Aims:
In this article we have developed an eco-friendly one-pot multi-component reaction methodology was employed for the green synthesis of functionalized pyrazole derivatives viz cyclo-condensation of aromatic aldehydes, ethyl
acetoacetate and phenyl hydrazine and/or hydrazine hydrate in the presence of cetyltrimethylammoniumbromide (CTAB) at
90°C temperature in aqueous medium.
Method:
In the present protocol we developed a green method for the synthesis of functionalized pyrazole derivatives
through one-pot, multi-component cyclo-condensation of aromatic aldehydes, phenyl hydrazine or hydrazine hydrate and
ethyl acetoacetate using cetyltrimethylammoniumbromide (CTAB) as a catalyst in water as solvent. Our methodology confers advantages such as short reaction time, atom economy, purification of product without using column chromatographic
and hazardous solvent. The reaction is being catalyzed by cetyltrimethylammoniumbromide (CTAB) and thus products are
formed under the green reaction conditions.
Results: Initially the reaction of benzaldehyde and phenylhydrazine with ethyl acetoacetate was carried out in water at room
temperature in the absence of the catalyst; no product was obtained after 24 h (Table 1 entry 1). When the reaction was carried out using L-proline as catalyst in ethanol at 70°C the yield of product was 20.
Conclusion:
This research not only provides a green and efficient method for the synthesis of sulfinic esters but also shows
new applications of electrochemistry in organic synthesis. We consider that this green and efficient synthetic protocol used
to prepare sulfinic esters will have good applications in future. In conclusion, we have developed successfully a green and
efficient one-pot multi-component methodology for the synthesis of substituted pyrazoles using CTAB as a catalyst in water
as solvent with excellent yields. Purifications of compounds were achieved without the use of traditional chromatographic
procedures. This methodology has advantages of operational simplicity, clean reaction profiles and relatively broad scope
which make it more attractive for the diversity oriented synthesis of these heterocyclic libraries. In this methodology we
suggest the further alternative possibility for formation of substituted pyrazoles. The compound 7h can be used as an anticancer drug in pharma industry.
Combinatorial Libraries on Rigid Scaffolds: Solid Phase Synthesis of Variably Substituted Pyrazoles and Isoxazoles
