Palladium nanoparticles in glycerol: a clear-cut catalyst for one-pot multi-step processes applied in the synthesis of heterocyclic compounds

Abstract

Palladium nanoparticles immobilised in a glycerol phase have been successfully applied in multi-step syntheses of heterocycles by a one-pot/one catalytic precursor approach. Actually, two- and three-component carbonylative couplings followed by an intramolecular cyclisation led to N-substituted (na)phthalimides, isoindole-1-ones and tetrahydroisoquinolin-1,3-diones in high isolated yields. 2-Benzofurans and dihydrobenzofurans could be likewise obtained by Cu-free Sonogashira coupling/hetero-cyclisation tandem processes. Drawing on the dual homogeneous/heterogeneous catalytic behaviour of PdNPs, sequential coupling/cyclisation/hydrogenation transformations were efficiently carried out, without isolation of intermediates. The Pd-based catalytic glycerol phase was recycled up to ten times preserving its activity and selectivity.