This document describes a one-pot method for synthesizing quinoxalines from vicinal diols and keto alcohols with diamines using a gold-carbon nanotube nanohybrid catalyst. The reaction involves an oxidation-condensation cascade where the vicinal diols and keto alcohols are first oxidized to the corresponding diketones or ketones under mild conditions, and these products then condense in situ with aromatic diamines to form various substituted quinoxalines in excellent yields of 87-96% within 26-40 hours. The gold-carbon nanotube nanohybrid catalyst provides high activity, recyclability, and heterogeneous catalysis
1) An efficient protocol has been developed for the synthesis of biaryls via Pd/Cu catalyzed coupling of phenylhydrazines in water without using any ligands.
2) Both Pd and Cu catalysts were found to be essential for the reaction, with Pd(TFA)2 and Cu(OAc) providing the best results.
3) A range of substituted phenylhydrazines underwent homo- and cross-coupling reactions under the optimized conditions to provide the biaryl products in good to excellent yields.
1) A new reaction is reported that uses ethylene-1,2-diamines or o-phenylenediamines, aromatic aldehydes, and TMSCN to provide a straightforward route to synthesize 2-aminopyrazines and 2-aminoquinoxalines.
2) DBU is found to be a superior promoter of this reaction, accelerating the rate and providing good yields. The reaction involves desilylation, Strecker reaction, amidine-forming cyclization, and dehydrogenative aromatization in a tandem sequence.
3) The reaction scope is investigated and found to work for a variety of aromatic aldehydes containing electron-withdrawing and electron
1) Torulaspora delbrueckii was used to biotransform 30g of benzaldehyde into 22.9g of L-phenylacetylcarbinol (L-PAC) in a 5L stirred tank reactor.
2) L-PAC was then converted to ephedrine in two microwave-assisted steps: first L-PAC was transformed to 2-(methylimino)-1-phenyl-1-propanol, then this was reduced to ephedrine.
3) The identities of the products were confirmed using 1H NMR and FT-IR analysis, demonstrating a facile synthesis of ephedrine from benzaldehyde using biocatalysis and microwave-assisted chemistry.
1) Self-assembled monolayer coated gold nanoparticles catalyze the aerobic oxidation of alpha-hydroxy ketones to aryl 1,2-diketones in water.
2) This provides an efficient one-pot synthesis of quinoxaline derivatives by in situ oxidation of alpha-hydroxy ketones and subsequent condensation with aryl 1,2-diamines in water.
3) 4-Aminothiophenol self-assembled monolayer coated gold nanoparticles were found to be an effective catalyst for these reactions, providing good to excellent yields of products under mild conditions in water.
The document describes the carbon nanotube-gold nanohybrid (AuCNT) catalyzed N-formylation of various primary and secondary amines using aqueous formaldehyde. Key findings include:
1) AuCNT catalyzes the room temperature N-formylation of various primary and secondary amines with aqueous formaldehyde, affording formamides in excellent yields.
2) The reaction proceeds with low catalyst loading (0.34 mol%), excellent chemoselectivity, and recyclability of the AuCNT catalyst.
3) Control experiments confirm the AuCNT nanohybrid is the active catalytic species, and the reaction proceeds through a hemiaminal intermediate that is oxidized to the
This document summarizes the total synthesis of 2,6-dideoxy-2,6-imino-7-O-β-D-glucopyranosyl-D-glycero-L-gulo-heptitol hydrochloride (8), a potent inhibitor of α-glucosidases. The key steps involve homologation and amination of 2,3,4,6-tetra-O-benzyl-D-glucopyranose (1) to form the protected amine 4. An intramolecular cyclization of 4 catalyzed by mercuric acetate formed the piperidine ring. Glycosylation of aglycon 6 with acetob
Benzoquinone Ketene intermediate in the synthesis of poly 2-HBAMatt Hettinger
This document summarizes a research article that investigated the role of a benzoquinoneketene intermediate in the base-catalyzed polymerization of poly-2-hydroxybenzoic acid (poly-2-HBA). The researchers synthesized a dimer of 2-hydroxybenzoic acid (2-HBA) and showed that it polymerizes to poly-2-HBA with a base, implicating the ketoketene intermediate. A control dimer that cannot form the ketoketene did not polymerize. Additionally, secondary amines trapped the ketoketene as monomeric amides, further supporting it as an intermediate. The results indicate that ketoketene formation and reaction plays a
1) An efficient protocol has been developed for the synthesis of biaryls via Pd/Cu catalyzed coupling of phenylhydrazines in water without using any ligands.
2) Both Pd and Cu catalysts were found to be essential for the reaction, with Pd(TFA)2 and Cu(OAc) providing the best results.
3) A range of substituted phenylhydrazines underwent homo- and cross-coupling reactions under the optimized conditions to provide the biaryl products in good to excellent yields.
1) A new reaction is reported that uses ethylene-1,2-diamines or o-phenylenediamines, aromatic aldehydes, and TMSCN to provide a straightforward route to synthesize 2-aminopyrazines and 2-aminoquinoxalines.
2) DBU is found to be a superior promoter of this reaction, accelerating the rate and providing good yields. The reaction involves desilylation, Strecker reaction, amidine-forming cyclization, and dehydrogenative aromatization in a tandem sequence.
3) The reaction scope is investigated and found to work for a variety of aromatic aldehydes containing electron-withdrawing and electron
1) Torulaspora delbrueckii was used to biotransform 30g of benzaldehyde into 22.9g of L-phenylacetylcarbinol (L-PAC) in a 5L stirred tank reactor.
2) L-PAC was then converted to ephedrine in two microwave-assisted steps: first L-PAC was transformed to 2-(methylimino)-1-phenyl-1-propanol, then this was reduced to ephedrine.
3) The identities of the products were confirmed using 1H NMR and FT-IR analysis, demonstrating a facile synthesis of ephedrine from benzaldehyde using biocatalysis and microwave-assisted chemistry.
1) Self-assembled monolayer coated gold nanoparticles catalyze the aerobic oxidation of alpha-hydroxy ketones to aryl 1,2-diketones in water.
2) This provides an efficient one-pot synthesis of quinoxaline derivatives by in situ oxidation of alpha-hydroxy ketones and subsequent condensation with aryl 1,2-diamines in water.
3) 4-Aminothiophenol self-assembled monolayer coated gold nanoparticles were found to be an effective catalyst for these reactions, providing good to excellent yields of products under mild conditions in water.
The document describes the carbon nanotube-gold nanohybrid (AuCNT) catalyzed N-formylation of various primary and secondary amines using aqueous formaldehyde. Key findings include:
1) AuCNT catalyzes the room temperature N-formylation of various primary and secondary amines with aqueous formaldehyde, affording formamides in excellent yields.
2) The reaction proceeds with low catalyst loading (0.34 mol%), excellent chemoselectivity, and recyclability of the AuCNT catalyst.
3) Control experiments confirm the AuCNT nanohybrid is the active catalytic species, and the reaction proceeds through a hemiaminal intermediate that is oxidized to the
This document summarizes the total synthesis of 2,6-dideoxy-2,6-imino-7-O-β-D-glucopyranosyl-D-glycero-L-gulo-heptitol hydrochloride (8), a potent inhibitor of α-glucosidases. The key steps involve homologation and amination of 2,3,4,6-tetra-O-benzyl-D-glucopyranose (1) to form the protected amine 4. An intramolecular cyclization of 4 catalyzed by mercuric acetate formed the piperidine ring. Glycosylation of aglycon 6 with acetob
Benzoquinone Ketene intermediate in the synthesis of poly 2-HBAMatt Hettinger
This document summarizes a research article that investigated the role of a benzoquinoneketene intermediate in the base-catalyzed polymerization of poly-2-hydroxybenzoic acid (poly-2-HBA). The researchers synthesized a dimer of 2-hydroxybenzoic acid (2-HBA) and showed that it polymerizes to poly-2-HBA with a base, implicating the ketoketene intermediate. A control dimer that cannot form the ketoketene did not polymerize. Additionally, secondary amines trapped the ketoketene as monomeric amides, further supporting it as an intermediate. The results indicate that ketoketene formation and reaction plays a
A green synthesis of isatoic anhydrides from isatins with urea–hydrogen perox...fer18400
The document describes a green synthesis method for producing isatoic anhydrides from isatins using urea-hydrogen peroxide complex and ultrasound irradiation. Four reaction procedures were tested using urea-hydrogen peroxide as the oxidizing agent and sulfuric acid as a catalyst. The procedures used either acetic anhydride/acetic acid or formic acid as solvents. Ultrasound irradiation was found to dramatically reduce reaction times from 2-24 hours down to 20-135 minutes. The method provides isatoic anhydrides in good yields and with high purity under mild conditions. Combining formic acid and ultrasound yielded the best results for most isatins tested.
