Thus, one embodiment is a method of preparing a polyester comprising: reacting a Group 4 transition metal hydride with an oxygen-containing compound selected from the group consisting of aldehydes, ketones, epoxides, peroxides, anhydrides, carboxylic acids, esters, amides, and vinyl ethers to form a Group 4 transition metal alkoxide intermediate; and polymerizing a cyclic ester in the presence of