Isomerization of Safrole and Eugenol Under Microwave Irradiation

Abstract: Safrole and eugenol isomerization reactions were carried out under microwave irradiation at atmospheric pressure and homogeneous medium with various alcohols used as solvents and different base concentrations. The rate reaction enhancement shown was 2.3 to 13.2 times faster than conventional reflux.     

Further Improvements in Isomerization of Olefins in Solvent-Free Conditions

Isomerization of safrole and ethyleugenol are performed quasi-quantitatively within 5 minutes at 80°C using KOH or KOtBu and catalytic amount of transfer agent in the absence of solvent. Transfer agent can be avoided in the case of KOtBu with eventually increase in reaction time. Isolated yields of 99% are obtained from 10 g of materials.     

Microwave Promoted Rapid Oxidative Deoximation of Oximes under Solvent-Free Conditions

Aldeydes and ketones are easily obtained in high yields by microwave promoted rapid oxidative deoximation of the corresponding oximes with zinc nitrate hexahydrate adsorbed on silica gel under solvent free conditions.     

微波辐射和加热条件下的无催化剂无溶剂Knoevenagel缩合反应

芳香醛和丙二腈在无催化剂无溶剂存在下在微波辐射或加热条件下可以发生Knoevenagel缩合反应,反应产率良好.     

Silylation of Hydroxy Groups with HMDS Under Microwave Irradiation and Solvent-Free Conditions

Phenols and alcohols are silylated with hexamethyldisilazane (HMDS) under microwave irradiation in solvent-free condition in good to excellent yields.     

Synthesis of Ferrocenyl Schiff Bases Under Solvent-Free Conditions Using Microwave Irradiation

Ferrocenyl imines 3a–f were synthesized using solvent-free methods by mixing ferrocene carbaldehyde 1 with amines 2a–f under microwave irradiation. The imines were obtained in good yield in short reaction times.     

One-Pot Synthesis of N-Substituted 4-Aryl-1,4-dihydropyridines Under Solvent-Free Conditions and Microwave Irradiation

Summary.  The three-component condensation of benzaldehyde derivatives, alkyl propiolates, and primary amines catalyzed by silica gel, zeolite HY, montmorillonite K-10, and acidic alumina under microwave irradiation gave N-substituted 4-aryl-1,4-dihydropyridines in short reaction times and high yields. The best results were obtained with silica gel. Received March 26, 2001. Accepted (revised) June 18, 2001     

One-Pot Synthesis of N-Substituted 4-Aryl-1,4-dihydropyridines Under Solvent-Free Conditions and Microwave Irradiation

 The three-component condensation of benzaldehyde derivatives, alkyl propiolates, and primary amines catalyzed by silica gel, zeolite HY, montmorillonite K-10, and acidic alumina under microwave irradiation gave N-substituted 4-aryl-1,4-dihydropyridines in short reaction times and high yields. The best results were obtained with silica gel.     

Synthesis of Eugenol Esters by Lipase-Catalyzed Reaction in Solvent-Free System

Enzymatic esterification of eugenol is a matter of great scientific and technological interest due to the well-known drawbacks of the chemical-catalyzed route as well as the potential use of produced compounds as natural antimicrobials. This work reports the maximization of eugenil acetate production by esterification of eugenol and acetic anhydride in a solvent-free system using Novozym 435 as catalyst. The antimicrobial activity of eugenol and eugenil acetate was also determined. The operating conditions that maximized eugenil acetate production were 50?°C, eugenol to acetic anhydride of 1:3, 150?rpm, and 5.5?wt% of enzyme, with a conversion of 99?%. A kinetic study was performed to assess the influence of substrates molar ratio, enzyme concentration, and temperature on eugenil acetate yield. Results show that an excess of anhydride, low enzyme concentration (1?wt%), and 60?°C afforded nearly complete conversion after 6?h of reaction. The highest antimicrobial activity of eugenil acetate was observed against Acinetobacter sp. (48.66?mm) at concentration of 20???L. Results indicate that the esterification of eugenol improved its antimicrobial properties. New experimental data on enzymatic esterification of eugenol and acetic anhydride are reported in this work, showing a promising perspective to overcome the inconvenient of the chemical-catalyzed route for obtaining antimicrobial natural compounds.     