Synthesis, Characterization and Electrical Properties of Polyaniline Doped wi...IJERA Editor
The polyaniline were prepared by using different inorganic and organic acids via oxidative polymerization
method. The prepared samples were characterized by FTIR, the peaks are found to be at 507 cm˗1, 592 cm˗1, 798
cm˗1, 1138 cm˗1, 1244 cm˗1, 1302 cm˗1, 1471 cm˗1 and 1556 cm˗1. These predominant peaks may be
confirming the formation of polyaniline. The structural analysis was studied by employing XRD; found that
polyaniline is amorphous in nature. The SEM studies reveal that they are agglomerated, irregular and size of
these grain increases with increasing amount of polyaniline with different organic and inorganic acids. The dc
conductivity (dc) as a function of temperature (T) for polyaniline is studied in the temperature range from 30 to
1600C. At higher temperature it is found that conductivity increases because of hopping of polarons from one
localized states to another localized states. The ac conductivity of polyaniline was prepared by oxalic acid show
high conductivity at 106 Hz. This is due to the space charge polarization and electrode polarizations.
A ruthenium-carbamato-complex derived from a siloxylated amine and carbon dio...Pawan Kumar
The rutheniumcarbamate complex derived from3-trimethoxysilyl-1-
propyl amine and carbon dioxidewas found to be a novel catalyst for
the oxidative cyanation of aromatic and cyclic tertiary amines to
corresponding a-amino nitriles in high to excellent yields by using
hydrogen peroxide and molecular oxygen as enviro-economic
oxidants. The developed protocol suggested an efficient alternative
for recycling carbon dioxide.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Sipma, 2004, Effect Of Carbon Monoxide, Hydrogen And Sulfate On Thermophilic ...roelmeulepas
This document summarizes a study on the conversion of carbon monoxide (CO) by two anaerobic sludge samples at 55°C. The study aimed to elucidate the conversion routes and determine the effect of substrate (CO) concentration and the presence of hydrogen gas. Inhibition experiments showed CO conversion occurred via a hydrogenogenic population producing hydrogen and carbon dioxide, with the products then used by methanogens, acetogens, or sulfate reducers depending on sludge source and inhibitors. Both sludges could produce hydrogen from CO, indicating potential for biological hydrogen production from synthesis gas containing CO. The paper mill sludge was also capable of sulfate reduction using hydrogen produced from high CO concentrations, showing CO-rich synthesis gas can efficiently
This document describes the development of an improved synthesis for a 2,3-disubstituted 4,7-diazaindole compound. Key improvements included using an iron-catalyzed cross-coupling reaction to prepare 2-propylpyrazine in over 60% yield, avoiding issues with the original ethylation process. Additionally, a modified Chichibabin cyclization was developed where methylation of the ketone occurred prior to cyclization, improving yields and purity. The optimized processes were successfully scaled to the pilot plant level to produce kilogram quantities of the target molecule.
Magnetic Fe3O4@MgAl–LDH composite grafted with cobalt phthalocyanine as an ef...Pawan Kumar
Magnetically separable layered double hydroxide MgAl–LDH@Fe3O4 composite supported cobalt
phthalocyanine catalyst was synthesized and used for the aerobic oxidation of mercaptans to corresponding
disulfides under alkali free conditions. The catalyst exhibited excellent activity for the oxidation of
mercaptans using molecular oxygen as an oxidant which can be effectively recovered by using an external
magnetic field. In addition, the covalent immobilization of cobalt phthalocyanine to MgAl–LDH@Fe3O4
support prevents the leaching of the catalyst and improves its activity and stability
Effects of Acid on Chlorophyll Production of CommonCorinne Breymeier
This study examined the effects of different acidity levels on the growth and chlorophyll content of common duckweed (Lemna minor L.). Duckweed was exposed to pH levels of 4.1, 5.4, and 6.5 (control) for 10-12 days. The results showed that more acidic conditions reduced biomass in some experiments, but did not significantly affect chlorophyll content. While the hypothesis that acid would reduce chlorophyll and inhibit growth was only partially supported, the study provides insight into duckweed's tolerance of acidic water pollution from abandoned mines.
The document describes a study of acid-base reactions on alumina-supported niobia catalysts. Catalysts containing 8-28% niobia supported on gamma-alumina were prepared by impregnation. The catalysts were characterized using infrared spectroscopy, CO2 adsorption, and UV-vis spectroscopy. The density and strength of Lewis acid and basic sites decreased with increasing niobia content, while the density of Brønsted acid sites increased. The catalysts were tested in isopropanol dehydration, 1-butene isomerization, and cumene dealkylation reactions. Reaction performance varied with different reactions responding differently to niobia addition depending on the changes in surface acid-base properties.
This document summarizes research evaluating Pt/GMC and Pt/rGO electrocatalysts for electro-oxidation of methanol. Graphitic mesoporous carbon (GMC) and reduced graphene oxide (rGO) were synthesized and used to support platinum nanoparticles. The materials were characterized using various techniques and their electrocatalytic performance for methanol oxidation was measured via cyclic voltammetry. The results showed that Pt/GMC exhibited the highest mass activity and best resistance to carbon monoxide poisoning compared to Pt/rGO and a commercial Pt/C catalyst. Therefore, Pt/GMC demonstrated the best electrocatalytic performance for methanol electrooxidation.
2014_Belkheiri et al._Cellulose Chemistry and TechnologyHuyen Lyckeskog
This document summarizes a study investigating the depolymerization of kraft lignin into valuable chemicals using near-critical water with methanol as a co-solvent and hydrogen donor. Adding phenol was found to suppress char formation. Increasing the methanol concentration decreased char yield on the catalyst from 26.2% to 14.1% and increased yields of phenolic compounds like guaiacol and anisole in the aqueous phase. Analysis showed the aqueous phase contained phenolic monomers and dimers, with higher methanol concentrations producing more dimers. The highest methanol condition of 61% yielded 3.14% phenol and 0.52% dimers in the aqueous phase.
Carboxy-terminal Degradation of Peptides using Perfluoroacyl Anhydrides : C-T...Keiji Takamoto
This document describes a new method for determining the carboxy-terminal (C-terminal) amino acid sequence of peptides using perfluoroacyl anhydride vapor. Exposure of peptides to the vapor at -20°C for 0.5-1 hours sequentially degrades the peptide from the C-terminus. Analysis of the truncated peptide fragments by fast-atom-bombardment mass spectrometry allows determination of the C-terminal sequence based on mass differences. The method provides C-terminal sequence information as a complement to the common Edman degradation method for amino-terminal sequencing. The perfluoroacyl anhydride vapor method results in more extensive C-terminal degradation than a previous method using perfluoric acid
The document summarizes a study on using palladium supported on hydrotalcite as a heterogeneous catalyst for the Suzuki cross-coupling reaction. Various palladium salts were tested as catalysts with different bases and temperatures. PdCl2 supported on hydrotalcite with potassium carbonate as the base provided the best results, with conversions comparable to homogeneous catalysts at temperatures above 90°C. The catalyst was characterized and found to have a palladium content of 1% without changing the structure of the hydrotalcite support. It was an effective catalyst for the reaction, with higher temperatures, bromobenzene, and chlorobenzene providing better conversions than other conditions tested.
This document summarizes the chemical synthesis of 2-amino-4-heteroarylpyrimidines and related compounds for use as JNK1 inhibitors. Key steps include:
1) Microwave-induced SNAr reactions of primary amines with 2-methylsulfonylpyrimidines or 2-chloropyrimidines to access initial targets.
