Benzaldehyde → 1H-Pyrazole, 3,5-diphenyl-

Participants

Reaction Conditions

Reaction Steps

60 parts (0.5 mol) of acetophenone and 53 parts (0.5 mol) of benzaldehyde were simultaneously added dropwise at 40° C. to 326.7 parts (2.0 mol) of 60% strength by weight sulfuric acid in the course of 30 minutes. The mixture was stirred at 40° C. for 30 minutes and the phases were then separated. The sulfuric acid phase was initially introduced intoa four-necked flask with 0.5 parts (0.0033 mol) of sodium iodide and heatedto 130° C. The upper phase was then simultaneously added dropwise with 25 parts (0.5 mol) of hydrazine hydrate in the course of 30 minutes. The temperature fell from 130° C. to 120° C. during the addition. The temperature was again brought to 130° C. by distilling off water and kept at 130° C. for 2 hours by further distillation of water. The amount of water distilled off was 70 ml. The mixture was diluted at 100° C. with 250 ml of water and neutralizedat 70° C. with 497 parts (3.1 mol) of 25% strength sodium hydroxide solution. The precipitate was filtered off with suction at 25° C. and washed with water until sulfate-free. After drying, 105.5 parts of 3,5-diphenylpyrazole were obtained having a purity of 98.5% (HPLC), which corresponds to a yield of 94.4% of theory. M.p.: 199° C.

Provenance & Evidence