Synthesis, antichagasic in vitro evaluation, cytotoxicity assays, molecular modeling and SAR/QSAR studies of a 2-phenyl-3-(1-phenyl-1H-pyrazol-4-yl)-acrylic acid benzylidene-carbohydrazide series

Magnetically recoverable Fe3O4 nanocatalyst for the synthesis of biodynamically significant 1H-pyrazolo[1,2-b]phthalazine-5,10-diones derivatives and its DFT study

An environmentally sustainable and proficient method is reported for the synthesis of medicinally important pyrazolo[1,2-b] phthalazine dione derivatives by aqueous micellar medium catalysed by Fe3O4 NPs. Dialkyl acetylenedicarboxylate with isocyanides in the presence of phthalhydrazide is used as starting material. The main advantages of this protocol are the availability of starting materials, short reaction times, green solvents and practical simplicity.

Superparamagnetic Polyaniline-co-m-phenylenediamine@Fe3O4 Nanocomposite as an Efficient Heterogeneous Catalyst for the Synthesis of 1H-pyrazolo [1,2- a]pyridazine-5,8-diones & 1H-pyrazolo[1,2-b]phthalazine-5, 10-diones" Instead of 1H-pyrazolo[1,2-b] Phthalazinedione Derivatives

BACKGROUND

The use of polymer-based catalysts has increased because of their high potential application as an effective catalyst in organic reactions. They have benefits such as high efficiency and reactivity, simple separation, and safety compared to other heterogeneous catalysts.

AIM AND OBJECTIVE

The objective of the current research is to prepare solid polymer-based catalysts, poly(aniline-co- m-phenylenediamine) (PAmPDA), and its superparamagnetic nanocomposite. Then, the catalytic activity of the resulting superparamagnetic nanocomposite was investigated in the synthesis of 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives. A series of some 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives was tested for its antibacterial properties against the Staphylococcus aureus and E.coli bacteria.

MATERIALS AND METHODS

PAmPDA copolymer was synthesized in a 1:2 molar ratio of Ani to mPDA via radical oxidative polymerization at room temperature. Superparamagnetic PAmPDA@Fe3O4 nanocomposite was synthesized from a mixture of Fe(II), Fe(III) solution, and PAmPDA copolymer via the in-situ co-precipitation technique. 1H-pyrazolo[1,2-b]phetalazine-5,10-diones were synthesized via one-pot three-component condensation reaction of Phthalhydrazide, aromatic aldehyde derivatives, and malononitrile in the presence of PAmPDA under solvent-free conditions at 80 °C. The synthesis of 1Hpyrazolo[1,2-a]pyridazine-5,8-dione derivatives was carried out via a one-pot three-component condensation reaction of maleic hydrazide, aromatic aldehyde derivatives, and malononitrile in the presence of PAmPDA under reflux conditions at EtOH/H2O 1:1. The antibacterial activity of some derivatives was tested against Gram-positive and Gram-negative bacteria.

RESULTS

First, superparamagnetic PAmPDA@Fe3O4 nanocomposite was synthesized and characterized successfully, and then the resulting nanocatalyst was used for the synthesis of pyrazolo[1,2-b]phthalazine and pyrazolo[1,2-a]pyridazine. We obtained the maximum yield of the desired 1H-pyrazolo[1,2- b]phthalazine-5,10 dione derivatives with 0.05 g of catalyst at 80°C, under solvent free conditions, whereby the reaction was complete within 30 min. A wide range of 1H-pyrazolo[1,2-b]phthalazine-5,10 dione derivatives were synthesized in good to excellent yield. On the other hand, pyrazolo[1,2- a]pyridazine derivative was synthesized successfully in high yield using PAmPDA as a nanocatalyst. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good activity against Staphylococcus aureus and E.coli.

