Solvent‐free three‐component synthesis of 7‐aryl‐1,1‐dioxothieno[3,2‐b]pyran derivatives catalyzed by ammonium acetate

An efficient synthesis of 7‐aryl‐1,1‐dioxothieno[3,2‐b]pyran derivatives via the reaction of aryl aldehyde, tetrahydrothiophene‐3‐one‐1,1‐dioxide and malononitrile or ethyl 2‐cyanoacetate was performed at room temperature catalyzed by ammonium acetate under solvent‐free conditions. Compared with the conventional methods, this protocol features mild reaction conditions, high yields, and eco‐friendliness. J. Heterocyclic Chem., (2011).     

Catalyst‐free Synthesis of 5‐Arylimidazo[1,2‐c]quinazoline Derivatives in Ionic Liquids

The reaction of 2‐(4,5‐diphenyl‐1H‐imidazol‐2‐yl)aniline and aromatic aldehyde was treated in ionic liquids under catalyst‐free condition and gave dehydrogenated 5‐aryl‐2,3‐diphenylimidazo[1,2‐c ]quinazolines. The same reaction gave un‐aromatized 5‐aryl‐2,3‐diphenyl‐5,6‐dihydroimidazo[1,2‐c ]quinazoline derivatives while it was controlled in an inert gas. This procedure approach to imidazo[1,2‐c ]quinazolines has the advantages of milder reaction conditions, one‐pot, catalyst free, high yields, and environmentally benign.     

溴化镁催化的1,2,3,4-四氢吡啶酮无溶剂合成研究

An efficient and environmentally friendly procedure for the one-pot synthesis of tetrahydropyrimidinones from aldehydes, β-diketones and urea/thiourea by using magnesium bromide as an inexpensive and easily available catalyst under solvent-free conditions was described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields (74%-94%) and short reaction time (45-90 min). The structure of the Biginelli reaction product from β-diketone, salicylaldehyde and urea has been proposed to possess an oxygen-bridge by cyclization (intramolecular Michael-addition).     

Green Biginelli‐type Reaction: Solvent‐free Synthesis of 5‐unsubstituted 3,4‐dihydropyrimdin‐2(1H)‐ones

The Biginelli‐type compounds, 5‐unsubstituted 3,4‐dihydropyrimdin‐2(1H)‐ones were synthesized by a one‐pot three‐component condensation of aromatic aldehydes, aromatic ketones and urea in the presence of SnCl₄ · 5H₂O under solvent‐free conditions. The advantages of this method are short reaction time (4–10 min), excellent yields (74–97%), inexpensive catalyst and solvent‐free conditions. A plausible mechanism was proposed.     

Reaction of 1,3‐dicarbonyl compounds with o‐phenylenediamine or 3,3′‐diaminobenzidine in water or under solvent‐free conditions via microwave irradiation

Reaction of ophenylenediamine with β‐diketones or β‐ketoesters in water formed 2‐substituted benzimi‐dazoles. Reaction of 3,3′‐diaminobenzidine gave similar results. Under microwave irradiation conditions solvent‐free reaction of o‐phenylenediamine with β‐ketoesters afforded l,5‐benzodiazepin‐2‐one derivatives. An exception is the reaction of o‐phenylenediamine with ethyl acetoacetate under microwave irradiation, which gave 2‐methylbenzimidazole.     

One‐pot three components synthesis of alkyl indeno [1,2‐b]‐quinoxalin‐11‐ylideneacetates in water and under solvent‐free conditions

We introduced a very simple, one‐pot three component procedure for preparation of alkyl indeno[1,2‐b]quinoxalin‐11‐ylideneacetates 4 from reaction of ninhydrin 1 , phenylenediamines 2 , (alkoxycarbonylmethyl)triphenylphosphonium bromides 3 , and sodium acetate in water and under solvent‐free conditions. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:549–552, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20136     

Catalyst‐free Synthesis of Tetrahydroacenaphtho[1,2‐b]indolone Derivatives via One‐pot Four‐component Reaction

A simple and efficient one‐pot synthesis of tetrahydroacenaphtho[1,2‐b]indolone derivatives via four‐component reaction of 5,5‐dimethylcyclohexane‐1,3‐dione (dimedone), arylamines, acenaphthoquinone, and active methylene compounds under catalyst‐free conditions is described. The reactions were carried out under mild conditions using ethanol as solvent. Advantages of this method include simple experimental and workup procedure, readily available starting materials, and high yields.     

