A study on the oxidation of 1‐(4‐chlorophenyl) pyrazolidin‐3‐one to 1‐(4‐chlorophenyl)‐3‐pyrazolol by oxygen

Abstract BACKGROUND Pyraclostrobin manifests a bright promise in agriculture with the characteristics of a broad spectrum, high efficiency, low toxicity, non‐target biosafety, and friendliness to users and the environment due to its ability to inhibit mitochondrial respiration in a novel mode of action. 1‐(4‐chlorophenyl)‐3‐pyrazolol is an essential intermediate for the preparation of pyraclostrobin. The commercial technology for the production of 1‐(4‐chlorophenyl)‐3‐pyrazolol by oxidizing 1‐(4‐chlorophenyl)pyrazolidan‐3‐one with H 2 O 2 in strong an alkali solution is risky and not friendly to the environment. RESULTS A solid Fe/AC catalyst is constructed by loading ferric on commercial activated carbon. The activated carbon and ferric act cooperatively to upgrade the oxidation rate of 1‐(4‐chlorophenyl)pyrazolidan‐3‐one and the yield of 1‐(4‐chlorophenyl)‐3‐pyrazolol with air. The best catalyst is Fe/AC supported with 15% Fe 2 O 3 on activated carbon of 100 ~ 120 mesh without activation. CONCLUSION The Fe / AC catalyst is able to not only accelerate the oxidation of 1‐(4‐chlorophenyl) pyrazolidin‐3‐one but also obtain a higher yield of 1‐(4‐chlorophenyl)‐3‐pyrazolol than FeCl 3 or activated carbon can in 5%(wt.) NaOH solution. The highest 1‐(4‐chlorophenyl)‐3‐pyrazolol yield is obtained by a gas stream containing 60%(wt.) oxygen with a Fe/AC dosage of 1.25 g L −1 . © 2023 Society of Chemical Industry.