Surface modified SPIONs‐Cr(VI) ions‐immobilized organic‐inorganic hybrid as a magnetically recyclable nanocatalyst for rapid synthesis of polyhydroquinolines under solvent‐free conditions at room temperature

In this work, a magnetic hybrid dichromate nanocomposite with triphenylphosphine surface modified superparamagnetic iron oxide nanoparticles (SPIONs) as a recyclable nanocatalyst was designed, prepared and characterized by Fourier transform infrared spectroscopy (FT‐IR) spectra, X‐ray diffraction (XRD) pattern analysis, vibrating sample magnetometer (VSM) curves, X‐ray fluorescence (XRF) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images and dynamic light scattering (DLS) analysis. Then, it was used in a green and efficient procedure for one‐pot multicomponent synthesis of polyhydroquinoline derivatives by the condensation of aldehydes, dimedone or 1,3‐cyclohexadione, ethyl acetoacetate and ammonium acetate. This protocol includes some new and exceptional advantages such as short reaction times, low catalyst loading, high yields, solvent‐free and room temperature conditions, easy separation and reusability of the catalyst.     

Novel marine-based gold nanocatalyst in solvent-free synthesis of polyhydroquinoline derivatives: Green and sustainable protocol

We report an ecofriendly synthetic approach for the fabrication of biogenic gold nanoparticles (AuNPs) using electron-rich sea cucumber extract as a bio-reductant and stabilizing agent in reducing gold cations into AuNPs at the optimal conditions. The produced AuNPs are spherical in shape with an average particle size of 11 ± 1.5 nm in transmission electron microscopy (TEM) and exhibited a crystal structure of face-centered cubic in X-ray diffraction (XRD) analyses. Our results indicated that bioinspired AuNPs demonstrate superior catalytic activity in the safe and facile one-pot synthesis of polyhydroquinoline derivatives under solvent-free reaction conditions. This green route encompasses multiple benefits including highly recyclable bioinspired catalyst (5 cycles), short reaction times, convenient workout, high to excellent product yields (82%–97%), and nonhazardous conditions.     

3-甲基-1-磺酸咪唑硫酸氢盐催化剂用于四组分一锅法合成不对称聚羟基喹啉衍生物(英文)

3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free,and reusable Brnsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl- hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.     

Solvent-free synthesis of polyhydroquinoline and 1,8-dioxodecahydroacridine derivatives through the Hantzsch reaction catalyzed by a natural organic acid: A green method

Solvent-free and high yielding one-pot synthesis of 1,8-dioxodecahydroacridine and polyhydroquinoline derivatives have been described through Hantzsch condensation of various aldehydes, ammonium acetate with cyclic 1,3-dicarbonyl compounds and ethyl acetoacetate in a very simple, efficient, and environmentally benign method using ascorbic acid as a nontoxic organocatalyst.     

MgO Nanoparticles as a Recyclable Heterogeneous Catalyst for the Synthesis of Polyhydroquinoline Derivatives under Solvent Free Conditions

Magnesium oxide nanopartticels in average size between 35–120 nm were prepared by sonochemistry method. Synthesis of polyhydroquinoline derivatives using MgO nanoparticles from the reaction of dimedone, benzaldehyde, ethyl acetoacetate and ammonium acetate under solvent‐free conditions is reported. Easy handling, reusability, thermal stability and non‐toxicity of the catalyst make the present protocol as an eco‐friendly and economically acceptable method for synthesis of these heterocycles.     

二氧化钛纳米粒子催化合成Hantzsch酯和多氢喹啉衍生物(英文)

1,4-Dihydropyridine and polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using nanosized titanium dioxide as a heterogeneous catalyst.The present methodology offers several advantages such as excellent yields,short reaction times (30-120 min),environmentally benign,and mild reaction conditions.The catalyst can be readily separated from the reaction products and recovered in excellent purity for direct reuse.     

Efficient One-Pot Synthesis of Polyhydroquinoline Derivatives Using Silica Sulfuric Acid as a Heterogeneous and Reusable Catalyst Under Conventional Heating and Energy-Saving Microwave Irradiation

An efficient Hantzsch four-component condensation reaction for the synthesis of polyhydroquinoline derivatives was reported under two conditions: solvent-free conventional heating and energy-saving microwave irradiation. The process is simple and environmentally benign, and the use of a heterogeneous and reusable catalyst, high yields, and short reaction times are the key features of this protocol.     

Straightforward Hantzsch four‐ and three‐component condensation in the presence of triphenyl(propyl‐3‐sulfonyl)phosphoniumtrifluoromethanesulfonate {[TPPSP]OTf} as a reusable and green mild ionic liquid catalyst

Triphenyl(propyl‐3‐sulfonyl)phosphoniumtrifluoromethanesulfonate {[TPPSP]OTf} as a reusable, green and benign ionic liquid catalyst has been used in the Hantzsch four‐component (synthesis of polyhydroquinolines) and three‐component (synthesis of acridines) condensation reactions of 1,3‐diones, β‐ketoesters, aldehydes, ammonium acetate and aniline derivatives in the presence of 0.5 mol% of {[TPPSP]OTf} at room temperature under solvent‐free conditions. The new ionic liquid catalyst was fully characterized using infrared, ¹H NMR, ¹³C NMR, ³¹P NMR, ¹⁹F NMR and mass spectroscopies, and thermogravimetric and derivative thermogravimetric analyses. Additionally, the recovered catalyst can be recycled at least five times in subsequent reactions without significant loss in catalytic activity. The new synthesis technique presented offers numerous advantages of safety, mild conditions, simplicity, short reaction time, high yields and easy workup compared to the traditional synthesis method. Twenty products have been reported for the first time. Copyright © 2016 John Wiley & Sons, Ltd.     

One-Pot Synthesis of 1,4-Dihydropyridine and Polyhydroquinoline Derivatives via L-Proline Catalyzed Hantzsch Multicomponent Reaction under Ultrasound Irradiation

L‐Proline efficiently catalyzed the multi‐component Hantzsch reaction in EtOH at 60°C under ultrasound irradiation to afford the corresponding 1,4‐dihydropyridine and polyhydroquinoline derivatives in high yields. This method offers the advantages of neutral and mild reaction conditions, high to excellent yields of the products and simple workup.     

Montmorillonite K10 Clay: An Effective Solid Catalyst for One‐Pot Synthesis of Polyhydroquinoline Derivatives

An efficient one‐pot four‐component coupling process for the synthesis of polyhydroquinoline derivatives catalyzed by montmorillonite K10 clay is described. This procedure has such advantages as short reaction time, high yields, and simple workup. The catalyst could be reused several times and keeps its initial activity in the recycle reactions.