Poly(pivalolactone) (PPVL) is a crystalline polyester with attractive physical and mechanical properties; however, prohibitively expensive syntheses of pivalolactone have thwarted efforts to produce PPVL on an industrial scale. Therefore, we developed a class of highly regioselective sandwich-type catalysts for the carbonylation of isobutylene oxide. These sterically encumbered complexes install carbon monoxide at the substituted epoxide carbon, generating a high level of contrasteric selectivity (up to >99:1). Further catalyst development improved catalyst solubility and reproducibility while maintaining high regioselectivity. In addition, a dibasic ester solvent extended catalyst lifetimes and suppressed side product formation. This contrasteric carbonylation of isobutylene oxide offers a route to sought-after pivalolactone and, therefore, PPVL.
Bibliographical noteFunding Information:
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-FG02-05ER15687, and ExxonMobil. J.R.L. acknowledges a graduate fellowship from the National Science Foundation (No. DGE-1144153). A.K.H. acknowledges a training grant fellowship from the National Institute of General Medical Sciences (NIGMS No. T32-GM008500). This content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of General Medical Sciences or the National Institutes of Health. This work made use of the NMR Facility at Cornell University, which is supported, in part, by the NSF (No. CHE-1531632), as well as the Mass Spectrometry Lab at the University of Illinois, which is supported by the NSF, Division of Biological Infrastructure (No. DBI-0100085).
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- Epoxide carbonylation
- Isobutylene oxide