An Efficient Microwave-Assisted Propylphosphonic Anhydride (T3P®)-Mediated One-Pot Chromone Synthesis via Enaminones

Domino Approach to Heterocycles-Based Unsymmetrical Triarylmethanes through Heteroannulation of 2-(2-Enynyl)-pyridines with Enaminones

Herein, we report a copper-catalyzed protocol to access unsymmetrical triarylmethanes containing both indolizine and the chromone scaffolds in the same molecule via a 5-endo-dig cyclization of 2-(2-enynyl)-pyridines followed by reaction with 2-hydroxyaryl enaminones. A variety of 2-hydroxyaryl enaminones and 2-(2-enynyl)-pyridines were subjected to reaction under the optimal reaction conditions, and the respective triarylmethanes were obtained in good to excellent yields.

Discovery of 5,7-Dimethoxy-2-(3,4,5-trimethoxyphenoxy)-chromen-4-one with Lipid Lowering Effects in Hepatocytes

The population with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) is increasing. However, no medicine is indicated for treating these diseases clinically nowadays. Therefore, there is an urgent need to develop a new drug to overcome NAFLD and NASH. Capillarisin, a 2-phenoxychromone originating from Artemisia capillaris Thunb., is well-known for its liver-protective effects. As a result, a series of 2-phenoxychromones was prepared and evaluated for its protective activity against lipid droplet formation in oleic acid (OA)-treated Huh7 cells by means of high-content screening. In the light of the results, the compounds with trimethoxy groups on the phenyl ring possessed better inhibitory properties against lipid accumulation in Huh7 cells, compared to other functional groups on the same ring. Nonetheless, the compounds with a hydroxy group at the C-5 position of the chromone exhibited apparent cytotoxicity. Finally, the active compound, 5,7-dimethoxy-2-(3,4,5-trimethoxyphenoxy)-chromen-4-one (7e), with an IC₅₀ value of 32.2 ± 2.1 μM against lipid accumulation and no significant cytotoxicity, reduced the accumulation of lipid droplets by up-regulating peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) to facilitate the catabolism of fat, which shows promise for further optimization to manage NAFLD and NASH.

Iodine-Mediated Synthesis of 2-(Methylthio)-4H-chromen-4-ones and Study of Their Halogenation Reactions

An efficient iodine-mediated method is developed for the synthesis of functionalized 2-(methylthio)-4H-chromen-4-ones by intramolecular cyclization of easily accessible 1-(2-benzyloxy-aryl)-3,3-bis-methylsulfanyl-propenones. The synthesized chromen-4-ones turn out to be a key precursor for various kinds of chemical reactions. Mechanistically, we observed that iodine-mediated intramolecular cyclization of ketene dithioacetal proceeded through a radical pathway. 3-Halo-2-(methylthio)-4H-chromen-4-ones were achieved via various two- or one-pot halogenation approaches.

Optimizing the Synthetic Route of Chromone-2-carboxylic Acids: A Step forward to Speed-Up the Discovery of Chromone-Based Multitarget-Directed Ligands

6-Bromochromone-2-carboxylic acid (3) was synthesized by a microwave-assisted process. The optimization of the reaction was performed varying parameters, such as type of base/number of reagent equivalents, solvent, temperature and reaction time. The yield of the reaction was improved to 87%. The new synthetic route is versatile as several chromone-2-carboxylic acids (compounds 4B-10B) were obtained with good yields (54-93%). Only in the case of the nitro substituent (compound 11B), an ester was obtained instead of the desired carboxylic acid. Following this synthetic route chromone carboxylic acids can be attained with a high degree of purity, without the need of the tedious and expensive purification processes through column chromatography. The reaction is safe, cost-effective, fast and robust, and can be used in the development of concise and diversity-oriented libraries based on chromone scaffold. The overall study can be looked as a step forward to speed-up the discovery of chromone-based multitarget-directed ligands.