Presence Of Silica Gel Research Articles

Silica gel‐Mediated Friedel‐Crafts Reaction of Indoles with Functionalized Nitroallylic Acetates via an SN1 Process

AbstractAn environmentally friendly Friedel‐Crafts reaction was demonstrated between indoles and functionalized nitroallylic acetates in the presence of silica gel, providing the corresponding C‐3‐selective regioisomers in good to high overall chemical yields (70‐93%).

ChemInform Abstract: Selective Aerobic Oxidation of Alcohols Catalyzed by Iron Chloride Hexahydrate/TEMPO in the Presence of Silica Gel.

AbstractA simple and efficient catalyst system is used for the oxidation of benzylic alcohols in the presence of silica gel using molecular oxygen as terminal oxidant.

Efficient One‐Pot Synthesis of Alkyl 2‐(Dialkylamino)‐4‐phenylthiazole‐5‐carboxylates and Single‐Crystal X‐Ray Structure of Methyl 2‐(Diisopropylamino)‐4‐phenylthiazole‐5‐carboxylate

AbstractThe reaction between secondary amines, benzoyl isothiocyanate, and dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates) in the presence of silica gel (SiO2) led to alkyl 2‐(dialkylamino)‐4‐phenylthiazole‐5‐carboxylates in fairly high yields. The structures of the products were confirmed by their IR, 1H‐ and 13C‐NMR, and mass spectra, and by a single‐crystal X‐ray structure determination.

Selective aerobic oxidation of alcohols catalyzed by iron chloride hexahydrate/TEMPO in the presence of silica gel

An environmentally friendly and efficient process whereby FeCl3•6H2O/2,2,6,6‐tetramethylpiperidine N‐oxyl (TEMPO)‐catalyzed oxidation of alcohols to the corresponding aldehydes and ketones is accomplished in the presence of silica gel using molecular oxygen or air as the terminal oxidant. The electron‐deficient benzyl alcohol was smoothly oxidized to the corresponding aldehydes with up to 99% isolated yield. It was found that silica gel not only could enhance the catalytic reaction rate but also increase the selectivity for the product. The high performance of FeCl3•6H2O/TEMPO catalyst system in the presence of silica gel might be attributed to the surface silanol groups. UV–visible spectra analysis showed that the Fe (III)–TEMPO complex could serve as the active intermediate species in the present catalytic system. A plausible mechanism of the catalytic system is proposed. Copyright © 2012 John Wiley & Sons, Ltd.

Infrared heat aided solid state synthesis of pyrroles from 1,4‐diketones and ammonium acetate

AbstractA facile amination of 1,4‐diketones with ammonium acetate has been achieved by mechanochemical grinding assisted by infrared irradiation in the presence of silica gel. The wastes are reduced and the energy resources saved. J. Heterocyclic Chem., (2012).

Microwave-assisted efficient synthesis of 2-arylbenzo[b]furans and 2-ferrocenylbenzo[b]furans from readily prepared propargylic alcohols and o-iodophenols

A simple, efficient and expeditious method for synthesis of 2-arylbenzo[b]furans and 2-ferrocenylbenzo[b]furans from readily prepared propargylic alcohols, o-iodophenols and silica gel with the catalyst of PdCl2(PPh3)2 (2 mol%)/CuI (2 mol%) and microwave-promoted Sonogashira coupling/cyclization reaction is developed. The methodology can produce good to excellent yields. In addition, this method can also be completed in one-pot with iodobenzene, 2-methyl-3-butyn-2-ol and 2-iodo-4-methylphenol as reactants. A simple and efficient method for synthesis of 2-arylbenzo[b]furnas and 2-ferrocenylbenzo[b]furans has been developed from the Sonogashira coupling/cyclization reaction of propargylic alcohols and o-iodophenols in the presence of silica gel and catalytic amounts of PdCl2(PPh3)2 (2 mol%) and CuI (2 mol%) under microwave conditions.

Reductive aminopropylation of ketene silyl (thio)acetals leading to the synthesis of δ-amino esters

In the presence of silica gel or titanium tetrachloride, ketene silyl acetals or ketene silyl thioacetals underwent 1,4-addition with α,β unsaturated aldimines which possess a large triphenylmethyl group at the imino nitrogens followed by reduction with sodium cyanoborohydride to give aminopropylated products, δ-amino esters, in good yields.

Efficient Syntheses of New Chromone- and Chromanequinoline Hybrids and their Aza-analogs

Some novel chromone- and chromanequinoline hybrids and their aza-analogs were synthesized from 2-chloro- 3-quinolinecarboxaldehydes as starting materials. The cyclization of 2-hydroxychalcones in the presence of AcONa yielded chroman-4-ones, while, in the typical AFO conditions, the 2-corresponding quinolyl-3-hydroxyflavonols were obtained. These approaches were extended to 2-aminochalcones, which delivered the 3-hydroxy-2,3-dihydroquinolin- 4(1H)-one via an epoxy-ketone and 2-quinolyl-2,3-dihydroquinoline-4(1H)-one under microwave irradiation in the presence of silica gel impregnated with indium (III) chloride.

Silica Gel Promotes Cascade Synthesis of 2-(Heteroaryl)acetamide Derivatives from Isocyanides, Dialkylamines, and Heteroarylcarbaldehydes

Addition of an isocyanide to an iminium ion intermediate that forms from the reaction between a heteroarylcarbaldehyde and a secondary amine leads to formation of sterically congested 2-(heteroaryl)acetamide derivatives in the presence of silica gel at room temperature. The structures of the products were deduced from their 1H NMR, 13C NMR, and infrared spectra and mass spectrometry.

