Bulk and supported tungstophosphoric acid as friendly,efficient, recyclable catalysts for the synthesis of bis‐indolylmethanes under solvent‐free conditions

The treatment of indole with structurally diverse aldehydes in the presence of catalytic amount of inorganic‐supported polyoxometalates, heterogeneous, reusable and efficient catalysts at room temperature gave the corresponding bis‐indolylmethanes in excellent yields and shorter reaction times under solvent‐free conditions. The catalyst can be reused for several times, but it will be less active. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:325–331, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20554     

Copper‐catalyzed highly efficient aerobic oxidative synthesis of benzimidazoles,benzoxazoles and benzothiazoles from aromatic alcohols under solvent‐free conditions in open air at room temperature

Solvent‐free oxidative synthesis of benzimidazoles, benzoxazoles and benzothiazoles from aromatic alcohols and o‐phenylenediamine, o‐aminophenol and o‐aminothiophenol has been achieved by using CuCl, 2,2′‐bipyridine and TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl). The reaction proceeds via a dehydrogenation in open air at room temperature, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a mild and efficient access to substituted benzimidazoles, benzoxazoles and benzothiazoles. Copyright © 2013 John Wiley & Sons, Ltd.     

Sulfamic acid: An efficient and green catalyst for synthesis of 1,5‐benzodiazepines under solvent‐free conditions

It is described that sulfamic acid can be utilized as an effective and green catalyst for the synthesis of 1,5‐benzodiazepines in high yields from the solvent‐free condensation of o‐phenylenediamine ( 1 ) and ketones ( 2 ). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:354–358, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20305     

Eco‐friendly synthesis of quinoxaline derivatives by grinding under solvent‐free conditions

An efficient and facile synthesis of quinoxaline derivatives in excellent isolated yields by the condensation of 1,2‐diamines and 1,2‐diketones on grinding under solvent‐free conditions at ambient temperature has been developed. The important features of this method are that it is reasonably fast, very clean, high yielding, simple workup, and environmentally benign. J. Heterocyclic Chem., 00 , 00 (2011).     

Efficient synthesis of 5,10,15‐triarylcorroles using amberlyst 15 under solvent‐free conditions

An efficient and convenient synthesis of 5,10,15‐triarylcorroles by the condensation of aryl aldehydes with pyrrole catalyzed by Amberlyst 15 followed by oxidative cyclization with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) at room temperature has been reported. Amberlyst 15 is more efficient catalyst under solvent free conditions and DDQ is more suitable oxidant in dichloromethane than those of other catalysts and oxidants, respectively, for the synthesis of corroles at room temperature.     

An efficient one‐pot synthesis of 2‐aminopyrimidinomethylnaphtols under solvent‐free conditions

A novel one‐pot three‐component condensation reaction of an aldehyde, 2‐aminopyrimidine and 2‐naphthol to afford the corresponding 2‐aminopyrimidinomethylnaphtols in good yields. The remarkable features of this new procedure are high conversions, short reaction time, clean reaction profiles, and environmentally benign and simple work‐up procedures.     

Phenylphosphinic acid‐catalyzed synthesis of 6‐unsubstituted dihydropyrimidinones under solvent‐free conditions

Phenylphosphinic acid is found to catalyze the three‐component condensation of an aldehyde, enaminone, and urea or thiourea to afford the corresponding 6‐unsubstituted dihydropyrimidinones in high to excellent yields. This methodology is simple and fast synthetic route for the preparation of interesting class of heterocycles.     

Selectfluor™: A simple and efficient catalyst for the synthesis of substituted coumarins under solvent‐free conditions

Selectfluor? is used as an alternative catalyst to conventional catalysts for the synthesis of substituted coumarins via Pechmann condensation of phenols with β‐ketoesters under solvent‐free conditions at 120 °C. This method of synthesis is simple, cost‐effective, requires short reaction time, solvent‐free and gives good yields.     

Cobalt manganese oxide nanoparticles as recyclable catalyst for efficient synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions

Cobalt manganese oxide nanocatalyst was synthesized and it was found that it is a highly efficient green catalyst for the synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions. The marked advantages of this method are the simple experimental procedures, shorter reaction times, high yields of product, reusable and non‐toxic catalyst and solvent‐free conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Expeditious and highly efficient synthesis of propargylamines using a Pd‐Cu nanowires catalyst under solvent‐free conditions

A heterogeneous Pd‐Cu NWs‐catalyzed expeditious and solvent‐free synthesis of propargylamines via A³‐coupling of aldehydes, alkynes, and amines has been proposed. A wide range of aldehydes, alkynes and amine substrates undergo A³‐coupling to produce propargylamines in good to excellent yields with good functional tolerance, such as that towards alkoxy, hydroxy, C‐X (X = F, Cl, Br) as well as amide and C=C bonds. Furthermore, the catalyst could be recovered easily and reused for at least 5 cycles without showing significant loss of catalytic activity.     

