Niobium Oxides as Heterogeneous Catalysts for Biginelli Multicomponent Reaction

Abstract

This study reports a simple, reusable, and recoverable niobium-based heterogeneous catalysts for Biginelli multicomponent reactions. Different methods of catalysts preparation were investigated. For this purpose, HY-340 (Nb 2 O 5 • nH 2 O) and Nb 2 O 5 were chemically and/or thermally treated and investigated as catalysts for dihydropyrimidinones (DHPMs) production. The catalysts were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, temperature-programmed desorption of NH 3 , adsorption/desorption of N 2 at −196 °C, and thermogravimetric and differential thermal analysis. The characterization results showed that niobium oxides have the potential to be used as catalysts because of high crystallinity and large surface area. Among the tested catalysts, Nb 2 O 5 chemically treated (Nb 2 O 5 /T) showed the best catalytic performance. In the absence of solvents, 94% yield of DHPMs was achieved. Also, Nb 2 O 5 /T can be reused three times without a significant yield decrease. Additionally, a feasible reaction pathway was suggested based on the Knoevenagel mechanism for DHPM synthesis using niobium-based catalysts.

Dimensional Reduction of Lewis Acidic Metal–Organic Frameworks for Multicomponent Reactions

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Sulfonated carbons from agro-industrial residues: simple and efficient catalysts for the Biginelli reaction

“…For this purpose, the reaction conditions were defined following a previous optimization study of our group. 44 Reaction tests were performed using 1 mmol benzaldehyde, 1.5 mmol methyl acetoacetate, 1.5 mmol urea, 5% by mass of catalyst (relative to the aldehyde), solvent-free, and a temperature of 130 °C. It is important to highlight that these reaction conditions were adopted just to evaluate the performance of the catalysts.…”

Efficient One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones via a Three-Component Biginelli Reaction

“…Methyl 6-methyl-2-oxo-4-p-tolyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate ( 4l ) [ 37 ]. White solid (0.858 g).…”