Bioderived Acrylates from Alkyl Lactates via Pd-Catalyzed Hydroesterification

The conversion of methyl and ethyl lactate to their corresponding alkyl 2-(propionyloxy)propanoate esters was achieved by Pd catalyzed hydroesterificative coupling with carbon monoxide (CO) and ethylene (C₂H₄) at moderate temperatures and CO/C₂H₄ pressures. A screening of reaction conditions showed that the reaction could be carried out at low loadings of catalyst, which was generated in situ from inexpensive and commercially available reagents. High conversions and product yields were obtained in a variety of solvents and even under neat conditions. Product analysis identified transesterification to be the primary competing reaction, which could be mitigated by changing solvents, as well as minimizing the amount of excess acid present in solution. Pyrolysis of methyl and ethyl 2-(propionyloxy)propanoate transformed these esters into their respective acrylates suitable for subsequent polymerization, along with propionic acid as a valuable coproduct.