Oxidative hydroxylation of arylboronic acids to phenols catalyzed by copper nanoparticles ellagic acid composite

•Ellagic acid (EA) is a naturally occurring polyphenolic compound.•Copper nanoparticles (CuNPs) prepared using EA as a support and reducing agent.•CuNPs characterized well by UV–vis, FT-IR, powder XRD and HR-TEM.•Catalytic activity of CuNPs is tested in oxidative hydroxylation of phenylboronic acid.•No ligands and no bases were needed; high yield and reusability are the other advantages.

Copper nanoparticles (Cu NPs) were prepared by in situ reduction of CuSO4·5H2O using ellagic acid (EA) as the reducing agent as well as stabilizer and its catalytic activity is tested in the oxidative hydroxylation of phenylboronic acids to phenol without any added base or ligand. The synthesized Cu NPs-EA composite was characterized by UV–Vis., FT-IR, powder XRD and HRTEM analyses. The average particle size of Cu NPs is found to be in the range of 20–25 nm as evident from HRTEM and copper content is estimated to be 3.18 wt%. EA acts both as a reducing agent as well as a stabilizer for the in situ formation of Cu NPs. A small portion of Cu NPs is also found to undergo aerobic oxidation to give Cu2O NPs which does not take part in the reactions. A series of arylboronic acids are converted to the corresponding phenols in high yields at short reaction time under milder reaction conditions. It is also observed that Cu NPs-EA composite can be reused at least four times with a significant decrease in the yield.

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