Efficient and facile synthesis of pyrazoles using Guar-gum as organocatalyst and their in vitro herbicidal activity

Abstract

A green efficient and facile synthesis of pyrazoles is reported via condensation reaction between substituted aldehydes (1a-1i), malononitrile (2) and 2,4-dinitrophenyl hydrazine (3) in presence of acylated Guar-gum as organocatalyst under solvent-free conditions. The progress of reaction was checked by thin layer chromatography and melting points reported are uncorrected. All synthesized compounds (4a-4i) were characterized by using 1HNMR and FTIR spectral techniques and evaluated for in vitro herbicidal activity against Raphanus sativus L. (Radish seeds). All compounds (4a-4i) were also evaluated for their antifungal activity against Rhizoctonia solani and Aspergillus niger by poisoned food techniques method. Antioxidant activity of synthesized compound was also determined. From activity results, it was found that compound 4f was most active against both Raphanus sativus L. (root) and Raphanus sativus L. (shoot) respectively. Compounds 4e and 4h were found most active against Rhizoctonia solani and Aspergillus niger fungus respectively at highest concentration. Compound 4e has shown maximum percentage DPPH free radical scavenging activity i.e. 61.47% at 100 ​μg/mL concentration. Less reaction time, excellent yield of products, mild reaction conditions and simple work-up are some merits of present methodology.

Keywords

• Pyrazoles
• Guar-gum
• Raphanus sativus L.
• Rhizoctonia solani
• Aspergillus niger