Dendrons containing boric acid and 1,3,5-tris(2-hydroxyethyl)isocyanurate covalently attached to silica-coated magnetite for the expeditious synthesis of Hantzsch esters

Abstract

A new multifunctional dendritic nanocatalyst containing boric acid and 1,3,5-tris(2-hydroxyethyl)isocyanurate covalently attached to core–shell silica-coated magnetite (Fe3O4@SiO2@PTS-THEIC-(CH2)3OB(OH)2) was designed and properly characterized by different spectroscopic or microscopic methods as well as analytical techniques used for mesoporous materials. It was found that the combination of both aromatic π–π stacking and boron–oxygen ligand interactions affords supramolecular arrays of dendrons. Furthermore, the use of boric acid makes this dendritic catalyst a good choice, from corrosion, recyclability and cost points of view. The catalytic activity of Fe3O4@SiO2@PTS-THEIC-(CH2)3OB(OH)2, as an efficient magnetically recoverable catalyst, was investigated for the synthesis of polyhydroacridines (PHAs) as well as polyhydroquinolines (PHQs) via one-pot multicomponent reactions of dimedone and/or ethyl acetoacetate, different aldehydes and ammonium acetate in EtOH under reflux conditions. Very low loading of the catalyst, high to quantitative yields of the desired PHAs or PHQs products, short reaction times, wide scope of the substrates, eliminating any toxic heavy metals or corrosive reagents for the modification of the catalyst, and simple work-up procedure are remarkable advantages of this green protocol. An additional advantage of this magnetic nanoparticles catalyst is its ability to be separated and recycled easily from the reaction mixture with minimal efforts in six subsequent runs without significant loss of its catalytic activity. This magnetic and dendritic catalyst can be extended to new two- and three-dimensional covalent organic frameworks with different applications.

Application of Cyclohexane‐1,3‐diones in the Synthesis of Six‐Membered Nitrogen‐Containing Heterocycles

“…Heterogeneous catalysts have their own importance in terms of easy recovery by simple filtration and reusability [166,167] . Several easily recoverable and recyclable catalysts have been utilized for the synthesis of acridine‐1,8‐diones with high to excellent yields for illustration Fe 3 O 4 @Sap/Cu(II) [168] Pt NPs@graphene oxide [169,170] Au/NiAlTi layered double hydroxide nanocatalyst, [171] functionalized multi‐walled carbon nanotubes (f‐MWCNT) [172] and silica‐supported metal NPs [173–176] . Safaei et al .…”

“…[166,167] Several easily recoverable and recyclable catalysts have been utilized for the synthesis of acridine-1,8-diones with high to excellent yields for illustration Fe 3 O 4 @Sap/Cu(II) [168] Pt NPs@graphene oxide [169,170] Au/NiAlTi layered double hydroxide nanocatalyst, [171] functionalized multi-walled carbon nanotubes (f-MWCNT) [172] and silica-supported metal NPs. [173][174][175][176] Scheme 21. Phenyldiazenyl acridinedione-carboxylic acid derivatives synthesis from cyclohexane-1,3-diones.…”

l-Asparagine–EDTA–amide silica-coated MNPs: a highly efficient and nano-ordered multifunctional core–shell organocatalyst for green synthesis of 3,4-dihydropyrimidin-2(1H)-one compounds

“…In continuation of our ongoing research toward development of various catalytic systems for green synthesis of different heterocyclic scaffolds, 40,101–104 we herein report the synthesis and characterizations of new l -asparagine grafted on the 3-aminopropyl-modified Fe 3 O 4 @SiO 2 core–shell magnetic nanoparticles using the EDTA linker (Fe 3 O 4 @SiO 2 –APTS–EDTA–asparagine), as a magnetically recoverable organocatalyst having excellent thermal and magnetic stability, and specific morphology as well as acidic and basic sites with proper geometry, 122,123 to promote the Biginelli reaction efficiently under solvent-free conditions at 60 °C (Scheme 1).…”

Synthesis of (E)-2-(1H-tetrazole-5-yl)-3-phenylacrylenenitrile Derivatives Under Green Conditions Catalyzed by New Thermally Stable Magnetic Periodic Mesoporous Ognosilica Embedded With ZnO Nanoparticles

“…Recovery and reuse of catalysts is an important aspect of catalytic reactions, especially in organic synthesis. Compared to conventional methods for catalyst separation from reactants, the use of a magnetic catalyst that is easily separated by a magnet near the reaction solution is an intelligently approach that increases separation speed, high e ciency, and less wastage catalyst and product during separation 64,83,84 .…”