2) Elaboration of pendant piperidine functionality using silica-bound reagents in microwave reductive amination and amide bond formation.
3) Exploration of variations to the core pyrimidine scaffold and piperidine substitutions using efficient parallel synthesis methods.
A powerful and convenient reaction procedure for the C-N coupling reaction (the Buchwald-Hartwig reaction), yielding products of N-arylanilines and N-arylamines in both conventional heating and microwave irradiation has been reported. The protocol utilizes a stable and new supper ferromagnetic nanoparticle chelating N-heterocyclic dicarbene palladium(II) complex (Pd-NHC) as catalyst which helps/allows us to complete the reaction with only 0.002 mol% Pd producing high yield products. We also examined the reusability of the catalyst. It was found that the catalyst could be recovered by external magnetic field and reused for seven times without obvious loss in catalytic activity.
This document describes a new method for N-acylation of carbazoles using TFAA/H3PO4, which facilitates direct and metal-free N-acylation leading to a number of N-acylated derivatives. Several of these compounds showed promising anti-proliferative properties against oral cancer cell lines. The reaction proceeds through in situ generation of an acylation precursor from TFAA and the carboxylic acid. Phosphoric acid then converts this into an arylacetyl bis(trifluoroacetyl)phosphate which participates in the N-acylation of carbazole. This novel C-N bond forming reaction under mild conditions expands the scope of N-acylated carbazole synthesis
IOSR Journal of Applied Chemistry (IOSR-JAC) is an open access international journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Studies on Nitration of Phenol over Solid Acid Catalyst | Crimson PublishersDanesBlake
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al(NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 ᴼC for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated.
Microwave assisted organic synthesis and importanceKiran Kumar
Microwave assisted organic synthesis and importance is a presentation that discusses the theory, instrumentation, and importance of microwave assisted organic synthesis. It also briefly touches on future prospects and provides a conclusion to the presentation.
This document summarizes a refresher course on chemistry that included a presentation on the ultrasound assisted one-pot synthesis of imidazole derivatives. Key points include:
- Imidazoles and benzimidazoles are important structures in drug chemistry, with examples like omeprazole cited.
- Literature methods for synthesis include using acids, metal chlorides, and other reagents.
- The presented method uses diethyl bromophosphate under ultrasonic irradiation to efficiently synthesize imidazole derivatives from benzil or benzoin, an aldehyde, and ammonium acetate in 30 minutes with yields of 90-98%.
- Optimization of reaction conditions like molar ratios,
The document summarizes the web development experience and technical skills of a junior full stack developer. It details three web applications they conceived and developed - WhoCuts, a social app for finding hair stylists using MEAN stack technologies, Vybz, a social exchange platform using MEAN stack where they focused on scaffolding and routing with ExpressJS, and .Active, a Ruby on Rails companion app for workout tracking where they created the MVC structure and database using ActiveRecord. It also lists the developer's proficiency with technologies including Ruby, Rails, JavaScript, AngularJS, Express, HTML5, CSS3, MongoDB, and more.
A green synthesis of isatoic anhydrides from isatins with urea–hydrogen perox...fer18400
The document describes a green synthesis method for producing isatoic anhydrides from isatins using urea-hydrogen peroxide complex and ultrasound irradiation. Four reaction procedures were tested using urea-hydrogen peroxide as the oxidizing agent and sulfuric acid as a catalyst. The procedures used either acetic anhydride/acetic acid or formic acid as solvents. Ultrasound irradiation was found to dramatically reduce reaction times from 2-24 hours down to 20-135 minutes. The method provides isatoic anhydrides in good yields and with high purity under mild conditions. Combining formic acid and ultrasound yielded the best results for most isatins tested.
Synthesis, Characterization and Electrical Properties of Polyaniline Doped wi...IJERA Editor
The polyaniline were prepared by using different inorganic and organic acids via oxidative polymerization
method. The prepared samples were characterized by FTIR, the peaks are found to be at 507 cm˗1, 592 cm˗1, 798
cm˗1, 1138 cm˗1, 1244 cm˗1, 1302 cm˗1, 1471 cm˗1 and 1556 cm˗1. These predominant peaks may be
confirming the formation of polyaniline. The structural analysis was studied by employing XRD; found that
polyaniline is amorphous in nature. The SEM studies reveal that they are agglomerated, irregular and size of
these grain increases with increasing amount of polyaniline with different organic and inorganic acids. The dc
conductivity (dc) as a function of temperature (T) for polyaniline is studied in the temperature range from 30 to
1600C. At higher temperature it is found that conductivity increases because of hopping of polarons from one
localized states to another localized states. The ac conductivity of polyaniline was prepared by oxalic acid show
high conductivity at 106 Hz. This is due to the space charge polarization and electrode polarizations.
A ruthenium-carbamato-complex derived from a siloxylated amine and carbon dio...Pawan Kumar
The rutheniumcarbamate complex derived from3-trimethoxysilyl-1-
propyl amine and carbon dioxidewas found to be a novel catalyst for
the oxidative cyanation of aromatic and cyclic tertiary amines to
corresponding a-amino nitriles in high to excellent yields by using
hydrogen peroxide and molecular oxygen as enviro-economic
oxidants. The developed protocol suggested an efficient alternative
for recycling carbon dioxide.
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Sipma, 2004, Effect Of Carbon Monoxide, Hydrogen And Sulfate On Thermophilic ...roelmeulepas
This document summarizes a study on the conversion of carbon monoxide (CO) by two anaerobic sludge samples at 55°C. The study aimed to elucidate the conversion routes and determine the effect of substrate (CO) concentration and the presence of hydrogen gas. Inhibition experiments showed CO conversion occurred via a hydrogenogenic population producing hydrogen and carbon dioxide, with the products then used by methanogens, acetogens, or sulfate reducers depending on sludge source and inhibitors. Both sludges could produce hydrogen from CO, indicating potential for biological hydrogen production from synthesis gas containing CO. The paper mill sludge was also capable of sulfate reduction using hydrogen produced from high CO concentrations, showing CO-rich synthesis gas can efficiently
This document describes the development of an improved synthesis for a 2,3-disubstituted 4,7-diazaindole compound. Key improvements included using an iron-catalyzed cross-coupling reaction to prepare 2-propylpyrazine in over 60% yield, avoiding issues with the original ethylation process. Additionally, a modified Chichibabin cyclization was developed where methylation of the ketone occurred prior to cyclization, improving yields and purity. The optimized processes were successfully scaled to the pilot plant level to produce kilogram quantities of the target molecule.
Magnetic Fe3O4@MgAl–LDH composite grafted with cobalt phthalocyanine as an ef...Pawan Kumar
Magnetically separable layered double hydroxide MgAl–LDH@Fe3O4 composite supported cobalt
phthalocyanine catalyst was synthesized and used for the aerobic oxidation of mercaptans to corresponding
disulfides under alkali free conditions. The catalyst exhibited excellent activity for the oxidation of
mercaptans using molecular oxygen as an oxidant which can be effectively recovered by using an external
magnetic field. In addition, the covalent immobilization of cobalt phthalocyanine to MgAl–LDH@Fe3O4
support prevents the leaching of the catalyst and improves its activity and stability
Effects of Acid on Chlorophyll Production of CommonCorinne Breymeier
This study examined the effects of different acidity levels on the growth and chlorophyll content of common duckweed (Lemna minor L.). Duckweed was exposed to pH levels of 4.1, 5.4, and 6.5 (control) for 10-12 days. The results showed that more acidic conditions reduced biomass in some experiments, but did not significantly affect chlorophyll content. While the hypothesis that acid would reduce chlorophyll and inhibit growth was only partially supported, the study provides insight into duckweed's tolerance of acidic water pollution from abandoned mines.
The document describes a study of acid-base reactions on alumina-supported niobia catalysts. Catalysts containing 8-28% niobia supported on gamma-alumina were prepared by impregnation. The catalysts were characterized using infrared spectroscopy, CO2 adsorption, and UV-vis spectroscopy. The density and strength of Lewis acid and basic sites decreased with increasing niobia content, while the density of Brønsted acid sites increased. The catalysts were tested in isopropanol dehydration, 1-butene isomerization, and cumene dealkylation reactions. Reaction performance varied with different reactions responding differently to niobia addition depending on the changes in surface acid-base properties.
