C-⁺P to C–P(O) Bond Exchange of Organophosphonium Salts: Synthesis of 3-(Phosphoryl)methylindoles under Additive- and Catalyst-Free Conditions

A straightforward, mild, additive-free, and catalyst-free method for the phosphorylation of indolyl-containing quaternary phosphonium salts with phosphine oxides has been developed. This process involves a formal C-⁺P to C-P(O) bond exchange, encompassing the cleavage of a C-⁺P bond and the formation of a C-P(O) bond. Through this method, a variety of structurally diverse and potentially bioactive 3-(phosphoryl)methylindoles were synthesized in moderate to good yields with good functional group tolerance. Furthermore, the protocol exhibits excellent scalability and facilitates the easy transformation of the resulting products.