Non-expensive,open-flask and selective catalytic systems for the synthesis of sulfinate esters and thiosulfonates

Two simple and efficient methods for the synthesis of sulfinate esters and thiosulfonates from sodium salts of sulfinic acids are described. Different alcohols were converted into the corresponding sulfinate esters in good yields and purity in an open flask. By the adjustment of the reaction conditions thiosulfonates could also be obtained in a very short reaction time.     

A facile and efficient method for the synthesis of novel pyridone analogues by aminolysis of an ester under solvent-free conditions

A series of 15 pure novel N-alkylated pyridone derivatives have been synthesized in 73-96% yields on treatment of ethyl (2-pyridone)acetates with structurally diverse amines in an efficient aminolysis procedure under ‘solvent-free’ conditions.     

An efficient and solvent-free one-pot synthesis of dihydropyrimidinones under microwave irradiation

An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives using formic acid as catalyst, from aldehydes,β-ketoester and urea(thiourea) without solvent under the irradiation of microwave is described. Compared with the classical Biginelli reaction, this new method has the advantage of good yields (77-94% for aromatic aldehydes) and short reaction time (3-8 min).     

Selenonium ionic liquid as an efficient catalyst for the synthesis of thioacetals under solvent-free conditions

Acidic ionic liquid butyl ethyl phenyl selenonium tetrafluoroborate, [BEPSe]BF₄, was successfully employed as a catalyst for the synthesis of several dithioacetals in the absence of a solvent. The method is general and selectively afforded thioacetals derived from aldehydes and ketones in good yields.     

The first synthesis of β-phenylchalcogeno-α,β-unsaturated esters via hydrochalcogenation of acetylenes using microwave and solvent-free conditions

A simple, clean, and efficient solvent-free protocol was developed for hydrochalcogenation of methyl propiolate derivatives with phenylchalcogenolate anion generated in situ from the respective diphenyl dichalcogenide (S, Se, Te) using alumina supported sodium borohydride. This efficient and improved method is general and furnishes the (Z)-β-phenylchalcogeno-α,β-unsaturated esters in yields and with selectivity comparable to those using organic solvent and inert atmosphere. The use of MW irradiation facilitates the procedure and accelerates the reaction.     

Microwave-promoted solvent-free synthesis of N-(diphenylmethylene)glycine alkyl esters

The efficient synthesis of N-(diphenylmethylene) glycine alkyl esters was achieved for the first microwave irradiation under solvent-free condition,using PEG or quaternary ammonium salts as phase transfer catalysts(PTCs).Under the optimum conditions, N-(diphenylmethylene) glycine alkyl esters were obtained in excellent yields in most cases.     

Xanthan sulfuric acid: An efficient and biodegradable solid acid catalyst for the synthesis of bis(indolyl)methanes under solvent-free conditions

Xanthan sulfuric acid (XSA) is found to be an efficient catalyst for the electrophilic substitution reaction of indole with aromatic aldehydes to afford the corresponding bis(indolyl)methanes at room temperature under solvent-free conditions. The catalyst was characterized for the first time with the help of powder XRD, SEM–EDX and DSC–TGA. The attractive features of this green, new methodology are excellent yield of products, clean reaction profile, reusability of the catalyst, energy sustainable protocol, simple experimental and easier work-up procedures.     

Boric acid as an efficient catalyst for the synthesis of 1,1-diacetate under solvent-free condition

Boric acid (BO₃H₃) is an inexpensive, efficient and mild catalyst for the synthesis of 1,1-diacetate (acylal) from the various aromatic and heteroaryl aldehydes with acetic anhydride at room temperature under solvent-free condition. The present method does not involve any hazardous organic solvents or catalysts. This method gives notable advantages such as excellent chemoselectivity, mild reaction condition, short reaction times and excellent yield.     

An efficient synthesis of quinolines under solvent-free conditions

An efficient synthesis of substituted quinolines has been achieved in a one-pot reaction from o-nitrobenzaldehyde and enolizable ketones using SnCl₂·2H₂O as the reductant under microwave irradiation without any solvent or catalyst     

PPA-SiO_2 catalyzed efficient synthesis of polyhydroquinoline derivatives through Hantzsch multicomponent condensation under solvent-free conditions

Silica gel-supported polyphosphoric acid（PPA-SiO₂） was found to be an efficient catalyst for the one-pot four-component Hantzsch condensation reaction of aryl aldehydes,dimedone,ethyl acetoacetate and ammonium acetate to afford the corresponding polyhydroquinoline derivatives in high yields.The main advantages of the present approach are short reaction times,clean reaction profiles,simple experimental and workup procedures.     