This document summarizes research evaluating Pt/GMC and Pt/rGO electrocatalysts for electro-oxidation of methanol. Graphitic mesoporous carbon (GMC) and reduced graphene oxide (rGO) were synthesized and used to support platinum nanoparticles. The materials were characterized using various techniques and their electrocatalytic performance for methanol oxidation was measured via cyclic voltammetry. The results showed that Pt/GMC exhibited the highest mass activity and best resistance to carbon monoxide poisoning compared to Pt/rGO and a commercial Pt/C catalyst. Therefore, Pt/GMC demonstrated the best electrocatalytic performance for methanol electrooxidation.
2014_Belkheiri et al._Cellulose Chemistry and TechnologyHuyen Lyckeskog
This document summarizes a study investigating the depolymerization of kraft lignin into valuable chemicals using near-critical water with methanol as a co-solvent and hydrogen donor. Adding phenol was found to suppress char formation. Increasing the methanol concentration decreased char yield on the catalyst from 26.2% to 14.1% and increased yields of phenolic compounds like guaiacol and anisole in the aqueous phase. Analysis showed the aqueous phase contained phenolic monomers and dimers, with higher methanol concentrations producing more dimers. The highest methanol condition of 61% yielded 3.14% phenol and 0.52% dimers in the aqueous phase.
Carboxy-terminal Degradation of Peptides using Perfluoroacyl Anhydrides : C-T...Keiji Takamoto
This document describes a new method for determining the carboxy-terminal (C-terminal) amino acid sequence of peptides using perfluoroacyl anhydride vapor. Exposure of peptides to the vapor at -20°C for 0.5-1 hours sequentially degrades the peptide from the C-terminus. Analysis of the truncated peptide fragments by fast-atom-bombardment mass spectrometry allows determination of the C-terminal sequence based on mass differences. The method provides C-terminal sequence information as a complement to the common Edman degradation method for amino-terminal sequencing. The perfluoroacyl anhydride vapor method results in more extensive C-terminal degradation than a previous method using perfluoric acid
The document summarizes a study on using palladium supported on hydrotalcite as a heterogeneous catalyst for the Suzuki cross-coupling reaction. Various palladium salts were tested as catalysts with different bases and temperatures. PdCl2 supported on hydrotalcite with potassium carbonate as the base provided the best results, with conversions comparable to homogeneous catalysts at temperatures above 90°C. The catalyst was characterized and found to have a palladium content of 1% without changing the structure of the hydrotalcite support. It was an effective catalyst for the reaction, with higher temperatures, bromobenzene, and chlorobenzene providing better conversions than other conditions tested.
This document summarizes the chemical synthesis of 2-amino-4-heteroarylpyrimidines and related compounds for use as JNK1 inhibitors. Key steps include:
1) Microwave-induced SNAr reactions of primary amines with 2-methylsulfonylpyrimidines or 2-chloropyrimidines to access initial targets.
2) Elaboration of pendant piperidine functionality using silica-bound reagents in microwave reductive amination and amide bond formation.
3) Exploration of variations to the core pyrimidine scaffold and piperidine substitutions using efficient parallel synthesis methods.
A powerful and convenient reaction procedure for the C-N coupling reaction (the Buchwald-Hartwig reaction), yielding products of N-arylanilines and N-arylamines in both conventional heating and microwave irradiation has been reported. The protocol utilizes a stable and new supper ferromagnetic nanoparticle chelating N-heterocyclic dicarbene palladium(II) complex (Pd-NHC) as catalyst which helps/allows us to complete the reaction with only 0.002 mol% Pd producing high yield products. We also examined the reusability of the catalyst. It was found that the catalyst could be recovered by external magnetic field and reused for seven times without obvious loss in catalytic activity.
This document describes a new method for N-acylation of carbazoles using TFAA/H3PO4, which facilitates direct and metal-free N-acylation leading to a number of N-acylated derivatives. Several of these compounds showed promising anti-proliferative properties against oral cancer cell lines. The reaction proceeds through in situ generation of an acylation precursor from TFAA and the carboxylic acid. Phosphoric acid then converts this into an arylacetyl bis(trifluoroacetyl)phosphate which participates in the N-acylation of carbazole. This novel C-N bond forming reaction under mild conditions expands the scope of N-acylated carbazole synthesis
IOSR Journal of Applied Chemistry (IOSR-JAC) is an open access international journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Studies on Nitration of Phenol over Solid Acid Catalyst | Crimson PublishersDanesBlake
Phenol was selectively nitrated in liquid phase to produce ortho-nitrophenol using dilute nitric acid (30%) at room temperature in presence of hydrochloric acid treated γ-alumina. Initially Al(NO3) and NH4HCO3 were reacted to prepare Al (OH)3 which on successive calcinations at 550 ᴼC for 5h produce γ-alumina. The γ-alumina was characterized by BET, XRD, SEM and NH3-TPD analysis. The XRD profile confirmed the crystalline structure of the solid acid catalyst γ-alumina. The NH3-TPD analysis showed the development of lewis acidity on the surface of hydrochloric acid treated γ-alumina. The effects of various parameters such as concentration of reactants, types of catalyst, weight of the catalyst, solvent, temperature and time of reaction have been studied. The kinetics of the reaction was also investigated.
Microwave assisted organic synthesis and importanceKiran Kumar
Microwave assisted organic synthesis and importance is a presentation that discusses the theory, instrumentation, and importance of microwave assisted organic synthesis. It also briefly touches on future prospects and provides a conclusion to the presentation.
This document summarizes a refresher course on chemistry that included a presentation on the ultrasound assisted one-pot synthesis of imidazole derivatives. Key points include:
- Imidazoles and benzimidazoles are important structures in drug chemistry, with examples like omeprazole cited.
- Literature methods for synthesis include using acids, metal chlorides, and other reagents.
- The presented method uses diethyl bromophosphate under ultrasonic irradiation to efficiently synthesize imidazole derivatives from benzil or benzoin, an aldehyde, and ammonium acetate in 30 minutes with yields of 90-98%.
- Optimization of reaction conditions like molar ratios,
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The document discusses microwave assisted synthesis of metallic nanostructures. Some key points:
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2) Microwave heating allows for faster, cleaner reactions compared to traditional heating methods. It enables selective heating and precise temperature control.
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Microwave assisted synthesis is a green chemistry approach that uses microwave irradiation to accelerate chemical reactions. It has several advantages over traditional heating methods, such as faster reaction times, higher product purity, and lower energy usage. Microwaves work by causing polarization and ionic conduction in polar solvents and reagents, quickly generating heat. Common applications include coupling reactions like Suzuki, Heck, and Negishi reactions. SiC microwave vessels are preferable to Pyrex as they absorb microwaves more efficiently and allow for better temperature control of exothermic reactions.
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Some past incidents show the dangers of pollution, such as the Cuyahoga River catching fire due to chemical pollution. Green chemistry aims to reduce hazardous waste and pollution through principles like preventing waste, using renewable resources, safer solvents and feedstocks, and designing chemicals and processes to be less toxic and hazardous. The principles emphasize safer and more environmentally friendly chemical synthesis and products. Examples show how green chemistry has helped reduce pollution through alternatives like supercritical carbon dioxide for dry cleaning and replacing toxic additives like tetraethyl lead in gasoline.