Microwave Assisted Selective Oxidation of Benzylic Alcohols with Calcium Hypochlorite under Solvent-Free Conditions

Summary.  A remarkably fast microwave assisted selective oxidation of benzylic alcohols with calcium hypochlorite under solvent-free conditions is described. Received August 28, 2000. Accepted September 21, 2000     

Synthesis of the Tetrasulfo- and Tetranitrophthalocyanine Complexes Under Solvent-Free and Reflux Conditions Using Microwave Irradiation

Abstract

The tetrasulfophthalocyanine complexes of Ni, Cu, Co, Pd, Pt, and tetranitrophthalocyanine complexes of Ni, Cu, Co, Mn, Fe, Pd are prepared in high purity upon exposure to microwave irradiation under solvent-free and reflux conditions and reaction times are considerably reduced.     

新的芳杂环酰腙分子钳的微波无溶剂快速有效合成

在微波辐射无溶剂条件下,以间苯二酚为起始原料,固体Al2O3为载体,设计并高产率地合成了12个新的芳杂环酰腙分子钳人工受体.其结构均经1HNMR,IR,MS及元素分析确证.同传统的方法相比,该法具有简单、快速、高效和对环境友好等优点.利用紫外滴定光谱初步考察了这类分子钳对芳胺的识别性能.     

The Synthesis of Gallic Esters of Higher Fatty Alcoholsunder Solvent-Free Conditions Using Microwave Irradiation

Higherfattyalcoholgallicestersarereportedasfinefoodantioxidantslandcolordevelopingagents'forheatsensitiverecordingpaperorcarbonlesspaper.Theyareusuallysynthesizedbyoneoftwomainmethods:esterificationofgallicacid3andtransesterificationofmethylorethylesters4.Themaindisadvantagesofsomeofthosemethodsaretheuseofuncommonreagentsanddifficultwork-up.Wewishtoreportasimplesyntheticprocedureutilizingmicrowaveirradiations'6undersolventffreeconditions,differentacids,includingMontmorilloniteK10andp-toluenes…     

Synthesis of 1,5-Benzodiazepines with Unusual Substitution Pattern from Chalcones Under Solvent-Free Microwave Irradiation Conditions

1,5-Benzodiazepines have been synthesized from the corresponding 2′-hydroxychalcones [1-(2-hydroxyphenyl)-3-aryl-2-propen-1-ones] and o-phenylenediamine, both in methanol, under reflux and under solvent-free microwave irradiation conditions on alumina. The latter method proved to be advantageous.     

微波促进下无溶剂一锅法合成含氟喹唑啉-4(3H)-酮类化合物

采用邻胺基苯甲酸、原甲酸三乙酯及含氟苯胺为原料,在微波促进下,无溶剂一锅法高效合成了系列3-氟苯基-喹唑啉-4(3H)-酮类化合物,同时测试了新化合物的荧光性能,并与不含氟同类化合物的荧光发射光谱进行了比较.     

Synthesis of Quinizarin and Its Derivatives under Conditions of Microwave Activation

In a microwave field, phthalic anhydride reacts with p-chlorophenol to give 1,4-dihydroxyanthraquinone (quinizarin) within 10 min. The reaction with 4-chlorophthalic anhydride occurs similarly. Phthalic and chlorophthalic acids can be used instead of anhydrides. 3-Nitrophthalic acid and 3,4,5,6-tetrabromophthalic anhydride do not react with p-chlorophenol under these conditions.     

Tetrahydropyranylation of Alcohols Under Solvent-Free Conditions

A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported.     

Microwave Promoted Reductive Coupling of Carbonyl Compounds to Bis(Trimethylsilyl) Pinacols Under Solvent-Free Conditions

Reductive coupling of carbonyl compounds was performed with trimethylchlorosilane (TMS-Cl) on montmorillonite K10 clay in conventional microwave oven in short time wih quantitative yields of bis(trimethylsilyl) pinacols.     

Solvent-Free C-Benzoylation and N-Benzoylation Reactions Using Microwave Heating

An ecofriendly and efficient microwave-irradiated solvent-free benzoylation method was developed. The procedure for C-benzoylation used 50 mol% AlCl₃ as a Lewis acid catalyst at 130 °C and was completed in 10 min. The isolated yield was between 71% and 100%. N-benzoylation was conducted in a catalyst-free environment at 130 °C in 10 min. The isolated yield was between 80% and 100%.