Abstract

Aim and Objective: Ceria loaded on solid zirconia was employed as heterogeneous catalyst for the synthesis of pyridine derivatives via a one-vessel, four-component reaction consisting of substituted aldehyde, malononitrile, dimethylacetylenedicarboxylate and dimethylaniline with good to excellent product yields (87 to 95%). The noteworthy advantages of the facile method with ethanol as solvent are excellent yields with short reaction times. Catalyst is reusable with little loss of activity up to six rounds.

Materials and Method: All the catalyst materials were synthesized by using simple wet-impregnation method. The powder X-ray diffraction, TEM, SEM and N2 adsorption/desorption analysis techniques were employed for the structural interpretation of CeO2/ZrO2, the identity of target products were established and confirmed by diverse spectral (1H NMR, 13C NMR, 15N NMR, FT-IR and HRMS) techniques.

Results: As convincingly demonstrated by the synthetic approaches reported in this review, MCRs have facilitated many new methodologies with significant advantages for efficient and well organized synthesis of varied pyrazole derivatives. The methodology involved variety of options for catalysts that can be chosen using different solvents or solvent-free conditions and/or using alternative energy-efficient options such as microwave irradiation and sonification. This review brings together ample material about synthesis of varied pyrazole derivatives that may have prodigious scope, in drug design and therapeutics. It is anticipated that research efforts in this direction will endure in the search for novel, atom efficient, small molecules with excellent drug-like properties.

Conclusion: In this study, we report on a green and efficient one-pot protocol for the synthesis of functionalized 1,4-dihydropyridine-2,3-dicarboxylate derivatives through a four-component reaction between malononitrile, dimethylacetylenedicarboxylate, dimethylaniline and substituted aldehydes using 2.5% CeO2/ZrO2 as a catalyst in EtOH and at room temperature. This methodology has several advantages such as short reaction times (< 30 min), high product yields (87-95%), ease of handling, facile and green work-up. The easy recoverable and reusable catalyst meets the industrial and environmental requirements and is versatile and cost effective.

Keywords: Green synthesis, CeO2/ZrO2, heterogeneous catalysis, reusable catalyst, One-pot synthesis, pyridines, multicomponent reaction.

Graphical Abstract