ChemInform Abstract: Silica Chloride Mediated Alkylation of Electron‐Rich Aromatics by Benzyl or tert‐Butyl Chloride.

o C. TLC monitored the progress of reaction. After completion of the reaction, the mixture was diluted with ethyl acetate and filtered. The solution was washed with sodium carbonate (5% in water) and water. The organic layer separated and evaporated. The residue was applied to a silica gel column. Elution with CCl4 gave pure product. We also tried a similar reaction in the presence of silica gel and HCl (gas) without using silica chloride. The reaction was not successful and the starting materials remained intact. However, we found that this method was applicable for preparation of alkyl aromatic compounds from reaction of tert- butyl chloride and structurally and electronically diverse benzyl chloride with aromatic rings substituted with electron-donating groups (Table 1, entries 2-11 and 13-15). The presence of elec- tron-donating groups in aromatics is necessity for progress of

Silica-supported 1,3-dichloro-5,5-dimethylhydantoin (DCH) as a useful reagent for microwave-assisted aromatization of 1,3,5-trisubstituted pyrazolines under solvent-free conditions

Abstract 1,3,5-Trisubstituted pyrazolines are rapidly and conveniently oxidized to their corresponding pyrazoles by 1,3-dichloro-5,5-dimethylhydantoin (DCH) in solution and solvent-free conditions under microwave irradiation. The presence of silica gel as a supporting agent is shown to be effective in reducing the reaction times and increasing the yields.

Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon

A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700°C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450°C and with 5A molecular sieve was 700°C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000J/g), similar to the heat of combustion of commercial fuels.

ChemInform Abstract: Use of N‐Allylidene‐1,1‐diphenylethanamine as a Latent Acrolein Synthon in the Double Nucleophilic Addition Reaction of Ketene Silyl (Thio)acetals and Allylborolanes.

AbstractThis allows efficient access to adducts of type (IV).

Silica Chloride Mediated Alkylation of Electron-rich Aromatics by Benzyl or tert-Butyl Chloride

o C. TLC monitored the progress of reaction. After completion of the reaction, the mixture was diluted with ethyl acetate and filtered. The solution was washed with sodium carbonate (5% in water) and water. The organic layer separated and evaporated. The residue was applied to a silica gel column. Elution with CCl4 gave pure product. We also tried a similar reaction in the presence of silica gel and HCl (gas) without using silica chloride. The reaction was not successful and the starting materials remained intact. However, we found that this method was applicable for preparation of alkyl aromatic compounds from reaction of tert- butyl chloride and structurally and electronically diverse benzyl chloride with aromatic rings substituted with electron-donating groups (Table 1, entries 2-11 and 13-15). The presence of elec- tron-donating groups in aromatics is necessity for progress of

Silica Gel, an Effective Catalyst for the Reaction of Electron-Deficient Nitro-Olefins with Nitrogen Heterocycles

The reaction of electron-deficient olefins with nitrogen heterocycles such as pyrrole and indole was examined in the presence of silica gel at room temperature under stirring at solvent-free conditions. It was found that silica gel is an effective catalyst for this conjugate addition. This work resulted in the formation of monosubstituted pyrroles selectively as a major product except in a few cases where disubstituted pyrroles were also formed as side products. Thus, a simple, rapid, efficient, environmentally benign, and solvent-free method was established.

ChemInform Abstract: Oxidation of Ethers by Nitrogen Dioxide in the Presence of Silica Gel.

Ethers are efficiently oxidized by nitrogen dioxide to give the corresponding aldehydes or ketones in the presence of silica gel under mild conditions.

Use of N-Allylidene-1,1-diphenylethanamine as a Latent Acrolein Synthon in the Double Nucleophilic Addition Reaction of Ketene Silyl (Thio)acetals and Allylborolanes

In the presence of silica gel and water, a mixture of ketene silyl acetals and 2-allyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane underwent 1,4- and subsequently 1,2-addition with N-allylidene-1,1-diphenylethanamine to give delta-hydroxyesters in good yields, where the allylideneamine was successfully used as an acrolein equivalent.

A mild and convenient one-pot two-step synthesis of hydroxy- iminodihydrobenzofurans mediated by silica gel under microwave activation conditions

A convenient one-pot two-step procedure for the synthesis of hydroxyiminodihydrobenzofurans assisted by microwave irradiation in presence of silica gel is described herein. Cyclic 1,3-dicarbonyl compounds reacted smoothly with various nitroolefins to furnish hydroxyiminodihydrobenzofuran derivatives as the mixture of E and Z isomers. Clean reaction conditions, no work-up procedure, easy isolation and good yields of the products are the salient features of the methodology.

ChemInform Abstract: A Novel Three‐Component Reaction of a Secondary Amine and a 2‐Hydroxybenzaldehyde Derivative with an Isocyanide in the Presence of Silica Gel: An Efficient One‐Pot Synthesis of Benzo[b]furan Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Reaction Between 1,3‐Dicarbonyl‐Containing CH Acids and Dialkyl Acetylenedicarboxylates in the Presence of Silica Gel in Solvent‐Free Conditions: An Efficient Method for the Synthesis of Electron‐Poor Alkenes and Pyranes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.