CONCLUSION

In this research, PAmPDA was used for mild preparation of 1H-pyrazolo [1,2-a]pyridazine5,8-diones & 1H-pyrazolo[1,2-b]phetalazine-5,10-diones derivatives with excellent yields and short reaction times. The attractive features of this protocol are simple procedure, cleaner reaction, and the use of recyclable nanocatalyst. Satisfactory yields of products and easy workup make this a useful protocol for the green synthesis of this class of compounds. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good activity against Staphylococcus aureus and E.coli.

Decoding Directing Groups and Their Pivotal Role in C-H Activation

Synthetic organic chemistry has witnessed a plethora of functionalization and defunctionalization strategies. In this regard, C-H functionalization has been at the forefront due to the multifarious applications in the development of simple to complex molecular architectures and holds a brilliant prospect in drug development and discovery. Despite been explored tremendously by chemists, this functionalization strategy still enjoys the employment of novel metal catalysts as well metal-free organic ligands. Moreover, the switch to photo- and electrochemistry has widened our understanding of the alternative pathways via which a reaction can proceed and these strategies have garnered prominence when applied to C-H activation. Synthetic chemists have been foraging for new directing groups and templates for the selective activation of C-H bonds from a myriad of carbon-hydrogen bonds in aromatic as well as aliphatic systems. As a matter of fact, by varying the templates and directing groups, scientists found the answer to the challenge of distal C-H bond activation which remained an obstacle for a very long time. These templates have been frequently harnessed for selectively activating C-H bonds of natural products, drugs, and macromolecules decorated with multiple C-H bonds. This itself was a challenge before the commencement of this field as functionalization of a site other than the targeted site could modify and hamper the biological activity of the pharmacophore. Total synthesis and pharmacophore development often faces the difficulty of superfluous reaction steps towards selective functionalization. This obstacle has been solved by late-stage functionalization simply by harnessing C-H bond activation. Moreover, green chemistry and metal-free reaction conditions have seen light in the past few decades due to the rising concern about environmental issues. Therefore, metal-free catalysts or the usage of non-toxic metals have been recently showcased in a number of elegant works. Also, research groups across the world are developing rational strategies for directing group free or non-directed protocols that are just guided by ligands. This review encapsulates the research works pertinent to C-H bond activation and discusses the science devoted to it at the fundamental level. This review gives the readers a broad understanding of how these strategies work, the execution of various metal catalysts, and directing groups. This not only helps a budding scientist towards the commencement of his/her research but also helps a matured mind searching out for selective functionalization. A detailed picture of this field and its progress with time has been portrayed in lucid scientific language with a motive to inculcate and educate scientific minds about this beautiful strategy with an overview of the most relevant and significant works of this era. The unique trait of this review is the detailed description and classification of various directing groups and their utility over a wide substrate scope. This allows an experimental chemist to understand the applicability of this domain and employ it over any targeted substrate.

Antiparasitic activities of novel pyrimidine N-acylhydrazone hybrids

In this article, a series of 29 new pyrimidine N-acylhydrazone hybrids were synthesized and evaluated in vitro against Leishmania amazonensis and Trypanosoma cruzi protozoa that cause the neglected diseases cutaneous leishmaniasis and Chagas disease, respectively. Eight of the target compounds showed significant antiprotozoal activities with IC₅₀ values in 4.3-33.6 μM range. The more active compound 4f exhibited selectivity index greater than 15 and drug-like properties based on Lipinski's rule.

Anti-Trypanosoma cruzi Activity and Molecular Docking Studies of 1Hpyrazolo[ 3, 4-b]pyridine Derivatives

Background:

Untargeted studies led to the development of some pyrazolopyridine derivatives for the antiparasitic profile, particularly the derivatives containing the structural carbohydrazide subunit. In this work, we proceeded in the biological screening of 27 N’- (substitutedphenylmethylene)- 4-carbohydrazide-3-methyl-1-phenyl-1H-pyrazolo[3, 4-b]pyridine derivatives against T. cruzi as well as the cytotoxic evaluation. To obtain more information about the trypanocidal activity of this class of compounds, we carried out molecular docking simulations to get an insight into putative targets in T. cruzi.

