Simultaneous sonication assistance for the synthesis of tetrahydropyridines and its efficient catalyst ZrP2O7 nanoparticles

Recent developments in the nanomaterial-catalyzed green synthesis of structurally diverse 1,4-dihydropyridines

1,4-Dihydropyridine (1,4-DHP), a privileged heterocyclic scaffold, has been extensively utilized in various biological and therapeutic applications. In this review article, we discussed the role of different nano-catalysts, nanoflakes, nanocomposites, and other green-supported nanomaterials in the synthesis of a biologically active and vital pharmaceutical precursor 1,4-DHP and its derivatives such as polyhydroquinoline, benzopyranopyridines, and dihydropyridine since 2015. It is evident that although the use of various tailored nanostructures under different conditions to optimize the synthesis of 1,4-DHP and its compounds has provided sustainable and efficient proposals, yet the development of greener practices in the synthesis of 1,4-DHPs, which can be applied to design new synthetic routes and sequences in process development, is a far-reaching task to be accomplished.

Single pot multicomponent approaches using different nanomaterials as green catalysts for synthesis of 1,4-dihydropyridine (1,4-DHP), a privileged heterocyclic scaffold with vital biological and therapeutic applications are reviewed.

Access to molecular complexity. Multicomponent reactions involving five or more components

The evaluation of the significance of a chemical transformation addresses many factors, including such important characteristics as the number of chemical bonds formed in one step, the reaction time, labour intensity, the cost of reactants and catalysts and so on. The amount of waste produced in the reaction has also gained increasing importance in recent years. Multicomponent reactions (MCRs) occupy a special place as a synthetic tool in modern organic chemistry. These reactions allow the synthesis of target products with complex structures, minimizing labour costs. This review summarizes the literature on multicomponent reactions involving five or more components. The data in the review are classified according to the number of reactants participating in the reaction and the types of reactions. It is worth noting that in some cases, these transformations can be a part of a domino process, making this classification difficult, if not impossible. The structural diversity of the reaction products greatly increases with increasing number of components involved in the MCR, which becomes virtually unlimited when using combinations of MCRs. This review highlights the main trends of past decades in the field of MCRs. The last two decades have witnessed an explosive growth in the number of publications in this area of chemistry.

The bibliography includes 309 references.

Ultrasonic accelerated Knoevenagel condensation by magnetically recoverable MgFe2O4 nanocatalyst: A rapid and green synthesis of coumarins under solvent-free conditions

The novel and green procedure to synthesis of 3-substituted coumarins was performed through the Knoevenagel condensation between various salicylaldehydes and 1,3-dicarbonyl compounds by MgFe₂O₄ nanoparticles as an efficient catalyst under solvent-free condition using ultrasound irradiation. The nano catalyst was easily recovered by an external magnet and reused for several times without significant loss of its catalytic performance. Compare to the previous works, this progressive protocol have advantages such as simple workup, high yields of coumarins, solvent free condition, environmentally benign and short reaction times.

Catalyst-free ultrasonic-promoted multicomponent synthesis of tertiary α-amino phosphonates

A highly efficient and green protocol has been developed for the synthesis of novel tertiary α-amino phosphonates via a catalyst-free multi-component Kabachnik–Fields reaction under ultrasound irradiation.

Cu(ii)-grafted SBA-15 functionalized S-methylisothiourea aminated epibromohydrin (SBA-15/E-SMTU-CuII): a novel and efficient heterogeneous mesoporous catalyst

The catalytic activity of novel synthesized SBA-15/E-SMTU-Cu^II nanocatalyst was investigated for the green, one-pot, pseudo five-component synthesis of tetrahydropyridine derivatives.

One-pot sonochemical synthesis of 1,3-thiazolidin-4-ones using nano-CdZr4(PO4)6 as a robust heterogeneous catalyst

An efficient three-component synthesis of 1,3-thiazolidin-4-ones is described by one-pot condensation of aldehydes, aniline and thioglycolic acid with nano-CdZr4(PO4)6 as a robust heterogeneous catalyst under ultrasonic irradiation. Use of simple and readily available starting materials, experimental simplicity, applying the sonochemical methodology as an efficient method and innocuous means of activation in synthetic chemistry are some advantages of this protocol.

