Enantiodivergent Sulfoxidation Catalyzed by a Photoswitchable Iron Salen Phosphate Complex

Here we describe a photoswitchable iron(III) salen phosphate catalyst, which is able to catalyze the enantiodivergent oxidation of prochiral aryl alkyl sulfides to chiral aryl alkyl sulfoxides. The stable (S)-axial isomer of the catalyst produced enantioenriched sulfoxides with the (R)-configuration in up to 75 % e.e., whereas the photoisomerized metastable (R)-axial isomer of the catalyst favored the formation of (S)-sulfoxides in up to 43 % e.e. The maximum Delta e.e. value obtained in the enantiodivergent sulfoxidation was 118 %, which is identical to the maximum Delta e.e. value that was measured in the enantiodivergent epoxidation of alkenes by a related recently described Mn1 catalyst. This iron-based catalyst broadens the scope of photoswitchable enantiodivergent catalysts and may be used in the future to develop a photoswitchable catalytic system that can write digital information on a polymer chain in the form chiral sulfoxide functions.

Automated summary

We report a photoswitchable iron(III) salen phosphate catalyst for enantiodivergent oxidation of prochiral aryl alkyl sulfides to chiral aryl alkyl sulfoxides. The stable (S)-axial isomer of the catalyst produced enantioenriched sulfoxides with (R)-configuration up to 75% e.e., while the photoisomerized metastable (R)-axial isomer favored the formation of (S)-sulfoxides up to 43% e.e. The maximum Delta e.e. value obtained in enantiodivergent sulfoxidation was 118%, identical to that observed in the enantiodivergent epoxidation of alkenes by a related Mn1 catalyst. This iron-based catalyst expands the range of photoswitchable enantiodivergent catalysts and shows potential for development of a catalytic system capable of writing digital information on a polymer chain in the form of chiral sulfoxide functions.