Direct Phosphonation of Quinolinones and Coumarins Driven by the Photochemical Activity of Substrates and Products

Light-promoted phosphonation of quinolinones and coumarins was developed without the need for an external photocatalyst. Investigations support a mechanism whereby both starting materials and products act as photosensitizers upon excitation using compact fluorescent light sources to photochemically promote the dissociation of the N-O bond in the pyridinium salt by a single electron transfer pathway. A wide range of quinolinone and coumarin substrates can be utilized in the phosphonation process under mild reaction conditions.