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This document describes a study that developed an efficient method for synthesizing 2-amino-3-cyano-4H-pyran derivatives using a three-component reaction. The reaction involves the cyclocondensation of aldehydes, malononitrile, and ethyl acetoacetate using ammonium hydroxide as a catalyst under infrared irradiation. The method offers high yields, short reaction times of 10 minutes, and does not require hazardous reagents or conditions. Various substituted aromatic, heteroaromatic, and aliphatic aldehydes successfully provided the desired pyran products in good to excellent yields. The reaction mechanism is proposed to occur through initial Knoevenagel condensation and subsequent Michael addition and cyclization
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Thermal regeneration of activated carbon saturated with nitrate ions from an ...IJAEMSJORNAL
The present study was initiated to help the simple and less expensive regeneration of activated carbons after saturation in rural area. In order to determine a regeneration time and the number of regeneration cycles, an adsorption test was necessary. Thus, 3h and 4 cycles of carbon regeneration are obtained after evaluation of the performance, percentage and adsorption capacity after each cycle. Regeneration percentages of 71.29, 54.05, 40.40, 28.06 % and 72.6, 69.84, 64.33, 34.98 %for respective concentrations of 30± 1.2 mg/L and 55 ± 1.6 mg/L are observed. Also, the performances of activated carbon 8.5, 10, 12, 20 g/L and capacities 24.04, 19.93, 14.9 and 10.35mg/g 35.7, 34.12, 31.43 and 17.09 mg/g respectively for dry season and rainy season were necessary to fix the number of cycles. The artisanal furnace with its ease of installation and its maximum temperature of 500±2°C is suitable for the regeneration of saturated activated carbon.
Quinoxaline as a potent heterocyclic moietyiosrphr_editor
The IOSR Journal of Pharmacy (IOSRPHR) is an open access online & offline peer reviewed international journal, which publishes innovative research papers, reviews, mini-reviews, short communications and notes dealing with Pharmaceutical Sciences( Pharmaceutical Technology, Pharmaceutics, Biopharmaceutics, Pharmacokinetics, Pharmaceutical/Medicinal Chemistry, Computational Chemistry and Molecular Drug Design, Pharmacognosy & Phytochemistry, Pharmacology, Pharmaceutical Analysis, Pharmacy Practice, Clinical and Hospital Pharmacy, Cell Biology, Genomics and Proteomics, Pharmacogenomics, Bioinformatics and Biotechnology of Pharmaceutical Interest........more details on Aim & Scope).
This document summarizes the development of a mild and efficient method for synthesizing symmetrical and unsymmetrical azo compounds from aromatic anilines using copper bromide (CuBr) and N-methylmorpholine N-oxide (NMO) as an oxidizing system. Optimization experiments showed that CuBr with 1 equivalent of NMO in an acetonitrile/water solvent mixture gave the best yields. A variety of substituted anilines underwent homocoupling to produce symmetrical azo compounds in good to excellent yields. Unsymmetrical azo compounds were also synthesized via cross-coupling of different anilines in moderate to good yields. The reaction was shown to proceed via single electron transfer from Cu(I) to NMO
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Water as a solvent in microwave assisted organic synthesisPrashantChavan93
Prashant Chavan
Reserach Scholar
M.S.(Pharm) in Medicinal Chemistry
National Institute of Pharmaceutical Education and Research Mohali, Punjab (India) 160062
mcm20_prashant@niper.ac.in
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V mn-mcm-41 catalyst for the vapor phase oxidation of o-xylene
Shah_et_al-2015-ChemCatChem (1)
1. Synthesis of Quinoxalines by a Carbon Nanotube–Gold
Nanohybrid-Catalyzed Cascade Reaction of Vicinal Diols
and Keto Alcohols with Diamines
Nimesh Shah,[a]
Edmond Gravel,[b]
Dhanaji V. Jawale,[b]
Eric Doris,*[b]
and
Irishi N. N. Namboothiri*[a]
A one-pot oxidation–condensation method for the synthesis of
quinoxalines from readily available benzoins or benzhydrols
and 1,2-phenylenediamines or 2,3-diaminopyridine by use of
a gold–carbon nanotube nanohybrid as a heterogeneous cata-
lyst is reported. Quinoxalines are formed under mild conditions
in air and in excellent yields. The simple and efficient method-
ology offers a safe and sustainable alternative to conventional
acid and/or base-catalyzed thermal processes.
Quinoxalines constitute a quintessential class of N-containing
heterocycles due to their wide range of applications as syn-
thetic intermediates, biological agents, and advanced materi-
als.[1]
The diverse biological properties of functionalized qui-
noxalines as anticancer, antituberculosis and DNA intercalating
agents have generated considerable interest.[2]
Quinoxalines
have also carved out a unique niche in materials science due
to their properties as luminescent materials, organic dye sensi-
tizers, and building blocks for the synthesis of cavitand-based
molecular switches, to name a few.[3]
The condensation of an
aromatic 1,2-diamine with a 1,2-dicarbonyl compound is the
classical method for the synthesis of quinoxalines.[1,4]
However,
more recently, readily available 1,2-ketoalcohols have been em-
ployed as reactants with aromatic 1,2-diamines in a cascade
oxidation–condensation process by using a multitude of cata-
lysts and conditions for the synthesis of 2-substituted[5]
and
2,3-disubstituted quinoxalines.[6]
Synthesis of substituted qui-
noxalines from aromatic 1,2-diamines and phenacyl bromide
through cyclization–oxidation has also been reported.[1,4,7]
Though quinoxalines can be synthesized in excellent yields by
some of the above methods, requirement of high temperature
and/or microwave irradiation, high catalyst loading, and poor
recyclability of the catalyst are major limitations. Surprisingly,
there are only two reports, to our knowledge, on the synthesis
of substituted quinoxalines directly from 1,2-diols. In one case,
aromatic 1,2-diamines were treated with 1,2-diols in the pres-
ence of 4.5 mol% ceria-supported Au nanoparticles (AuNPs) at
1408C for 20 h[8]
and, in the other case, the reaction was per-
formed in the presence of 4 mol% [RuCl2(PPh3)3] in diglyme
under reflux conditions for 30 h.[9]
In both cases, many exam-
ples of 2-substituted quinoxalines and selected examples of
2,3-disubstituted quinoxalines in moderate to good yields
were reported. There is also one report for the synthesis of 2,3-
diaryl quinoxalines in high yield from benzoin (1,2-ketoalcohol)
and aromatic 1,2-diamine by using 4 mol% of 4-aminothiophe-
nol-coated AuNPs in aqueous basic medium at 808C.[10]
Although the catalytic activity of AuNPs with a variety of
supports has been extensively investigated for over
a decade,[11]
carbon nanotube (CNT)-supported AuNPs have
emerged as highly efficient and recyclable heterogeneous cata-
lysts only recently.[12–16]
In this context, we have exploited the
robustness of CNTs and their ability to stabilize a metal’s transi-
ent higher oxidation states[17]
in the development of an AuCNT
nanohybrid in which Au nanoparticles were stabilized by
a polyanionic–polycationic two-layer assembly around CNTs
(Figure 1). The exceptional catalytic efficiency of this nanohy-
brid in comparison to other supported and colloidal AuNPs
has been demonstrated in the oxidation of silanes,[12]
alco-
hols,[13]
and phenols,[14]
and in the reductive amination[15]
and
N-formylation of aldehydes.[16]
Building on this work, we de-
sired to develop an efficient methodology for the synthesis of
quinoxalines from 1,2-ketoalcohols and 1,2-diols by using our
AuCNT catalyst under simple and mild conditions. In our re-
Figure 1. TEM image of the AuCNT hybrid with the general reaction scheme
of the reported organic transformation.[a] Dr. N. Shah, Prof. Dr. I. N. N. Namboothiri
Department of Chemistry
Indian Institute of Technology Bombay
Mumbai 400 076 (India)
E-mail: irishi@chem.iitb.ac.in
[b] Dr. E. Gravel, Dr. D. V. Jawale, Dr. E. Doris
CEA, iBiTecS, Service de Chimie Bioorganique et de Marquage
91191 Gif-sur-Yvette (France)
E-mail: eric.doris@cea.fr
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402782.
ChemCatChem 2015, 7, 57 – 61 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim57
CommunicationsDOI: 10.1002/cctc.201402782
2. cently reported procedure for the AuCNT-catalyzed oxidation
of benzylic and allylic alcohols,[13]
the benzylic alcohols includ-
ed benzoin 2a and benzhydrol 3a. We envisioned that benzil
and other 1,2-diketones thus generated could be condensed
in situ with suitable aromatic 1,2-diamines to afford quinoxa-
lines. Such a one-pot cascade oxidation–condensation protocol
for the synthesis of polynitrogen-containing aromatic heterocy-
cles from readily available aromatic 1,2-diamines and a-hydroxy-
ketones or 1,2-diols at room temperature, in air, and in aque-
ous medium appeared very attractive.
