Photo Redox Catalysis

Mechanism + Description

Probably mainly via radical processes using light to generate a reactive oxidation species.

General comments

A methodology rapidly gaining in prominence for greener transformations which allows for the use of green oxidants like O₂, singlet O₂ and H₂O₂ under mild conditions. Often found to be a very selective route for the clean conversion of sulfides to sulfoxides. A photo redox catalyst is sometimes employed.

Probably no scaled examples to date, but will come with the general advances in technology to scale-up photo-and photo-redox reactions.

Key references

Zhang, X.; Rakesh, K. P.; Ravindar, L.; Qin, H. L. Visible-light initiated aerobic oxidations: a critical review. Green Chem. 2018, 20, 4790-4833.

Zen, J-M.; Liou, S. L.; Kumar, A. S.; Hsia, M-S. Efficient and Selective Photocatalytic System for the Oxidation of Sulfides to Sulfoxides. Angew. Chem. Int. Ed. 2003, 42, 577-579.

Zhao, W.; Yang, C.; Huang, J.;  Jin, X.; Deng, Y.; Wang, L.; Su, F.;  Xie, H.; Wong, P. K.; Ye, L. Selective aerobic oxidation of sulfides to sulfoxides in water under blue light irradiation over Bi4O5Br2. Green Chem. 2020, 22, 4884-4889.

Li, C.; Mizuno, N.; Murata, K.; Ishii, K.; Suenobu, T.; Yamaguchi, K.; Suzuki, Selectivity switch in the aerobic oxygenation of sulfides photocatalyzed by visible-light-responsive. Green Chem. 2020, 22, 3896-3905.

Cui, H.; Wei, W.; Yang, D.; Zhang, Y.; Zhao, H.; Wang, L.; Wang, H. Visible- light- induced selective synthesis of sulfoxides from alkenes and thiols using air as the oxidant. Green Chem. 2017, 19, 3520-3524. 

Liu, K-J.; Wang, Z.; Lu, L-H.; Chen, J-Y.; Zeng,  F.; Lin, Y-W.; Cao, Z.; Yud, X.;  He, W-M Synergistic cooperative effect of CF3SO2Na and bis(2-butoxyethyl)ether towards selective oxygenation of sulfides with molecular oxygen under visible-light irradiation. Green Chem., 2021, Advance Article

Relevant scale up examples

None found.