Bahubali M. Chougala

Effects of Base for the Efficient Synthesis of 4-Formylcoumarins and 4-Formylcarbostyrils

Abstract The first efficient transformation of 4-bromomethylcoumarins and 4-bromomethylcarbostyrils to 4-formylcoumarins and 4-formylcarbostyril under aqueous conditions has been achieved by modifying the Kornblum method, resulting in excellent yield. The experimental method is very simple and economical; no further purification is required and the experimental conditions have been optimized. All the isolated compounds were characterized by infrared, NMR, and mass spectroscopy, and some of the compounds have been analyzed by single-crystal x-ray analysis. GRAPHICAL ABSTRACT

3,4-Dihydropyrimidinone-coumarin analogues as a new class of selective agent against S. aureus: Synthesis, biological evaluation and molecular modelling study

Bacterial infections are increasingly difficult to combat as bacteria evolve resistance to antibiotic drugs and have severely compromised the arsenal of antibiotic drugs. On the other hand matrix metalloproteinases (MMPs) play a fundamental role in inflammation and extracellular matrix degradation in physiological and pathological conditions. In search of potent antibiotic, taking coumarin and dihydropyrimidinone as lead compound, a green, eco-friendly and efficient protocol has been developed and synthesized the dihydropyrimidin-2(1H)-one/thione derivatives of coumarin 3/4 from substituted 4-formylcoumarins 2 and ethylacetoacetate using urea/thiourea in the presence of catalytic amount of ceric ammonium nitrate is reported. All the synthesized compounds were evaluated for their antibacterial activity against four bacterial strains by broth dilution method. The tested compounds have exhibited promising in vitro potency with low MIC values against the drug susceptive S. aureus strain with low MIC values ranging from 0.2 to 6.25μg/mL. The in vivo anti-inflammatory potency of 3a-e and 4a-e by gelatin zymography is comparable to that of tetracycline. Molecular docking study performed for all the synthesized compounds with S. aureus DNA gyrase and results obtained were quite promising.

Synthesis, anti-microbial and anti-cancer evaluation study of 3-(3-benzofuranyl)-coumarin derivatives

The series of 3-coumarin-substituted benzofuran derivatives 4a–4j have been synthesized under optimized experimental condition with excellent yields. All the isolated compounds were characterized and screened anti-microbiological and anti-cancer activity. The anti-microbiological results observed were extremely good against S. aureus, C. albicans and A. niger. The comparative docking studies with gyrase type IIA topoisomerase from mycobacteriumtuberculosis docked with ligands and 4j have found lowest docked energy.

One-pot, green synthetic route for construction of coumarin C-4 bridged 2,6-dicyanoanilines and their photophysical study

ABSTRACT A highly selective and more efficient green protocol has been developed via a one-pot, three-component approach for the synthesis of coumarin 2,6-dicyanoanilines in aqueous ethanol. From the mechanism, two molecules of malanonitrile condensed with aldehyde and ketone resulted in the adducts, which on intramolecular cyclization via two new C-C bonds formed to afford the title compound. The present methodology offers simplified purification and environmentally benign conditions, avoids the use of toxic solvents, and gives excellent yield with high purity. All the synthesized compounds have been characterized by spectral analysis. Optical and thermal screening studies of all newly synthesized compounds showed excellent photophysical and thermal stability properties. GRAPHICAL ABSTRACT

Design and synthesis of coumarin–imidazole hybrid and phenyl-imidazoloacrylates as potent antimicrobial and antiinflammatory agents

An improved one pot, multi-component synthesis of tri- and tetrasubstituted coumarin–imidazole hybrid has been synthesized at C4 position in good to excellent yield. The reaction was performed under various catalysts and optimization condition results obtained are satisfactory. Wherein, trisubstituted coumarin–imidazole hybrid compounds were converted into phenyl-imidazole acrylates. Further, all the newly synthesized compounds were screened for their antimicrobial activity against Gram-positive Bacillus flexus and Gram-negative Pseudomonas spp. bacterial strains and two strains of fungi studies having Scopulariopsis spp. and Aspergillus terreus organisms. Similarly, antiinflammatory activity of all the compounds was screened against MMP-2 and MMP-9. Both antimicrobial and antiinflammatory results are excellent, among all compounds, sodium acrylate compounds are quite promising against microbial strains and matrix metalloproteins (MMPs). All the isolated compounds were characterized by IR, NMR, and mass spectral analysis.Graphical abstract

An efficient and catalyst free methylthiolation of 4-(bromomethyl)-2H-chromen-2-ones with DMSO

GRAPHICAL ABSTRACT ABSTRACT The first simple, metal free, and efficient protocol has been established for the methylthiolation of structurally diverse 4-bromomethyl-2H-chromen-2-ones using dimethyl sulfoxide (DMSO) as methylthiolation source at higher temperature. The experimental method is highly economical and provides excellent yields of highly pure products which do not require further purification. All novel 4-[(methylthio)methyl]-2H-chromen-2-ones were characterized by 1H, 13C NMR, and single-crystal X-ray analysis.

Synthesis of coumarin analogous of decursivine derivatives

ABSTRACT The first synthesis of decursivine derivatives of coumarins is described via intramolecular Friedel–Craft aromatic alkylation. The Lewis acid (LA)–catalyzed reaction facilitated the rapid construction of the desired product. The targeted molecule obtained has been confirmed by spectral analysis. GRAPHICAL ABSTRACT

Highly stereoselective direct aldol reaction of 4-formylcoumarins with acetone catalyzed by L-proline in water–acetone mixtures

ABSTRACT Organocatalyzed direct intermolecular aldol reactions have been developed for substituted 4-formylcoumarins with acetone in water using L-proline and phthalimido-prolinamide catalysts without use of additives. Stereoselective products obtained were in excellent yields (up to 97%) with high purity (up to 99%) and enatioselectivities (up to 95%). The isolated compounds were confirmed by infrared, NMR, high-performance liquid chromatography, and mass spectrometry and some of them by single-crystal x-ray crystallography. GRAPHICAL ABSTRACT

Efficient and Convenient Synthesis of 1,4-Benzoxazines, 1,4-Benzothiazines, Spiro-1,4-benzoxazines, and Spiro-1,4-benzothiazines

Abstract An efficient, convenient synthesis of 1,4-benzoxazines, 1,4-benzothiazines, spiro-1,4-benzoxazines, and spiro-1,4-benzothiazines derivatives was accomplished in good yields via the novel intramolecular cyclization mediated by mild base K2CO3 in ethanol solvent. A variety of substrates can participate in the process with good yields, making this methodology have broad applicability. All the structures of synthesized compound have been confirmed by spectral analysis. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications ® to view the free supplemental file. GRAPHICAL ABSTRACT