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.