Aromatic phosphonate esters are privileged structural motifs employed as ligands in catalysis, photoelectric materials, pharmaceutically active molecules, and play integral roles within biological chemistry. Typical synthetic routes involve cross-coupling of aryl derivatives and phosphorous analogues using transition-metal catalysts including Ni, Cu, Fe, and Pd but these methods often require harsh reaction conditions and are toxic. Additionally, these reactions exhibit air sensitivity, functional group incompatibility, and require the use of expensive ligands. Alternative syntheses employing milder reaction conditions have been investigated and include dual catalytic strategies or the use of photoredox catalysis, but these methods still exhibit air and water sensitivity and require expensive photocatalysts. Herein, we report an efficient photoredox-catalyzed cross-coupling of aryl halides with trialkyl phosphites and triphenylphosphine in good to excellent yields under atmospheric conditions. This photoredox reaction uses 10H-phenothiazine, a commodity chemical, as a photocatalyst in the absence of expensive transition metals, ligands, or external oxidants. The reaction scope also includes the use of ammonium salts as coupling partners and aqueous solvent mixtures could be used as green solvents for these transformations. The scope was expanded to include additional phosphite esters, increasing the potential synthetic utility of this strategy. The reaction exhibits good functional group compatibility across alcohol, amine, ketone, and ester moieties. Reaction optimization, substrate scope, and mechanistic investigation will be presented.

Visible light-induced C-P bond formation of C-X bonds with trialkyl phosphites and triphenylphosphine under mild conditions

ACS Spring 2022

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