Palladium‐Based Catalysts‐Supported onto End‐Functionalized Poly(lactide) for C–C Double and Triple Bond Hydrogenation Reactions

Poly(lactide) (PLA), which is the polymer that will be discussed in this chapter, was functionalized with nitrogen containing aromatic groups by means ring opening polymerization (ROP) reactions. The obtained macroligands were successfully employed to coordinate Pd(II), which chemoselectively hydrogenated αβ–unsaturated carbonyl compounds to give the saturated counterparts as main product. The catalyst could be easily recycled upon a simple filtration process. End-functionalized isotactic PLA chains were used to generate stereocomplexes, featured by a higher thermal and hydrolytic resistance. The chemical nature of the nitrogen ligand introduced at the chain end of PLA was exploited to stabilize Pd-nanoparticles (Pd-NPs) by interactions of the aromatic or nitrogen functionality with the NPs– surface. The polymer-anchored Pd-NPs were generated by a classical approach which comprised the coordination of Pd(II) by the functional group followed by reduction with hydrogen or by the metal vapor synthesis technique. The polymer-supported Pd-NPs were successfully applied to catalyze the selective hydrogenation of alkynes to the corresponding alkene and cinnamylalcohol to the corresponding saturated aldehyde. In this book chapter the synthesis and structure-performance relationship of the new hydrogenation catalysts will be discussed.