Aliphatic linear polyesters of different chain lengths, such as semi-crystalline polycaprolactone (PCL), are ideal model substrates to transfer the reactivity from molecular esters to polyesters, as their morphology and the role of entanglements is well understood. Using the previously optimized conditions for molecular esters, we utilized 1 mol% of complex 1 with respect to the average number of ester groups (M) together with 5 mol% of KO t Bu co-catalyst (B) in the reaction of PCL (Mn = 5 -54 kDa) in toluene-d8 at different temperatures. We analyzed the resulting reaction mixture by gel permeation chromatography (GPC), as well as NMR spectroscopy (Table ).