15 results on '"Daniele Ragno"'
Search Results
2. Phenyl-substituted aminomethylene-bisphosphonates inhibit human P5C reductase and show antiproliferative activity against proline-hyperproducing tumour cells
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Davide Petrollino, Daniele Ragno, Giuseppe Sabbioni, Giuseppe Forlani, and Monica Borgatti
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Antiproliferative activity ,P5C reductase inhibitors ,proline-overproducing tumours ,proline-P5C cycle ,Proline ,RM1-950 ,Reductase ,01 natural sciences ,NO ,Prostate ,Neoplasms ,Drug Discovery ,medicine ,Humans ,Gene ,Cell Proliferation ,Pharmacology ,chemistry.chemical_classification ,Diphosphonates ,010405 organic chemistry ,General Medicine ,0104 chemical sciences ,010404 medicinal & biomolecular chemistry ,medicine.anatomical_structure ,Enzyme ,Biochemistry ,chemistry ,Proline synthesis ,Pyrroline Carboxylate Reductases ,Therapeutics. Pharmacology ,Research Article ,Research Paper - Abstract
In certain cancers, such as breast, prostate and some lung and skin cancers, the gene for the enzyme catalysing the second and last step in proline synthesis, δ1-pyrroline-5-carboxylate (P5C) reductase, has been found upregulated. This leads to a higher proline content that exacerbates the effects of the so-called proline-P5C cycle, with tumour cells effectively using this method to increase cell survival. If a method of reducing or inhibiting P5C reductase could be discovered, it would provide new means of treating cancer. To address this point, the effect of some phenyl-substituted derivatives of aminomethylene-bisphosphonic acid, previously found to interfere with the catalytic activity of plant and bacterial P5C reductases, was evaluated in vitro on the human isoform 1 (PYCR1), expressed in E. coli and affinity purified. The 3.5-dibromophenyl- and 3.5-dichlorophenyl-derivatives showed a remarkable effectiveness, with IC50 values lower than 1 µM and a mechanism of competitive type against both P5C and NADPH. The actual occurrence in vivo of enzyme inhibition was assessed on myelogenous erythroleukemic K562 and epithelial breast cancer MDA-MB-231 cell lines, whose growth was progressively impaired by concentrations of the dibromo derivative ranging from 10−6 to 10−4 M. Interestingly, growth inhibition was not relieved by the exogenous supply of proline, suggesting that the effect relies on the interference with the proline-P5C cycle, and not on proline starvation.
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- 2021
- Full Text
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3. Exploring Oxidative NHC-Catalysis as Organocatalytic Polymerization Strategy towards Polyamide Oligomers
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Alessandro Massi, Daniele Ragno, Graziano Di Carmine, Giada Belletti, Sara Buoso, Olga Bortolini, Monica Bertoldo, Arianna Brandolese, and Costanza Leonardi
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Condensation polymer ,oxidation ,010405 organic chemistry ,Organic Chemistry ,Ambientale ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Quinone ,carbenes ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymerization ,polymerization ,Organocatalysis ,Polymer chemistry ,Polyamide ,organocatalysis ,polyamides ,Methylene ,carbenes, organocatalysis, oxidation, polyamides, polymerization ,Carbene - Abstract
The polycondensation of diamines and dialdehydes promoted by an N-heterocyclic carbene (NHC) catalyst in the presence of a quinone oxidant and hexafluoro-2-propanol (HFIP) is herein presented for the synthesis of oligomeric polyamides (PAs), which are obtained with a number-average molecular weight (Mn ) in the range of 1.7-3.6 kg mol-1 as determined by NMR analysis. In particular, the utilization of furanic dialdehyde monomers (2,5-diformylfuran, DFF; 5,5'-[oxybis(methylene)]bis[2-furaldehyde], OBFA) to access known and previously unreported biobased PAs is illustrated. The synthesis of higher molecular weight PAs (poly(decamethylene terephthalamide, PA10T, Mn = 62.8 kg mol-1 ; poly(decamethylene 2,5-furandicarboxylamide, PA10F, Mn = 6.5 kg mol-1 ) by a two-step polycondensation approach is also described. The thermal properties (TGA and DSC analyses) of the synthesized PAs are reported.
