Fe3O4@SiO2–NH2 core-shell nanocomposite as an efficient and green catalyst for the multi-component synthesis of highly substituted chromeno[2,3-b]pyridines in aqueous ethanol media

ABSTRACT

An efficient and green approach for synthesizing chromeno[2,3-b]pyridine derivatives through one-pot three-component reactions of salicylaldehydes, thiols, and malononitrile has been developed by Fe₃O₄@SiO₂–NH₂ nanocatalyst in aqueous ethanol media under re?ux conditions. The present procedure provides several advantages such as environmentally benign, straightforward, excellent yields, short reaction times, cost-effective, good recyclability, little catalyst loading, and facile catalyst separation for the preparation of chromeno[2,3-b]pyridines as important privileged medicinal scaffold. In addition, aminopropyl-coated Fe₃O₄@SiO₂ nanoparticles were fully characterized by scanning electron microscopy, X-ray diffraction, energy dispersive analysis of X-ray, vibrating sample magnetometer, and FT-IR analysis.     

Recent Advances in One-Pot Modular Synthesis of 2-Quinolones

It is known that 2-quinolones are broadly applicable chemical structures in medicinal and agrochemical research as well as various functional materials. A number of current publications about their synthesis and their applications emphasize the importance of these small molecules. The early synthetic chemistry originated from the same principle of the classical Friedländer and Knorr procedures for the preparation of quinolines. The analogous processes were developed by applying new synthetic tools such as novel catalysts, the microwave irradiation method, etc., whereas recent innovations in new bond forming reactions have allowed for novel strategies to construct the core structures of 2-quinolones beyond the bond disconnections based on two classical reactions. Over the last few decades, some reviews on structure-based, catalyst-based, and bioactivity-based studies have been released. In this focused review, we extensively surveyed recent examples of one-pot reactions, particularly in view of modular approaches. Thus, the contents are categorized as three major sections (two-, three-, and four-component reactions) according to the number of reagents that ultimately compose atoms of the core structures of 2-quinolones. The collected synthetic methods are discussed from the perspectives of strategy, efficiency, selectivity, and reaction mechanism.     

碱催化醛、丙二腈和邻苯二甲酰肼的、三组分反应合成酞嗪衍生物

经过实验验证引入水有利于芳香醛、丙二腈和邻苯二甲酰肼三组分的反应进行,催化量的有机碱三乙胺(Et 3 N)或无机碱磷酸氢二钾(K 2 HPO 4[DK1]·3H 2 O)可以在常规条件下促进该反应。本文以39%~97%的产率合成一系列1 H-吡唑[1,2-b]酞嗪-5,10-二酮衍生物。两种催化剂均溶于水,因此,反应结束后催化剂的分离与产物提纯简便易行。此方法具有反应条件温和、绿色环保、操作简单、后处理方便等特点。     

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

Many interesting target guest molecules have low symmetry, yet most methods for synthesising hosts result in highly symmetrical capsules. Methods of generating lower symmetry pores are thus required to maximise the binding affinity in host–guest complexes. Herein, we use mixtures of tetraaldehyde building blocks with cyclohexanediamine to access low‐symmetry imine cages. Whether a low‐energy cage is isolated can be correctly predicted from the thermodynamic preference observed in computational models. The stability of the observed structures depends on the geometrical match of the aldehyde building blocks. One bent aldehyde stands out as unable to assemble into high‐symmetry cages‐and the same aldehyde generates low‐symmetry socially self‐sorted cages when combined with a linear aldehyde. We exploit this finding to synthesise a family of low‐symmetry cages containing heteroatoms, illustrating that pores of varying geometries and surface chemistries may be reliably accessed through computational prediction and self‐sorting.     

An efficient synthesis of benzylidene-2-alkoxy-4-aryl-2,3-cycloalkenopyridine-3-carbonitrile derivatives

An efficient procedure for the synthesis of a novel class of benzylidene-2-alkoxy-4-aryl-6,7-dihydro-5H-cyclopenta[b]pyridine-, -5,6,7,8-tetrahydroquinoline and/or -6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile was introduced through the one-pot multi-component reaction of cyclopentanone, cyclohexanone, and/or cycloheptanone with different aromatic aldehydes and malononitrile. The same products were also produced by classical route by the two-component reaction of dibenzylidine cyclopentanone, cyclohexanone, and/or cycloheptanone derivatives with malononitrile. The reactions were achieved using sodium alkoxide solution as catalyst and reagent.     

Microwave-Promoted Facile and Rapid Synthesis Procedure for the Efficient Synthesis of 5,5-Disubstituted Hydantoins

A fast, general, environmentally friendly, and facile method for preparation of 5, 5-disubstituted hydantoins from the reaction between ketone (or aldehyde) derivatives with KCN and ammonium carbonate under microwave irradiation is presented. The microwaves remarkably accelerated this reaction, the reaction times decreased dramatically, the reaction conditions were milder, and the yields were also greater. Also a comparative study of microwave versus classical conditions has been done. All the products were characterized by infrared, NMR, and CHN analysis, and their melting points are identical to those of the known compounds reported in the literature. This method might be useful in the future for the preparation of similar derivatives.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]     

An efficient bakers’ yeast catalyzed synthesis of 3,4-dihydropyrimidin-2-(1H)-ones

Bakers’ yeast (Saccharomyces cerevisiae) efficiently catalyzes the three-component Biginelli reaction of aldehydes, β-keto esters, and urea/thiourea to form 3,4-dihydropyrimidin-2-(1H)-ones in good to excellent yields.     

3D SPH flow predictions and validation for high pressure die casting of automotive components

The geometric complexity and high fluid speeds involved in high pressure die casting (HPDC) combine to give strongly three-dimensional fluid flow with significant free surface fragmentation and splashing. A Lagrangian simulation technique that is particularly well suited to modelling HPDC is smoothed particle hydrodynamics (SPH). Materials are approximated by particles that are free to move around rather than by fixed grids, enabling the accurate prediction of fluid flows involving complex free surface motion.     

具有良好光学表面的玻璃透镜模压成形技术

介绍具有良好光学表面的玻璃透镜模压成形技术的发展现状和利用这项技术制造玻璃透镜的方法及其关键的技术问题。