Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 41
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Org Chem ; 89(13): 9521-9542, 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38965936

RESUMO

The solvent parameters DI, ES, α1, and ß1 are intended for the description of solute-solvent intermolecular forces, i.e., dispersion-induction, electrostatic, hydrogen-bond donation, and hydrogen-bond acceptance, respectively. An up-to-date collection of these parameters is presented for 380 solvents including green solvents, ionic liquids, and deep eutectic solvents. Their determination for additional solvents requires three commercial indicators, betaine dye B(30), 4-F-phenol, and 4-F-anisole (as well as the refractive index). The chemical significance of these parameters is outlined. Their use in the linear solvation energy relationship P = P° + di DI + e ES + a α1 + b ß1 for 62 physicochemical properties P (reaction rates, equilibrium constants, and IR, UV, and NMR spectra) yields determination coefficients generally greater than 0.90 and regression coefficients whose sign and relative magnitude provide consistent information on the intermolecular forces acting on these properties.

2.
Chemistry ; 30(34): e202303697, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38619531

RESUMO

Dearomative Diels-Alder cycloadditions between nitroarenes and 2-trimethylsilyloxycyclohexadiene are carried out under high pressure at room temperature in the absence of any chemical promoter. Reactions are performed with different arenes, including the highly aromatic naphthalenes and quinolines. They lead to 3D-scaffolds with exquisite exo-diastereoselectivity. The exo approach is characterized by lower distortion of the substrates in a late TS and by more favorable orbital interactions presumably between the nitro group and the dienic part, explaining the stereoselectivity.

3.
Chembiochem ; : e202400137, 2024 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-38591336

RESUMO

The biocatalyzed oxidative detoxification of the V-series simulant PhX, by mean of the microperoxidase AcMP11, affords the corresponding phosphonothioate as the prominent product instead of the classical P-S and P-O bond cleavage. While PhX is structurally very close to the live agent VX (the methyl group is replaced by a phenyl), assessment with other surrogates missing the nucleophilic amino function displayed more resistance under the same conditions with no phosphonothioate observed. These encouraging results highlight 1) the efficacy of AcMP11 microperoxidase to efficiently detoxify V-series organophosphorus nerve agents (OPNA), and 2) the necessity to use representative alkyl or aryl phosphonothioates simulants such as PhX bearing the appropriate side chain as well as the P-O and P-S cleavable bond to mimic accurately the V-series OPNA to prevent false positive or false negative results.

4.
Org Lett ; 25(48): 8580-8584, 2023 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-37991751

RESUMO

1,4-Disubstituted cubyl aryl thioethers were generated from the corresponding iodocubanes and aryl thiolates upon UV irradiation in dimethyl sulfoxide at room temperature. This simple procedure was found to be compatible with a variety of substituted aryl thiolates. This finding paved the way to a synthesis of the monocubyl analogue of dapsone, a key molecule in the treatment of leprosy, also known as Hansen's disease, and of acne.

5.
Chemistry ; 29(49): e202301567, 2023 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-37306243

RESUMO

The photocatalyzed dearomative reaction between various electron-deficient aromatic compounds and a non-stabilized azomethine ylide is successfully performed in a flow system. Whereas the use of supported eosin as organic photocatalyst exhibits limited efficiency, turning to the soluble Rose Bengal allows to transform a broad range of substrates from hetarenes (indole, benzofuran, quinoline, pyridine) to naphthalenes and benzenes. This photocatalyzed (3+2) dearomative cycloaddition under green light irradiation provides a simple and efficient access to tridimensional pyrrolidino scaffolds with a tetrasubstituted carbon center at ring junction and can be performed in the friendly ethyl acetate. Computational studies support the mechanism involving azomethine ylide as reactive species toward the electron-poor arene.

