Solvent-Free Biginelli Reaction Using Heterogeneous CuS-Carbon Nanoflakes Nanocomposites

Herein, we developed copper sulfide (CuS) nanoparticles (NPs)-decorated carbon nanoflakes (CNFs) nanocomposites (CuS-CNFs) and used it as an efficient heterogeneous catalyst for a very fast one-pot solvent-free multicomponent Biginelli reaction via dehydrative condensation of aromatic aldehydes with acetylacetone/ethyl acetoacetates and urea/thiourea, yielding 3,4-dihydropyrimidinones/thiones (DHPMs) derivatives. The reaction was completed within 5 min with a high yield of the desired products. The reaction exhibited a broad substrate scope, tolerating both electron-withdrawing and donating substituents with good to excellent yield. The reactions were monitored by gas chromatography–mass spectrometry (GC–MS), and further the products were confirmed through 1H NMR, 13C NMR, and mass spectrometry analysis. The plausible reaction mechanism was explored based on mass spectrometry analysis of the intermediates and a literature survey. The catalytic performance of the CuS-CNFs nanocomposite can be attributed to the high-surface area of the CNFs and the uniform dispersion of CuS NPs on the surface of CNFs, which provide more active sites. Additionally, the heterogeneous nature of the CuS-CNFs facilitates easy recovery and recyclability under solvent-free reaction conditions, with the catalyst retaining its activity over up to five consecutive cycles without significant loss. This transformation presents several advantages, including very short reaction time, solvent-free reaction condition, good compatibility with various substrates, reusability, and operational simplicity.