Investigation of the catalytic activity of metallic copper and copper dispersed SiO2 for the reductive acetylation of aromatic nitro compounds

N-Arylacetamides such as acetaminophen are important systems in medicinal chemistry. Reductive acetylation of nitroarenes is noted to be an efficient route for their preparation. Protocols were developed for one-pot reductive acetylation of nitroarenes in the presence of various catalysts under varied conditions. Current work studied the catalytic effect of metallic copper and supported copper systems towards the reductive acetylation of nitroarenes under mild condition. The influence of the supporting materials such as SiO2, Al2O3, TiO2 and HAp (hydroxyapatite) was studied by comparing the activity of Cu/SiO2 with that of Cu/TiO2, Cu/Al2O3 and Cu/HAp. Cu/SiO2 system emerged out as an efficient catalyst. In the first part of the reaction of reduction of nitrobenzene to aniline, both 4 wt% Cu-Al2O3 and 4 wt% Cu-HAp lead to partial conversion till the formation of azoxybenzene, whereas 4 wt% Cu-TiO2 showed 31% conversion of aniline. However, with 4 wt% Cu-SiO2, 100% conversion of aniline was achieved. Acetylation of the system afforded 97% yield of N-phenylacetamide. The activity of the catalyst was also tested for selected nitroarenes. Characterization by powder XRD, XPS, TEM, BET measurements, TPR study assisted in demonstrating the efficacy of SiO2-supported Cu.

Automated summary

N-Arylacetamides such as acetaminophen play a crucial role in medicinal chemistry. This study explored the catalytic effect of metallic copper and supported copper systems on the reductive acetylation of nitroarenes. Cu/SiO2 was identified as an efficient catalyst.