ACS Catalysis, Journal Year: 2022, Volume and Issue: 12(12), P. 6906 - 6922

Published: May 26, 2022

A heterogeneously catalyzed protocol for the acceptorless dehydrogenative condensation between N,N′-disubstituted ureas and 1,2-diols to afford imidazolones was developed. Palladium nanoaggregates stabilized onto an alumina matrix with suitable acidic properties, namely, [Pd/Al2O3], designed successfully applied as efficient reusable heterogeneous nanocatalyst this relevant transformation. The methodology developed showed its wide applicability through synthesis of more than 25 moderate good yields, reaching a turnover number (TON) up 19444 initial frequency (TOF0) > 290 h–1. active nanostructured catalyst fully characterized [X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning (HR-STEM), energy-dispersive X-ray (EDX), Raman spectroscopy, temperature-programmed reduction (TPR), desorption (TPD)-NH3, TPD-CO2, photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) area], mechanistic studies were performed. Moreover, other related Pd-based nanomaterials composed different or basic inorganic supports synthesized extensively compared in reaction. These revealed that presence Pd nanoparticles range sizes (average particle size 2.8 nm) over metal oxide support high density acid sites is key point activity material, γ-Al2O3 being optimum support. Furthermore, Pd–Zn cooperation effect described unactivated 1,2-diols, including ethylene glycol, ureas. Two bimetallic materials ([Pd/ZnO] [Pd(5%)–Zn(5%)/Al2O3]) also properly. materials, well [Pd/Al2O3] system combination catalytic amounts ZnO, selectivity 1,2-diols. nature all systems demonstrated, reusability catalysts proven.

Language: Английский