Catalyst-Controlled Regioselective Carbonylation of Isobutylene Oxide to Pivalolactone
Aran K. Hubbell, Jessica R. Lamb, Kristīne Kļimoviča, Michael Mulzer, Timothy D. Shaffer, Samantha N. MacMillan, Geoffrey W. Coates
Abstract
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.