We began our experiments by treating 1,2-phenylenedia-
mine 1a with benzoin 2a under previously established oxida-
tion conditions[13]
of AuCNT (0.2 mol%) in toluene/H2O (1:1
v/v) at room temperature (Table 1, entry 1). Much to our de-
light, quinoxaline 4a was isolated in 96% yield after 26 h of re-
action (entry 1, path A). This prompted us to probe the oxida-
tion of benzhydrol 3a and the in situ condensation of the re-
sulting benzil with 1,2-phenylenediamine 1a. Though this one-
pot transformation took longer (38 h), we were pleased to iso-
late quinoxaline 4a in 94% yield (entry 1, path B). The turnover
number (TON) and turnover frequency (TOF) calculated for the
above two experiments were 480 and 18 hÀ1
, respectively, for
path A and 470 and 12 hÀ1
, respectively, for path B.
Having confirmed the efficacy of our experimental condi-
tions, we investigated the scope of our one-pot protocol, first,
by screening various 1,2-diamines 1b–e with benzoin 2a and
benzhydrol 3a as model substrates for paths A and B, respec-
tively (Table 1, entries 2–5). Representative examples of dia-
mines with weakly electron-donating substituents 1b, elec-
tron-withdrawing substituents 1c and 1d, and a heteroaromat-
ic diamine 1e were chosen for our studies. It may be noted
that benzoin 2a reacted with 1,2-diamines 1b–e to provide
quinoxalines 4b–e in 87–91% yields in 28–30 h (entries 2–5,
path A). Benzhydrol 3a, on the other hand, required more time
(38–40 h), but delivered quinoxalines 4b–e in comparable
yields (88–92%, entries 2–5, path B). Notably, there was no ap-
preciable effect of substituent on the reaction time or isolated
yield. The above results encouraged us to study the scope of
benzoin 2 and benzhydrol 3 as well (Table 2 and Scheme 1).
Treatment of p-methoxybenzoin 2b with diamines 1a–d under
our standard conditions led to the formation of quinoxalines
4 f–j in 87–92% yields in 27–30 h (Table 2, entries 1–5, path A).
As in the case of benzhydrol 3a, reaction of benzhydrol 3b
with diamines 1a–e also took around 40 h and the yields of
quinoxalines 4 f–j were high (87–93%, path B).
Finally, synthesis of fused polycyclic quinoxalines 4k–l was
performed under our reaction conditions by treating hydroxy-
ketone 2c and diol 3c with selected diamines 1a–
b (Scheme 1). As in the case of 2a–b, the reaction of hydroxy-
ketone 2c with diamines 1a–b required less time (27–28 h) to
Table 1. AuCNT-catalyzed one-pot synthesis of quinoxalines from aromat-
ic 1,2-diamines and benzoin or benzhydrol.[a]
Entry 1,2-Diamine Quinoxaline Path t
[h]
Yield[b]
[%]
1 1a 4a
A
B
26
38
96
94
2 1b 4b
A
B
28
38
91
92
3 1c 4c
A
B
28
39
87
90
4 1d 4d
A
B
30
40
88
88
5 1e 4e
A
B
28
39
90
90
[a] Conditions: 2a or 3a (0.1 mmol), 1,2-diamine 1 (0.1 mmol), AuCNT
(0.2 mol%), toluene/water 1:1 (1 mL), NaOH (3 equiv), RT, open flask (air).
[b] Yield of purified isolated product.
Table 2. AuCNT-catalyzed one-pot synthesis of quinoxalines from aromat-
ic 1,2-diamines and methoxybenzoin or 4-methoxybenzhydrol.[a]
Entry 1,2-Diamine Quinoxaline Path t
[h]
Yield[b]
[%]
1 1a 4 f
A
B
30
39
88
89
2 1b 4g
A
B
27
40
92
90
3 1c 4h
A
B
29
40
87
91
4 1d 4i
A
B
30
41
90
93
5 1e 4j
A
B
30
40
89
87
[a] Conditions: 2b or 3b (0.1 mmol), 1,2-diamine 1 (0.1 mmol), AuCNT
(0.2 mol%), toluene/water 1:1 (1 mL), NaOH (3 equiv), RT, open flask (air).
[b] Yield of purified isolated product.
Scheme 1. Synthesis of fused polycyclic quinoxalines from hydroxyketone
2c or diol 3c and selected diamines.
ChemCatChem 2015, 7, 57 – 61 www.chemcatchem.org 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim58
Communications
3. go to completion and afford quinoxalines 4k–l in excellent
yields (91–93%) compared to 3c, which took longer (37–39 h)
to reach complete conversion. Nevertheless, the reaction of 3c
with diamines 1a–b also delivered quinoxalines 4k–l in com-
parable (91–94%) yields. The catalytic efficiency of AuCNT was
compared to that of colloidal AuNPs and a Au salt by perform-
ing the reaction with identical loading (0.2 mol%) of the differ-
ent catalysts (Table 3, path A). As reported in Table 1, the
AuCNT-catalyzed reaction of diamine 1a with benzoin 2a pro-
vided quinoxaline 4a in 96% yield within 26 h (entry 1). On
the other hand, the colloidal AuNP-catalyzed reaction provided
only traces of 4a in 48 h (entry 2) and the use of HAuCl4 did
not lead to any product formation (entry 3). A similar trend
was observed on comparison of the catalytic activity of AuCNT
with that of other catalysts in the reaction of diol 3a with dia-
mine 1a (Table 3, path B).
The requirement of only very low catalyst loading and
simple and mild reaction conditions are attractive features of
our methodology. Another remarkable feature is the recyclabil-
ity of the catalyst. This was demonstrated by performing 5 con-
secutive reactions by using the same catalyst recovered by
centrifugation after each cycle. Reactions were completed in
25–26 h without any appreciable drop in the yield of quinoxa-
line 4a (94–96%) over the course of the experiment (Table 4,
path A). Similar results were obtained if benzoin 2a was re-
placed by benzhydrol 3a (Table 4, path B).
The catalytic role of AuCNT nanohybrid and its heterogene-
ous nature were verified through a series of experiments:
1) The AuCNT-catalyzed oxidation of benzoin 2a and benzhy-
drol 3a was performed in the absence of 1,2-phenylenedi-
amine 1a. After 24 h, the catalyst was removed by centrifu-
gation, which was followed by addition of 1,2-phenylenedi-
amine 1a. After stirring the catalyst-free reaction mixture
overnight (12 h) at room temperature, quinoxaline 4a was
isolated in only 22 and 18% yields, respectively, for benzoin
2a and benzhydrol 3a. This result indicated that the nano-
hybrid catalyst was also active in the condensation step.
2) The reaction between benzoin 2a and diamine 1a in the
presence of the catalyst under our standard conditions was
interrupted by removing the catalyst by centrifugation
after 6 h. There was only 36% conversion to quinoxaline
4a at this point and further stirring the catalyst-free reac-
tion mixture for another 18 h did not improve the yield,
thus showing the heterogeneous nature of the catalysis.
3) Authentic benzil was treated with diamine 1a under the
above conditions but in the absence of the catalyst. After
24 h of reaction, only 12% conversion was observed. How-
ever, upon addition of the catalyst to the reaction mixture
and continued stirring, complete conversion was achieved
in just 1.5 h to afford quinoxaline 4a in 96% yield.
4) The above two-step process, involving oxidation and con-
densation, was evaluated further by performing a kinetic
experiment under the standard conditions. Thus the
AuCNT-catalyzed reaction of benzoin 2a with diamine 1a
was examined at specific intervals by withdrawing aliquots
at 1, 6, and 12 h. The yields were, respectively, 8, 35, and
55%. Almost complete conversion was achieved in 24 h to
give product 4a in 95% yield. The 1
H NMR analysis of the
reaction mixture at the above intervals indicated no appre-
ciable amount of benzil in the reaction mixture, confirming
that the rate limiting step was the oxidation.
