Cobalt oxide–carbon nanocatalysts with highly enhanced catalytic performance for the green synthesis of nitrogen heterocycles through the Friedländer condensation

Abstract

A novel series of eco-sustainable catalysts developed by supporting CoO nanoparticles on different carbon supports, highly efficient in the synthesis of quinolines and naphthyridines, through the Friedländer condensation.

Enhanced catalytic performance of ZnO/carbon materials in the green synthesis of poly-substituted quinolines

“…6c), suggesting a negative effect of the mesopores on the catalytic performance of this series. These results contrast with those previously obtained [17] using CoO/carbon catalysts, where the activity of the catalysts is favored using CNT as supports (Fig. 6d).…”

“…While mesoporous silica or CuBTC worked at higher temperature, in general, carbon catalysts yielded similar or notably improved conversions to quinolines, even operating at lower temperature, in the presence of a notable increase of reactants amounts and shorter reaction times. Among the explored carbon materials, metal-free carbons are able to catalyze the reaction affording the corresponding quinoline 3a in low yields whereas metals supporting carbon materials, particularly cobalt catalysts in which cobalt is as its metallic [16] form or even as CoO [17] in both cases improved the conversion values. Although cobalt has a biologically importance as metal constituent of vitamin B12, excessive exposure can induce adverse health effects [18].…”

“…Considering that the carbon surface and even the functionalities influence the dispersion and accessibility of the metallic phase, and therefore, the catalytic performance, we selected a microporous carbon (Norit RX 3 AC) and two mesoporous carbon samples comprising oxidized multi-walled carbon nanotubes and a pure carbon aerogel prepared by polymerization of resorcinol-formaldehyde (R-F). All samples were impregnated with aqueous solutions of the corresponding metallic salt to obtain a metal loading of 1 or 3 wt.% and subsequently submitted to thermal treatment, for comparison with CoO samples previously reported [17].…”

Eco‐sustainable Synthesis of N‐containing Heterocyclic Systems Using Porous Carbon Catalysts

“…In addition, the effect of the surface chemistry when using the corresponding aerogels submitted to oxidant treatment with H 2 O 2 was analyzed, the presence of OSGs leading to worse catalytic performances. Considering that, a novel series of eco‐sustainable catalysts based on CoO nanoparticles supported on different carbon supports and applied to the synthesis of quinolines, under the same reaction conditions, have been also reported [77a] . In this case, different metal loadings (1, 3 and 5 %) were supported on i) commercial Norit carbon, ii) oxidized commercial CNTs (CNT ox ) and, iii) a carbon aerogel calcined at 500 °C (B500).…”

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

“…Another application of cobalt oxide NPs supported on different carbon supports was reported by Pérez-Mayoral et al (Scheme 86) for the synthesis of quinolines (35f) using similar starting materials. 175 CoO-carbon was synthesized via the treatment of cobalt nitrate or acetate with a carbon support. dehydrogenation, Friedel-Cras reactions, C-C bond formation and borylation.…”