A Facile and One‐pot Synthetic Route to Functionalized Ethyl 3‐(Alkanoyl)‐2‐(alkyl imino)‐2,3‐dihydrothiazole‐4‐carboxylate Derivatives under Mild,Solventand Catalyst‐free Conditions

A new one‐pot, four‐component synthetic rout is reported for the preparation of functionalized N‐acyl‐2alkylimino‐2,3‐dihydrothiazole derivatives from the reaction between acid chlorides, ammonium thiocyanate, primary alkylamines, and ethyl bromopyruvate under mild, solvent‐ and catalyst‐free conditions at room temperature. This completely green and efficient straight forward procedure led to the desired products in good to high yields without any need to catalyst or solvent assistance and no by product was observed in all the reactions     

Piperazine‐functionalized nickel ferrite nanoparticles as efficient and reusable catalysts for the solvent‐free synthesis of 2‐amino‐4H‐chromenes

Piperazine‐functionalized nickel ferrite (NiFe₂O₄) nanoparticles were synthesized as recoverable heterogeneous base catalysts using a routine method. The synthesized materials were characterized using various spectroscopic techniques such as infrared, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray, thermogravimetry analysis, and vibrating sample magnetometry. Catalytic efficiency was investigated in the synthesis of 2‐amino‐4H‐chromene derivatives via a one‐pot three component reaction of aldehyde and malononitrile with β or α‐naphthol/5‐methyle resorcinol under solvent‐free conditions with good to high yields. This method is operationally simple and has several advantages such as good to high yield, short reaction times, solvent‐free conditions, and easy synthesis. Moreover, the catalyst was recovered easily using an external magnet and reused three times without distinctive loss in catalytic activity.     

One‐pot acid‐free ferrocenylalkylation of azoles with α‐ferrocenyl alcohols: ferrocene‐based plant growth regulators and herbicide safeners

α‐Ferrocenylalkylation of azoles or S‐nucleophiles with FcCH(R)OH (Fc = ferrocenyl) can be accomplished under acid‐free conditions as one‐pot process via an intermediate formation of the α‐ferrocenylalkyl carbonates FcCH(R)OC(O)OEt. The reaction allows the alkylation of acid sensitive substrates like imidazole derivatives or sodium N,N‐diethyldithiocarbamate. The reaction with ambident azoles proceeds as the N‐alkylation. Some α‐ferrocenylalkyl azoles were found to exhibit plant growth stimulating or herbicidal effects on corn seeds or act as the herbicide safeners against sulfonylurea herbicides.     

Tandem synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones on grinding under solvent‐free conditions

Citric acid promoted synthesis of a mini‐library 2,3‐dihydroquinazolin‐4(1H)‐ones with good to excellent yields is achieved by tandem reaction of anthranilamides (or anthranilhydrazides) with aldehydes on grinding at room temperature under solvent‐free conditions. This method has notable advantages in terms of simple workup, short reaction time, cost‐effective, and environmentally benign. J. Heterocyclic Chem., (2012).     

An Efficient and Facile Synthesis of 5‐(Thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydro‐pyrimidin‐2(1H)‐one and 6‐(Thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one from Same Substrates Under Different Conditions

A series of 5‐(thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydropyrimidin‐2(1H)‐one and 6‐(thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one derivatives have been synthesized from the reactions of aromatic aldehydes, 4,4,4‐trifluoro‐1‐(thien‐2‐yl)butane‐1,3‐dione and urea under the different conditions with high yields. In this research, it was found that the p‐toluenesulfonic acid was an efficient catalyst for obtaining 5‐(thiophene‐2‐carbonyl)‐6‐(trifluoromethyl)‐tetrahydropyrimidin‐2(1H)‐one derivative. At the same time, solvent‐free and NaOH were the preferred conditions for the synthesis of 6‐(thiophen‐2‐yl)‐4,5‐dihydropyrimidin‐2(1H)‐one derivative. Moreover, because of short reaction time, excellent yields, simple setup, this research offered an efficient process for preparing these kind compounds.     

Solvent‐free synthesis of pyrrole derivatives

A one‐pot synthesis of pyrrole derivatives via reaction between activated carbonyl compounds, primary amines, and 1,3‐dicarbonyls under solvent‐free conditions is described. J. Heterocyclic Chem., (2012).     

A Catalyst‐Free Aqueous Synthesis of 2‐Amino‐7,9‐dihydrothieno[3′,2′:5,6]pyrido[2,3‐d]pyrimidine‐4,6(3H,5H)‐dione Derivatives

A series of novel 7,9‐dihydrothieno[3′,2′:5,6]pyrido[2,3‐d]pyrimidine‐4,6(3H,5H)‐dione derivatives were synthesized efficiently via the catalyst‐free reaction of aldehyde, ethyl 2,4‐dioxotetrahydrothiophene‐3‐carboxylate, and 2,6‐diaminopyrimidine‐4(3H)‐one through the sequence of deethoxycarbonylation and three‐component condensation in aqueous media. This protocol featured mild reaction conditions, high yields, easy work‐up, and environmentally friendly procedure.     

