Co–Nx catalyst: an effective catalyst for the transformation of nitro compounds into azo compounds

The selective hydrogenation of nitro compounds into their corresponding azo compounds is challenging in organic synthesis. In this study, we have developed a facile and efficient catalytic system for the transformation of nitro compounds into azo compounds under mild conditions over a heterogeneous cobalt catalyst (Co–Nx/C-800-AT). The Co–Nx/C-800-AT catalyst was found to be highly active for the reductive-coupling of nitro compounds into azo compounds in ethanol at 110 °C and 2.5 bar H2 pressure with the addition of NaOH as an additive, affording structurally-diverse azo compounds with satisfactory yields (70.4–98.3%). The developed method demonstrated several advantages such as high catalytic activity and high selectivity with tolerance to other functional groups and high stability.