Current scenario of pyrazole hybrids with in vivo therapeutic potential against cancers

The Role of Flow Chemistry on the Synthesis of Pyrazoles, Pyrazolines and Pyrazole-Fused Scaffolds

Nitrogen-containing heterocycles are fundamental scaffolds in organic chemistry, particularly due to their prevalence in pharmaceuticals, agrochemicals and materials science. Among them, five-membered rings, containing two nitrogen atoms in adjacent positions-such as pyrazoles, pyrazolines and indazoles-are especially significant due to their versatile biological activities and structural properties, which led to the search for greener, faster and more efficient methods for their synthesis. Conventional batch synthesis methods, while effective, often face challenges related to reaction efficiency, scalability and safety. Flow chemistry has emerged as a powerful alternative, offering enhanced control over reaction parameters, improved safety profiles and opportunities for scaling up synthesis processes efficiently. This review explores the impact of flow chemistry on the synthesis of these pivotal heterocycles, highlighting its advantages over the conventional batch methods. Although indazoles have a five-membered ring fused with a benzene ring, they will also be considered in this review due to their biological relevance.

Innovative Pyrazole Hybrids: A New Era in Drug Discovery and Synthesis

Heterocyclic compounds that include nitrogen and their derivatives have long been regarded as excellent sources of medicinal substances. Pyrazole is a compound with two nitrogen atoms and an aromatic structure. It has several uses and intricate stereochemistry arranged in a five-membered ring. The knowledge of different pyrazole derivatives and their range of physiological and pharmacological actions has grown significantly in recent years. The scientific community has recently increasingly focused on exploring the chemistry of various pyrazole hybrids due to their enhanced biological activities. This review investigates the chemistry of these diverse pyrazole hybrids, emphasizing their synthesis and their antidiabetic, antibacterial, anticancer, antimicrobial, antioxidant, and anti-inflammatory activities. Articles published from 2014 onward with an emphasis on the last 5 years are included in this review. This review is anticipated to be useful for future investigations and innovative concepts in the pursuit of designs for creating more promising hybrids of pyrazoles.

New molecular hybrids integrated with quinoxaline and pyrazole structural motifs: VGFR2 inhibitors and apoptosis inducers

The vascular endothelial growth factor receptor is essential for the angiogenesis of cancer. Tumor propagation was effectively suppressed by inhibiting VEGFR-2 activity. As a result, the target quinoxaline-pyrazole hybrids were created in a way that closely resembled the structural characteristics of VEGFR-2 inhibitors. The synthesized compounds were assessed in vitro using the MTT assay with doxorubicin serving as a reference standard for their cytotoxic properties against the HCT-116 and MCF-7 cell lines. Additionally, when tested on human normal fibroblasts (WI38), the promising cytotoxic compounds 8, 11, 13, and 15 were shown to be selective to cancer cells. Using ELISA, they showed mechanistically inhibitory activities against VEGFR-2; compound 13 was the most effective inhibitor, with an IC50 of 0.045 ± 6.24 uM, surpassing sorafenib (IC50 of 0.049 ± 5.24 μM). Notably, it was discovered that our target compound, 13, was 1.1 times more potent than sorafenib and 3.19 times more potent than sunitinib as a VGFRA2 inhibitor. Furthermore, Western blot analysis revealed that its VEGFR2 protein levels were noticeably higher than the control. Compound 13's selectivity towards VEGFR2 was further confirmed by testing it against other kinases, such as PDGFRA (IC50 0.329 ± 0.014 μM) and EGFR (IC50 0.6 ± 0.019 μM). Furthermore, 13 demonstrated a 50 % decrease in VEGF-A secretion in comparison to the control group, demonstrating its anti-angiogenic quality. A scratch closure percentage of 57.78 %, which was much lower than the 97.04 percent of untreated control cells, showed 13's anti-migratory capability. According to the cell cycle study, compound 13 induces apoptosis at the sub-G1 phase and terminates the cell cycle at the G1 phase. Consequently,flow cytometric analysis revealed that it caused apoptosis; compound 13 increases the BAX/Bcl-2 ratio from control to 13.66, and it also activates caspase 3 to 422.48 ± 43.82 and induces p53 to 366.79 ± 40.21. Docking simulations revealed potential binding modes and crucial structural elements of active drugs, and they were almost in agreement with enzymatic examination. For every hybrid, in silico physicochemical attributes, drug likeness metrics, and ligand efficiency were plausible. It's interesting to note that 13 and 15 are plausible medication candidates.

