Conversion of Racemic Alkyl Aryl Sulfoxides into Pure Enantiomers Using a Recycle Photoreactor: Tandem Use of Chromatography on Chiral Support and Photoracemization on Solid Support.

Chiral sulfoxides are valuable in the fields of medicinal chemistry and organic synthesis. A recycle photoreactor utilizing the concept of deracemization, where a racemate is converted into a pure enantiomer, is developed and successfully applied in the syntheses of chiral alkyl aryl sulfoxides. The recycling system consists of rapid photoracemization using an immobilized photosensitizer and separation of the enantiomers via chiral high-performance liquid chromatography, and the desired pure chiral sulfoxides are obtained after 4-6 cycles. The key to the success of the system is the photoreactor site, wherein the photosensitizer 2,4,6-triphenylpyrylium is immobilized on the resin and irradiated (405 nm) to enable the rapid photoracemizations of the sulfoxides. As the green recycle photoreactor requires no chiral components, it should be a useful alternative system for application in producing chiral compounds.