A four-component synthesis of novel spiro[pyrazoloquinoline-oxindoles] under solvent-free conditions

A domino reaction for the rapid and diverse synthesis of spiro[1H-pyrazolo[3,4-b]benzo[h]dihydroquinolin-4,3-indolin-2-ones] is reported. The synthesis represents a thermodynamically-favored four-component reaction between phenylhydrazine, isatins, naphthylamines, and 3-ketoesters giving the novel products in excellent yields under solvent-free conditions. Similar applications of anilines in place of naphthylamines have not led to formation of the expected 4-substituted pyrazolo[3,4-b]quinoline derivatives. The difference was ascribed to lower aromatic character of naphthylamines, with respect to anilines, which enables them to act easier as enamines in reaction with the postulated intermediates formed from condensation of isatins and the in situ generated pyrazolones. Surprisingly, 6-aminouracils in despite of their known enamine properties did not participate in reaction with isatins and pyrazolones, the merit of naphthylamines for this synthesis seems to be met by the favorable balance of their N- and C-nucleophilicity.     

An efficient procedure for the synthesis of coumarin derivatives using TiCl4 as catalyst under solvent-free conditions

The ability of titanium(IV) chloride as a catalyst to promote the Pechmann condensation reaction with a range of phenols and β-keto esters is described.The reaction was carried out by addition of TiCl₄ to a mixture of the phenol and the β-keto ester with thorough stirring in the absence of a solvent and represents an improvement on the classical Pechmann conditions. The yields of coumarins obtained via this novel protocol were significantly higher than those using the conventional method and the reaction duration was reduced to a few minutes or even a few seconds.     

One-pot synthesis of pyrimidines under solvent-free conditions

N,N,N’,N’-Tetrabromobenzene-1,3-disulfonamide was used as an efficient catalyst for the one-pot synthesis of pyrimidine derivatives in excellent yields from triethoxymethane, ammonium acetate, and various ketone derivatives at 100–110 °C under solvent-free conditions.     

A novel and efficient strategy for the synthesis of various carbamates using carbamoyl chlorides under solvent-free and grinding conditions using microwave irradiation

We present an efficient,fast and simple strategy of generating the intermediate carbamoyl chlorides from secondary amines using stoichiometric amounts of bis(trichloromethyl)carbonate(BTC) in solution and solvent-free conditions with excellent yields.The results obtained showed the yield increasing on whether a base was used.Finally,an efficient and rapid synthesis of variety carbamate derivatives was developed by the reaction with a high variety of different alcohols,phenols,diols and this intermediate at room temperature with grinding and in solvent-free conditions under microwave irradiation.The presence of various safe bases is shown to be effective in reducing the reaction times,increasing the yields and easing purification.The present method does not involve any hazardous phosgene.     

Microwave-assisted efficient synthesis of spiro-fused heterocycles under solvent-free conditions

Spiro-fused heterocycles were synthesized in good to high yields by a pseudo four-component reaction of an aldehyde, urea and a cyclic β-diester or a β-diamide such as Meldrum’s acid or barbituric acid derivatives using microwave irradiation under solvent-free conditions.     

An efficient and green preparation of 5-aminophosphonate substituted pyrimidine nucleosides under solvent-free conditions

<正>An environmentally benign and highly efficient one-pot preparation ofα-aminophosphonates under solvent-free conditions was developed.By employing this method,5-aminophosphonate substituted pyrimidine nucleosides were synthesized in good to excellent yields starting from 5-formyl-2'-deoxyuridine,aniline and dimethylphosphite.     

Phosphomolybdic acid-catalyzed efficient one-pot three-component aza-Diels-Alder reactions under solvent-free conditions: a facile synthesis of trans-fused pyrano- and furanotetrahydroquinolines

trans-Fused pyrano- and furanotetrahydroquinoline derivatives have been synthesized via a one-pot three-component aza-Diels-Alder reaction of aryl imines formed in situ from aromatic amines and arylaldehydes with cyclic enol ethers,such as 3,4-dihydro-2H-pyran and 2,3-dihydrofuran,in the presence of 1 mol % of phosphomolybdic acid under solvent-free conditions at room temperature in good to excellent yields.     

An expeditious and one-pot synthesis of unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles under microwave irradiation and solvent-free conditions

A one-pot synthesis of some unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles via cyclocondensation of benzoylhydrazines with orthoesters under solvent-free and microwave conditions are described here. The reaction is efficiently catalyzed by silica- supported sulfuric acid as it provided the title compounds in high yields and relatively short times. The catalyst is reusable and can be applied several times without considerable decrease in the yields and rates of the reactions.     

Microwave-assisted synthesis of asymmetric thiocarbonohydrazones under solvent-free conditions

Six new asymmetric thiocarbonohydrazones 3a-3f were synthesized from following steps:firstly hydrazine hydrate reacted with carbon disulfide to form thiocarbonohydrazide(1) under microwave irradiation.Then compound(1) reacted with ketone and different aldehydes step by step to give 3a-3f with excellent yields under solvent-free conditions using microwave irradiation.Their structures have been determined by elemental analysis,IR,MS and ~1H NMR data.     

Protic guanidinium ionic liquid as a green and highly efficient catalyst for the synthesis of functionalized spirochromenes under solvent-free conditions

A simple and efficient method for the synthesis of functionalized spirochromenes is explained using protic guanidinium ionic liquid as a catalyst under solvent-free conditions at room temperature. This procedure is simple, clean, and excellent yields are obtained in short reaction times.