Enhanced Anticancer Selectivity of Cyclometalated Imidazole/Pyrazole-Imine IridiumIII Complexes Through the Switch from Cationic to Zwitterionic Forms

Cyclometalated iridiumIII complexes have shown promising anticancer properties, with variations in charge and ligand substitution significantly influencing their biological activity. However, zwitterionic iridiumIII complexes remain scarcely explored. Herein, we report a series of zwitterionic cyclometalated imidazole/pyrazole-imine iridiumIII complexes and compare their biological activity to analogous cationic complexes with sulfonate counteranions. X-ray crystallography confirmed the structural differences between the cationic and zwitterionic forms. These complexes exhibited cytotoxicity against A549, HeLa, and HepG2 cancer cells, with IC50 values ranging from 14.35 to 69.12 μM. While cationic complexes showed higher cytotoxicity, zwitterionic complexes demonstrated enhanced selectivity for A549 cancer cells over BEAS-2B normal cells (selectivity index: 3.72-5.90 for zwitterionic forms vs 1.16-1.44 for cationic forms). This selectivity is attributed to distinct cellular uptake mechanisms: zwitterionic complexes use an energy-dependent pathway in cancer cells and an energy-independent pathway in normal cells, leading to differences in cellular accumulation and redox activity. Mechanistic studies revealed that both complex types induce ROS generation and mitochondrial membrane depolarization (MMP), with apoptosis as the primary cell death pathway.

Design and discovery of carboxamide-based pyrazole conjugates with multifaceted potential against Triple-Negative Breast cancer MDA-MB-231 cells

We report the design, synthesis, and validation of carboxamide-based pyrazole and isoxazole conjugates with a multifaceted activity against Breast Cancer Cell Line MDA-MB-231. The study established that amongst the series, N-(3,5-bis(trifluoromethyl)benzyl)-3-(3,4,5-trimethoxyphenyl)-1H-pyrazole-5-carboxamide (5g) exhibits the highest potency in inhibiting Breast Cancer Cell Line MDA-MB-231 with an IC50 value of 15.08 ± 0.04 µM. The MDA-MB-231 cells, upon treatment with compound 5g, exhibited characteristic apoptotic specific activities such as nuclear fragmentation, phosphatidylserine translocation to the outer plasma membrane, release of lactate dehydrogenase (LDH), and upregulation of caspase 3 and caspase 9 activities. Also, the modulation of pro and antiapoptotic proteins in 5g treated MDA-MB-231 cells was revealed by membrane array analysis. More importantly, the combination of paclitaxel and compound 5g has exhibited improved activity by several folds via their synergistic effects.

Photocatalytic One-Pot Three-Component Reaction for the Regioselective Synthesis of Bromo-Substituted Pyrazoles

A photocatalytic three-component cascade reaction of readily available enaminones, hydrazines, and CBr4 for the synthesis of bromo-substituted pyrazoles in one pot has been demonstrated. This strategy involves intermolecular C-N/C-Br bond formation and represents an efficient approach to the construction of 4-bromo-substituted pyrazoles with high regioselectivity, broad substrate scope, good functional group tolerance, convenient operation, and mild reaction conditions. Mechanistic investigations show that this reaction proceeds via intermolecular cyclization of enaminones with hydrazines, followed by a regioselective bromination of pyrazoles using CBr4 as a "Br" source.

Base-promoted multicomponent synthesis of 1,2,4-triazole-based hybrids from 1,3-diones, β-nitrostyrenes, and hydrazones

Herein, we report a metal-free, base-promoted route for the synthesis of hybrid molecular scaffolds in which various 1,3-diones and 1,2,4-triazoles are linked by a benzyl bridge. This three-component, one-pot reaction was accomplished by first treating 4-hydroxycoumarin, trans-β-nitrostyrene, and aldehyde hydrazone in the presence of sodium carbonate. Further, this protocol was successfully expanded to other 1,3-diones, such as dimedone and 4-hydroxy-2-quinolone. A broad substrate scope, mild reaction conditions, and the metal and ligand/additive-free approach are the prominent features of this strategy.

