Synthesis of 1-aryl(hetaryl)pyrazol-5-ols and azopyrazoles on their basis

Abstract

Treatment of 3,5-dichloropyrid-2-ylhydrazine, and of mono-and dinitrophenylhydrazines with acetoacetic ester gave hydrazones and the products of their cyclization, namely pyrazolols. It was shown that acetoacetic ester 2,4-dinitrophenylhydrazone cyclizes to the pyrazolol only by using PPA while other studied hydrazones undergo tarring under these conditions. The products of azocoupling of pyrazolols with 3-diazonio-4-hydroxy-5-nitrobenzenesulfonate or 2-hydroxy-5-nitrophenyldiazonium salts are able to color textile materials. The fungicidal activity of the synthesized compounds has been studied.Our analysis of literature sources based on CAS data and available through STN has shown that the interest in the synthesis and studies of the properties of pyrazole derivatives has persisted at a constantly high level while, in the last 20 years, there has occurred an increasing trend in the number of publications and a jump has been noted in the number of patents to 30-35 per year [1, 2]. This is explained by the fact that, amongst pyrazole derivatives, there are known chemical agents for plant protection, chemico-pharmaceutical preparations, antioxidants, reagents for chemical analysis and for organic synthesis, dyes, and pigments.In our work we have synthesized a series of pyrazol-5-ol derivatives containing a substituent in the 1 position which can undergo further chemical transformation, and of derived azopyrazoles.One of the most convenient and widely used methods for preparing pyrazol-5-ols is the heterocyclization of substituted hydrazines with acetoacetic ester [3] and it is known that the process can occur both with and without the separation of the intermediate hydrazones 3. R NHNH 2 Me O O OEt Me N O N H OEt R N N Me O H R + 1a-e 2 3a-e 4a-e -EtOH -H 2 O1,3,4 а R = Ph, b R = 4-nitrophenyl, c R = 2,4-dinitrophenyl, d R = 2-methoxy-5-nitrophenyl, e R = 3,5-dichloropyrid-2-yl