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1.
J Colloid Interface Sci ; 606(Pt 1): 158-166, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34388568

RESUMO

Sulfonated polydivinylbenzene bamboo-like nanotube (SPDVB) with effective olefins oxidation activity is prepared by combining cationic polymerization and sulfonation. By merely adjusting sulfonation time, SPDVB with different sulfonic acid group (-SO3H) contents is achieved. SPDVB is used as both a solid emulsifier and catalyst to fabricate Pickering emulsion interface catalytic system for oxidizing olefins with 30% H2O2 acting as oxidant/water phase and olefins acting as reactants/oil phase. It is shown that Pickering emulsion interface catalytic system stabilized by SPDVB exhibits enhanced olefins oxidation efficiency than the conventional ones. At the optimum catalyst and reaction condition, the conversion of olefins by Pickering emulsion interface catalytic system stabilized by SPDVB for cyclohexene, 1-methylcyclohexene, cyclooctene, 2,3-dimethyl-2-butene oxidation is higher than 90.00% and the corresponding 1,2-diol selectivity exceeds 93.00% except the selectivity to 1-methyl-1,2-cyclohexanediol. The catalytic system also exhibits excellent cycling performance (>95.00% olefins conversion and >89.00% 1,2-diol selectivity for cyclohexene/2,3-dimethyl-2-butene oxidation after four cycles). A possible mechanism for oxidation of olefins to 1,2-diol by SPDVB stabilized Pickering emulsion is proposed: the high catalytic interface area between sulfonic acid group and H2O2 in water phase enhances the sulfonic acid group of SPDVB to convert into peroxysulfonic acid (catalytic activity centre) firstly; then the formed peroxysulfonic acid attacks the double bond of olefins to form epoxide intermediates, which will be hydrolyzed to 1,2-diol.


Assuntos
Peróxido de Hidrogênio , Nanotubos , Alcenos , Emulsões , Oxirredução , Tamanho da Partícula
2.
Bioorg Chem ; 116: 105362, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34598089

RESUMO

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a serious threat to global health. One attractive antiviral target is the membrane fusion mechanism employed by the virus to gain access to the host cell. Here we report a robust protein-based fluorescent polarization assay, that mimicking the formation of the six-helix bundle (6-HB) process during the membrane fusion, for the evaluation and screening of SARS-CoV-2 fusion Inhibitors. The IC50 of known inhibitors, HR2P, EK1, and Salvianolic acid C (Sal-C) were measured to be 6.1 nM, 2.5 nM, and 8.9 µM respectively. In addition, we found Sal-A has a slightly lower IC50 (3.9 µM) than Sal-C. Interestingly, simple caffeic acid can also disrupt the formation of 6-HB with a sub-mM concentration. Pilot high throughput screening (HTS) of a small marine natural product library validates the assay with a Z' factor close to 0.8. We envision the current assay provides a convenient way to screen SARS-CoV-2 fusion inhibitors and assess their binding affinity.


Assuntos
Alcenos/análise , Antivirais/análise , Polarização de Fluorescência , Ensaios de Triagem em Larga Escala , Peptídeos/análise , Polifenóis/análise , Alcenos/farmacologia , Antivirais/farmacologia , Avaliação Pré-Clínica de Medicamentos , Humanos , Estrutura Molecular , Peptídeos/farmacologia , Polifenóis/farmacologia , SARS-CoV-2/efeitos dos fármacos
3.
Chemistry ; 27(60): 14846-14850, 2021 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-34611939

RESUMO

Alkyne aminopalladation reactions starting from tosylamides are reported. The emerging vinylic Pd species are converted either in an intramolecular Heck reaction with olefinic units or in an intermolecular Suzuki reaction by using boronic acids exhibiting broad functional group tolerance. Tetra(hetero)substituted tosylated enamines are obtained in a simple one-pot process.


