Synthesis of 2,3‐dihydroquinazolin‐4(1 H )‐ones in the presence of Fe 3 O 4 @nano‐cellulose–OPO 3 H as a bio‐based magnetic nanocatalyst

Wang resin catalysed sonochemical synthesis of pyrazolo[4,3-d]pyrimidinones and 2,3-dihydroquinazolin-4(1H)-ones: Identification of chorismate mutase inhibitors having effects on Mycobacterium tuberculosis cell viability

The enzyme chorismate mutase (or CM that is vital for the survival of bacteria) is an interesting pharmacological target for the identification of new anti-tubercular agents. The 5,5-disibstituted pyrazolo[4,3-d]pyrimidinone derivatives containing the fragment based on 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide were designed and explored as the potential inhibitors of chorismate mutase. Based on encouraging docking results of two representative molecules evaluated in silico against MtbCM (PDB: 2FP2) the Wang resin catalysed sonochemical synthesis of target N-heteroarenes were undertaken. The methodology involved the reaction of 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide with the appropriate cyclic/acyclic ketones to afford the desired products in acceptable (51-94%) yields. The methodology was also extended successfully towards the synthesis of 2,2-disubstituted 2,3-dihydroquinazolin-4(1H)-ones in excellent (85-90%) yields. In vitro MTT assay against the RAW 264.7 cell line followed by enzymatic assay against MtbCM identified 3b and 3c as active compounds that showed two H-bonding via their NH (at position 6) and CO group with MtbCM in silico and encouraging (54-57%) inhibition at 30 µM in vitro. Notably, none of the 2,2-disubstituted 2,3-dihydroquinazolin-4(1H)-ones showed any significant inhibition of MtbCM suggesting the favourable role of the pyrazole moiety in case of pyrazolo[4,3-d]pyrimidinones. The favourable role of cyclopentyl ring attached to the pyrazolo[4,3-d]pyrimidinone moiety and that of two methyl groups in place of cyclopentyl ring was also indicated by the SAR study. Besides showing effects against MtbCM in the concentration response study, 3b and 3c showed little or no effects on mammalian cell viability up to 100 µM in an MTT assay but decreased the % Mtb cell viability at 10-30 µM with > 20% decrease at 30 µM in an Alamar Blue Assay. Moreover, no adverse effects were noted for these compounds when tested for teratogenicity and hepatotoxicity in zebrafish at various concentrations. Overall, being the only example of MtbCM inhibitors that showed effects on Mtb cell viability the compound 3b and 3c are of further interest form the view point of discovery and development of new anti-tubercular agents.

Sulfamic acid grafted to cross-linked chitosan by dendritic units: a bio-based, highly efficient and heterogeneous organocatalyst for green synthesis of 2,3-dihydroquinazoline derivatives

In this work, novel cross-linked chitosan by the G1 dendrimer from condensation of melamine and toluene-2,4-diisocyante terminated by sulfamic acid groups (CS-TDI-Me-TDI-NHSO3H), as a bio-based and heterogeneous acidic organocatalyst, was designed and prepared. Also, the structure of the prepared organocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis/derivative thermogravimetry (TGA/DTA). Subsequently, the catalytic performance of the biobased and dendritic CS-TDI-Me-TDI-NHSO3H, as a multifunctional solid acid, was evaluated for the preparation of 2,3-dihydroquinazoline derivatives through a three-component reaction by following green chemistry principles. Some of the advantages of this new protocol include high to excellent yields and short reaction times as well as easy preparation and remarkable catalyst stability of the introduced acidic organocatalyst. The CS-TDI-Me-TDI-SO3H catalyst can be used for up to five cycles for the preparation of quinazoline derivatives with a slight decrease in its catalytic activity.

NiII NPs entrapped within a matrix of l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube: a new and efficient multi-task catalytic system for the green one-pot synthesis of diverse heterocyclic frameworks

In the present study, a new l-glutamic acid cross-linked chitosan supported on magnetic carboxylic acid-functionalized multi-walled carbon nanotube (Fe3O4/f-MWCNT-CS-Glu) nanocomposite was prepared through a convenient one-pot multi-component sequential strategy. Then, nickelII nanoparticles (NiII NPs) were entrapped within a matrix of the mentioned nanocomposite. Afterward, the structure of the as-prepared Fe3O4/f-MWCNT-CS-Glu/NiII nanosystem was elucidated by various techniques, including FT-IR, PXRD, SEM, TEM, SEM-based EDX and elemental mapping, ICP-OES, TGA/DTA, and VSM. In the next part of this research, the catalytic applications of the mentioned nickelII-containing magnetic nanocomposite were assessed upon green one-pot synthesis of diverse heterocyclic frameworks, including bis-coumarins (3a-n), 2-aryl(or heteroaryl)-2,3-dihydroquinazolin-4(1H)-ones (5a-r), 9-aryl-3,3,6,6-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-diones (7a-n), and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles (9a-n). The good-to-excellent yields of the desired products, satisfactory reaction rates, use of water solvent or solvent-free reaction medium, acceptable turnover numbers (TONs) and turnover frequencies (TOFs), along with comfortable recoverability and satisfying reusability of the as-prepared nanocatalyst for at least eight successive runs, and also easy work-up and purification procedures are some of the advantages of the current synthetic protocols.

Recent advances in the application of magnetic bio-polymers as catalysts in multicomponent reactions

Magnetic nanoparticles have attracted significant attention due to their high surface area and superparamagnetic properties. Bio-polymers composed of polysaccharides including alginate, cellulose, glucose, dextrin, chitosan, and starch can be immobilized on magnetic nanoparticles. Bio-polymers can be obtained from natural sources, such as plants, tunicates, algae, and bacteria. Bio-polymers obtained from natural sources have attracted attention due to their various properties including efficient functional groups, non-toxicity, low cost, availability, and biocompatibility. According to the targets of "green chemistry", the application of bio-polymers is effective in reducing pollution. Furthermore, they are excellent agents for the functionalization of magnetic nanoparticles to yield nanomagnetic bio-polymers, which can be applied as recoverable and eco-friendly catalysts in multicomponent reactions.

Preparation and characterization of graphitic carbon nitride-supported L-arginine as a highly efficient and recyclable catalyst for the one-pot synthesis of condensation reactions

In this work, graphitic carbon nitride-supported l-arginine (g-C₃N₄@l-arginine) nanocatalyst was synthesized and evaluated using FT-IR, EDX, XRD, TGA, and FESEM analyses. The performance of the prepared nanocatalyst was examined in the synthesis of 1,4-dihydropyridine, 4H-chromene, and 2,3-dihydro quinazoline derivatives. The novel g-C₃N₄@l-arginine nanocatalyst showed high thermal stability, easy separation from reaction media, the capability to be used in various multicomponent reactions, and acceptable reusability.