A Sustainable Approach toward Oxidation of Benzylic sp³ C–H Bond with Molecular Oxygen Using Recyclable Heterogeneous 2D-Supported CuO/rGO Catalyst

A sustainable approach for the benzylic C(sp3)–H bond oxidation of oxindoles to isatins has been developed using a reduced graphene oxide-supported copper oxide (CuO/rGO) nanocomposite. This catalytic system enables efficient oxidation under mild conditions with molecular oxygen as the sole oxidant, eliminating the need for additional reagents. The CuO/rGO nanocomposite was thoroughly characterized using XRD, FT-IR, TGA, SEM, FE-SEM, and BET analysis. It demonstrated excellent recyclability, maintaining a catalytic performance over six cycles. The method exhibits broad functional group tolerance, affording isatin derivatives in moderate to good yields with a high reaction mass efficiency (98.6%). The CHEM21 green metrics toolkit was used to evaluate the sustainability and environmental impact of the protocol.