Assuntos
Alcenos , Alcinos , Ácidos Borônicos , Catálise , Estrutura Molecular , Paládio
4.
Chemistry ; 27(62): 15277-15326, 2021 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-34499378

RESUMO

This review discusses recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in the design of boron-containing drugs are surveyed, with special emphasis on α-amino boronic derivatives. A general overview of saturated boronic compounds as modern tools to construct C(sp3 )-C and C(sp3 )-heteroatom bonds is given, including recent developments in the Suzuki-Miyaura and Chan-Lam cross-couplings, single-electron-transfer processes including metallo- and organocatalytic photoredox reactions, and transformations of boron "ate" complexes. Finally, an attempt to summarize the current state of the art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with a brief mention of the "classical" methods (transmetallation of organolithium/magnesium reagents with boron species, anti-Markovnikov hydroboration of alkenes, and the modification of alkenyl boron compounds) and a special focus on recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative C-H activation, novel approaches to alkene hydroboration, and 1,2-metallate-type rearrangements).


Assuntos
Alcenos , Ácidos Borônicos , Boro , Compostos de Boro , Química Farmacêutica
5.
J Agric Food Chem ; 69(38): 11382-11394, 2021 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-34533305

RESUMO

Aromatized wines and regular table wines are often filled on the same bottling line. Sealing polymers in the filling line absorb volatiles from aromatized wines and may migrate due to insufficient cleaning into the subsequently bottled regular wine. Unintentional carryover of volatiles may lead to accusation of illegal aromatization of wine. Absorption, cleaning efficacy, and migration of volatiles into ethylene propylene diene monomer rubber were investigated in a model system. Direct thermal desorption-gas chromatography-mass spectrometry analysis of seven aroma compounds monitored variation in the polymer (µg/g). Absorption of volatiles was mostly driven by their octanol/water partition coefficients. Cleaning of polymers removed 11 to 62% of the absorbed volatiles. Subsequent immersion of cleaned polymers into model wine revealed migration of 20 to 57% of the remaining volatiles. Sensory tests suggested the impact of transferred volatiles into subsequent model wine. For α-ionone, an odor activity value of 1.03 indicated a potential sensory impact.


Assuntos
Compostos Orgânicos Voláteis , Vinho , Alcenos , Etilenos , Odorantes/análise , Polímeros , Borracha , Compostos Orgânicos Voláteis/análise , Vinho/análise
6.
J Agric Food Chem ; 69(38): 11204-11215, 2021 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-34544239

RESUMO

Herbivore-induced plant volatiles (HIPVs) play an important role in insect resistance. As a common HIPV in tea plants (Camellia sinensis), ß-ocimene has shown anti-insect function in other plants. However, whether ß-ocimene in tea plants also provides insect resistance, and its mechanism of synthesis and emission are unknown. In this study, ß-ocimene was confirmed to interfere with tea geometrid growth via signaling. Light was identified as the key factor controlling regular emission of ß-ocimene induced by the wounding from tea geometrids. ß-Ocimene synthase (CsBOS1) was located in plastids and catalyzed ß-ocimene formation in overexpressed tobacco. CsBOS1 expression in tea leaves attacked by tea geometrids showed a day-low and night-high variation pattern, while CsABCG expression involved in volatile emission showed the opposite pattern. These two genes might regulate the regular ß-ocimene emission from tea plants induced by tea geometrid attack. This study advances the understanding on HIPV emission and signaling in tea plants.


Assuntos
Camellia sinensis , Monoterpenos Acíclicos , Alcenos , Animais , Herbivoria , Insetos , Folhas de Planta , Chá
7.
J Agric Food Chem ; 69(39): 11656-11664, 2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34554738

RESUMO

As the major contributors to the floral odors of tea products, terpenoid volatiles play critical roles in the defense response of plants to multiple stresses. Until now, only a few TPS genes in tea plants (Camellia sinensis) have been functionally validated. In this study, by comparative studies conducted at gene, protein, and metabolite levels during oolong tea processing, we isolated an ocimene synthase gene, CsOCS, which displays a low similarity to previously characterized tea ocimene synthases. Further prokaryotic expression and subcellular localization analysis showed that it is plastid-located and could produce (E)-ß-ocimene and (Z)-ß-ocimene using GPP as the substrate. The optimum temperature and pH of the enzyme were 30 °C and 7.5, respectively. Treatment with exogenous methyl jasmonate elevated the transcript level of CsOCS and enhanced the emission of ocimene from tea leaves. Collectively, CsOCS is implicated as a key enzyme for ß-ocimene synthesis during oolong tea processing.