Selective α-Bromination of β-Keto Esters in Reusable PEG-400 under Mild and Catalyst-free Conditions

An efficient bromination protocol for the synthesis of α-bromo-β-keto esters has been developed. In PEG-400 （poly（ethylene glycol-400））, a variety of β-keto esters were treated with NBS （N-bromosuccinimide） at room temperature to selectively afford the corresponding α-monobromination products in excellent yields. It is noteworthy that the reaction was conducted under mild, environmentally benign and catalyst-free conditions.     

Methanesulfonic Acid‐Catalyzed One‐Pot Synthesis of 12‐Aryl or 12‐Alkyl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one Derivatives

An efficient synthesis of 12‐aryl or 12‐alkyl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one derivatives has been developed under solvent‐free conditions by one‐pot condensation of aldehydes, 2‐naphthol, and cyclic 1,3‐dicarbonyl compounds in the presence of a catalytic amount of methanesulfonic acid. The protocol has advantages of mild condition, short reaction time, high yield, and operational simplicity.     

Solvent‐free microwave synthesis of bis‐pyrazolo[3,4‐b:4′,3′‐e]‐pyridines and study of their antifungal properties

The synthesis of a series of bis‐pyrazolo[3,4‐b:4′,3′‐e]pyridines ( 3 ) in the reaction of 5‐amino‐3‐methyl‐1‐phenylpyrazole ( 1 ) with aldehydes ( 2 ) under microwave irradiation and solvent‐free conditions is described. The structure elucidation of the products is based on detailed nmr analysis of experiments such as ¹H‐COSY, NOESY, DEPT, HSQC and HMBC. These compounds showed moderate antifungal in vitro activity against dermatophytes.     

One‐pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalysed by Cupric Acetate under Solvent‐free Conditions

A solvent‐free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones from aromatic aldehydes, β‐keto ester/acetyl acetone and urea catalysed by cupric acetate under thermal condition is reported as a simple and an efficient protocol. Compared with classical Biginelli reaction reported in 1893, this new method provides much improved modification in terms of yield and reaction time. The usage of milder catalyst, environmental friendly procedures and excellent yields within a very short time (5–15 min) are the advantages of the method in which the involvement of solvent‐free condition adds an edge to the method. Thus, the efficiency of the protocol enabled the rapid synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one derivatives in a short duration.     

Cross‐Linked‐Polymer‐Supported N‐{2′‐[(Arylsulfonyl)amino][1,1′‐binaphthalen]‐2‐yl}prolinamide as Organocatalyst for the Direct Aldol Intermolecular Reaction under Solvent‐Free Conditions

A bottom‐up strategy was used for the synthesis of cross‐linked copolymers containing the organocatalyst N‐{(1R)‐2′‐{[(4‐ethylphenyl)sulfonyl]amino}[1,1′‐binaphthalen]‐2‐yl}‐D ‐prolinamide derived from 2 (Scheme 1). The polymer‐bound catalyst 5b containing 1% of divinylbenzene as cross‐linker showed higher catalyst activity in the aldol reaction between cyclohexanone and 4‐nitrobenzaldehyde than 5a and 5c . Remarkably, the reaction in the presence of 5b was carried out under solvent‐free, mild conditions, achieving up to 93% ee (Table 1). The polymer‐bound catalyst 5b was recovered by filtration and re‐used up to seven times without detrimental effects on the achieved diastereo‐ and enantioselectivities (Table 2). The catalytic procedure with polymer 5b was extended to the aldol reaction under solvent‐free conditions of other ketones, including functionalized ones, and different aromatic aldehydes (Table 3). In some cases, the addition of a small amount of H₂O was required to give the best results (up to 95% ee). Under these reaction conditions, the cross‐aldol reaction between aldehydes proceeded in moderate yield and diastereo‐ and enantioselectivity (Scheme 2).     

Zr(HSO4)4‐catalyzed one‐pot three‐component synthesis of 7‐alkyl‐6H,7H‐naphtho[1′,2′:5,6]pyrano[3,2‐c]chromen‐6‐ones

A new, one‐pot, simple thermally efficient and solvent‐free method for the preparation of 7‐alkyl‐6H,7H‐naphtho[1′,2′:5,6]pyrano[3,2‐c]chromen‐6‐ones by condensation of β‐naphthol, aromatic aldehydes, and 4‐hydroxycoumarin using Zr(HSO₄)₄ as a safe and efficient catalyst is described. This method has the advantages of high yields, a cleaner reaction, simple methodology, short reaction times, easy workup, and greener conditions. J. Heterocyclic Chem., (2011).