclic carbene-catalyzed reactions. These powerful new processes include the catalytic generation of activated carboxylates for-functionalized aldehydes, enantioselective annulations via catalytically generated ester enolate equivalents, and the NHC-catalyzed generation of formal homoenolate equivalents. The history of these new reactions and an overview of the reactions, their substrate scope, and mechanistic pathways are summarized in this chapter.
Díez-González S, 2017, Preface, ISBN: 9781782624233
Collinson J-M, Wilton-Ely JDET, Diez-Gonzalez S, 2016, Functionalised [(NHC)Pd(allyl)Cl] complexes: Synthesis, immobilisation and application in cross-coupling and dehalogenation reactions, Catalysis Communications, Vol: 87, Pages: 78-81, ISSN: 1566-7367
A novel NHC–palladium(II) (NHC = N-heterocyclic carbene) complex and itsimmobilised version have been prepared and fully characterised. Optimisation studies led to goodcatalytic activities in Suzuki-Miyaura cross coupling and chloroarene dehalogenation reactions.Furthermore, the unexpected palladium-mediated transfer hydrogenation of a carbonyl compound isreported.
Zelenay B, Frutos-Pedreño R, Markalain-Barta J, et al., 2016, Homo- and Heteroleptic Copper(I) Complexes with Diazabutadiene Ligands: Synthesis, Solution- and Solid-State Structural Studies, European Journal of Inorganic Chemistry, Vol: 2016, Pages: 4649-4658, ISSN: 1434-1948
The preparation of novel copper(I) complexes of diazabutadiene (DAB) ligands with aliphatic backbones is reported. [Cu(DABR)2](BF4), [Cu(DABR)(NCMe)2](BF4) and [CuCl(DABR)] are easily synthesised and air-stable. These complexes, which remain scarce in the literature, have been fully characterised, and their behaviour both in the solid state as well as in solution has been studied by means of X-ray crystallography, NMR and UV/Vis spectroscopy.
Diez-Gonzalez S, Lal S, Perez J, et al., 2016, Copper(I)-Phosphinite Complexes in Click Cycloadditions: Three-Component Reactions and Preparation of 5-Iodotriazoles, ChemCatChem, Vol: 8, Pages: 2222-2226, ISSN: 1867-3880
The remarkable activity displayed by copper(I)-phosphinite complexes of general formula [CuBr(L)] in twochallenging cycloadditions is reported: a) the one potazidonation/cycloaddition from boronic acids, NaN3 and terminalalkynes; b) the cycloaddition of azides and iodoalkynes. These airstablecatalysts led to very good results in both cases and theexpected triazoles could be isolated pure under ‘Click-suitable’conditions.
Diez-Gonzalez S, 2016, Copper(I)-Acetylides: Access, Structure, and Relevance in Catalysis, ADVANCES IN ORGANOMETALLIC CHEMISTRY, VOL 66, Editors: Perez, Publisher: ELSEVIER ACADEMIC PRESS INC, Pages: 93-141, ISBN: 978-0-12-804709-5
Barreiro EB, Sanz Vidal ASV, Tan ET, et al., 2015, HBF4 Catalysed Nucleophilic Substitutions of Propargylic Alcohols, European Journal of Organic Chemistry, Vol: 2015, Pages: 7544-7549, ISSN: 1434-193X
The activity of HBF4 (aqueous solution) as a catalyst inpropargylation reactions is presented. Diverse types of nucleophileswere employed in order to form new C–O, C–N and C–C bonds intechnical acetone, and in air. Good to excellent yields were obtainedusing low acid loading (typically 1 mol %) under simple reactionconditions and good chemoselectivity.