Assuntos
Camellia sinensis , Monoterpenos Acíclicos , Alcenos , Folhas de Planta , Proteínas de Plantas/genética , Chá
8.
Anal Chem ; 93(39): 13284-13292, 2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34549946

RESUMO

Silver(I) ions undergo selective olefin complexation and have been utilized in various olefin/paraffin separation techniques such as argentation chromatography and facilitated transport membranes. Ionic liquids (ILs) are solvents known for their low vapor pressure, high thermal stability, low melting points, and ability to promote a favorable solvation environment for silver(I) ion-olefin interactions. To develop highly selective separation systems, a fundamental understanding of analyte partitioning to the stationary phase and the thermodynamic driving forces behind solvation is required. In this study, a chromatographic model treating silver(I) ions as a pseudophase is constructed and employed for the first time to investigate the olefin separation mechanism in silver(I) salt/IL mixtures. Stationary phases containing varying amounts of noncoordinated silver(I) salt ([Ag+][NTf2-]) dissolved in the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C10MIM+][NTf2-]) IL are utilized to determine the partition coefficients of various analytes including alkanes, alkenes, alkynes, aromatics, aldehyde, esters, and ketones. As ligand coordination to silver(I) ions is known to lower its olefin complexation capability, this study also examines two different types of coordinated silver(I) ion pseudophases, namely, monocoordinated silver(I) salt ([Ag+(1-decyl-2-methylimidazole, DMIM)][NTf2-]) and dicoordinated silver(I) salt ([Ag+(1-methylimidazole, MIM)(DMIM)][NTf2-]). The extent of olefin partitioning to the coordinated silver(I) ion pseudophases over the carrier gas and IL decreased by up to two orders of magnitude. Values for enthalpy, entropy, and free energy of solvation were determined for the three silver(I) ion-containing systems. Olefin retention was observed to be enthalpically dominated, while ligand coordination to the silver(I) ion pseudophase resulted in variations for both enthalpic and entropic contributions to the free energy of solvation. The developed model can be used to study chemical changes that occur in silver(I) ions over time as well as identify optimal silver(I) salt/IL mixtures that yield high olefin selectivity.


Assuntos
Líquidos Iônicos , Alcenos , Cromatografia , Íons , Prata
9.
Nat Commun ; 12(1): 5328, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34493725

RESUMO

Aliphatic esters are essential constituents of biologically active compounds and versatile chemical intermediates for the synthesis of drugs. However, their preparation from readily available olefins remains challenging. Here, we report a strategy to access aliphatic esters from olefins through a photocatalyzed alkoxycarbonylation reaction. Alkyloxalyl chlorides, generated in situ from the corresponding alcohols and oxalyl chloride, are engaged as alkoxycarbonyl radical fragments under photoredox catalysis. This transformation tolerates a broad scope of electron-rich and electron-deficient olefins and provides the corresponding ß-chloro esters in good yields. Additionally, a formal ß-selective alkene alkoxycarbonylation is developed. Moreover, a variety of oxindole-3-acetates and furoindolines are prepared in good to excellent yields. A more concise formal synthesis of (±)-physovenine is accomplished as well. With these strategies, a wide range of natural-product-derived olefins and alkyloxalyl chlorides are also successfully employed.


Assuntos
Alcenos/química , Técnicas de Química Sintética , Ésteres/química , Indóis/síntese química , Oxindóis/síntese química , Álcoois/química , Catálise , Cloretos/química , Humanos , Estrutura Molecular , Oxalatos/química , Oxirredução , Processos Fotoquímicos , Fisostigmina/análogos & derivados , Fisostigmina/síntese química , Estereoisomerismo
10.
Nat Commun ; 12(1): 5300, 2021 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-34489427

RESUMO

Isobutene is a high value gaseous alkene used as fuel additive and a chemical building block. As an alternative to fossil fuel derived isobutene, we here develop a modified mevalonate pathway for the production of isobutene from glucose in vivo. The final step in the pathway consists of the decarboxylation of 3-methylcrotonic acid, catalysed by an evolved ferulic acid decarboxylase (Fdc) enzyme. Fdc belongs to the prFMN-dependent UbiD enzyme family that catalyses reversible decarboxylation of (hetero)aromatic acids or acrylic acids with extended conjugation. Following a screen of an Fdc library for inherent 3-methylcrotonic acid decarboxylase activity, directed evolution yields variants with up to an 80-fold increase in activity. Crystal structures of the evolved variants reveal that changes in the substrate binding pocket are responsible for increased selectivity. Solution and computational studies suggest that isobutene cycloelimination is rate limiting and strictly dependent on presence of the 3-methyl group.


