Stereodivergent Synthesis of Enantioenriched gamma-Butyrolactones Bearing Two Vicinal Stereocenters Enabled by Synergistic Copper and Iridium Catalysis

摘要

By virtue of a fundamentally new reaction model of azomethine ylide serving as a two-atom synthon, we present the first example of stereodivergent preparation of gamma-butyrolactones via synergistic Cu/Ir-catalyzed asymmetric cascade allylation/lactonization, and all four stereoisomers of gamma-butyrolactones bearing two vicinal stereocenters are accessible with excellent diastereoselective and enantioselective control. The chiral Ir-III-pi-allyl intermediate was separated and characterized to understand the origin of the regio- and stereoselectivity of the initial C-C bond formation process. Control experiments shed some light on the catalyst/substrate and catalyst/catalyst interactions in this dual catalytic system to rationalize the related kinetic/dynamic kinetic resolution process with different catalyst combinations. The enantioenriched gamma-butyrolactone products were converted into an array of structurally complex chiral molecules and organocatalysts that were otherwise inaccessible.