Methods:

The assays were evaluated against both trypomastigote and amastigote forms of T. cruzi and cytotoxicity assays on LLCMK2 cells. The predominant conformational compounds were analyzed and molecular docking simulations performed.

Results:

The results from trypanocidal activity screening of this series showed that just the compounds with phenyl group at C-6 position exhibited activity and the N’-4-hydroxyphenylmethylene derivative presented the best profile against both trypomastigote and amastigote forms of T. cruzi. Docking simulation results showed that this compound has a binding affinity with both CYP51 and cruzain targets of T. cruzi.

Conclusion:

Our results indicate that the hydroxyl substituent at the N’-substituted-phenylmethylene moiety and the phenyl ring at C-6 of 1H-pyrazolo[3,4-b]pyridine system are relevant for the trypanocidal activity of this class of compounds. Also, docking simulations showed that activity presented can be related to more than one target of the parasite.

l -( -) -Quebrachitol as a Ligand for Selective Copper(0)-Catalyzed N-Arylation of Nitrogen-Containing Heterocycles

l-(-)-Quebrachitol (QCT) has been found as a ligand of copper powder for selective N-arylation of nitrogen-containing heterocycles with aryl halides. Furthermore, another potential catalytic system (copper powder/QCT/ t-BuOK) was successfully adapted to unactivated aryl chlorides.

Synthesis, characterization, in silico molecular docking study and biological evaluation of a 5-(phenylthio) pyrazole based polyhydroquinoline core moiety

A combinatorial library of polyhydroquinoline scaffolds is successfully attempted by multicomponent cyclocondensation reaction.

An Introduction to the Basic Concepts in QSAR-Aided Drug Design

The need for the development of new drugs to combat existing and newly identified conditions is unavoidable. One of the important tools used in the advanced drug development pipeline is computer-aided drug design. Traditionally, to find a drug many ligands were synthesized and evaluated for their effectiveness using suitable bioassays and if all other drug-likeness features were met, the candidate(s) would possibly reach the market. Although this approach is still in use in advanced format, computational methods are an indispensable component of modern drug development projects. One of the methods used from very early days of rationalizing the drug design approaches is Quantitative Structure-Activity Relationship (QSAR). This chapter overviews QSAR modeling steps by introducing molecular descriptors, mathematical model development for relating biological activities to molecular structures, and model validation. At the end, several successful cases where QSAR studies were used extensively are presented.

Coumarin heterocyclic derivatives: chemical synthesis and biological activity

This review highlights the broad range of science that has arisen from the synthesis of coumarin-linked and fused heterocycle derivatives. Specific topics include their synthesis and biological activity.

Synthesis and characterization of dicationic 4,4′-bipyridinium dichloride ordered mesoporous silica nanocomposite and its application in the preparation of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives

Application of SBA@BiPy²⁺ 2Cl⁻ nanocomposite as a novel environmentally safe heterogeneous nanoreactor for the one-pot solvent-free synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives.

New aryloxy-quinone derivatives as potential anti-Chagasic agents: synthesis, trypanosomicidal activity, electrochemical properties, pharmacophore elucidation and 3D-QSAR analysis

A set of new aryloxy-quinones were synthesized and evaluated in vitro against the epimastigote form of Trypanosoma cruzi and their unspecific cytotoxicity was tested on murine macrophages J-774 cells.

An Introduction to the Basic Concepts in QSAR-Aided Drug Design

The need for the development of new drugs to combat existing and newly identified conditions is unavoidable. One of the important tools used in the advanced drug development pipeline is computer-aided drug design. Traditionally, to find a drug many ligands were synthesized and evaluated for their effectiveness using suitable bioassays and if all other drug-likeness features were met, the candidate(s) would possibly reach the market. Although this approach is still in use in advanced format, computational methods are an indispensable component of modern drug development projects. One of the methods used from very early days of rationalizing the drug design approaches is Quantitative Structure-Activity Relationship (QSAR). This chapter overviews QSAR modeling steps by introducing molecular descriptors, mathematical model development for relating biological activities to molecular structures, and model validation. At the end, several successful cases where QSAR studies were used extensively are presented.

