Hydroarylation of alkynes and alkenes through alumina-sulfuric acid catalyzed regioselective CC bond formation

A highly atom-efficient synthetic protocol for hydroarylation of terminal-aryl alkynes and styrene through the regioselective CC bond formation via the electrophilic addition of naphthols and substituted phenols has been developed using alumina-sulfuric acid as a heterogeneous supported solid acid catalyst. This methodology shows excellent regioselectivity and affords the desired product in good to excellent yield. The heterogeneous catalyst can also be recycled efficiently without much loss of activity.     

An efficient 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU)-mediated synthesis of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides

A series of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides 4 has been effectively achieved in high yield and purity from the reaction of pyrazole carboxylic acid 2 with amines 3 in the presence of TBTU as a catalyst and diisopropyl ethylamine as a base in acetonitrile at room temperature.     

H4SiW12O40-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides: An efficient synthesis of 3,4-disubstituted 1H-pyrazoles

A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid(H₄Si W₁₂O₄₀)-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides/aldehydes were smoothly reacted with sulfonyl hydrazides to furnish regioselectivity 3,4-disubstituted 1H-pyrazoles. The application of such an earth-abundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of 3,4-di...     

Performance of C1-symmetric chiral ammonium betaines as catalysts for the enantioselective Mannich-type reaction of α-nitrocarboxylates

The catalytic performance of C₁-symmetric chiral ammonium betaines in the enantioselective direct Mannich-type reaction of α-nitrocarboxylates with N-Boc imines has been investigated. The most effective catalyst structure has been identified; this provides a reliable synthetic route to a variety of enantiomerically enriched α-tetrasubstituted α,β-diamino acid derivatives.     

One-pot synthesis of 1-aryl-1H,3H-thiazolo[3,4-a]benzimidazoles using magnetite-linked sulfonic acid as catalyst

Abstract

A series of 1-aryl-1H,3H-thiazolo[3,4-a]benzimidazole derivatives have been synthesized via the three-component reaction of o-phenylenediamine, aromatic aldehydes, and 2-mercaptoacetic acid, catalyzed by magnetite-linked sulfonic acid. This method has the advantages of high yield, extensive adaptability, easy operation, and environmental friendliness. Supporting this acid catalyst on magnetite particles offers a simple and nonenergy-intensive method for recovery and reuse of the catalyst by applying an external magnet.     

Revisit to the Biginelli reaction: a novel and recyclable bioglycerol-based sulfonic acid functionalized carbon catalyst for one-pot synthesis of substituted 3,4-dihydropyrimidin-2-(1H)-ones

A simple and efficient synthetic protocol has been developed for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones by using a novel bioglycerol-based sulfonic acid functionalized carbon catalyst, devoid of moisture sensitive metal catalysts and corrosive acidic reagents. The developed method has the advantages of good to excellent yields, short reaction times, operational simplicity, and a recyclable catalyst. The catalyst can be prepared by a simple procedure from inexpensive and readily available glycerol and has been shown to be recoverable and reusable up to four cycles without any loss of activity.     

A new and highly efficient water-soluble copper complex for the oxidation of secondary 1-heteroaryl alcohols by tert-butyl hydroperoxide

The water-soluble copper complex generated in situ from CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), has been revealed as a highly efficient and selective catalyst for the oxidation of secondary 1-heteroaryl alcohols to the corresponding heteroaromatic ketones with aqueous tert-butyl hydroperoxide, under mild conditions. The catalytic system is compatible with different heterocycles such as pyridines, pyrroles, indoles, thiophens, furans, thiazoles, and imidazoles.     

Polymeric catalyst for the synthesis of new pyrido[2,3-b]indoles

A new and efficient method has been developed for the one-pot synthesis of novel 2,9-dihydro-2-oxo-4-aryl-1H-pyrido[2,3-b]indole-3-carbonitrile derivatives by condensation of substituted (triethoxymethyl)arene, 1-methyl-1H-indol-2-ol and cyanoacetamide in the presence of a catalytic amount of crosslinked poly(2-acrylamido-2-methyl propane sulfonic acid) (AMPS) as an efficient and heterogeneous catalyst. This polymeric solid acid catalyst is stable and can be easily recovered and reused without significant change in its activity.     