N‐Alkylation of imides using phase transfer catalysts under solvent‐free conditions

N‐Alkylation of imides in the reaction of imides and alkylhalides, catalyzed by PT catalysts under solvent‐free conditions, has been developed. The reaction occurs in the presence of K₂CO₃, and in many cases it takes place spontaneously. In the N‐benzylation reaction, it has been recognized that TBAB (tetrabutylammonium bromide) and TBATFB (tetrabutylammonium tetrafluoroborate) show highest catalytic effect. Versatility and synthetic capacity of the solvent‐free alkylation has been confirmed by N‐benzylation and N‐ethylation of various imides. The developed procedure gives easy access to N‐(ω‐bromoalkyl)imides.     

Silica‐supported synthesis of some 1,3,5‐trisubstituted 2‐pyrazolines under solvent‐free and microwave irradiation conditions

A simple method for the synthesis of 2‐pyrazolines is described which occurs on silica surface under solvent‐free conditions within 110‐180 sec using microwave irradiation. The results obtained indicate that the use of silica gel as a support in pyrazoline formation reactions can have a profound effect on reaction rates and yields and cause cleaner reaction conditions.     

Controllable synthesis of bio‐based polylactide diols using an organocatalyst in solvent‐free conditions

Controllable synthesis of bio‐based polylactide (PLA) diols was realized by the ring‐opening polymerization (ROP) of lactide (LA) in the presence of 1,4‐butanediol (BDO) using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as an organocatalyst in solvent‐free conditions. The catalytic activity and conversion of LA could reach ∼1 kg g⁻¹ DBU and >97%, respectively, and the polymerization yielded polymers with narrow polydispersity index (PDI) (1.15–1.29). Interestingly, the number average molecular weight (M_n) of the obtained PLA diol was in excellent linear relation with the molar ratio of LA and BDO, and hence can be precisely controlled. The structure of the diol was clearly confirmed by ¹H and ¹³C NMR, FTIR, and MALDI‐TOF mass spectra, proving BDO as an initiation‐transfer agent to participate in the polymerization. Kinetic study of the ROP demonstrates a pseudo‐first‐order kinetic model and a controlled “living” nature. Notably, it is found that the glass transition temperature (T_g) of the diol significantly depends on the M_n. Furthermore, various chain transfer agents and organocatalysts can also be used to successfully synthesize well‐defined PLA diols. Especially, functional bio‐based dihydric alcohols such as 2,5‐furandimethanol (FDMO)‐initiated ROP in this system could result in fully bio‐based PLA diols with functionality. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 968–976     

Mechanochemical synthesis and cycloaddition reactions of fluoro nitrone under solvent‐free conditions and potential antimicrobial activities of the cycloadducts

Synthesis and cycloaddition reactions of fluoro nitrone under solvent‐free conditions using ball‐milling technique have been reported. Significant change in rate and yields of the cycloadducts have been noticed compared with solvent‐free microwave‐induced reactions of fluoro nitrones. The present study reports synthesis of N‐benzyl fluoro nitrone and its cycloaddition reactions with maleimides and few electron deficient alkynes under solvent‐free conditions. The synthesized fluoro cycloadducts were found to exhibit potential antimicrobial activities.     

Microwave assisted aqueous phase synthesis of benzothiazoles and benzimidazoles in the presence of Ag2O

Russian Journal of General Chemistry - A simple and high yielding method for synthesized benzothiazoles and benzimidazole in water under micro wave irradiation by the reaction of 2-amino thiophenol...     

One‐pot synthesis of pyrano‐ and furanoquinolines catalyzed by molten tetra‐n‐butylphosphonium bromide under solvent‐free conditions

Molten tetra‐n‐butylphosphonium bromide is found to be a practical and inexpensive catalytic media for stereoselective one‐pot synthesis of pyranoquinoline and furanoquinoline derivatives in good to excellent yields. Products of undesirable reactions resulting from polymerization are not observed. The use of this catalyst media avoids the use of any cocatalysts or toxic organic solvents. J. Heterocyclic Chem., (2011).     

An efficient synthesis of 2,3‐dihydroquinazolin‐4(1H)‐one derivatives under catalyst‐free and solvent‐free conditions

A simple, efficient and convenient one‐pot synthesis of 2,3‐dihydroquinazolin‐4(1H)‐one derivatives under solvent‐free and catalyst‐free conditions by the reaction of aromatic aldehydes, isatoic anhydride, and ammonium acetate was reported. The advantages of this protocol include short reaction time, mild reaction conditions, easy work‐up, high yields, and environmental friendliness. J. Heterocyclic Chem., (2011).