Bis(benzofuran-enaminone) hybrid possessing piperazine linker: Versatile precursor for microwave assisted synthesis of bis(pyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidines)

MRSA Inhibitory Activity of Some New Pyrazolo[1,5-a]pyrimidines Linked to Arene and/or Furan or Thiophene Units

Methicillin-resistant Staphylococcus aureus (MRSA) is a major contributor to hospital-acquired infections and is highly resistant to treatment. Ongoing research focuses on developing new antimicrobial medications to prevent the spread of resistance. A facile method was employed to efficiently synthesize new pyrazolo[1,5-a]pyrimidines in 84-93 % yields by reacting 4-benzyl-1H-pyrazole-3,5-diamine with the respective α,β-unsaturated ketones. The reaction was carried out in ethanol containing 1.2 equivalents of potassium hydroxide at reflux for 5-6 h. The new products are attached to a para-substituted aryl group with variable electronic properties at pyrazolopyrimidine-C5, in addition to one of three units at C7, namely phenyl, thiophen-2-yl, or furan-2-yl units. A wide spectrum of antibacterial activity was displayed by the new pyrimidines against six different bacterial strains. In general, pyrimidines attached to furan-2-yl units at C7, in addition to another aryl unit at C5, attached to 4-Me or 4-OMe groups, demonstrate significant antibacterial activity, particularly against S. aureus strain. They had MIC/MBC of 2.5/5.1 and 2.4/4.9 μM, respectively, which exceeded that of ciprofloxacin. Moreover, they demonstrate more effective MRSA inhibitory activity than linezolid, with MIC/MBC values up to 4.9/19.7 and 2.4/19.7 μM against MRSA ATCC:33591 and ATCC:43300 strains, respectively.

[3+2] Cycloaddition Synthesis of New Piperazine-Linked Bis(chromene) Hybrids Possessing Pyrazole Units as Potential Acetylcholinesterase Inhibitors

Two series of piperazine-linked bis(chromene) hybrids that are attached to pyrazole units were synthesized in the current study. Both series are attached to an acyl unit at pyrazole-C3, with one series attached to an acetyl unit and the other to an ethoxycarbonyl unit. A [3+2] cycloaddition protocol was conducted to produce the target hybrids with good yields by reacting the appropriate hydrazonoyl chlorides with chromene-based bis(enaminone) in dioxane containing triethylamine at reflux for 4 h. New hybrids were tested for acetylcholinesterase inhibitory activity at concentrations of 15 and 25 μM, as well as their ability to quench 2,2-diphenylpicrylhydrazyl (DPPH) free radicals at a concentration of 25 μg/mL. In general, the inhibitory activity is related to the electronic properties of the para-substituent that is attached to the arene unit at pyrazole-N1. Furthermore, the acyl unit attached to pyrazole-C3 has a significant effect on the new hybrids' inhibitory activity. At the previous concentrations, the (3-acetylpyrazole)-linked hybrid attached to p-NO₂ units demonstrated the best acetylcholinesterase inhibitory activity, with inhibition percentages of 79.7 and 90.2. Furthermore, the previous hybrid demonstrated the most effective DPPH inhibitory activity, with an inhibition percentage of 87.5.

3-Aminopyrazolo[3,4-b]pyridine: Effective Precursor for Barium Hydroxide-Mediated Three Components Synthesis of New Mono- and Bis(pyrimidines) with Potential Cytotoxic Activity

In this study, an efficient one-pot procedure for preparing a new series of pyrazolo[3,4-b]pyridine-fused pyrimidines was described. The target hybrids were developed through a three-component reaction of 3-amino-1H-pyrazolo[3,4-b]pyridine, benzaldehydes, and acetophenones (molar ratio 1 : 1 : 1). The best conditions for the previous reaction were 2.5 equivalents of barium hydroxide in DMF at 150 °C for 6 h. New bis(pyrimidines) were synthesized in high yields using a similar one-pot reaction protocol with some modifications. Thus, two equivalents of each of the appropriate acetophenones and 3-aminopyrazolopyridine were reacted with one equivalent of the appropriate bis(aldehydes). The reaction was carried out at 150 °C for 8 h using 4.5 equivalents of barium hydroxide in DMF. Repeating the previous reaction with the appropriate bis(acetyl) derivatives and benzaldehydes resulted in good yields of the target bis(pyrimidines). The in vitro cytotoxic activity of new pyrimidines against the MCF-7, HEPG2, and Caco2 cell lines was evaluated using the reference doxorubicin (IC₅₀ values of 4.34-6.97 μM). Hybrid 6h had the best activity against Caco2 and MCF-7 cell lines, IC₅₀ values of 12.62 and 14.50 μM, respectively. The IC₅₀ values for hybrids 6c, 6e, and 6f against MCF-7 and Caco2 cell lines were 23.99-41.69 and 33.14-43.33 μM, respectively. Furthermore, hybrid 6e displayed IC₅₀ value of 20.06 μM HEPG2 cell lines, while the hybrids 6c, 6f and 6h exhibited IC₅₀ values ranging between 26.29-50.51 μM. Furthermore, hybrid 6e had an IC₅₀ value of 20.06 μM for the HEPG2 cell lines, whereas hybrids 6c, 6f, and 6h had IC₅₀ values ranging from 26.29 to 50.51 μM.

Functional Pyrazolo[1,5-a]pyrimidines: Current Approaches in Synthetic Transformations and Uses As an Antitumor Scaffold

Pyrazolo[1,5-a]pyrimidine (PP) derivatives are an enormous family of N-heterocyclic compounds that possess a high impact in medicinal chemistry and have attracted a great deal of attention in material science recently due to their significant photophysical properties. Consequently, various researchers have developed different synthesis pathways for the preparation and post-functionalization of this functional scaffold. These transformations improve the structural diversity and allow a synergic effect between new synthetic routes and the possible applications of these compounds. This contribution focuses on an overview of the current advances (2015-2021) in the synthesis and functionalization of diverse pyrazolo[1,5-a]pyrimidines. Moreover, the discussion highlights their anticancer potential and enzymatic inhibitory activity, which hopefully could lead to new rational and efficient designs of drugs bearing the pyrazolo[1,5-a]pyrimidine core.