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- 2020
4. Enantioselective Dearomatization of Alkylpyridiniums by N-Heterocyclic Carbene-Catalyzed Nucleophilic Acylation
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Daniele Ragno, Olga Bortolini, Pier Paolo Giovannini, Graziano Di Carmine, Alessandro Massi, Marco Fogagnolo, Andrea Mazzanti, Di Carmine, Graziano, Ragno, Daniele, Bortolini, Olga, Giovannini, Pier Paolo, Mazzanti, Andrea, Massi, Alessandro, and Fogagnolo, Marco
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Organic Chemistry, N-heterocycle Carbenes, Organocatalysis, Asymmetric Synthesis, Dearomatization, 1,4-Dihydropyridine ,Organocatalysis ,010405 organic chemistry ,N-heterocycle Carbenes ,Organic Chemistry ,Enantioselective synthesis ,Ambientale ,Regioselectivity ,010402 general chemistry ,Circular dichroism spectra ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Catalysis ,Acylation ,Dearomatization ,chemistry.chemical_compound ,chemistry ,Nucleophile ,4-Dihydropyridine ,Carbene ,Asymmetric Synthesis - Abstract
A chiral NHC-catalyzed dearomatizing reaction of activated N-alkylpyridinium salts with aliphatic aldehydes is described. The resulting acylated 1,4-dihydropyridines have been obtained with complete C4 regioselectivity and enantioselectivities in the range 52-78% ee. The (4R)-absolute configuration of the synthesized compounds has been determined by the TD-DFT simulation of the electronic circular dichroism spectra.
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- 2018
5. Oxidative NHC-Catalysis as Organocatalytic Platform for the Synthesis of Polyester Oligomers by Step-Growth Polymerization
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Arianna Brandolese, Monica Bertoldo, Daniele Ragno, Giancarlo Fantin, Graziano Di Carmine, Pier Paolo Giovannini, Alessandro Massi, and Olga Bortolini
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Condensation polymer ,oxidation ,carbenes ,organocatalysis ,polyesters ,polymerization ,010402 general chemistry ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Oligoester ,Polyethylene terephthalate ,Organic chemistry ,010405 organic chemistry ,Organic Chemistry ,Ambientale ,General Chemistry ,0104 chemical sciences ,Step-growth polymerization ,Polyester ,Monomer ,renewable polymers ,chemistry ,Polymerization ,Ethylene glycol - Abstract
The application of N-heterocyclic carbene (NHC) catalysis to the polycondensation of diols and dialdehydes under oxidative conditions is herein presented for the synthesis of polyesters using fossil-based (ethylene glycol, phthalaldehydes) and bio-based (furan derivatives, glycerol, isosorbide) monomers. The catalytic dimethyl triazolium/1,8-diazabicyclo[5.4.0]undec-7-ene couple and stoichiometric quinone oxidant afforded polyester oligomers with a number-average molecular weight (Mn ) in the range of 1.5-7.8 kg mol-1 as determined by NMR analysis. The synthesis of a higher molecular weight polyester (polyethylene terephthalate, PET) by an NHC-promoted two-step procedure via oligoester intermediates is also illustrated together with the catalyst-controlled preparation of cross-linked or linear polyesters derived from the trifunctional glycerol. The thermal properties (TGA and DSC analyses) of the synthesized oligoesters are also reported.