Current scenario of pyrazole hybrids with anti-breast cancer therapeutic applications

Breast cancer stands as the leading cause of cancer-related deaths among women globally, but current therapy is restricted to the serious adverse effects and multidrug resistance, necessitating the exploration of novel, safe, and efficient anti-breast cancer chemotherapeutic agents. Pyrazoles exhibit excellent potential for utilization as effective anti-breast cancer agents due to their ability to act on various biological targets. Particularly, pyrazole hybrids demonstrated the advantage of targeting multiple pathways, and some of them, which are exemplified by larotrectinib (pyrazolo[1,5-a]pyrimidine hybrid), can be applied for breast cancer therapy. Thus, pyrazole hybrids hold great promise as useful therapeutic interventions for breast cancer. The aim of this review is to summarize the current scenario of pyrazole hybrids with in vitro and/or in vivo anti-breast cancer potential, along with the modes of action and structure-activity relationships, covering articles published from 2020 to the present, to streamline the development of rational, effective and safe anti-breast cancer candidates.

Design, Synthesis, and Biological Evaluation of HDAC Inhibitors Containing Natural Product-Inspired N-Linked 2-Acetylpyrrole Cap

Drawing inspiration from the structural resemblance between a natural product N-(3-carboxypropyl)-2-acetylpyrrole and phenylbutyric acid, a pioneer HDAC inhibitor evaluated in clinical trials, we embarked on the design and synthesis of a novel array of HDAC inhibitors containing an N-linked 2-acetylpyrrole cap by utilizing the pharmacophore fusion strategy. Among them, compound 20 exhibited potential inhibitory activity on HDAC1, and demonstrated notable potency against RPMI-8226 cells with an IC50 value of 2.89 ± 0.43 μM, which was better than chidamide (IC50 = 10.23 ± 1.02 μM). Western blot analysis and Annexin V-FTIC/propidium iodide (PI) staining showed that 20 could enhance the acetylation of histone H3, as well as remarkably induce apoptosis of RPMI-8226 cancer cells. The docking study highlighted the presence of a hydrogen bond between the carbonyl oxygen of the 2-acetylpyrrole cap group and Phe198 of the HDAC1 enzyme in 20, emphasizing the crucial role of introducing this natural product-inspired cap group. Molecular dynamics simulations showed that the docked complex had good conformational stability. The ADME parameters calculation showed that 20 possesses remarkable theoretical drug-likeness properties. Taken together, these results suggested that 20 is worthy of further exploration as a potential HDAC-targeted anticancer drug candidate.

Development and assessment of novel pyrazole-thiadiazol hybrid derivatives as VEGFR-2 inhibitors: design, synthesis, anticancer activity evaluation, molecular docking, and molecular dynamics simulation

Cancer remains a significant health challenge globally, requiring the development of targeted chemotherapeutics capable of specifically inhibiting cancer cell growth. Angiogenesis is one of the key features of tumor growth and metastasis and is, therefore, an important target for the treatment of many tumors. The vascular endothelial growth factor (VEGF) signaling pathway has proven to be a promising lead in anticancer therapy due to the central role it plays in tumor angiogenesis. Vascular endothelial growth factor receptor-2 (VEGFR-2) is a key mediator in the signaling pathway regulating angiogenesis. Targeting VEGFR-2 may disrupt angiogenesis, leading to a reduction in tumor blood supply and tumor progression. The design, synthesis, and assessment of novel VEGFR-2 inhibitor derivatives are the focus of this study, with particular emphasis on incorporating the pyrazole-thiadiazol pharmacophore into the molecular structure. Taking advantage of the pharmacophoric properties of pyrazole and 1,3,4-thiadiazol, compounds with different substituents in the main structure were designed and synthesized. The compounds were also evaluated for antiproliferative activity against cancer cell lines. Compound 4e demonstrated the highest activity among all compounds, with an IC50 of 9.673 ± 0.399 μM against HT-29 cells and 23.081 ± 0.400 μM against NIH3T3 cells. To further support the inhibitory activity of compound 4e, an in silico study was performed. Compound 4e demonstrated strong binding to the active site of VEGFR-2 in molecular docking studies, forming hydrogen bonds with key amino acid residues. The stability of the compound in the enzyme's active site was demonstrated through molecular dynamics simulations.

