Pd embedded in chitosan microspheres as tunable soft-materials for Sonogashira cross-coupling in water–ethanol mixture

Abstract

Easy shaping of chitosan (CS) as porous self-standing nanofibrillar microspheres allows their use as a palladium carrier. Amino-groups on CS enable the modulation of Pd coordination, giving rise to three different support-catalyst interactions: weakly-coordinated Pd-CS in native CS, incarcerated Pd-CS-Glu in cross-linked CS and strongly-ligated Pd-CS-SH, obtained by the introduction of thiol arms in CS. These catalysts efficiently promote Sonogashira cross-coupling of a large library of functional substrates under mild and sustainable conditions (water–ethanol as solvent at 65 °C) and stand as recyclable, metal-scavenging catalytic systems.