A One-Pot Biginelli Synthesis and Characterization of Novel Dihydropyrimidinone Derivatives Containing Piperazine/Morpholine Moiety

A Profound Insight into the Structure-activity Relationship of Ubiquitous Scaffold Piperazine: An Explicative Review

Despite extensive research in the field of drug discovery and development, still there is a need to develop novel molecular entities. Literature reveals a substantial heterocyclic nucleus named, piperazine, which shows an immense therapeutic voyage. For several decades, molecules having the piperazine nucleus have entered the market as a drug exhibiting biological potential. It was known to possess antipsychotic, antihistamine, antianginal, antidepressant, anticancer, antiviral, cardioprotective, and anti-inflammatory activity with a specific basis for structural activity relationship. Thus, it is regarded as a key structural feature in most of the already available therapeutic drugs in the market. Reports also suggest that the extensive utilization of these currently available drugs having a piperazine nucleus shows increasing tolerance significantly day by day. In addition to this, various other factors like solubility, low bioavailability, cost-effectiveness, and imbalance between pharmacokinetics and pharmacodynamics profile limit their utilization. Focusing on that issues, various structural modification studies were performed on the piperazine moiety to develop new derivatives/analogs to overcome the problems associated with available marketed drugs. Thus, this review article aims to gain insight into the number of structural modifications at the N-1 and N-4 positions of the piperazine scaffold. This SAR approach may prove to be the best way to overcome the above-discussed drawbacks and lead to the design of drug molecules with better efficacy and affinity. Hence, there is an urgent need to focus on the structural features of this scaffold which paves further work for deeper exploration and may help medicinal chemists as well as pharmaceutical industries.

Nickel-Catalyzed Reductive Borylation of Enaminones via C(sp2)-N Bond Cleavage

The cleavage and transformation of alkenyl C(sp²)-N bonds is a significant synthetic challenge. Herein we described an unprecedented nickel-catalyzed reductive borylation of enaminones to synthesize β-ketone boronic esters. Notably, B₂pin₂ played the dual role in this process, and water served as a hydrogen source, which was transferred to target products. The air-stable nickel catalyst was applied to the cleavage of alkenyl C(sp²)-N bonds, concomitant with the reductive process of the alkenyl boronic ester intermediates, on the basis of the mechanism study.

Facile synthesis and anticancer activity of novel dihydropyrimidinone derivatives

The enaminone, (2E)-3-(dimethylamino)-1-(3,4,5-trimethoxyphenyl) prop-2-en-1-one was prepared by refluxing 3,4,5-trimethoxy acetophenone with dimethylformamide dimethylacetal (DMF–DMA) without solvent for 12 h. The dihydropyrimidinone derivatives (1–9) were prepared by reacting enaminone, substituted benzaldehydes and urea in glacial acetic acid. The compounds (1–9) were synthesized in significant yield using one step multicomponent reaction. Structures of all the novel synthesized compounds were characterized and confirmed by various spectroscopic methods. The compounds were evaluated for their anti-cancer activity against HepG2 cancer cell line. Compound 9 displayed significant anti-cancer activity. During the apoptotic assay, it showed a significant increase in necrosis from 1.97% to 12.18% as compared to the control. Mechanism of anti-proliferation was performed by cell cycle distribution assay, which showed a decrease in G2+M from 12.90 to 8.13 as compared to control.

Biginelli Synthesis of Novel Dihydropyrimidinone Derivatives Containing Phthalimide Moiety

A new series of novel Biginelli compounds, 5-benzoyl-substituted phenyl-3,4-dihydropyrimidin-2(1H)-one-1H-isoindole-1,3(2H)-dione (1−10), were synthesized from enaminone, 2-{4-[(2E)-3-(dimethylamino)prop-2-enoyl]phenyl}-1H-isoindole-1,3(2H)-dione (IV), which was synthesized by refluxing 2-(4-acetylphenyl)-1H-isoindole-1,3(2H)-dione (III), with dimethylformamide-dimethylacetal (DMF-DMA) without solvent for 12 h. The compound 2-(4-acetylphenyl)-1H-isoindole-1,3(2H)-dione (III) was obtained by reacting phthalic anhydride (I) with para-aminoacetophenone (II) in glacial acetic acid for 2 h. The dihydropyrimidinone derivatives containing phthalimide moiety (1–10) were obtained by reacting enaminone, 2-{4-[(2E)-3-(dimethylamino) prop-2-enoyl] phenyl}-1H-isoindole-1,3(2H)-dione (IV), with urea and different substituted benzaldehydes in the presence of glacial acetic acid for 3 h. Simple and efficient method was employed to synthesize the dihydropyrimidinone derivatives containing phthalimide moiety. Structures of all the synthesized compounds were characterized by spectroscopic methods.

Enaminone-Derived Pyrazoles with Antimicrobial Activity

A series of pyrazoles derived from the substituted enaminones were synthesized and were evaluated for antimicrobial activity. All the compounds were characterized by the spectral data and elemental analysis. The synthesized compounds were initially screened for their antimicrobial activity against ATCC 6538, NCTC 10400, NCTC 10418, and ATCC 27853. During initial screening, compounds (P1, P6, and P11) presented significant antimicrobial activity through disc diffusion assay. These compounds were further evaluated for antimicrobial activity at different time points against Gram-positive and Gram-negative bacteria and presented significant activity for 6 hours. The activity was found to be greater against Gram-positive bacteria. In contrast at 24 hours, the activity was found only against Gram-positive bacteria except compound (P11), showing activity against both types of bacteria. Compound (P11) was found to have highest activity against both Gram-positive and Gram-negative bacteria.

Synthesis and Characterization of Novel Biginelli Dihydropyrimidinone Derivatives Containing Imidazole Moiety

Enaminone, (2E)-1-[4-(1H-imidazol-1-yl) phenyl]-4-methylpent-2-en-1-one (II) was synthesized by refluxing 1-[4-(1H-imidazol-1-yl) phenyl] ethan-1-one (I) with dimethylforamide dimethylacetal (DMF–DMA) under solvent-free condition for 12 hours. Finally, the dihydropyrimidinone derivatives containing imidazole moiety (1–15) were obtained by reacting enaminone, (2E)-1-[4-(1H-imidazol-1-yl) phenyl]-4-methylpent-2-en-1-one (II) with urea and different substituted benzaldehydes in the presence of glacial acetic acid. Dihydropyrimidinone derivatives containing imidazole moiety were synthesized in excellent yield by means of a simple and efficient method. All the compounds were confirmed by elemental analysis. The structures of all the compounds were confirmed by modern spectroscopic methods.