A rapid approach for the copper, amine, and ligand-free Sonogashira coupling of 4-methyl-7-nonafluorobutylsulfonyloxy coumarins under microwave irradiation

Evaluation of Anti-Inflammatory and Anti-Tubercular Activity of 4-Methyl-7-Substituted Coumarin Hybrids and Their Structure Activity Relationships

Four sets of previously synthesized 4-methyl-7-substituted coumarin derivatives were screened for their in vitro anti-inflammatory and anti-tubercular activities. The anti-inflammatory potential of 3a-t, 5a-o, 6a-n, and 7a-f synthesized compounds was evaluated by an anti-denaturation assay using diclofenac sodium as the reference standard. Evaluation of the anti-tuberculous activity of the mentioned compounds was performed by the Resazurin test method against four different TB strains using rifampicin and isoniazid as reference drugs. Based on the anti-inflammatory results, compounds 3o, 5f, 6c, and 7d proved to be the most active compounds in their respective series. Additionally, compounds 3k-n, 5b-d, 6d-f, 6k, 7a, and 7f were found to be the most potent anti-tuberculous agents. In fact, most of the screened compounds exhibited promising activity profiles compared to the respective standard drugs. The structure-activity connections revealed a few intriguing aspects, indicating that the presence of electron-donating and nitrogen-rich fragments boost the anti-inflammatory effects of the examined compounds. However, the presence of electron-withdrawing substituents was required to boost the anti-tubercular activity of the evaluated compounds.

Microwave-Assisted Palladium-Catalyzed Cross-Coupling Reactions: Generation of Carbon–Carbon Bond

Cross-coupling reactions furnishing carbon–carbon (C–C) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Negishi, Heck, Kumada, Sonogashira, Stille, Suzuki, and Hiyama, utilizing palladium or its salts as catalysis have, for decades, attracted and inspired researchers affiliated with academia and industry. Tremendous efforts have been paid to develop and achieve more sustainable reaction conditions, such as the reduction in energy consumption by applying the microwave irradiation technique. Chemical reactions under controlled microwave conditions dramatically reduce the reaction time and therefore resulting in increase in the yield of the desired product by minimizing the formation of side products. In this review, we mainly focus on the recent advances and applications of palladium catalyzed cross-coupling carbon–carbon bond formation under microwave technology.

Design, Synthesis and Antibacterial Activity of Coumarin-1,2,3-triazole Hybrids Obtained from Natural Furocoumarin Peucedanin

Synthesis of 1,2,3-triazole-substituted coumarins and also 1,2,3-triazolyl or 1,2,3-triazolylalk-1-inyl-linked coumarin-2,3-furocoumarin hybrids was performed by employing the cross-coupling and copper catalyzed azide-alkyne cycloaddition reaction approaches. The synthesized compounds were evaluated for their in vitro antibacterial activity against Staphylococcus aureus, Bacillius subtilis, Actinomyces viscosus and Escherichia coli bacterial strains. Coumarin-benzoic acid hybrids 4с, 42с and 3-((4-acetylamino-3-(methoxycarbonyl)phenyl)ethynyl)coumarin (29) showed promising activity against S. aureus strains, and the 1,2,3-triazolyloct-1-inyl linked coumarin-2,3-furocoumarin hybrid 37c was endowed with high selectivity against B. subtilis and E. coli species. The in vitro antibacterial activity of 4с, 29, 37c and 42с can potentially be compared with that of a number of modern antibiotic drugs used in the clinic, suggesting promising prospects for further research. A detailed study of the molecular interactions with the targeted protein MurB was performed using docking simulations and the obtained results are quite promising.

Synthesis and antimycobacterial activity of 1-(β-d-Ribofuranosyl)-4-coumarinyloxymethyl- / -coumarinyl-1,2,3-triazole

A series of β-d-ribofuranosyl coumarinyl-1,2,3-triazoles have been synthesized by Cu-catalyzed cycloaddition reaction between azidosugar and 7-O-/7-alkynylated coumarins in 62-70% overall yields. The in vitro antimycobacterial activity evaluation of the synthesized triazolo-conjugates against Mycobacterium tuberculosis revealed that compounds were bactericidal in nature and some of them were found to be more active than one of the first line antimycobacterial drug ethambutol against sensitive reference strain H37Rv, and 7 to 420 times more active than all four first line antimycobacterial drugs (isoniazid, rifampicin, ethambutol and streptomycin) against multidrug resistant clinical isolate 591. Study of in silico pharmacokinetic profile indicated the drug like characters for the test molecules. Further, transmission electron microscopic experiments revealed that these compounds interfere with the constitution of bacterial cell wall possibly by targeting mycobacterial InhA and DNA gyrase enzymes. Study conducted on the activities of the test compounds on bacterial InhA and DNA gyrase revealed that the most bactericidal test compound, N¹-(β-d-ribofuranosyl)-C⁴-(4-methylcoumarin-7-oxymethyl)-1,2,3-triazole (6b) and its corresponding directly linked conjugate N¹-(β-d-ribofuranosyl)-C⁴-(4-methylcoumarin-7-yl)-1,2,3-triazole (11b) significantly inhibited the activity of both the enzymes. The results were further supported by molecular docking studies of the compound 6b and 11b with bacterial InhA and DNA gyrase B enzymes. Further, the cytotoxicity study of some of the better active compounds on THP-1 macrophage cell line using MTT assay showed that the synthesized compounds were non-cytotoxic.

Mo(CO)6 as a Solid CO Source in the Synthesis of Aryl/Heteroaryl Weinreb Amides under Microwave-Enhanced Condition

The facile transformation of aryl/heteroaryl nonaflates into corresponding amides via Pd-catalyzed aminocarbonylation using Mo(CO)6 as a solid CO source under microwave-enhanced condition is reported. The method was found to be tolerant with respect to a diverse range of electronically biased aryl/heteroaryl nonaflates, and exceptional yields were obtained. The optimized protocol was further extended to a diverse range of amines.