Visible Light-Induced Metal-free Arylation of Coumarin-3-carboxylates with Arylboronic Acids

• Published in: Chemistry, an Asian journal p. e202400042
• Main Authors: Banik, Swarnayu, Saikiran, Aita, Permula, Prathyusha, Srivishnu, K S, Sridhar, B, Subba Reddy, B V
• Format: Journal Article
• Language: English
• Published: Germany 16.04.2024
• Subjects: 4-aryl coumarins; metal free reaction; organophotocatalysis; Alkenyl C-H arylation; aryl boronic acid
• ISSN: 1861-471X
• DOI: 10.1002/asia.202400042

The present work reports a novel methodology for the selective arylation of coumarin-3-carboxylates with arylboronic acids via a photochemical route, marking the first-ever attempt for the direct alkenyl C-H arylation using rose bengal as a photocatalyst, which is a readily available and cost-effective alternative to transition metal catalysis. The reaction proceeds smoothly in MeOH/H2O solvent media in the presence of radical initiator affording the arylated products in good yields (60-80%). The reaction parameters such as visible light, radical initiator, oxidant, anhydrous solvent, and inert atmosphere play a crucial role for the success of this methodology. The substituents present on the substrate show a significant effect on the conversion. This study provides a valuable contribution to the field of organic synthesis offering a new and efficient approach to the arylation of coumarin-3-carboxylic acid esters with a broad substrate scope and high functional group tolerance. It is a versatile method and provides a direct access to biologically relevant 4-arylcoumarin-3-carboxylates.