Deoxygenation of Epoxides with Carbon Monoxide

The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer‐iridium(I) complex in combination with a Lewis acid co‐catalyst to achieve a pre‐activation of the epoxide substrate, as well as the elimination of CO2 from a γ‐2‐iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate‐dependent change in the mechanism for the epoxide C−O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration. Deoxygenate it! Carbon monoxide is the direct and environmentally benign deoxygenation agent for epoxides. This reaction is catalyzed by an iridium pincer complex and co‐catalyst LiNTf2 via an unprecedented γ‐2‐iridabutyrolactone intermediate. LiNTf2 is not only necessary for the epoxide activation, but also for the decarboxylation of the iridalactone (see scheme).