In summary, the synthesis of quinoxalines from readily avail-
able benzoins or benzhydrols and aromatic 1,2-diamines has
been performed in excellent yield under the catalytic influence
of a gold–carbon nanotube nanohybrid. This one-pot oxida-
tion-condensation sequence takes place under ambient heter-
ogeneous conditions in air and is a superior alternative to ex-
isting methods for the synthesis of quinoxalines, which are
ubiquitous structural units in many biologically active
compounds.
Experimental Section
Catalyst preparation
The AuCNT hybrid was prepared according to a previously de-
scribed procedure.[12]
The catalyst was obtained as an aqueous sus-
Table 3. Comparison of various Au sources in the synthesis of quinoxa-
lines from 1,2-phenylenediamine and benzoin or benzhydrol.[a]
Path A Path B
Entry Catalyst t [h] Yield[b]
[%] t [h] Yield[b]
[%]
1 AuCNT 26 96 38 94
2 AuNP colloid 48 trace 48 trace
3 HAuCl4 48 n.r.[c]
48 n.r.
[a] Conditions: 2a or 3a (0.1 mmol), 1,2-diamine 1 (0.1 mmol), AuCNT
(0.2 mol%), toluene/water 1:1 (1 mL), NaOH (3 equiv), RT, open flask (air).
[b] Yield of purified isolated product. [c] No reaction.
Table 4. Recycling experiments with AuCNT catalyst for the reaction of
1,2-phenylenediamine and benzoin or benzhydrol.[a]
Entry Catalyst Path A Path B
t [h] Yield[b]
[%] t [h] Yield[b]
[%]
1 fresh 26 96 38 94
2 recycle 1 25 95 38 94
3 recycle 2 25 95 37 93
4 recycle 3 24 94 37 93
5 recycle 4 24 94 36 92
[a] Conditions: 2a or 3a (0.1 mmol), 1,2-diamine 1 (0.1 mmol), AuCNT
(0.2 mol%), toluene/water 1:1 (1 mL), NaOH (3 equiv), RT, open flask (air).
[b] Yield of purified isolated product.
ChemCatChem 2015, 7, 57 – 61 www.chemcatchem.org 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim59
Communications
4. pension with a Au concentration of 4 mm (determined by induc-
tively coupled plasma MS).
Synthesis of quinoxaline 4
General procedure: To a stirred solution of benzoin 2 (0.1 mmol) or
benzhydrol 3 (0.1 mmol) and diamine 1 (0.1 mmol) in a 1:1 (v/v)
mixture of toluene/water was added NaOH (12 mg, 0.3 mmol,
3 equiv) and aqueous AuCNT (50 mL, 0.2 mol%). The reaction mix-
ture was stirred until complete consumption of the starting materi-
al (monitored by TLC). The aqueous layer was then extracted with
EtOAc (3”10 mL). The combined organic layer was dried (anhy-
drous Na2SO4), filtered, and concentrated under vacuum. The crude
residue was directly subjected to column chromatography (5–15%
EtOAc/petroleum ether, gradient elution) to afford pure quinoxa-
line 4.
Characterization data
2,3-Diphenylquinoxaline (4a):[18]
White solid; yield 94% (26.5 mg)
from diol, 96% (27 mg) from a-hydroxyketone; m.p. 126–1288C
(Ref. [18]: 128–1298C); 1
H NMR (400 MHz, CDCl3): d=7.31–7.39 (m,
6H), 7.50–7.54 (m, 4H), 7.78 (dd, J=6.4, 3.4 Hz, 2H), 8.19 ppm (dd,
J=6.4, 3.4 Hz, 2H); 13
C NMR (CDCl3, 100 MHz): d=128.4, 128.9,
129.3, 130.0, 130.1, 139.2, 141.4, 153.6 ppm.
6-Methyl-2,3-diphenylquinoxaline (4b):[18]
White solid; yield 92%
(27.2 mg) from diol, 91% (26.9 mg) from a-hydroxyketone; m.p.
116–1178C (Ref. [18]: 117–1188C); 1
H NMR (400 MHz, CDCl3): d=
2.61 (s, 3H), 7.30–7.37 (m, 6H), 7.49–7.52 (m, 4H), 7.60 (dd, J=8.6,
1.8 Hz, 1H), 7.96 (d, J=1.8 Hz, 1H) 8.08 ppm (d, J=8.6 Hz, 1H);
13
C NMR (CDCl3, 100 MHz): d=22.0, 128.1, 128.3 (”2), 128.7, 128.7
(”2), 129.9, 129.9, 132.3, 139.3 (”2), 139.7, 140.5, 141.3, 152.6,
153.3 ppm.
6-Chloro-2,3-diphenylquinoxaline (4c):[18]
White solid; yield 90%
(28.4 mg) from diol, 87% (27.5 mg) from a-hydroxyketone; m.p.
115–1168C (Ref. [18]: 115–1168C); 1
H NMR (400 MHz, CDCl3): d=
7.31–7.41 (m, 6H), 7.49–7.53 (m, 4H), 7.71 (dd, J=9.0, 2.3 Hz, 1H),
8.11 (d, J=9.0 Hz, 1H), 8.17 ppm (d, J=2.3 Hz, 1H); 13
C NMR
(CDCl3, 100 MHz): d=128.1, 128.3 (”2), 129.1, 129.1, 129.9, 129.9,
130.4, 130.9, 135.6, 138.7, 138.7, 139.7, 141.5, 153.6, 154.2 ppm.
6,7-Dichloro-2,3-diphenylquinoxaline (4d):[19]
White solid; yield
88% (30.8 mg) from diol, 88% (31 mg) from a-hydroxyketone; m.p.
154–1568C (Ref. [19]: 154–1558C); 1
H NMR (400 MHz, CDCl3): d=
7.31–7.41 (m, 6H), 7.47–7.52 (m, 4H), 8.28 ppm (s, 2H); 13
C NMR
(CDCl3, 100 MHz): d=128.6, 129.3, 129.8, 129.9, 134.4, 138.4, 139.9,
154.4 ppm.
2,3-Diphenylpyrido[2,3-b]pyrazine (4e):[20]
Yellow solid; yield 90%
(25.5 mg) from diol, 90% (25.5 mg) from a-hydroxyketone; m.p.
142–1438C (Ref. [20]: 141–1438C); 1
H NMR (400 MHz, CDCl3): d=
7.30–7.42 (m, 6H), 7.53–7.66 (m, 4H), 7.74 (dd, J=8.0, 2.9 Hz, 1H),
8.55 (d, J=8.0 Hz, 1H), 9.17 ppm (d, J=2.9 Hz, 1H); 13
C NMR
(CDCl3, 100 MHz): d=125.4, 128.3, 128.6, 129.6, 129.8, 130.0, 130.5,
136.3, 138.0, 138.5, 138.9, 149.4, 153.7, 155.2, 156.8 ppm.
2,3-Bis(4-methoxy-phenyl)quinoxaline (4 f):[18]
Pale yellow solid;
yield 89% (30.5 mg) from diol, 88% (30 mg) from a-hydroxyke-
tone; m.p. 148–1508C (Ref. [18]: 148–1498C); 1
H NMR (400 MHz,
CDCl3): d=3.82 (s, 6H), 6.87 (d, J=9.6 Hz, 4H), 7.49 (d, J=9.6 Hz,
4H), 7.72 (dd, J=6.3, 3.4 Hz, 2H), 8.12 ppm (dd, J=6.3, 3.4 Hz, 2H);
13
C NMR (CDCl3, 100 MHz): d=55.5, 114.0, 129.2, 129.7, 131.4,
131.9, 141.2, 153.2, 160.3 ppm.