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- 2019
6. Kinetic Resolution, Dynamic Kinetic Resolution and Asymmetric Desymmetrization by N-Heterocyclic Carbene Catalysis
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Olga Bortolini, Daniele Ragno, Graziano Di Carmine, Alessandro Massi, and Carmela De Risi
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asymmetric desymmetrization ,010405 organic chemistry ,Organic Chemistry ,asymmetric synthesis ,Enantioselective synthesis ,010402 general chemistry ,01 natural sciences ,Desymmetrization ,Catalysis ,0104 chemical sciences ,Kinetic resolution ,NO ,chemistry.chemical_compound ,chemistry ,N-Heterocyclic carbenes (NHCs), kinetic resolution (KR), dynamic kinetic resolution (DKR), asymmetric desymmetrization, organocatalysis, asymmetric synthesis ,Computational chemistry ,Organocatalysis ,N-Heterocyclic carbenes (NHCs) ,Stereoselectivity ,organocatalysis ,kinetic resolution (KR) ,dynamic kinetic resolution (DKR) ,Carbene - Abstract
N-Heterocyclic carbenes (NHCs) are now well-established organocatalysts for a large number of asymmetric and non-asymmetric transformations. In the last 15 years, there has been significant interest in using NHCs in kinetic resolution (KR), dynamic kinetic resolution (DKR) and asymmetric desymmetrization reactions for the stereoselective synthesis of enantioenriched compounds, with diverse substrates and activation modes being adopted to this end. This short review brings into focus the progress made on NHC-catalyzed KR, DKR, and asymmetric desymmetrization from 2004 until December 2018. The literature discussed in this article is classified on the basis of the type of reaction involving the NHC catalyst.1 Introduction2 Acylation Strategies2.1 O-Acylation2.2 N-Acylation2.3 C-Acylation3 Aldol-Acylation Processes4 Benzoin Reactions5 Stetter Reactions6 Miscellaneous Approaches7 Conclusion
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- 2019
7. Enantioselective Desymmetrization of 1,4-Dihydropyridines by Oxidative NHC Catalysis
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Arianna Brandolese, Daniele Ragno, Olga Bortolini, Andrea Mazzanti, Alessandro Massi, Federica Sabuzi, Daniel Pecorari, Graziano Di Carmine, Di Carmine G., Ragno D., Brandolese A., Bortolini O., Pecorari D., Sabuzi F., Mazzanti A., and Massi A.
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dihydropyridine ,DHPS ,Oxidative phosphorylation ,010402 general chemistry ,01 natural sciences ,Desymmetrization ,Catalysis ,Settore CHIM/06 ,NO ,desymmetrization ,organocatalysis ,010405 organic chemistry ,Chemistry ,dihydropyridines ,Organic Chemistry ,Enantioselective synthesis ,General Chemistry ,density functional calculation ,Combinatorial chemistry ,0104 chemical sciences ,Quinone ,carbene ,Organocatalysis ,Carbenes ,density functional calculations - Abstract
The unprecedented desymmetrization of prochiral dialdehydes catalyzed by N-heterocyclic carbenes under oxidative conditions was applied to the highly enantioselective synthesis of 1,4-dihydropyridines (DHPs) starting from 3,5-dicarbaldehyde substrates. Synthetic elaboration of the resulting 5-formyl-1,4-DHP-3-carboxylates allowed for access to the class of pharmaceutically relevant 1,4-DHP-3,5-dicarboxylates (Hantzsch esters). DFT calculations suggested that the enantioselectivity of the process is determined by the transition state involving the oxidation of the Breslow intermediate by the external quinone oxidant.
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- 2019
8. Aerobic oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid and its derivatives by heterogeneous NHC-catalysis
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Tatiana Bernardi, Daniele Ragno, Pier Paolo Giovannini, Omar Pandoli, Arianna Brandolese, Alessandro Massi, Graziano Di Carmine, Alessandra Altomare, and Olga Bortolini
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MECHANISM ,SELECTIVE OXIDATION, 2,5-FURANDICARBOXYLIC ACID, PHOTOCATALYTIC OXIDATION, AROMATIC-ALDEHYDES, BIOMASS, CHEMICALS, 2,5-DIFORMYL, FURAN, MECHANISM, ALCOHOLS, GLYCEROL ,AROMATIC-ALDEHYDES ,010402 general chemistry ,Thioester ,Furfural ,01 natural sciences ,Biochemistry ,Catalysis ,BIOMASS ,CHEMICALS ,Hydrolysis ,chemistry.chemical_compound ,Amide ,FURAN ,Organic chemistry ,Hydroxymethyl ,Physical and Theoretical Chemistry ,5-DIFORMYL ,PHOTOCATALYTIC OXIDATION ,chemistry.chemical_classification ,010405 organic chemistry ,Butylamine ,Depolymerization ,5-FURANDICARBOXYLIC ACID ,Organic Chemistry ,Ambientale ,ALCOHOLS ,SELECTIVE OXIDATION ,GLYCEROL ,0104 chemical sciences ,chemistry - Abstract
The application of the oxidative system composed of a heterogeneous triazolium pre-catalyst, iron(ii) phthalocyanine and air is described for the selective conversion of 5-hydroxymethylfurfural (HMF) into the added-value 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). The disclosed one-pot two-step procedure involved sequential oxidative esterifications of HMF to afford a polyester oligomer having hydroxyl and carboxyl terminal groups (Mw = 389-1258), which in turn was hydrolyzed by a supported base (Ambersep 900 OH) to yield HMFCA in 87% overall yield. The same strategy was adopted for the effective synthesis of ester and amide derivatives of HMFCA by nucleophilic depolymerization of the oligomeric intermediate with methanol and butylamine, respectively. The utilization of the disclosed oxidative system for the direct conversion of HMF and furfural into their corresponding ester, amide, and thioester derivatives is also reported.