6.
Chemphyschem ; 24(4): e202200729, 2023 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-36264764

RESUMO

The solvent is of prime importance in biomass conversion as it influences dissolution, reaction kinetics, catalyst activity and thermodynamic equilibrium of the reaction system. So far, activity-based models were developed to predict kinetics and equilibria, but the influence of the catalyst on kinetics has not been succesfully predicted by thermodynamic models. In this work, the thermodynamic model ePC-SAFT advanced was used to predict the activities of the reactants and of the catalyst at various conditions (temperature, reactant concentrations, γ-valerolactone GVL cosolvent addition, catalyst concentration) for the homogeneously acid-catalyzed esterification of levulinic acid (LA) with ethanol. Different kinetic models were applied, and it was found that the catalyst influence on kinetics could be predicted correctly by simultaneously solving the dissociation equilibrium of H2 SO4 catalyst along the reaction coordinate and by relating reaction kinetics to proton activity. ePC-SAFT advanced model parameters were only fitted to reaction-independent phase equilibrium data. The key reaction properties were determined by applying ePC-SAFT advanced to one experimental kinetic curve for a set of temperatures, yielding the reaction enthalpy at standard state Δ R H 0 = 11 . 48 k J m o l - 1 ${{\Delta }^{R}{H}^{0}=11.48\ kJ\ mo{l}^{-1}}$ , activation energy E A = 30 . 28 k J m o l - 1 ${{E}_{A}=30.28\ kJ\ mo{l}^{-1}}$ and the intrinsic reaction rate constant k=0.011 s-1 at 323 K, which is independent of catalyst concentration. The new procedure allowed an a-priori identification of the effects of catalyst, solvent and reactant concentration on LA esterification.

7.
Lab Chip ; 23(5): 1349-1357, 2023 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-36278262

RESUMO

For decades, a production paradigm based on centralized, stepwise, large scale processes has dominated the chemical industry horizon. While effective to meet an ever increasing demand for high value-added chemicals, the so-called macroscopic batch reactors are also associated with inherent weaknesses and threats; some of the most obvious ones were tragically illustrated over the past decades with major industrial disasters and impactful disruptions of advanced chemical supplies. The COVID pandemic has further emphasized that a change in paradigm was necessary to sustain chemical production with an increased safety, reliable supply chains and adaptable productivities. More than a decade of research and technology development has led to alternative and effective chemical processes relying on miniaturised flow reactors (a.k.a. micro and mesofluidic reactors). Such miniaturised reactors bear the potential to solve safety concerns and to improve the reliability of chemical supply chains. Will they initiate a new paradigm for a more localized, safe and reliable chemical production?


Assuntos
COVID-19 , Humanos , Reprodutibilidade dos Testes , Reatores Biológicos
8.
Chemistry ; 28(71): e202202286, 2022 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-36200571

RESUMO

We describe herein the first halogen dance (HD) in continuous flow on 2-chloro-3-bromopyridine by selectively trapping a (pyridin-4-yl)lithium species that is known to undergo the halogen-dance process. In addition, this lithiated intermediate was trapped at lower temperature before the HD occurs. The HD process was extended to fluoro-iodopyridines by using various electrophiles to afford 28 examples with yields ranging from 42 to 97 % with very short residence times. Finally, scale up of the reaction was demonstrated, affording a promising space-time yield (STY) of 4.2 kg.h-1 .L-1 .


Assuntos
Dança , Halogênios , Lítio , Temperatura
9.
Chem Commun (Camb) ; 58(84): 11807-11810, 2022 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-36189685

RESUMO

Simple nitroarenes such as nitronaphthalenes and nitroquinolines smoothly undergo dearomatizing [4+2] cycloadditions with silyloxydienes under 16 kbar. Highly functionalized 3-dimensional polycyclic adducts bearing a tetrasubstituted carbon centre at the ring junction are obtained in one step from simple raw materials. This unprecedented dearomative Diels-Alder process is performed at room temperature without any chemical promoter, illustrating the exceptional role of high pressure as a physical promoter.


Assuntos
Nitroquinolinas , Compostos Orgânicos , Reação de Cicloadição , Carbono
10.
Org Biomol Chem ; 20(38): 7604-7608, 2022 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-36148796

RESUMO

The neutralisation of structurally varied chemical warfare agent simulants (blister and nerve agents) and pesticides (Paraoxon) with the assistance of high pressure is reported. Chloroethyl amines and sulfides (nitrogen and sulfur mustards), phosphonothioates (V-series nerve agents) and phosphates (pesticide) readily react with simple nucleophilic scavengers (alcohols, amines) at P > 14 000 bar.


