Stereoselective Iridium-N,P-Catalyzed Double Hydrogenation ofConjugated Enones to Saturated Alcohols

Asymmetric hydrogenation of prochiral substratessuch as ketones and olefins constitutes an important instrument forthe construction of stereogenic centers, and a multitude of catalyticsystems have been developed for this purpose. However, due to thedifferent nature of the pi-system, the hydrogenation of olefins andketones is normally catalyzed by different metal complexes. Herein,astudyontheeffect of additives on the Ir-N,P-catalyzedhydrogenation of enones is described. The combination ofbenzamide and the development of a reactive catalyst unlocked anovel reactivity mode of Crabtree-type complexes toward C???O bond hydrogenation. The role of benzamide is suggested to extendthe lifetime of the dihydridic iridium intermediate, which is prone to undergo irreversible trimerization, deactivating the catalyst.This unique reactivity is then coupled with C???C bond hydrogenation for the facile installation of two contiguous stereogeniccenters in high yield and stereoselectivity (up to 99%ee, 99/1 d.r.) resulting in a highly stereoselective reduction of enones

Automated summary

This study reveals a novel reactivity of Crabtree-type complexes in the Ir-N,P-catalyzed hydrogenation of enones by adding benzamide and developing a reactive catalyst, resulting in a highly stereoselective reduction of enones.