Sustainable Synthesis of Biogenic CuO Nanoparticles from Agro‐Waste for One‐Pot C–N Bond Formation

Abstract

We report a simple, green, and cost‐effective method for synthesizing copper oxide nanoparticles (CuONPs) using waste cotton shell (WCS) ash extract, which serves as a natural base (pH 12), replacing conventional inorganic bases. The green‐synthesized CuONPs exhibit excellent catalytic activity in heterogenous catalysis facilitating C–N bond formation, a key strategy for accessing various bioactive nitrogen heterocycles. TEM analysis reveals spherical morphology of the CuO nanostructure with an average particle size of 15.5 nm. The catalyst efficiently promotes the synthesis of quinoxaline derivatives via cyclization of terminal alkynes and o‐phenylenediamine, offering broad substrate scope (17 quinoxaline derivatives), good yields, and recyclability. This methodology is also applicable to aliphatic terminal alkynes. Additionally, CuONPs also catalyzed the aza‐Michael addition reactions of amines with α, β‐unsaturated compounds at room temperature, affording excellent yields. The protocol tolerates a wide range of amines, including acyclic, cyclic (up to seven‐membered rings), primary, secondary, and heterocyclic amines. Synthesis of 14 aza Michael addition products are reported. Furthermore, the CuO nanostructures exhibits high stability and reusability for up to five cycles with minimal loss of activity.