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.
Bibliographical noteFunding Information:
Financial support for this work was provided by the Minnesota Corn Growers Association. M.A.H. acknowledges the Center for Sustainable Polymers at the University of Minnesota, a National Science Foundation supported center for Chemical Innovation (CHE-1413862). Equipment for the Chemistry Department NMR facility were supported through a grant from the National Institutes of Health (S10OD011952) with matching funds from the University of Minnesota. I.A.T. is an Alfred P. Sloan Fellow. X-ray diffraction experiments were performed using a crystal diffractometer acquired through NSF-MRI Award CHE-1229400.
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- Alkyl lactates
- Lactic acid