Direct C4-H phosphonation of 8-hydroxyquinoline derivatives employing photoredox catalysis and silver catalysis

A simple and efficient protocol for the C4-H phosphonation of 8-hydroxyquinoline derivatives was developed under a photoredox/silver(i) cocatalysis system, providing a new approach to phosphonated 8-hydroxyquinoline derivatives. Note that the reaction did not occur at the C5 site, but regioselectively at an unusual C4 site. Moreover, the reaction proceeded smoothly under mild reaction conditions (a catalytic amount of silver salt and room temperature) with good functional group compatibility.