Assuntos
Alcenos/metabolismo , Carboxiliases/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/enzimologia , Mononucleotídeo de Flavina/química , Glucose/metabolismo , Alcenos/química , Biocatálise , Carboxiliases/genética , Crotonatos/metabolismo , Evolução Molecular Direcionada/métodos , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Fermentação , Mononucleotídeo de Flavina/metabolismo , Glucose/química , Hypocreales/enzimologia , Hypocreales/genética , Ácido Mevalônico/metabolismo , Prenilação
11.
J Environ Manage ; 300: 113772, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34560470

RESUMO

Plant design implies the best choice among a set of feedstock-to-product process pathways. Multiple sustainability performance indicators can blur the decision, and existing sustainability assessment methods usually focus only on environmental life-cycle performance and corporate metrics or solely on the gate-to-gate process. It is relevant to incorporate integrated system analysis to address sustainability comprehensively. To this end, the Sustainable Process Systems Engineering (S-PSE) method was previously introduced to select the most sustainable feedstock-process-product configuration via four-dimensional indicators (environment, efficiency, health-&-safety, and economic), and then pinpoint the sustainability hotspots of the best design to unveil possible improvements. This work expands S-PSE by adding new features: (i) cradle-to-gate environmental assessment; (ii) composition of flowsheets; (iii) new indicators; (iv) statistical screening of indicators; and (v) 2030 Agenda compliance. A biorefinery case-study demonstrates S-PSE: to select the best pathway from soybean-oil, palm-oil, and microalgae-oil to biodiesel, green-diesel, and propylene-glycol. Firstly, statistical screening reduces the indicator set by 62%. Results evince all routes from microalgae-oil as economically unfeasible due to oil cost, despite superior environmental performance. S-PSE evinces palm-oil-to-biodiesel as the most sustainable due to lower cradle-to-gate emissions and manufacturing cost, with sustainability hotspots associated to hazardous methanol input and energy-intensive distillations. 2030 Agenda analysis also outlines palm-oil-to-biodiesel as best for 5 out of 10 Sustainable Development Goals linked to the reduced indicator set.


Assuntos
Biocombustíveis , Microalgas , Alcenos , Glicóis
12.
Chemistry ; 27(63): 15722-15729, 2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34523761

RESUMO

In the context of new scaffolds obtained by photochemical reactions, Paternò-Büchi reactions between heteroaromatic, trifluoromethylphenyl ketone and electron rich alkenes to give oxetanes are described. A comprehensive study has then been carried out on the reaction of aromatic ketones with fluorinated alkenes. Depending on the substitution pattern at the oxetane ring, a metathesis reaction is described as a minor side process to give mono fluorinated alkenes. Overall, this last reaction corresponds to a photo-Wittig reaction and yield amid isosteres. In order to explain the uncommon regioselectivity of the Paternò-Büchi reaction with these alkenes, electrostatic-potential derived charges (ESP) have been determined. In a second computational study, the relative stabilities of the typical 1,4-diradical intermediates of the Paternò-Büchi reaction have been determined. The results well explain the regioselectivity. Further transformations of the oxetanes or previous functionalization of the fluoroalkenes open perspectives for oxetanes as core structures for biologically active compounds.


Assuntos
Alcenos , Cetonas , Estereoisomerismo
13.
Chem Commun (Camb) ; 57(77): 9807-9819, 2021 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-34486592

RESUMO

(1,n) annulation reactions using (de)-hydrogenative coupling with alcohols or diols represent a straightforward technique for the synthesis of cyclic moieties. Utilization of such renewable resources for chemical transformations in a one-pot manner is the main focus, which avoids generation of stoichiometric waste. Application of such (1,n) annulation approaches drives the catalysis research in a more sustainable way and generates dihydrogen and water as by-products. This feature article highlights the recent (from 2015 to March 2021) progress in the synthesis of stereo-selective cycloalkanes and cycloalkenes, saturated and unsaturated N-heterocycles (cyclic amine, imide, lactam, tetrahydro ß-carboline, quinazoline, quinazolinone, 1,3,5-triazines etc.) and other N-heterocycles with the formation of multiple bonds in a one pot operation. Mechanistic studies, new catalytic approaches, and synthetic applications including drug synthesis and post-drug derivatization, scope, and limitations are discussed.


