Reactions facilitating inversion of alkene stereochemistry are rare, sought-after transformations in the field of modern organic synthesis. Although a number of isomerization reactions exist, most methods require specific, highly activated substrates to achieve appreciable conversion without side product formation. Motivated by stereoinvertive epoxide carbonylation reactions, we developed a two-step epoxidation/deoxygenation process that results in overall inversion of alkene stereochemistry. Unlike most deoxygenation systems, carbon monoxide was used as the terminal reductant, preventing difficult postreaction separations, given the gaseous nature of the resulting carbon dioxide byproduct. Various alkyl-substituted cis- A nd trans-epoxides can be reduced to trans- A nd cis-alkenes, respectively, in >99:1 stereospecificity and up to 95% yield, providing an alternative to traditional, direct isomerization approaches.
Bibliographical noteFunding Information:
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DE-FG02-05ER15687. J.R.L. acknowledges a graduate fellowship from the National Science Foundation (DGE-1144153). A.K.H. acknowledges a training grant fellowship from the National Institute of General Medical Sciences (NIGMS 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 under Award CHE-1531632. We thank Dr. Michael Mulzer for synthesizing various epoxide starting materials.
© 2020 American Chemical Society.