Assuntos
Substâncias para a Guerra Química , Agentes Neurotóxicos , Praguicidas , Álcoois , Aminas , Nitrogênio , Paraoxon , Fosfatos , Sulfetos , Enxofre
11.
J Org Chem ; 87(9): 6273-6287, 2022 05 06.
Artigo em Inglês | MEDLINE | ID: mdl-35467876

RESUMO

Today, the hydrogen bonding donation (HBD) ability parameter of new solvents, α, is generally determined either by the Kamlet-Taft solvatochromic comparison of two probes, Reichardt betaine dye B(30) and 4-nitroanisole, or by the measurement of a single probe (e.g., solvatochromism of an iron coordination complex). This work highlights the shortcomings of these probes and recommends three replacement methods: (a) the theoretical comparison of the experimental and PCM-TD-DFT calculated transition energies ET(30) of B(30), (b) the semiempirical comparison of the experimental and McRae calculated ET(30), and, (c) for ionic liquids, the experimental comparison of ET(30) and ET(33) lying on the lower basicity of the betaine dye B(33) compared to B(30). These methods yield a new HBD parameter, α1, for 101 molecular solvents and 30 ionic liquids. The novelty is emblematic for water, with α1 = 1.54 instead of α (Kamlet-Taft) = 1.17. The solvent parameter α1 is not equivalent to the solute hydrogen-bond acidity parameter α2H, partly because of the self-association of HBD solvents.


Assuntos
Líquidos Iônicos , Betaína/química , Hidrogênio , Ligação de Hidrogênio , Solventes/química
12.
J Flow Chem ; 12(2): 147-151, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34631154

RESUMO

We describe the total flow synthesis of the widely prescribed anti-inflammatory COX-2 inhibitor Celecoxib from 2-bromo-3,3,3-trifluoropropene, as a convenient and available trifluoromethyl building block, to generate trifluoropropynyl lithium and to trap it immediately with an aldehyde. Oxidation of the obtained alcohol into ketone followed by condensation with 4-sulfamidophenylhydrazine afforded the targeted drug with full regioselectivity. It is noteworthy that the quality of these flow reactions (50% overall yield within 1 h cumulated residence time over 3 steps) directly furnished the target API and intermediates with excellent purity. Supplementary Information: The online version contains supplementary material available at 10.1007/s41981-021-00205-x.

13.
Molecules ; 26(23)2021 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-34885756

RESUMO

Herein, we report a continuous flow process for the synthesis of 2,6-diisopropylphenol-also known as Propofol-a short-acting intravenous anesthesia, widely used in intensive care medicine to provide sedation and hypnosis. The synthesis is based on a two-step procedure: a double Friedel-Crafts alkylation followed by a decarboxylation step, both under continuous flow.


Assuntos
Hipnose Anestésica , Propofol/síntese química , Anestesia Intravenosa , Humanos , Propofol/química , Propofol/uso terapêutico
14.
Chem Commun (Camb) ; 57(78): 10071-10074, 2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34515263

RESUMO

The electrophilicity of 4 different 3-nitroindole derivatives has been evaluated by Mayr's linear free energy relationship (log k(20 °C) = sN(E + N)) and reveals unexpected values for aromatic compounds, in the nitrostyrene range. 3-Nitroindoles are sufficiently electrophilic to interact with a common diene namely the Danishefsky's diene at room temperature, in the absence of any activator, to furnish smoothly the dearomatized (4+2) cycloadducts in good yields.

15.
J Org Chem ; 86(5): 4143-4158, 2021 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-33586436

RESUMO

A variety of physicochemical properties and several hydrogen-bond donors have been used to define methods and to build scales aiming at measuring the hydrogen-bond acceptance of solvents. There is a great deal of confusion in these scales and methods. Solvatochromic, solvatocalorimetric, solvatovibrational, and 19F solvatomagnetic comparison methods are critically reviewed. Only two methods, the solvatomagnetic and the solvatocalorimetric ones, are able to yield reliable solvent hydrogen-bond acceptance scales. The solvatomagnetic ß1 scale defined from the 19F chemical shift of 4-fluorophenol is extended to many solvents including ionic liquids and green solvents. The results for about 240 hydrogen-bond acceptor solvents are organized in a numerical ß1 database. The comparison of ß1 with solvatochromic scales highlights their shortcomings, in particular for the important class of amphiprotic solvents. Therefore, the use of the 19F solvatomagnetic comparison method and of the solvatomagnetic ß1 scale is recommended in solvent effect studies.


