Fluorescent Diarylindoles by Palladium-Catalyzed Direct and Decarboxylative Arylations of Carboxyindoles

A study was conducted to demonstrate the palladium-catalyzed 2,3-diarylation of carboxyindole derivatives with acryl bromides. The study also performed ester hydrolysis in the sequence to demonstrate a practical route to 2,3-diarylindoles that had different aryl substituents. The investigations revealed a highly fluorescent 2,3-diarylindole among the products, describing its photoluminescent properties. A stepwise diarylation with methyl esters as starting materials was investigated to achieve selective synthesis of indoles having different aryl groups at the 2- and 3-positions. It was demonstrated that the reaction of carboxylic acid at a higher temperature using mesitylene as a solvent generated 1-methyl-2,3-diphenyl-1H-indole in significant quantity. It was also observed that the approach also led to the discovery of a highly luminescent solid blue emitter.