Cellulose-SO3H: an efficient and biodegradable solid acid for the synthesis of quinazolin-4(1H)-ones

The condensation of 2-aminobenzamide with aldehydes or ketones has been achieved using cellulosesulfonic acid under mild reaction conditions to furnish 2,3-dihydroquinazolin-4(1H)-ones in good yields with a high selectivity. The use of biodegradable solid acid catalyst, cellulosesulfonic acid makes this method quite simple, more convenient, and practical. This catalyst was also found to be very active for the synthesis of hydroxyalkylquinazolin-4-ones from cyclic enol ethers.     

Magnetically recoverable copper ferrite catalyzed cascade synthesis of 4-Aryl-1H-1,2,3-triazoles under microwave irradiation

Magnetically active CuFe₂O₄ catalyzed cascade synthesis of 4-Aryl-1H-1,2,3-triazoles under microwave irradiation starting from aromatic aldehydes, sodium azide and nitromethane has been developed and demonstrated here. The catalyst system needed for the purpose was prepared following a procedure by A. Dandiya et al. with a slight modification and was characterized using FT-IR, XRD, SEM-EDX and TEM analysis. The most notable advantage of the developed methodology is the excellent time economy to carry out the transformation. Other features include simple operating procedure, wide substrate coverage and easy recovery of the catalyst. Reusability of the catalyst has been tested and found to be very satisfactory up to sixth cycle without significant loss in efficiency. All the synthesized compounds have been characterized using FTIR, ¹H & ¹³CNMR spectroscopy, HRMS.     

Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid

Abstract

Chemoselective protection of alkyl and aryl aldehydes has been accomplished through the formation of dioxolane on the surface of alumina-sulfuric acid under solvent-free conditions where dialkyl ketones, aryl alkyl ketones, and diaryl ketones remain intact.     

Identification and determination of carboxylic acids in food samples using 2-(2-(anthracen-10-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)ethyl 4-methylbenzenesulfonate (APIETS) as labeling reagent by HPLC with FLD and APCI/MS

A new labeling reagent for carboxylic acids, 2-(2-(anthracen-10-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)ethyl 4-methylbenzenesulfonate (APIETS) has been designed and synthesized. It was used to label eight fatty acids (lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid and linolenic acid) and four hydroxy pentacyclic triterpene acids (oleanolic acid, ursolic acid, betulinic acid and maslinic acid), successfully. APIETS could easily and quickly label carboxylic acids in the presence of K₂CO₃ catalyst at 85 °C for 35 min in N,N-dimethylformamide solvent. The carboxylic acids derivatives were separated on a C₈ reversed-phase column with gradient elution and fluorescence detection at λ_ex/λ_em = 315/435 nm. Identification of these derivatives was carried out by online mass spectrometry with atmospheric pressure chemical ionization in positive ion mode. The detection limits obtained were 13.37-30.26 fmol (signal-to-noise ratio of 3). The proposed method has been applied to the quantification of carboxylic acids in sultana raisin (Thompson seedless), hawthorn flake (Crataegus pinnatifida Bge.), Lycium barbarum seed oil and Microula sikkimensis seed oil with recoveries over 95.3%. It has been demonstrated that APIETS is a prominent labeling reagent for determining carboxylic acids with high performance liquid chromatography.     

Speciation in the ternary system Iron(III)-nitrilotrimethylphosphonic acid-1,3-dicarboxypropane-1-iminodiacetic acid

The interaction of iron(III) ions with nitrilotrimethylphosphonic acid and 1,3-dicarboxypro-pane-1-iminodiacetic acid in aqueous solutions has been studied by spectrophotometry. It has been shown that complex formation in the system is complicated by protonation, hydrolysis, and precipitation. Homoligand 1: 1 complexes of different proton composition have been identified. The stability constants of the iron(III) complexonates and their fractional distribution as a function of pH (T = 20 ± 2°C, I = 0.1) have been determined. Conditions that make it possible to prevent the precipitation of iron(III) nitrilotrimethylphosphonates in the presence of 1,3-dicarboxypropane-1-iminodiacetic acid have been selected.     