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- 2018
9. Esterification of glycerol and solketal by oxidative NHC- catalysis under heterogeneous batch and flow conditions
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Daniele Urbani, Carmela De Risi, Daniele Ragno, Pier Paolo Giovannini, Olga Bortolini, Graziano Di Carmine, Arianna Brandolese, and Alessandro Massi
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mechanism ,chemicals ,010402 general chemistry ,Furfural ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Solketal ,Glycerol ,Chemical Engineering (miscellaneous) ,Organic chemistry ,N-heterocyclic carbenes ,liquid ,conversion ,Fluid Flow and Transfer Processes ,010405 organic chemistry ,Chemistry ,Process Chemistry and Technology ,Vanillin ,Ambientale ,electron-transfer ,0104 chemical sciences ,Solvent ,azide-alkyne cycloaddition ,immobilization ,oxygen ,Chemistry (miscellaneous) ,Citronellal ,Selectivity - Abstract
The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95 : 5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity.
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- 2018
10. Native quercetin as a chloride receptor in an organic solvent
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Pedro Merino, Daniele Ragno, Olga Bortolini, Marco Fogagnolo, Ignacio Delso, Mohamed Lamin Abdi Bellau, Giancarlo Fantin, Ministerio de Economía y Competitividad (España), Gobierno de Aragón, European Commission, Fantin, Giancarlo, Fogagnolo, Marco, Merino, Pedro, Fantin, Giancarlo [0000-0002-6931-7976], Fogagnolo, Marco [0000-0002-3261-5355], and Merino, Pedro [0000-0002-2202-3460]
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chloride binding ,Spectrometry, Mass, Electrospray Ionization ,Magnetic Resonance Spectroscopy ,Electrospray ionization ,quantum mechanics density functional theory (QM-DFT) calculations ,Flavonoid ,Catechols ,Pharmaceutical Science ,Resorcinol ,Molecular Dynamics Simulation ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Chloride ,Medicinal chemistry ,Article ,Analytical Chemistry ,NO ,quercetin ,lcsh:QD241-441 ,chemistry.chemical_compound ,lcsh:Organic chemistry ,Quantum mechanics density functional theory (QM-DFT) calculations ,molecular dynamics (MD) calculations ,Drug Discovery ,medicine ,heterocyclic compounds ,Physical and Theoretical Chemistry ,Binding site ,Molecular dynamics (MD) calculations ,chemistry.chemical_classification ,Catechol ,010405 organic chemistry ,Organic Chemistry ,Resorcinols ,quercetin, chloride binding, NMR titrations, quantum mechanics density functional theory (QM-DFT) calculations, molecular dynamics (MD) calculations ,NMR titrations ,0104 chemical sciences ,chemistry ,Chemistry (miscellaneous) ,Solvents ,Molecular Medicine ,Quercetin ,Chloride binding ,medicine.drug - Abstract
The binding properties of quercetin toward chloride anions were investigated by means of ¹H-NMR, 13C-NMR, and electrospray ionization mass spectrometry (ESI-MS) measurements, as well as computational calculations. The results indicate that quercetin behaves primarily as a ditopic receptor with the binding site of the B ring that exhibits stronger chloride affinity compared to the A ring. However, these sites are stronger receptors than those of catechol and resorcinol because of their conjugation with the carbonyl group located on the C ring. The 1:1 and 1:2 complexation of this flavonoid with Cl- was also supported by ESI mass spectrometry., I.D. and P.M. acknowledge the MINECO and FEDER Program (Madrid, Spain, project CTQ2016-76155-R) and the Gobierno de Aragon (Zaragoza, Spain. Biological & Computational Chemistry Group. E34_R17).