Carmona D, Lamata MP, Sanchez A, et al., 2014, Chiral transition-metal complexes as Bronsted-acid catalysts for the asymmetric Friedel-Crafts hydroxyalkylation of indoles, DALTON TRANSACTIONS, Vol: 43, Pages: 11260-11268, ISSN: 1477-9226
Lal S, Rzepa HS, Diez-Gonzalez S, 2014, Catalytic and computational studies of N-Heterocyclic carbene or phosphine-containing Copper(I) complexes for the synthesis of 5-lodo-1,2,3-Triazoles, ACS Catalysis, Vol: 4, Pages: 2274-2287, ISSN: 2155-5435
Two complementary catalytic systems are reported for the 1,3-dipolar cycloaddition of azides and iodoalkynes. These are based on two commercially available/readily available copper complexes, [CuCl(IPr)] or [CuI(PPh3)3], which are active at low metal loadings (PPh3 system) or in the absence of any other additive (IPr system). These systems were used for the first reported mechanistic studies on this particular reaction. An experimental/computational-DFT approach allowed to establish that (1) some iodoalkynes might be prone to dehalogenation under copper catalysis conditions and, more importantly, (2) two distinct mechanistic pathways are likely to be competitive with these catalysts, either through a copper(III) metallacycle or via direct π-activation of the starting iodoalkyne.
Markalain Barta J, Diez-Gonzalez S, 2013, Well-Defined Diimine Copper(I) Complexes as Catalysts in Click Azide-Alkyne Cycloaddition Reactions, MOLECULES, Vol: 18, Pages: 8919-8928, ISSN: 1420-3049
Diez-Gonzalez S, 2013, Well-defined copper(I) catalysts for true Click cycloadditions reactions, 20th EuCheMS Conference on Organometallic Chemistry
Collinson J-M, Wilton-Ely JDET, Diez-Gonzalez S, 2013, Reusable and highly active supported copper(I)-NHC catalysts for Click chemistry, CHEMICAL COMMUNICATIONS, Vol: 49, Pages: 11358-11360, ISSN: 1359-7345
Martínez-Sarti L, Díez-González S, 2013, On the unique reactivity of Pd(OAc)2 with organic azides: Expedient synthesis of nitriles and imines, Chemcatchem
Gautier A, Cisnetti F, Díez-González S, et al., 2012, Synthesis of 1,3–bis(2,4,6–trimethylphenyl)–imidazolinium salts : SIMes.HCl, SIMes.HBr, SIMes.HBF4 and SIMes.HPF6, Protocol Exchange
N,N’–bis–(2,4,6–trimethylphenylamino)ethane dihydrobromide is obtained in a single step through the dialkylation of dibromoethane. It serves as a versatile starting material for the synthesis of imidazolium salts: SIMes.HBr, SIMes.HCl, SIMes.HPF6 and SIMes.HBF4
Díez-González S, 2012, Well-defined copper(I) catalysts for true Click cycloadditions reactions, XXV International Conference on Organometallic Chemistry
Lal S, Díez-González S, 2012, Expedient copper(I) catalysts for azide-iodoalkyne cycloaddition reactions – Scope and mechanistic studies, XXV International Conference on Organometallic Chemistry
Díez-González S, 2012, Well-defined copper(I) catalysts for true Click cycloadditions reactions, 24 Reunión Bienal de Química Orgánica
Lal S, McNally J, White AJP, et al., 2011, Novel Phosphinite and Phosphonite Copper(I) Complexes: Efficient Catalysts for Click Azide-Alkyne Cycloaddition Reactions, ORGANOMETALLICS, Vol: 30, Pages: 6225-6232, ISSN: 0276-7333
Lal S, Díez-González S, 2011, [CuBr(PPh3)3] for azide-alkyne cycloaddition reactions under strict Click conditions., J Org Chem, Vol: 76, Pages: 2367-2373
A careful methodological study revealed a true Click catalytic system based on commercially available [CuBr(PPh(3))(3)]. This system is active at room temperature, with 0.5 mol % [Cu] (or less), in the absence of any additive, and it does not require any purification step to isolate pure triazoles.
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