Synthesis Of1-aryl-1H-pyrazol-3-ol Derivatives

1-aryl-1H-pyrazol-3-ol as an important intermediate of fungicide and herbicide has a wide range of application in chemical industry and organic synthesis, especially in the research of synthesize pyraclostrobin and trifloxystrobin, which are new types of strobilurin fungicide. As1-aryl-1H-pyrazol-3-ol derivatives have high activity, low toxicity and environmentally friendly and more changes of structure, they are very significant to the field of medicine, dyes, conductance reagents and fluorescence materials.In this paper, the synthesis process of substituted phenyl hydrazine hydrochloride has been studied. Substituted phenyl hydrazine hydrochloride was synthesized from substituted aniline by diazotization, reduction and hydrolysis under acidic conditions. The process and the influences of factors on the yield were studied, such as temperature, time and the reducing agent. The reaction was occurred at80℃with substituted aniline, HCl, NaNO3, NaHSO4and NaOH on ratio with1:2.5:1.03:3:2through4h, giving yield of99.2%. Under the optimal reaction conditions,9kinds of derivatives were also prepared with high yields.Then, the synthesis process of1-aryl-1H-pyrazol-3-ol has been studied.4-chlorophenyl hydrazine hydrochloride reacted with acryl amide via cyclization and oxidation. We selected the reaction of1-(4-Chlorophenyl)-1H-pyrazol-3-ol as the model reaction. The effects of solvents, base, oxidants and catalysts on the reaction were screened to optimize the reaction conditions.4-Chlorophenyl hydrazine hydrochloride, CH3ONa, acrylamide and H2O2on ratio with1:6:1.15:1.16for8h, in yield of79.5%. Under the optimal reaction conditions,12kinds of derivatives were also synthesized.In addition, researches were also made to explore the one-pot synthesis of1-aryl-1H-pyrazol-3-ol in order to generate cost and improve the reaction yield. The ratio of water and methanol were selected to optimize the reaction conditions. Further efforts were also made to explore the synthesis of O-acylation, O-benzylation, and O-alkylation of1-aryl-1H-pyrazol-3-ol.6kinds of derivatives could also provide the desired products under the identical conditions with satisfactory yields and purity.