Assuntos
Líquidos Iônicos , Hidrogênio , Ligação de Hidrogênio , Solventes
16.
Chem Commun (Camb) ; 57(1): 27-44, 2021 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-33300929

RESUMO

The indol(in)e building block is one of the "privileged-structures" for the pharmaceutical industry since this fragment plays a central role in drug discovery. While the electron-rich character of the indole motif has been investigated for decades, exploiting the electrophilic reactivity of 3-nitroindole derivatives has recently been put at the heart of a wide range of new, albeit challenging, chemical reactions. In particular, dearomatization processes have considerably enriched the scope of C2[double bond, length as m-dash]C3 functionalizations of these scaffolds. This feature article showcases this remarkable electrophilic reactivity of 3-nitroindoles with electron-rich species and highlights their value in generating diversely substituted indol(in)es. This compilation underlines how these heteroaromatic templates have gradually become model substrates for electron-poor aromatic compounds in dearomatization strategies.


Assuntos
Reação de Cicloadição/métodos , Indóis/química , Compostos Azo/química , Catálise , Cobre/química , Elétrons , Compostos de Epóxi/química , Hidrocarbonetos Aromáticos/química , Estrutura Molecular , Paládio/química , Estereoisomerismo , Tiossemicarbazonas/química
17.
Org Biomol Chem ; 18(18): 3481-3486, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32347286

RESUMO

1,3-Dipolar dearomatizing cycloadditions between a non-stabilized azomethine ylide and 3-cyanoindoles or benzofuran afford the corresponding 3D-heterocycles bearing a quaternary carbon centre at the ring junction. While 6 equivalents of ylide precursor 1 are required for full conversion in a classical flask, working under flow conditions limits the excess (3 equiv., tR = 1 min) and leads to a cleaner process, affording cycloadducts that are easier to isolate.

18.
Org Biomol Chem ; 17(27): 6528-6537, 2019 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-31215586

RESUMO

Despite international prohibition, some ill-intentioned states and organisations have shown their will and capacity to run chemical weapon programs, and the number of incidents involving chemical warfare agents (CWA) has significantly increased in recent years. Herein, we aimed to offer a clear overview of chemical warfare agents to organic chemists not specialized in this field by (1) introducing the main CWAs and their relevant simulants legally usable in academic laboratories and (2) presenting a selection of recent and soft neutralisation methods, such as organocatalysis and continuous flow, and materials such as metal-organic frameworks and polyoxometalates. These modern approaches offer potential future alternatives to "heavy" decontamination methods.

19.
Chem Commun (Camb) ; 55(52): 7494-7497, 2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31185071

RESUMO

The dearomatization of conventional nitroarenes by lithiated enolates derived from methyl vinyl ketones easily takes place, following a formal (4+2) cycloaddition process. While nitroindoles react readily with in situ generated conjugated enolates, the deaggregation of these latter species using HMPA extends the reaction scope to the more aromatic nitronaphthalenes and pyridines.

20.
Angew Chem Int Ed Engl ; 56(26): 7568-7572, 2017 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-28474395

RESUMO

The fast and effective neutralization of the mustard-gas simulant 2-chloroethyl ethyl sulfide (CEES) using a simple and portable continuous flow device is reported. Neutralization takes place through a fully selective sulfoxidation by a stable source of hydrogen peroxide (alcoholic solution of urea-H2 O2 adduct/MeSO3 H freshly prepared). The reaction progress can be monitored with an in-line benchtop NMR spectrometer, allowing a real-time adjustment of reaction conditions. Inherent features of millireactors, that is, perfect control of mixing, heat and reaction time, allowed the neutralization of 25 g of pure CEES within 46 minutes in a 21.5 mL millireactor (tR =3.9 minutes). This device, which relies on affordable and nontoxic reagents, fits into a suitcase, and can be deployed by police/military forces directly on the attack site.


Assuntos
Substâncias para a Guerra Química/química , Espectroscopia de Ressonância Magnética/instrumentação , Espectroscopia de Ressonância Magnética/métodos , Gás de Mostarda/química , Oxirredução
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...