Photoinduced Charge-Transfer Complex-Mediated Decarboxylative Phosphoniumation

Phosphonium salts are valuable intermediates in organic synthesis, but their preparation often requires harsh conditions and specific carbon precursors. Herein, we report a photoinduced decarboxylative phosphoniumation of redox-active esters (RAEs) for the direct synthesis of alkyl and benzyl phosphonium salts. A photoresponsive ternary charge-transfer complex (CTC) formed from NaI, tertiary phosphines, and RAEs enables the reaction under transition-metal- and external-photocatalyst-free conditions. The method tolerates diverse benzyl and aliphatic RAEs and tertiary phosphines, including commercial phosphine ligand frameworks, and enables the late-stage phosphoniumation of complex carboxylic-acid-derived substrates.