Electrochemical C(sp ² )‐H Diphosphorylation With a Redox Mediator: Access to <i>Gem</i> ‐Bisphosphonates

A one‐step, one‐pot method for the preparation of dihydroacridine bisphosphonates at room temperature by Fc/Fc + ‐mediated electrochemical synthesis using (RO) 3 P (R=alkyl) and acridines in good yields at room temperature is proposed. This is the first example of twofold C–P formation via synchronous aromatic C–H phosphorylation. 9,10‐Dihydroacridine derivatives are commonly found as privileged structural motifs in OLEDs, bioactive substances, photocatalysts, and various materials for useful applications. However, synthesis of these compounds from starting materials usually involves multiple stages. To date, no examples have been reported of the formation of geminal bisphosphonates on a single carbon atom through the phosphorylation of a C(sp 2 )–H aromatic fragment. The proposed method is also applicable for xanthene and acridine orange derivatives, but the yields of the bisphosphonates are lower. The products were characterized using X‐ray crystallography. Their redox properties were determined through cyclic voltammetry. Paramagnetic compounds formed under oxidation conditions were analyzed using the electron paramagnetic resonance method.