Assuntos
Álcoois/química , Elementos de Transição/química , Alcanos/síntese química , Alcanos/química , Alcenos/síntese química , Alcenos/química , Catálise , Compostos Heterocíclicos/síntese química , Compostos Heterocíclicos/química , Hidrogenação , Estrutura Molecular
14.
J Org Chem ; 86(19): 13310-13321, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34551249

RESUMO

Intramolecular photocycloaddition reactions of 3,4-alkoxybenzonitriles derived from vanillin with alkenes have been investigated. In contrast to previous reports on photochemical reactions with these compounds, mainly [2 + 3] cycloaddition has been observed. A competing [2 + 2] photocycloaddition plays a minor role. Most probably, these additions occur at the singlet state S1. In the case of a triplet reaction, a different regioselectivity of the [2 + 2] cycloaddition would be observed. Linear and angular [2 + 3] cycloadducts are formed as major products. The first isomer is transformed in the second one by a photochemical vinyl-cyclopropane rearrangement, which increases the selectivity of the reaction. The influence of the substitution pattern on the reactivity and the selectivity has also been investigated.


Assuntos
Alcenos , Lignina , Reação de Cicloadição , Estrutura Molecular
15.
J Org Chem ; 86(19): 13475-13480, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34549964

RESUMO

The mechanism of Pd(II)-catalyzed meta-C-H bond olefination of arenes with a carboxyl directing group (DG)-containing template has been investigated with density functional theory. The reaction includes three major steps: C-H bond activation, alkene insertion, and ß-hydride elimination. The C-H activation step, which proceeds via a concerted metalation-deprotonation pathway, is found to be the rate- and regioselectivity-determining step. We proposed a mono-N-protected amino acid (MPAA)/DG-assisted C-H activation model, in which the carboxyl DG coordinates with the Pd center and delivers it to the meta-position of arene, and the bidentate dianionic MPAA acts as a base for deprotonation. There is a hydrogen bonding interaction between the carboxyl DG and the carboxylate group of MPAA. An alternative Pd(OAc)2-catalyzed mechanism without involvement of MPAA is also operative. The template is conformationally flexible, and multiple low-energy transition-state conformations contribute to the regioselectivity.


Assuntos
Alcenos , Paládio , Catálise , Conformação Molecular
16.
J Hazard Mater ; 416: 126234, 2021 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-34492987

RESUMO

Bioelectrochemical systems (BES) are promising technologies to enhance the growth of organohalide-respiring bacteria and to treat chlorinated aliphatic hydrocarbons. In this study, two carbon-based cathodic electrode materials, a graphite brush and a carbon cloth, were used as hydrogen suppliers to couple growth of Dehalogenimonas and dechlorination of 1,2-DCP to nontoxic propene in the cathode vessel. The BES with graphite brush electrode consumed ~4000 µM 1,2-DCP during 110 days and exhibited a degradation rate 5.6-fold higher than the maximum value obtained with the carbon cloth electrode, with a cathode potential set at -0.7 V. Quantitative PCR confirmed that Dehalogenimonas gene copies increased by two orders of magnitude in the graphite brush BES, with an average yield of 1.2·108±5·107 cells per µmol of 1,2-DCP degraded. The use of a pulsed voltage operation (cathode potential set at -0.6 V for 16 h and -1.1 V for 8 h) increased the coulombic efficiency and degradation of 1,2-DCP when compared with a continuous voltage operation of -1.1 V. Bacterial cell aggregates were observed in the surface of the graphite brush electrodes by electron scanning microscopy, suggesting biofilm formation. This study expands the range of chlorinated compounds degradable and organohalide-respiring bacteria capable of growing in BES.


