**1. Introduction**

In the realm of hydrogenation reactions, the selective hydrogenation of unsaturated carboncarbon bonds is very attractive [1]. Asymmetric and partial hydrogenation reactions are pivotal for the access of important compounds employed as pharmaceuticals, food additives, pesticides, flavors, and fragrances [2]. In this respect, α,β-unsaturated carbonyl compounds present an interesting group of chemicals whose enantio- [3], chemo [4], and regio-selectivities [5] are highly challenging. For instance, Lindlar's [6] and Lindlar types' catalysts [7] are widely used to chemoselectively hydrogenate alkynes to the corresponding alkene. In parallel, a variety of different selective hydrogenation methods have been developed [8]. In particular, bimetallic catalysts [9], noble metal-based catalysts supported onto carbon-based materials [10] or inorganic matrixes [11], in combination with supercritical solvents [12] and "*flow*" reactors [13], have been studied. Also for the partial alkyne hydrogenation, a great deal of catalytic systems were proposed based on the use of noble metals and different approaches like reactions conducted in gas [14] and liquid phase [15], combined with ultrasound techniques [16] and biphasic catalytic systems [17].

The interest on polymer-based catalysts applied for hydroformylation reactions [18], hydrotreatment [19], and strong acid/base [20, 21] catalyzed reactions is steadily increasing. Since functional polymer-based catalytic systems generally exhibit notable advantages over traditional catalysts such as the tunable solubility and improved catalytic selectivity [22], the biodegradable polyester, poly(lactide) (PLA) was used as a polymer matrix [23], which is rather straightforwardly end-capped as reported by Helle et al. [24]. The possibility to produce carboxylic end-capped PLA chains functionalized with nitrogen containing moieties, called macroligands by Giachi et al. [25], allowed the synthesis of well-defined macrocomplexes containing metal cations, such as Pd(II). The latter Pd-based macrocomplexes were efficiently used to catalyze hydrogenation reactions conducted in the homogeneous phase followed by an easy separation step, as reported by Giachi et al. [26] and Bartoli et al. [27]. Isotactic endfunctionalized PLA with opposite tacticity can be combined to form a supramolecular structure named stereocomplex [28]. Functionalized PLA stereocomplexes show high resistance against hydrolysis and thermal degradation and in addition, a poor solubility in all organic solvents. This latter property was exploited by Petrucci et al. [29] and Oberhauser et al. [30] for catalytic purposes to easily separate PLA-stereocomplex-based catalysts from catalytic solution.

In the following sections, synthesis, characterization, and catalytic application of homogeneous and heterogeneous Pd-catalysts supported on end-functionalized PLA were reported.