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- 2018
11. Immobilization of Privileged Triazolium Carbene Catalyst for Batch and Flow Stereoselective Umpolung Processes
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Daniele Ragno, Pier Paolo Giovannini, Graziano Di Carmine, Olga Bortolini, Arianna Brandolese, and Alessandro Massi
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enantioselective catalysis ,polystyrene-supported catalysts ,010405 organic chemistry ,flow chemistry ,Stetter reaction ,Ambientale ,chiral N-heterocyclic carbenes ,organocatalysis ,General Chemistry ,Flow chemistry ,010402 general chemistry ,Heterogeneous catalysis ,01 natural sciences ,Catalysis ,NO ,0104 chemical sciences ,Umpolung ,chemistry.chemical_compound ,chemistry ,Organocatalysis ,Organic chemistry ,Microreactor ,Carbene - Abstract
A strategy for the immobilization of the valuable triazolium carbene Rovis catalyst onto polystyrene and silica supports is presented. Initially, the catalyst activity and recyclability were tested under batch conditions in the model stereoselective intramolecular Stetter reaction leading to optically active chromanones. Good results in terms of yield (95%) and enantioselectivity (ee 81–95%) were detected for the polystyrene-supported catalyst (10 mol %), while poorer results were collected for the silica-supported analogue. Also, continuous-flow experiments were performed by fabricating the corresponding polystyrene monolithic microreactors (pressure-resistant stainless-steel columns) to prove the benefits of the heterogeneous catalysis and the flow regime observing a high stability of the catalytic bed (48 h) with unaltered conversion efficiency and stereoselectivity.
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- 2017
12. Synthesis of functionalized imidazolidine-2-thiones Via NHC/base-promoted aza-benzoin/aza-acetalization domino reactions
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Giancarlo Fantin, Daniele Ragno, Pier Paolo Giovannini, Alessandro Massi, Graziano Di Carmine, Olga Bortolini, and Carmela De Risi
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010405 organic chemistry ,Organic Chemistry ,Ambientale ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Domino ,0104 chemical sciences ,Adduct ,chemistry.chemical_compound ,chemistry ,Imidazolidine ,Benzoin ,Intramolecular force ,Yield (chemistry) ,Organic chemistry ,Physical and Theoretical Chemistry ,Carbene ,Triethylamine - Abstract
A strategy for the synthesis of biologically relevant 5-hydroxy-imidazolidine-2-thione derivatives is presented. A novel class of α-sulfonylamines have been suitably prepared (46–81% yield) as precursors of formal benzylidenethiourea acceptors; these are generated in situ and intercepted by N-heterocyclic carbene (NHC)-activated aldehydes affording open-chain aza-benzoin-type adducts, which in turn undergo an intramolecular aza-acetalization reaction in a one-pot fashion. A thiazolium salt/triethylamine couple proved to be the more effective system to trigger the domino sequence giving the target heterocycles in good yields (45–97%) and diastereoselectivities (up to 99 : 1 dr). The multigram scale synthesis and elaboration of a selected 5-hydroxy-imidazolidine-2-thione compound is also described.
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- 2017
13. Fluorous-tag assisted synthesis of bile acid-bisphosphonate conjugates via orthogonal click reactions: an access to potential anti-resorption bone drugs
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Daniele Ragno, Dario Cristofaro, Daniela Perrone, Alessandro Massi, Gianluca Toniolo, Chiara Massarenti, Giancarlo Fantin, Olga Bortolini, and Elena Marchesi
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Fluorophore ,medicine.drug_class ,Molecular Conformation ,010402 general chemistry ,chemistry ,01 natural sciences ,Biochemistry ,in-vivo ,cycloadditions ,Bile Acids and Salts ,chemistry.chemical_compound ,medicine ,analogs ,Organic chemistry ,oligosaccharide ,Bone Resorption ,Physical and Theoretical Chemistry ,Fluorescent Dyes ,chemistry.chemical_classification ,Solid-phase extraction ,Diphosphonates ,Bile acid ,terminal alkynes ,010405 organic chemistry ,Solid Phase Extraction ,Organic Chemistry ,Ambientale ,hydroxyapatite ,Combinatorial chemistry ,delivery ,nanoparticles ,Cycloaddition ,0104 chemical sciences ,Resorption ,Drug Design ,Thiol ,Surface modification ,Click Chemistry ,Azide ,Conjugate - Abstract
The synthesis of a small collection of novel bile acid-bisphosphonate (BA-BP) conjugates as potential drug candidates is reported. The disclosed methodology relied on the installation of azide and thiol functionalities at the head and tail positions, respectively, of the BA scaffold and its subsequent decoration by orthogonal click reactions (copper-catalyzed azide-alkyne cycloaddition, thiol-ene or thiol-yne coupling) to introduce BP units and a fluorophore. Because of the troublesome isolation of the target conjugates by standard procedures, the methodology culminated with the functionalization of the BA scaffold with a light fluorous tag to rapidly and efficiently purify intermediates and final products by fluorous solid-phase extraction.
