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

<div><p></p><p>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.</p></div

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

<p>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.</p

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

<p>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.</p

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

<p></p> <p>The first simple, metal free, and efficient protocol has been established for the methylthiolation of structurally diverse 4-bromomethyl-2<i>H</i>-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]-2<i>H</i>-chromen-2-ones were characterized by ¹H, ¹³C NMR, and single-crystal X-ray analysis.</p

Design, synthesis, characterization, photophysical and pH chemosensor studies of novel 2,4,6-trisubstituted pyridines

<p>For the application in organic electronics as well as pH meters, a series of novel 2,4,6-trisubstituted pyridines have been synthesized by the reaction of substituted aromatic aldehydes and substituted 3-acetylcoumarin with ammonium acetate. The structures of all the new compounds were characterized by IR, NMR, and GC–MS analysis. The important photo physical prerequisites for organoelectronic such as optical absorption and thermal stability were determined for the synthesized molecules. Optical properties were studied by UV–visible absorption and fluorescence spectroscopy. Optical band gaps of the 2,4,6-trisubstituted pyridines were found to be around 3.01–3.06 eV as calculated from their onset absorption edge. The pH-dependent changes in the fluorescence intensity suggest that 2,4,6-trisubstituted pyridines are useful applicants in intracellular pH meters.</p