Synthesis, characterization and pharmacological screening of some novel 5-imidazopyrazole incorporated polyhydroquinoline derivatives

A new category of polyhydroquinoline derivatives 8a-t were synthesized in moderate to good yield (64-85%) by one-pot three-component cyclocondensation reaction of 5-(1H-imidazol-1-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde 3 with various enaminones 6a-h and different active methylene compounds (malononitrile 7a, ethylcaynoacetate 7b and caynoacetamide 7c) in absolute ethanol. The newly synthesized compounds were evaluated for their in vitro antimalarial activity against Plasmodium falciparum, in vitro antibacterial activity against a panel of pathogenic strains of bacteria and fungi and also for their antitubercular activity against Mycobacterium tuberculosis H37Rv strain. Two of them (8n, 8t) exhibited excellent antimalarial activity. Some of them exhibited excellent antibacterial activity and moderate antituberculosis activity compared with the first line drugs.

Design, synthesis, characterization and anti-inflammatory evaluation of novel pyrazole amalgamated flavones

A series of novel pyrazole amalgamated flavones has been designed and synthesized from 1-methyl-5-(2,4,6-trimethoxy-phenyl)-1H-pyrazole 6. The structures of regioisomers 6 and 7 were resolved by 2D (1)H-(1)H COSY, (1)H-(13)C HSQC and (1)H-(13)C HMBC experiments. The newly synthesized compounds were tested for their in vitro COX inhibition and in vivo carrageenan induced hind paw edema in rats and acetic acid induced vascular permeability in mice. Although the compounds have inhibitory profile against both COX-1 and COX-2, some of the compounds are found to be selective against COX-2, supported by inhibition of paw edema and vascular permeability. Docking studies were also carried out to determine the structural features which sway the anti-inflammatory activity of the tested compounds. The keto and phenolic -OH are major factors that are prominently involved in interaction with COX-2 active site.

Design, synthesis, characterization and biological evaluation of novel pyrazole integrated benzophenones

A series of novel pyrazole integrated benzophenones (9a-j) have been designed, synthesized from 1-methyl-5-(2,4,6-trimethoxy-phenyl)-1H-pyrazole 6. The structures of the regioisomers 6 and 7 were determined by 2D (1)H-(1)H COSY, (1)H-(13)C HSQC and (1)H-(13)C HMBC experiments. The newly synthesized compounds (9a-j) were evaluated for in vivo anti-inflammatory activity by carrageenan paw edema in rats and in vitro COX-1/COX-2 inhibition and antioxidant potential. Among the synthesized compounds, compounds 9b, 9d and 9f, were found to be active anti-inflammatory agents in addition to having potent antioxidant activity.

2-[1-(1-Oxoindan-2-yl)eth-yl]indan-1-one

In the title compound, C(20)H(18)O(2), the fused-ring systems are essentially planar (r.m.s. deviations of the nine fitted atoms = 0.009 and 0.027 Å) and exhibit an orthogonal relationship [dihedral angle = 79.83 (5)°]. To a first approximation, the ketone-O atoms are directed to opposite sides of the mol-ecule. A three-dimensional architecture arises in the crystal packing owing to C-H⋯O, C-H⋯π and π-π inter-actions [between centrosymmetrically related benzene rings with centroid-centroid distance = 3.7647 (10) Å].

2-[(E)-4-Meth-oxy-benzyl-idene]-1,2,3,4-tetra-hydro-naphthalen-1-one

Two independent mol-ecules (A and B) comprise the asymmetric unit of the title compound, C(18)H(16)O(2). Mol-ecule B is virtually superimposable upon A. Minor differences are noted in the dihedral angles between the terminal benzene rings of 56.03 (10) and 54.62 (10)°, and in the orientations of meth-oxy groups with respect to the benzene rings to which they are attached [C-O-C-C torsion angles = 169.11 (19) and -172.37 (18)°]. The cyclo-hexene ring of each fused ring system has a screw-boat conformation. In the crystal, C-H⋯π inter-actions assemble mol-ecules into a supra-molecular array in the ab plane.