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- 2017
14. Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification
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Giancarlo Fantin, Pier Paolo Giovannini, Daniele Ragno, Carmela De Risi, Anna Zaghi, Graziano Di Carmine, Alessandro Massi, and Olga Bortolini
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Base (chemistry) ,continuos-flow ,010402 general chemistry ,01 natural sciences ,Full Research Paper ,lcsh:QD241-441 ,Electron transfer ,chemistry.chemical_compound ,lcsh:Organic chemistry ,Benzoin ,C–C coupling ,diketone ,electron-transfer ,umpolung ,Organic chemistry ,lcsh:Science ,chemistry.chemical_classification ,Polarity reversal ,Packed bed ,010405 organic chemistry ,Organic Chemistry ,Ambientale ,0104 chemical sciences ,Solvent ,Chemistry ,chemistry ,Chemical engineering ,lcsh:Q ,Polystyrene ,Microreactor - Abstract
A convenient heterogeneous continuous-flow procedure for the polarity reversal of aromatic α-diketones is presented. Propaedeutic batch experiments have been initially performed to select the optimal supported base capable to initiate the two electron-transfer process from the carbamoyl anion of the N,N-dimethylformamide (DMF) solvent to the α-diketone and generate the corresponding enediolate active species. After having identified the 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine on polystyrene (PS-BEMP) as the suitable base, packed-bed microreactors (pressure-resistant stainless-steel columns) have been fabricated and operated to accomplish the chemoselective synthesis of aroylated α-hydroxy ketones and 2-benzoyl-1,4-diones (benzoin- and Stetter-like products, respectively) with a good level of efficiency and with a long-term stability of the packing material (up to five days).
- Published
- 2016
15. Cross-benzoin and Stetter-type reactions mediated by KOtBu-DMF via an electron-transfer process
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Alessandro Venturini, Pier Paolo Giovannini, Graziano Di Carmine, Anna Zaghi, Alessandro Massi, Daniele Ragno, Marco Fogagnolo, Alessandra Molinari, and Olga Bortolini
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Stetter-type ,Reactive intermediate ,Ionic bonding ,mechanism ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Biochemistry ,DFT ,Umpolung ,Catalysis ,chemistry.chemical_compound ,Electron transfer ,Benzoin ,Polymer chemistry ,Physical and Theoretical Chemistry ,Chemoselectivity ,010405 organic chemistry ,Organic Chemistry ,Organic Synthesis ,Ambientale ,electron transfer ,Cross-benzoin ,0104 chemical sciences ,chemistry ,Benzil - Abstract
The condensation of aromatic alpha-diketones (benzils) with aromatic aldehydes ( benzoin-type reaction) and chalcones ( Stetter-type reaction) in DMF in the presence of catalytic ( 25 mol%) KOtBu is reported. Both types of umpolung processes proceed with good efficiency and complete chemoselectivity. On the basis of spectroscopic evidence ( MS analysis) of plausible intermediates and literature reports, the occurrence of different ionic pathways have been evaluated to elucidate the mechanism of a model cross-benzoinlike reaction along with a radical route initiated by an electron-transfer process to benzil from the carbamoyl anion derived from DMF. This mechanistic investigation has culminated in a different proposal, supported by calculations and a trapping experiment, based on double electron-transfer to benzil with formation of the corresponding enediolate anion as the key reactive intermediate. A mechanistic comparison between the activation modes of benzils in KOtBu-DMF and KOtBu-DMSO systems is also described.
- Published
- 2016
Catalog
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