Cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids.

The first cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids has been developed. This operationally simple protocol allows rapid access to synthetically useful coumarins on gram scale by employing CeCl3 as a photocatalyst and O2 as a terminal oxidant. Overall, this delivers an economical and environmentally amiable entry to diversely substituted coumarins, important structural motifs in bioactive molecules.