Efficient PhB(OH)2-catalyzed one-pot synthesis of 3-substituted isoindolin-1-ones and isobenzofuran-1(3H)-ones under solvent free conditions

An efficient and practical one-pot synthesis of 3-substituted isoindolin-1-ones and isobenzofuran-1(3H)-ones has been developed under solvent free-conditions using non-toxic and cheap phenylboronic acid as excellent catalyst. This strategy involves the sequential two-step Mannich/lactamization cascade reaction of inexpensive 2-formylbenzoic acid with primary amines and a wide variety of ketones, and an aldol/lactonization cascade reaction of 2-formylbenzoic acid with a broad range of ketones.     

Narasaka reaction: Desilylative acylation of 1-alkenylsilanes with acid anhydrides

Recent advances in the desilylative acylation of 1-alkenylsilanes with acid anhydrides under transition metal catalysis are summarized. This catalytic desilylative acylation of 1-alkenylsilanes provides an efficient route to α,β-unsaturated ketones by using rhodium or iridium as the catalyst. Moreover, various one pot sequence reactions have been developed, which can synthesize α,β-unsaturated ketones from simple starting materials in an economic way. Additionally, this approach is applied to the asymmetric synthesis of atropisomers possessing silanol groups with excellent enantioselectivity.     

Brönsted acid hydrotrope combined catalyst for environmentally benign synthesis of quinoxalines and pyrido[2,3-b]pyrazines in aqueous medium

A new Brönsted acid hydrotrope combined catalyst (BAHC) has been developed and applied in acid catalyzed synthesis of pyrido[2,3-b]pyrazines and quinoxalines in an aqueous medium at ambient temperature with excellent yields. Interestingly, the catalyst can be easily recovered after the reactions and reused. Furthermore, BAHC catalyst worked well and avoids the use of organic solvents. We have reported herein the synthetic pathway which has less disastrous effect in the atmosphere and human survival.     

A study of the chelation reaction of gallium and indium with Arsenazo 1

The chelation reactions of gallium and indium with Arsenazo 1, i.e., 3-[(o-arsonophenyl)azo]-4,5-dihydroxy-2,7-naphthalene disulfonic acid, have been studied in detail. The nature and number of complexes formed was studied and it was found that gallium and indium form only one complex with Arsenazo 1. The composition of the complexes formed was found by various methods and it was found that both the complexes have composition 1:1 (metal:reagent). The values of log K were calculated by different methods at four different fixed values of ionic strength. For both the complexes, the value of thermodynamic stability constant has been obtained by plotting values of log K against ionic strength and extrapolating the curves to zero ionic strength. A tentative suggestion about the structure of the chelate ring has been made. The studies were further extended to the analytical aspects of the complexes and a suitable procedure has been recommended for the spectrophotometric determination of gallium and indium using this reagent.     

A Keggin heteropoly acid as an efficient catalyst for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles

The Keggin heteropoly acid, silicotungstic acid, H₄SiW₁₂O₄₀, has been demonstrated to be highly efficient for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles from N-methyl-1,2-phenylenediamine and (hetero)aryl aldehydes in ethyl acetate at room temperature. The catalyst works equally well for N-phenyl-1,2-phenylenediamine.     

DABCO promoted one-pot synthesis of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine derivatives and their biological activities

A simple and efficient one-pot synthesis of heteroaryl substititued dihydropyrano(c)chromenes and pyrano[2,3-d]pyrimidines has been developed via initial Knoevenagel, subsequent Micheal and final heterocyclization reactions of heteroaryl aldehyde, malononitrile and barbituric acid/ dimedone. 1,4-Diazabicyclo [2.2.2] octane (DABCO) has been used as a catalyst. Short reaction time, environment friendly procedure and excellent yields are the main advantages of this procedure. All synthesized compounds have shown good antimicrobial activity against different microbial stains.     

Selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles in water at ambient temperature

A highly selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles from the reaction of o-phenylenediamines and aromatic aldehydes in the presence of silica sulfuric acid is reported. The reactions were performed in ethanol or water and the catalyst could be reused for several runs.