2,3-Bis(4-methoxy-phenyl)-6-methylquinoxaline (4g):[18]
Pale yellow
solid; yield 90% (32 mg) from diol, 92% (32.8 mg) from a-hydroxy-
ketone; m.p. 147–1488C (Ref. [18]: 148–1498C); 1
H NMR (400 MHz,
CDCl3): d=2.59 (s, 3H), 3.83 (s, 6H), 6.86 (d, J=8.7 Hz, 4H), 7.47 (d,
J=8.8 Hz, 2H), 7.48 (d, J=8.8 Hz, 2H), 7.54 (dd, J=8.5, 1.6 Hz, 1H),
7.91 (d, J=1.6 Hz, 1H), 8.01 ppm (d, J=8.5 Hz, 1H); 13
C NMR
(CDCl3, 100 MHz): d=22.0, 55.5 (”2), 113.9 (”2), 128.0, 128.6, 131.4,
131.4, 131.9, 131.9, 132.1, 139.7, 140.3, 141.2, 152.3, 153.0, 160.2,
160.3 ppm.
6-Chloro-2,3-Bis(4-methoxy-phenyl)-quinoxaline (4h):[21]
Pale yellow
solid; yield 91% (34 mg) from diol, 87% (32.8 mg) from a-hydroxy-
ketone; m.p. 150–1518C (Ref. [21]: 1518C); 1
H NMR (400 MHz,
CDCl3): d=3.83 (s, 6H), 6.87 (d, J=8.7 Hz, 4H), 7.48 (d, J=8.7 Hz,
2H), 7.49 (d, J=8.7 Hz, 2H), 7.65 (dd, J=8.9, 2.0 Hz, 1H), 8.04 (d,
J=8.9 Hz, 1H), 8.11 ppm (d, J=2.0 Hz, 1H); 13
C NMR (CDCl3,
100 MHz): d=55.5 (”2), 114.0 (”2), 128.0, 130.4, 130.6, 131.4 (”2),
131.4, 131.5, 135.3, 139.7, 141.5, 153.3, 154.0, 160.5, 160.6 ppm.
6,7-Dichloro-2,3-Bis(4-methoxy-phenyl)-quinoxaline (4i):[22]
Pale
yellow solid; yield 93% (38 mg) from diol, 90% (36.8 mg) from a-
hydroxyketone; m.p. 169–1708C (Ref. [22]: 168–1708C); 1
H NMR
(400 MHz, CDCl3): d=3.83 (s, 6H), 6.87 (d, J=8.7 Hz, 4H), 7.47 (d,
J=8.7 Hz, 4H), 8.21 ppm (s, 2H); 13
C NMR (CDCl3, 100 MHz): d=
55.5, 114.0, 129.7, 131.1, 131.4, 134.0, 139.9, 154.2, 160.7 ppm.
2,3-Bis(4-methoxyphenyl)pyrido[2,3-b]pyrazine (4j):[20]
Pale yellow
solid; yield 87% (29.8 mg) from diol, 89% (30.5 mg) from a-hydroxy-
ketone; m.p. 137–1388C; (Ref. [20]: 137–1388C); 1
H NMR (400 MHz,
CDCl3): d=3.88 (s, 6H), 6.83 (d, J=8.7 Hz, 2H), 6.86 (d, J=8.7 Hz,
2H), 7.51 (d, J=8.7 Hz, 2H), 7.60 (d, J=8.7 Hz, 2H), 7.63 (d, J=
8.4 Hz, 1H), 8.41 (dd, J=8.4, 1.7 Hz, 1H), 9.07 ppm (d, J=1.7 Hz,
1H); 13
C NMR (CDCl3, 100 MHz): d=55.4, 55.4, 113.7, 114.0, 124.9,
130.8, 131.2, 131.3, 131.9, 135.9, 137.9, 149.9, 153.6, 154.3, 155.9,
160.1, 160.8 ppm.
Acenaphtho[1,2-b]quinoxaline (4k):[18]
Pale yellow solid; yield 90%
(22.9 mg) from diol, 93% (23.7 mg) from a-hydroxyketone; m.p.
242–2458C (Ref. [18]: 241–2428C); 1
H NMR (400 MHz, CDCl3): d=
7.77 (dd, J=6.3, 3.4 Hz, 2H), 7.86 (dd, J=8.2, 7.0 Hz, 2H), 8.12 (d,
J=8.2 Hz, 2H), 8.22 (dd, J=6.3, 3.4 Hz, 2H), 8.44 ppm (d, J=7.0 Hz,
2H); 13
C NMR (CDCl3, 100 MHz): d=122.0, 128.8, 129.3, 129.6,
129.7, 130.1, 131.9, 136.6, 141.4, 154.2 ppm.
9-Methyl-acenaphtho[1,2-b]quinoxaline (4l):[18]
Pale yellow solid;
yield 92% (24.7 mg) from diol, 91% (24.4 mg) from a-hydroxyke-
tone; m.p. 3008C (Ref. [18]: 3008C); 1
H NMR (400 MHz, CDCl3):
d=2.53 (s, 3H), 7.45 (dd, J=8.5, 1.8 Hz, 1H), 7.67 (t, J=8.4 Hz, 2H),
7.84 (d, J=1.8 Hz, 1H), 8.05 (dd, J=8.4, 2.0 Hz, 1H), 7.95 (d, J=
8.5 Hz, 1H), 8.22 ppm (dd, J=8.4, 2.0 Hz, 2H); 13
C NMR (CDCl3,
100 MHz): d=21.8, 121.6, 121.8, 128.6, 128.6, 128.8, 129.1, 129.2,
129.4, 130.0, 131.4, 132.0, 139.6, 139.7, 141.3, 153.4, 154.1 ppm.
Recycling
To a stirred solution of benzoin 2a (0.1 mmol, 21.2 mg) or benzhy-
drol 3a (0.1 mmol, 21.4 mg) and o-phenylenediamine 1a
(0.1 mmol, 10.8 mg) in a 1:1 mixture of toluene/water was added
NaOH (12 mg, 0.3 mmol, 3 equiv) and aqueous AuCNT (50 mL,
0.2 mol%). The reaction mixture was stirred until complete con-
sumption of the starting material (monitored by TLC, Table 4) at RT.
The catalyst was then recovered by simple centrifugation and
reused without further purification.
ChemCatChem 2015, 7, 57 – 61 www.chemcatchem.org 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim60
Communications
5. TON and TOF
To a stirred solution of benzoin 2a (0.1 mmol, 21.2 mg) or benzhy-
drol 3a (0.1 mmol, 21.4 mg) and o-phenylenediamine 1a
(0.1 mmol, 10.8 mg) in a 1:1 mixture of toluene/water was added
NaOH (12 mg, 0.3 mmol, 3 equiv) and aqueous AuCNT (50 mL,
0.2 mol%). The reaction mixture was stirred until complete con-
sumption of the starting material (monitored by TLC) at RT, then
the catalyst was removed by centrifugation and the supernatant
worked up as described above. The crude residue was directly sub-
jected to silica gel column chromatography to afford pure 4a in
96% yield from 2a (path A) or 94% yield from 3a (path B). TONs
and TOFs were calculated as shown in Equations (1)–(4):
TON2a ¼
product ½mmolŠ
catalyst ½mmolŠ
¼
0:096
0:0002
¼ 480 ð1Þ
TOF2a ¼
TON2a
t ½hŠ
¼
480
26
¼ 18 hÀ1
ð2Þ
TON3a ¼
product ½mmolŠ
catalyst ½mmolŠ
¼
0:094
0:0002
¼ 470 ð3Þ
TOF3a ¼
TON3a
t ½hŠ
¼
470
38
¼ 12 hÀ1
ð4Þ
Acknowledgements
Support from the Indo-French Centre for the Promotion of Ad-
vanced Research (IFCPAR)/Centre Franco-Indien pour la Promo-
tion de la Recherche AvancØe (CEFIPRA) is gratefully acknowl-
edged (Project no. 4705-1). The TEM-team platform (CEA, iBiTec-
S) is acknowledged for help with TEM images. The “Service de
Chimie Bioorganique et de Marquage” belongs to the Laboratory
of Excellence in Research on Medication and Innovative Thera-
peutics (ANR-10-LABX-0033-LERMIT).
Keywords: carbon · gold · heterogeneous catalysis ·
nanotubes · oxidation
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Received: September 29, 2014
Published online on October 21, 2014
ChemCatChem 2015, 7, 57 – 61 www.chemcatchem.org 2015 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim61
Communications