Assuntos
Hidrocarbonetos Clorados , Alcenos , Eletrodos , Propano/análogos & derivados
17.
J Org Chem ; 86(18): 13160-13168, 2021 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-34478290

RESUMO

An efficient route for the synthesis of 1-aryl-2,2-difluoroalkenes via 1,2-desilylative defluorination is disclosed. Only a catalytic amount of fluoride source is required to initiate the desilylation and afford gem-difluoroalkenes in very good to quantitative yields, using mild reaction conditions in dimethyl carbonate as a green solvent. This reaction uses (1-aryl)-2,2,2-trifluoroethyl-silanes, which are easily prepared via the insertion reaction of trifluoroethyl diazo alkanes into the Si-H bond of tertiary organosilanes. (1-Aryl)-perfluoroalkyl-silanes cleanly afford the corresponding (Z)-1-benzylideneperfluoroalkanes, which upon hydrodefluorination furnish the (E)-ß(perfluoroalkyl)styrene derivatives with excellent yield and complete stereoselectivity. A one-pot system involving sequential insertion and desilylative-defluorination is also suitable for this transformation. This method demonstrates the usefulness of organosilanes toward the preparation of fluorinated alkenes as synthetically useful targets.


Assuntos
Compostos de Organossilício , Silanos , Alcenos , Catálise , Fluoretos
18.
Environ Sci Technol ; 55(17): 11733-11744, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34369153

RESUMO

Chemical reactivity, kinetics, degradation pathways and mechanisms, and ecotoxicity of the oxidation of 1-vinyl-3-ethylimidazolium bromide ([VEIm]Br), the most common alternative to organic solvents, by Fe(VI) (HFeO4-) were studied by lab experiments and theoretical calculations. Results show that Fe(VI) can efficiently remove VEIm through the dioxygen transfer-hydrolysis mechanism, which has not been reported yet. The reactivity of VEIm toward Fe(VI) mainly depends on the double bonds in the side chain of VEIm. The second-order rate constant for VEIm was 629.45 M-1 s-1 at pH 7.0 and 25 °C. Typical water constituents, except for SO32-, Cl-, and Cu2+, had no obvious effects on the oxidation. The oxidation products were determined by high-performance liquid chromatography hybrid quadrupole time-of-flight mass spectrometry, which proves that there were interactions between the oxidation intermediates of the anion and cation parts of [VEIm]Br during the degradation process. The structures of related products and oxidation mechanisms were further rationalized by theoretical calculations. The ecotoxicity of products from the three oxidation pathways all showed a trend of increase after the initial decrease. We hope that the findings of this work can give researchers some new inspirations on Fe(VI) degradation of other alkene-containing contaminants.


Assuntos
Líquidos Iônicos , Poluentes Químicos da Água , Purificação da Água , Alcenos , Imidazóis , Ferro , Cinética , Oxirredução , Poluentes Químicos da Água/análise
19.
Chemistry ; 27(54): 13534-13538, 2021 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-34369000

RESUMO

We report the sustainable and efficient synthesis of a new type of quinoline derivatives bearing one or two SO2 CF3 groups. The protocol is metal-, catalyst- and irradiation-free, involves the use of readily available and stable precursors, and avoids the formation of side products. Also, the mild conditions of the process allow the tolerance of a wide range of functional groups.


Assuntos
Alcenos , Quinolinas , Catálise , Metais
20.
J Org Chem ; 86(17): 11378-11387, 2021 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-34344155

RESUMO

This article describes continued studies on Pd-catalyzed alkene diamination reactions between N-allylguanidines or ureas and O-benzoylhydroxylamine derivatives, which serve as N-centered electrophiles. The transformations generate cyclic guanidines and ureas bearing dialkylaminomethyl groups in moderate to good yield. We describe new mechanistic experiments that have led to a revised mechanistic hypothesis that involves a key oxidative addition of the electrophile to a PdII complex, followed by reductive elimination from PdIV to form the alkyl carbon-nitrogen bond. In addition, we demonstrate that acac, not phosphine, serves as a key ligand for palladium. Moreover, simple acac derivatives bearing substituted aryl groups outperform acac in the catalytic reactions, and phosphines inhibit catalysis in many cases. These discoveries have led to a significant expansion in the scope of this chemistry, which now allows for the coupling of a variety of cyclic amines, acyclic secondary amines, and primary amines. In addition, we also demonstrate that these new conditions allow for the use of amide nucleophiles, in addition to guanidines and ureas.


Assuntos
Alcenos , Paládio , Catálise , Hidroxilaminas , Ligantes , Estrutura Molecular , Pentanonas
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