Facile Separation of 5-O-Galloylquinic Acid from Chinese Green Tea Extract using Mesoporous Zirconium Phosphate

INTRODUCTION

5-O-Galloylquinic acid from green tea and other plants is attracting increasing attention for its antioxidant and antileishmanial bioactivities. It is always isolated using a silica column, a Sephadex column and high-performance liquid chromatography (HPLC) methods, which are either laborious or instrument dependent.

OBJECTIVE

To develop a new method to easily separate 5-O-galloylquinic acid.

METHODOLOGY

Mesoporous zirconium phosphate (m-ZrP) was prepared to conveniently separate 5-O-galloylquinic acid from Chinese green tea extract, and the target compound was easily obtained by simple steps of adsorption, washing and desorption. The effects of the green tea extraction conditions, extract concentrations, and m-ZrP adsorption/desorption dynamics on the 5-O-galloylquinic acid separation were evaluated.

RESULTS

5-O-Galloylquinic acid that was separated from a 70% ethanol extract of green tea was of moderate HPLC purity (92%) and recovery (88%), and an increased non-specific binding of epigallocatechin gallate (EGCG) on m-ZrP was observed in the diluted tea extract. The times for maximal adsorption of 5-O-galloylquinic acid in 70% ethanol extract and maximal desorption of 5-O-galloylquinic acid in 0.4% phosphoric acid solution were confirmed as 7 h and 5 h, respectively.

CONCLUSION

A facile method to separate 5-O-galloylquinic acid from Chinese green tea extract using m-ZrP was established. Copyright © 2016 John Wiley & Sons, Ltd.

Ultrasound-promoted one-pot three component synthesis of tetrazoles catalyzed by zinc sulfide nanoparticles as a recyclable heterogeneous catalyst

Ultrasound irradiation was applied for the appropriate and rapid synthesis of 1-substituted tetrazoles through cyclization reaction of various primary amines, sodium azide and triethyl orthoformate. This reaction was effectively catalyzed by ZnS nanoparticles as an efficient, recoverable and reusable catalyst. Compared with conventional methods, this method has the considerable advantages such as shorter reaction times, easier work-up, purer products with high yields and mild conditions. The ZnS nanoparticles catalyst is an excellent instance to replace Brønsted acids for the preparation of 1-substituted tetrazole derivatives in very short reaction times with excellent yields. The catalyst can be recovered and reused several times without significant loss of its catalytic activity.

Sonochemical synthesis of 5-substituted 1H-tetrazoles catalyzed by ZrP2O7 nanoparticles and regioselective conversion into new 2,5-disubstituted tetrazoles

The ultrasound-assisted preparation of 2-(1H-tetrazol-5-yl) acrylonitrile derivatives via a one-pot multi-component method is described successfully using ZrP2O7 nanoparticles as a catalyst. Readily available tetrazoles can be transformed into the corresponding 1,5- and 2,5-disubstituted tetrazoles. 2,4′-Dibromoacetophenone gave the corresponding 2,5-disubstituted derivative as the only isomer. Synthesis of tetrazole derivatives with excellent yields in short times, a wide range of products under ultrasound irradiation, environmental benignity and a simple work-up procedure are some of the important features of this protocol.

Simultaneous sonication assistance for the synthesis of pyrroloacridinones and its efficient catalyst HBF4 supported on uniform spherical silica nanoparticles

Fluoroboric acid (HBF4) adsorbed on mesoporous silica nanoparticles of 600nm dimension was synthesized and characterized by N2 adsorption, HRTEM, EDX, XPS. The applicability of silica-HBF4 was probed through the sonication assisted synthesis of pyrroloacridinones in ecofriendly solvent ethanol. Standard leaching experiment was performed to show that the reaction was heterogeneous with this recyclable catalyst.

Sonochemically synthesis of arylethynyl linked triarylamines catalyzed by CuI nanoparticles: a rapid and green procedure for Sonogashira coupling

A simple and green method was performed to the preparation of copper iodide nanoparticles by ultrasound approach. Consequently the synthesis of aryl ethynyl linked triarylamines was carried out through the Sonogashira coupling between iodo-substituted triarylamine and aryl acetylenes in the presence of CuI nanoparticles/Pd(PPh3)2Cl2 as an efficient catalytic system and triethylamine as the base under ultrasonic irradiation. Good to excellent yields of products and short reaction times are some of the important advantages of this solvent free protocol which were attained by both nano CuI and ultrasound conditions.