Design, synthesis and potent anti-pancreatic cancer activity of new pyrazole derivatives bearing chalcone, thiazole and thiadiazole moieties: gene expression, DNA fragmentation, cell cycle arrest and SAR

Less than 5% of pancreatic cancer patients survive for more than five years after diagnosis. Therefore, there is an urgent need for novel therapeutic drugs to treat pancreatic cancer. Herein, we report the synthesis and full characterization of fifteen novel pyrazole derivatives bearing chalcone (4-10), thiazole (16-19) and thiadiazole (23-26) moieties. All the newly synthesized pyrazole derivatives were tested in vitro as anti-cancer agents against pancreatic cancer (PaCa-2), breast cancer (MCF-7), prostate cancer (PC3), and normal cell lines (BJ1). Three pyrazolyl-chalcone derivatives (4, 5, and 7) and a pyrazolyl-thiadiazole derivative (25) showed potent anti-cancer activity against the PaCa-2 cell line with IC50 values of 13.0, 31.5, 24.9, and 5.5 μg mL-1, respectively, compared with doxorubicin (IC50 = 28.3 μg mL-1). Compound 25 showed potent anti-cancer activity against the PC3 cell line with an IC50 value of 11.8 μg mL-1. In contrast, compounds 4, 5 and 7 are safer against the normal human-cell line (BJ1) with IC50 values of 74.2, 76.6 and 81.1 μg mL-1, respectively, compared with compound 25, which has an IC50 value of 23.7 μg mL-1. The mechanism of action of compounds 4, 5 and 7 against pancreatic cancer cells was studied by investigating gene expression, DNA fragmentation, comet assay and flow cytometry experiments using doxorubicin as a reference drug. Moreover, the structure-activity relationship between the structures of these compounds and their biological properties was discussed.

Multicomponent Synthesis of New Fluorescent Boron Complexes Derived from 3-Hydroxy-1-phenyl-1H-pyrazole-4-carbaldehyde

Novel fluorescent pyrazole-containing boron (III) complexes were synthesized employing a one-pot three-component reaction of 3-hydroxy-1-phenyl-1H-pyrazole-4-carbaldehyde, 2-aminobenzenecarboxylic acids, and boronic acids. The structures of the novel heterocyclic compounds were confirmed using 1H-, 13C-, 15N-, 19F-, and 11B-NMR, IR spectroscopy, HRMS, and single-crystal X-ray diffraction data. The photophysical properties of the obtained iminoboronates were investigated using spectroscopic techniques, such as UV-vis and fluorescence spectroscopies. Compounds display main UV-vis absorption maxima in the blue region, and fluorescence emission maxima are observed in the green region of the visible spectrum. It was revealed that compounds exhibit fluorescence quantum yield up to 4.3% in different solvents and demonstrate an aggregation-induced emission enhancement effect in mixed THF-water solutions.

A Proteomics Approach Identifies RREB1 as a Crucial Molecular Target of Imidazo-Pyrazole Treatment in SKMEL-28 Melanoma Cells

Cutaneous melanoma is the most dangerous and deadly form of human skin malignancy. Despite its rarity, it accounts for a staggering 80% of deaths attributed to cutaneous cancers overall. Moreover, its final stages often exhibit resistance to drug treatments, resulting in unfavorable outcomes. Hence, ensuring access to novel and improved chemotherapeutic agents is imperative for patients grappling with this severe ailment. Pyrazole and its fused systems derived thereof are heteroaromatic moieties widely employed in medicinal chemistry to develop effective drugs for various therapeutic areas, including inflammation, pain, oxidation, pathogens, depression, and fever. In a previous study, we described the biochemical properties of a newly synthesized group of imidazo-pyrazole compounds. In this paper, to improve our knowledge of the pharmacological properties of these molecules, we conduct a differential proteomic analysis on a human melanoma cell line treated with one of these imidazo-pyrazole derivatives. Our results detail the changes to the SKMEL-28 cell line proteome induced by 24, 48, and 72 h of 3e imidazo-pyrazole treatment. Notably, we highlight the down-regulation of the Ras-responsive element binding protein 1 (RREB1), a member of the zinc finger transcription factors family involved in the tumorigenesis of melanoma. RREB1 is a downstream element of the MAPK pathway, and its activation is mediated by ERK1/2 through phosphorylation.