(2E)-2-(Thio-phen-2-yl-methyl-idene)-1,2,3,4-tetra-hydro-naphthalen-1-one

In the title compound, C(15)H(12)OS, the cyclo-hexene ring has a twisted boat conformation with the C atom between the ketone and methyl-ene atom and this methyl-ene C atom lying 0.280 (3) and 0.760 (3) Å, respectively, from the plane through the remaining four atoms (r.m.s. deviation = 0.004 Å). The dihedral angle between the benzene and thio-phene rings [21.64 (9)°] indicates an overall twist in the mol-ecule. The thio-phene S and ketone O atoms are anti, an orientation that allows the close approach of these atoms [3.3116 (17) Å] in the crystal structure and which leads to the formation of helical supra-molecular chains along the c axis.

1-Phenyl-1H-pyrazole-4-carbaldehyde

In the title mol-ecule, C(10)H(8)N(2)O, the five- and six-membered rings form a dihedral angle of 10.14 (9)°. The aldehyde group is almost coplanar with the pyrazole ring to which it is connected [O-C-C-C torsion angle = -179.35 (17)°]. In the crystal, inversion dimers are linked by four C-H⋯O inter-actions as the carbonyl O atom accepts two such bonds. The dimeric aggregates are linked into supra-molecular layers in the ac plane by C-H⋯π and π-π [ring centroid(pyrrole)⋯ring centroid(phen-yl) = 3.8058 (10) Å] inter-actions.

(2E)-2-(Furan-2-yl-methyl-idene)-2,3-dihydro-1H-inden-1-one

In the title compound, C₁₄H₁₀O₂, the five-membered ring of the inden-1-one residue is almost planar (r.m.s. deviation = 0.035 Å). A twist about the single bond linking the two residues is evident [C—C—C—C torsion angle = −13.2 (5)°]. The three-dimensional architecture is stabilized by C—H⋯O (involving the trifurcated carbonyl O atom), C—H⋯π and π–π inter­actions [between the five- and six-membered rings of inden-1-one residues; ring centroid–centroid distance = 3.7983 (17) Å]. The sample studied was a non-merohedral twin; the minor component refined to approximately 36%.

(2E)-2-[(2H-1,3-Benzodioxol-5-yl)methyl-idene]-2,3-dihydro-1H-inden-1-one

In the title compound, C(17)H(12)O(3), each of the five-membered rings in the inden-1-one and 1,3-benzodioxole residues is almost planar (r.m.s. deviations = 0.041 and 0.033 Å, respectively). A small twist about the single bond linking the two residues is evident [the C-C-C-C torsion angle = 8.7 (4)°]. Supra-molecular zigzag layers propagating in the ac plane are formed in the crystal via C-H⋯O inter-actions. The layers are linked via π-π inter-actions between the five- and six-membered rings of 1,3-benzodioxole residues [centroid-centroid distance = 3.4977 (14) Å].

Pyrazole carbohydrazide derivatives of pharmaceutical interest

The main purpose of this paper is to provide an insight into the biological activities of pyrazole derivatives which contain the carbohydrazide moiety.

(2E)-2-[(2E)-3-Phenyl-prop-2-en-1-yl-idene]-2,3-dihydro-1H-inden-1-one

The title indan-1-one derivative, C₁₈H₁₄O, is planar with an r.m.s. deviation for all 19 non-H atoms of 0.098 Å. The conformation about each of the C=C bonds [1.343 (3) and 1.349 (3) Å] is E. Supra­molecular layers in the bc plane, mediated by C—H⋯O and π–π [ring centroid–centroid distance = 3.5282 (15) Å] inter­actions, feature in the crystal packing.