An efficient, catalyst- and solvent-free, four-component, and one-pot synthesis of polyhydroquinolines on grinding

An efficient synthesis of polyhydroquinolines is achieved via a four-component reaction of aldehydes, dimedone, active methylene compounds, and ammonium acetate in one-pot under solvent-free conditions at room temperature on grinding. The present method does not involve any hazardous organic solvent or catalyst. The key advantages are the short reaction time, high yields, simple workup, and purification of products by non-chromatographic methods, i.e., by simple recrystallization from ethanol.     

Synthesis of sulfides under solvent- and catalyst-free conditions

Abstract  A simple, highly efficient, and green protocol has been developed for preparation of sulfides from alkyl or aryl thiols and benzyl-, allyl-, t-butyl, and adamantyl halides under solvent- and catalyst-free conditions. Graphical abstract        

Catalyst-free and solvent-free method for the synthesis of quinoxalines under microwave irradiation

A facile procedure for the synthesis.of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. Thereactions were carried out catalyst-free, solvent-free and under microwave irradiation conditions in high yield (84-98%) with short time (3-6 rain) and environmental benign, as well as convenient operation. The structures of all the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, mass spectral data.     

Iodine induced transformations of alcohols under solvent-free conditions

Iodine has been shown to be an efficient catalyst for transformations of alcohols under solvent-free conditions. In the presence of 5% of iodine, tertiary alcohols underwent dehydration forming the corresponding alkenes, while in the case of 2-phenylpropane-2-ol cyclodimerisation to 1,1,3-trimethyl-3-phenylindane took place. Secondary and primary benzyl alcohols under the same conditions gave the corresponding ethers.     

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 catalyst- and solvent-free three-component reaction for the regioselective one-pot access to polyfunctionalized pyrroles

A facile method for the regioselective synthesis of tetrasubstituted pyrroles, from readily accessible 1,3-dicarbonyls, benzoin derivatives and ammonium acetate, has been developed. The one-pot three-component reactions were performed to afford tetrasubstituted pyrroles under solvent- and catalyst-free conditions.     

Synthesis of thiohydantoins under one-pot three-component solvent-free conditions

A direct and efficient one-pot three-component synthesis protocol was developed for the synthesis of thiohydantoins from readily and widely available substrates (isothiocyanates, ethyl chloroacetate, and amines) employing solvent-free conditions. Correspondence: Song Cao, Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China.     

Simple and practical procedure for Knoevenagel condensation under solvent-free conditions

The Knoevenagel condensation reaction between araldehyde and active methylene using gallium chloride catalyst under solvent-free conditions has been described. The reaction takes place at room temperature by grind stone method and offers good purity of product in high yield. Work-up is very simple and the products do not need further purification. The reaction conditions are very mild and this protocol is applicable to various aldehydes such as araldehydes and heteroaromatic aldehydes as well as active methylene compounds, namely, malononitrile or ethyl cyanoacetate.

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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.     

Dual behavior of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions

The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry.     

Synthesis of vinyl sulfides via hydrothiolation of alkynes using Al2O3/KF under solvent-free conditions

We present here a clean, solvent-free hydrothiolation of alkynes using solid supported catalyst (Al₂O₃/KF). This efficient and improved method selectively furnishes the corresponding anti-Markovnikov vinyl sulfides in good to excellent yields. The method is applicable for aliphatic and aromatic thiols and the catalytic system can be re-used up to two times without previous treatment and with comparable activity.     

Catalyst- and solvent-free mechanochemical synthesis of isoxazoles from N-hydroxybenzimidoyl chlorides and enamino carbonyl compounds

A regioselective, solvent-free and catalyst-free synthesis of isoxazoles has been successfully developed under ball milling conditions. Milling the mixtures of N-hydroxybenzimidoyl chlorides and enamino carbonyl compounds in a ball mill at a frequency of 14.6?Hz for 20–60?min afforded isoxazoles in up to 86% yields. A possible reaction mechanism leading to the formation of the observed isoxazoles is proposed.     

Ring-fused aminals: catalyst and solvent-free microwave-assisted α-amination of nitrogen heterocycles

A high-yield synthesis of ring-fused aminals via microwave (MW)-assisted α-amination of nitrogen heterocycles at 130 °C under solvent- and catalyst-free conditions is described.     

Studies on oxidations with IBX: oxidation of alcohols and aldehydes under solvent-free conditions

A variety of allylic and benzylic alcohols are oxidized to their respective carbonyl compounds with IBX under solvent-free conditions at ca. 60-70 °C. It has also been found that some of the aromatic aldehydes also undergo oxidation when heated with IBX at 90 °C under solvent-free conditions; notably, this transformation does not occur under the otherwise identical but heterogeneous conditions.     

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.     

Visible light irradiation promoted catalyst-free and solvent-free synthesis of pyrano[2,3-d]pyrimidine scaffolds at room temperature

A catalyst-free and solvent-free synthetic route for convenient one-pot synthesizing pyrano[2,3-d] pyrimidine scaffolds through Knoevenagel-Michael cyclocondensation is reported using visible light irradiation as a green promoter at room temperature based on green chemistry principles. Completing the reactions takes thoroughly less time while obtaining the products in outstanding yields. This green method includes the application of non-hazardous reaction circumstances, direct work-up without column chromatographic separation, catalyst-free, solvent-free, cost effective, simple synthesis, one-pot procedure, and high atom-economy.     

Clean and fast oxidative transformation of thiols to disulfides under solvent-free conditions

We present here a fast, solvent-free synthesis of symmetrical disulfides using solid supported catalyst (Al₂O₃/KF). The reaction was performed at room temperature, by gentle heating or under MW irradiation. This efficient and improved method is general for liquid thiols, affording the disulfides in good to excellent yields. The catalytic system can be re-used two times without previous treatment and with comparable activity.     

NHC triggered cascade metal-free synthesis of 2,3-diarylated indoles under solvent-free conditions

A new cascade strategy to the synthesis of 2,3-diarylated indoles via the metal-free reaction of aryl aldehyde and aryl amine triggered by N-heterocyclic carbene (NHC) under solvent-free conditions, has been disclosed. The protocol has the advantages of easy work-up, high yields, wide application scope, and an environmentally benign procedure compared with the reported methods.     

Acetylation of alcohols and phenols under solvent-free conditions using copper zirconium phosphate

Copper zirconium phosphate nanoparticles have been used as an efficient catalyst for the acetyla‐tion of a wide range of alcohols and phenols with acetic anhydride in good to excellent yields under sol...     

Highly efficient three-component Strecker-type reaction catalyzed by MgI2 etherate under solvent-free conditions

A concise, straightforward and efficient method has been developed for the synthesis of α-aminonitriles by an one-pot three-component condensation of aldehydes or ketones, amines and trimethylsilyl cyanide catalyzed by MgI₂ etherate under solvent-free conditions. This protocol has some advantages such as mild reaction condition, simple work-up, short reaction time and high product yields.