Novel Pyrazole-4-Carboxamide Derivatives Containing Oxime Ether Group as Potential SDHIs to Control Rhizoctonia solani

In the search for novel succinate dehydrogenase inhibitor (SDHI) fungicides to control Rhizoctonia solani, thirty-five novel pyrazole-4-carboxamides bearing either an oxime ether or an oxime ester group were designed and prepared based on the strategy of molecular hybridization, and their antifungal activities against five plant pathogenic fungi were also investigated. The results indicated that the majority of the compounds containing oxime ether demonstrated outstanding in vitro antifungal activity against R. solani, and some compounds also displayed pronounced antifungal activities against Sclerotinia sclerotiorum and Botrytis cinerea. Particularly, compound 5e exhibited the most promising antifungal activity against R. solani with an EC50 value of 0.039 μg/mL, which was about 20-fold better than that of boscalid (EC50 = 0.799 μg/mL) and 4-fold more potent than fluxapyroxad (EC50 = 0.131 μg/mL). Moreover, the results of the detached leaf assay showed that compound 5e could suppress the growth of R. solani in rice leaves with significant protective efficacies (86.8%) at 100 μg/mL, superior to boscalid (68.1%) and fluxapyroxad (80.6%), indicating promising application prospects. In addition, the succinate dehydrogenase (SDH) enzymatic inhibition assay revealed that compound 5e generated remarkable SDH inhibition (IC50 = 2.04 μM), which was obviously more potent than those of boscalid (IC50 = 7.92 μM) and fluxapyroxad (IC50 = 6.15 μM). Furthermore, SEM analysis showed that compound 5e caused a remarkable disruption to the characteristic structure and morphology of R. solani hyphae, resulting in significant damage. The molecular docking analysis demonstrated that compound 5e could fit into the identical binding pocket of SDH through hydrogen bond interactions as well as fluxapyroxad, indicating that they had a similar antifungal mechanism. The density functional theory and electrostatic potential calculations provided useful information regarding electron distribution and electron transfer, which contributed to understanding the structural features and antifungal mechanism of the lead compound. These findings suggested that compound 5e could be a promising candidate for SDHI fungicides to control R. solani, warranting further investigation.

Structure-Activity Relationship Studies on Highly Functionalized Pyrazole Hydrazones and Amides as Antiproliferative and Antioxidant Agents

Aminopyrazoles represent interesting structures in medicinal chemistry, and several derivatives showed biological activity in different therapeutic areas. Previously reported 5-aminopyrazolyl acylhydrazones and amides showed relevant antioxidant and anti-inflammatory activities. To further extend the structure-activity relationships in this class of derivatives, a novel series of pyrazolyl acylhydrazones and amides was designed and prepared through a divergent approach. The novel compounds shared the phenylamino pyrazole nucleus that was differently decorated at positions 1, 3, and 4. The antiproliferative, antiaggregating, and antioxidant properties of the obtained derivatives 10-22 were evaluated in in vitro assays. Derivative 11a showed relevant antitumor properties against selected tumor cell lines (namely, HeLa, MCF7, SKOV3, and SKMEL28) with micromolar IC50 values. In the platelet assay, selected pyrazoles showed higher antioxidant and ROS formation inhibition activity than the reference drugs acetylsalicylic acid and N-acetylcysteine. Furthermore, in vitro radical scavenging screening confirmed the good antioxidant properties of acylhydrazone molecules. Overall, the collected data allowed us to extend the structure-activity relationships of the previously reported compounds and confirmed the pharmaceutical attractiveness of this class of aminopyrazole derivatives.

Design, synthesis, and anticancer evaluation of alkynylated pyrrole derivatives

A series of alkynylated pyrrole derivatives were meticulously designed, drawing inspiration from the structure of 3-alkynylpyrrole-2,4-dicarboxylates, which were synthesized via a cyclization process involving methylene isocyanides and propiolaldehydes under mild conditions. These derivatives were subsequently subjected to evaluation for their anticancer properties against a panel of cell lines, including U251, A549, 769-P, HepG2, and HCT-116. According to the detailed analysis of structure-activity relationship, compound 12l emerged as the most promising molecule, with IC50 values of 2.29 ± 0.18 and 3.49 ± 0.30 μM toward U251 and A549 cells, respectively. Subsequent mechanistic investigations revealed that compound 12l exerts its effects by arresting the cell cycle in the G0/G1 phase and inducing apoptosis specifically in A549 cells. These innovative alkynylated pyrrole derivatives hold the potential to serve as a valuable template for the discovery of novel anticancer molecules.

