Synthesis of 7-hydroxydibenzopyran-6-ones via benzannulation of coumarins

We have successfully demonstrated a facile synthesis of a variety of 7-hydroxydibenzopyran-6-ones via a two-step protocol from 3-acylcoumarins having a latent Nazarov dienone functionality. Condensation of 3-acylcoumarins and ethyl cyanoacetate under basic (wet K₂CO₃) and microwave irradiation conditions followed by decarboethoxylative aromatization with Br₂ or DDQ furnished dibenzopyran-6-ones in high yields. The formation of ring C of the dibenzopyran-6-one motif critically depended on an active methylene compound and C7 substitution on coumarins. The Ar-Br or ArOTf substitution in dibenzopyran-6-ones was leveraged for the palladium-catalysed Suzuki coupling with diverse aryl boronic acids to increase the structural diversity. Reductive decyanation of C10 cyano dibenzopyran-6-ones furnished some of the isomers of urolithin A.

Synthesis of the Sex Pheromone of the Oleander Scale ( Aspidiotus nerii)

A total synthesis of the oleander scale [ Aspidiotus nerii (Bouche)] sex pheromone, the unique sesquiterpenoid containing a cyclobutane moiety of this class of compounds, has been developed. In order to implement this sex pheromone as a new environmentally friendly tool to manage this pest, a more cost-effective, multigram synthesis was required. This new synthetic route, having a Blaise reaction, iron-catalyzed carbon-carbon coupling, and [2 + 2] photocycloaddition reactions as key steps, provides a general access to 4-alkyl lactones as well as a robust access to the target sex pheromone. Starting from readily available compounds as 3-hydroxypropanenitrile, ethyl bromoacetate, and 2-acetyl butyrolactone, the synthetic sequence afforded the A. nerii sex pheromone with minimum intermediate purification and good overall yield in nine linear steps.

An “off–on” fluorescent naphthalimide-based sensor for anions: its application in visual F− and AcO− discrimination in a self-assembled gel state

Herein, we report a novel fluorescent organogelator that could discriminate F⁻ from AcO⁻ in both solution and gel systems.

Aggregation-induced emission in fluorophores containing a hydrazone structure and a central sulfone: restricted molecular rotation

SEM and fluorescence microscope images of BAHDS derivatives showed their nanoscale size and strong fluorescence in the solid state.

‘Naked-eye’ colorimetric/fluorimetric detection of F− ions by biologically active 3-((1H-indol-3-yl)methyl)-4-hydroxy-2H-chromen-2-one derivatives

An improved synthetic protocol has been developed to construct highly functionalized heterologous alkyl and benzyl indolyl-coumarin derivatives using a rapid, catalyst-free and solvent-free one-pot three-component reaction of indole, aldehyde and 4-hydroxy-coumarin.

Microwave-assisted synthesis and photophysical studies of novel fluorescent N-acylhydrazone and semicarbazone-7-OH-coumarin dyes

Emissive 7-OH-coumarins were synthesized by a microwave-assisted protocol and spectral changes were induced after conformational changes in low polarity media.