Visible light-promoted enantioselective aerobic oxidation of pyrazolones by phase transfer catalysis

An efficient and enantioselective aerobic oxidation of 4-substituted pyrazolones has been developed by phase transfer catalysis. Using visible light as the driving force and O 2 (in air) as the oxidant, broad scopes (38 examples) of pyrazolones bearing an oxygen-attached carbon stereocenter at C-4 position were obtained in high yields (up to 98%) and excellent enantioselectivities (up to 93% ee ) under mid conditions. The ready availability of catalyst, ease of operation, and low-cost and eco-friendly nature highlighted the practical utility of this visible light-promoted enantioselective aerobic oxidation. Using visible light as the driving force and O 2 (in air) as the oxidant, we developed an efficient and enantioselective aerobic oxidation of 4-substituted pyrazolones by phase transfer catalysis. Broad scopes (38 examples) of pyrazolones bearing an oxygen-attached carbon stereocenter at C-4 position were obtained in high yields (up to 98%) and excellent enantioselectivities (up to 93% ee ) under mid conditions.