A novel class of pyrazole analogues as aurora kinase A inhibitor: design, synthesis, and anticancer evaluation

Pyrazole, as a small molecule, was discovered for higher cytotoxicity and affinity towards Aurora-A kinase. Based on these facts, a novel pyrazole substituted at the 4th position was designed, synthesized, and evaluated against MCF-7, MDA-MB-23, and Vero (non-cancerous kidney cell) cell lines. Compounds5hand5eexhibited greater cytotoxicity in the series against MCF-7 and MDA-MB-231, with GI50 values of 0.12 µM and 0.63 µM, respectively, as compared to Imatinib (GI50 values of 16.08 µM and 10.36 µM). All of the compounds displayed selective cytotoxicity against cancer cells but not on normal Vero cells, supporting the design strategy to be a selective anticancer agent. Furthermore, compounds 5h and 5e inhibited Aurora-A kinase with IC50 values of 0.78 µM (4.70-fold) and 1.12 µM (2.84-fold), respectively, as compared to alisertib (IC50 = 3.36 µM). In addition, compound 5h significantly arrested the cell cycle at G2/M (34.89 %, 5.56-fold) and the apoptotic phase (25.04 %, 11.81-fold) compared to the control. It also triggered an increase in early (7.43 %) and late (14.89 %) phase apoptosis compared to vehicle (0.235 and 0.36 %, respectively), causing 37.89-fold higher total apoptosis in the annexin-V assay. These data imply that Aurora-A kinase inhibition may be linked to apoptosis induction and cell cycle arrest. Furthermore, their higher docking score in the study confirmed evidence of Aurora-kinase suppression. It was observed that fluorine and imidazole increased the H-bond and lipophilic interactions with the binding residue. Also, the substitution of electron-rich and lipophilic groups increased hydrophobic interactions. Moreover, the three-atom linkage (CH2NHCH2) expanded compound 5h to fill the cavity. Based on current findings, it is concluded that compounds 5h and 5e with strong Aurora-A kinase suppression may be promising anticancer agents.

Pyrazole: an emerging privileged scaffold in drug discovery

Pyrazole or 1H-pyrazole, a five-membered 1,2-diazole, is found in several approved drugs and some bioactive natural products. A myriad number of derivatives of this small molecule have been reported in clinical and preclinical studies for the potential treatment of several diseases. The number of drugs containing a pyrazole nucleus has increased significantly in the last 10 years. Some of the best-selling drugs in this class are ibrutinib, ruxolitinib, axitinib, niraparib and baricitinib, and are used to treat different types of cancers; lenacapavir to treat HIV; riociguat to treat pulmonary hypertension; and sildenafil to treat erectile dysfunction. Several aniline-derived pyrazole compounds have been reported as potent antibacterial agents with selective activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Here, we discuss the pyrazole-derived drugs reported up to September 2023.

The Importance of the Pyrazole Scaffold in the Design of Protein Kinases Inhibitors as Targeted Anticancer Therapies

The altered activation or overexpression of protein kinases (PKs) is a major subject of research in oncology and their inhibition using small molecules, protein kinases inhibitors (PKI) is the best available option for the cure of cancer. The pyrazole ring is extensively employed in the field of medicinal chemistry and drug development strategies, playing a vital role as a fundamental framework in the structure of various PKIs. This scaffold holds major importance and is considered a privileged structure based on its synthetic accessibility, drug-like properties, and its versatile bioisosteric replacement function. It has proven to play a key role in many PKI, such as the inhibitors of Akt, Aurora kinases, MAPK, B-raf, JAK, Bcr-Abl, c-Met, PDGFR, FGFRT, and RET. Of the 74 small molecule PKI approved by the US FDA, 8 contain a pyrazole ring: Avapritinib, Asciminib, Crizotinib, Encorafenib, Erdafitinib, Pralsetinib, Pirtobrutinib, and Ruxolitinib. The focus of this review is on the importance of the unfused pyrazole ring within the clinically tested PKI and on the additional required elements of their chemical structures. Related important pyrazole fused scaffolds like indazole, pyrrolo[1,2-b]pyrazole, pyrazolo[4,3-b]pyridine, pyrazolo[1,5-a]pyrimidine, or pyrazolo[3,4-d]pyrimidine are beyond the subject of this work.