Visible-Light Photo-Arbuzov Reaction of Aryl Bromides and Trialkyl Phosphites Yielding Aryl Phosphonates

Aryl phosphonates are functional groups frequently found in pharmaceutical and crop protection agents. For their synthesis via C–P bond formation typically transition-metal-catalyzed reactions are used. We report a visible-light photo-Arbuzov reaction as an efficient, mild, and metal-free alternative. Rhodamine 6G (Rh.6G) is used as the photocatalyst, generating aryl radicals under blue light. Coupling of the radicals with a wide range of trivalent phosphites gives aryl phosphonates in good to very good isolated yields. The mild reaction conditions allow the introduction of a phosphonate group into complex and sensitive pharmaceutically active molecules such as benzodiazepams and nicergoline by the activation of a carbon–halogen bond.