Tetraethylammonium 2-(carbamoyl)benzoate as a bifunctional organocatalyst for one-pot synthesis of Hantzsch 1,4-dihydropyridine and polyhydroquinoline derivatives

Novel acyl hydrazide derivatives of polyhydroquinoline as potent anti-diabetic and anti-glycating agents: Synthesis, in vitro α-amylase, α-glucosidase inhibition and anti-glycating activity with molecular docking insights

In this study, eleven novel acyl hydrazides derivative of polyhydroquinoline were synthesized, characterized and screened for their in vitro anti-diabetic and anti-glycating activities. Seven compounds 2a, 2d, 2i, 2 h, 2j, 2f, and 2 g exhibited notable α-amylase inhibitory activity having IC50 values from 3.51 ± 2.13 to 11.92 ± 2.30 µM. Similarly, six compounds 2d, 2f, 2 h, 2i, 2j, and 2 g displayed potent α-glucosidase inhibitory activity compared to the standard acarbose. Moreover, eight derivatives 2d, 2 g, 2f, 2j, 2a, 2i, 2 g, and 2e showed excellent anti-glycating activity with IC50 values from 6.91 ± 2.66 to 15.80 ± 1.87 µM when compared them with the standard rutin (IC50 = 22.5 ± 0.90 µM). Molecular docking was carried out to predict the binding modes of all the compounds with α-amylase and α-glucosidase. The docking analysis revealed that most of the compounds established strong interactions with α-amylase and α-glucosidase. All compounds fitted well into the binding pockets of α-amylase and α-glucosidase. Among all compounds 2a and 2f were most potent based on docking score -8.2515 and -7.3949 against α-amylase and α-glucosidase respectively. These results hold promise for the development of novel candidates targeted at controlling postprandial glucose levels in individuals with diabetes.

Tetramethylguanidine-functionalized melamine as a multifunctional organocatalyst for the expeditious synthesis of 1,2,4-triazoloquinazolinones

Novel nano-ordered 1,1,3,3-tetramethylguanidine-functionalized melamine (Melamine@TMG) organocatalyst was prepared and adequately identified by various techniques including FTIR, EDX, XRD and SEM spectroscopic or microscopic methods as well as TGA and DTG analytical methods. The Melamine@TMG, as an effective multifunctional organocatalyst, was found to promote smoothly the three-component synthesis of 1,2,4-triazoloquinazolinone derivatives using cyclic dimedone, 3-amino-1,2,4-triazole and different benzaldehyde derivatives in EtOH at 40 °C. This practical method afforded the desired products in high to excellent yields (86-99%) and short reaction times (10-25 min). The main advantages of this new method are the use of heterogeneous multifunctional nanocatalyst, simple work-up procedure with no need for chromatographic purification, highly selective conversion of substrates and recyclability of the catalyst, which could be used in five consecutive runs with only a small decrease in its activity.

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

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.

Amine-functionalized graphene oxide nanosheets (AFGONs): an efficient bifunctional catalyst for selective formation of 1,4-dihydropyridines, acridinediones and polyhydroquinolines

We report here selective formation of functionalized 1,4-dihydropyridines (DHP), acridinediones and polyhydroquinolines in high yields using amine-functionalized graphene oxide nanosheets (AFGONs) as the bifunctional catalyst. The method overcomes the limitations of previous protocols affording a mixture of DHP and pyridine derivatives using graphene oxide as the catalyst. The mild reaction conditions are found compatible with a wide range of functional groups. It is presumed that a cooperative effect between the acidic and basic functionalities present in AFGONs may have exerted high catalytic efficiency as well as prevented further oxidation to pyridine derivatives. A plausible mechanism is proposed on the basis of some control experiments. The reactions can be scaled up conveniently, and the catalyst can be recycled for five consecutive runs without loss of its activity.