In this contribution, the catalytic behavior of a phenoxy-imine aluminum catalyst and of a bimetallic salen aluminum complex in ring-opening polymerization (ROP) of macrolactones such as ω-pentadecalactone (PDL), ω-6-hexadecenlactone (HDL) and ethylene brassylate (EB), and in the ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and phthalic anhydride (PA) is described. A significant difference in terms of activity emerged between the two catalysts in the ROP of the macrolactones, while similar behaviors were observed in the ROCOP process. The synthesis of diblock polyesters, by combination of two distinct processes, was performed in a onepot procedure. The semi-aromatic polyester block was formed first, followed by the polyethylene-like portion produced by ROP of macrolactones.