Asymmetric Inverse-Electron-Demand Oxa-Diels-Alder Reaction with Morita-Baylis-Hillman Carbonates of 2-Cyclopentenone via a Palladium-Catalyzed Umpolung Strategy.

Here we uncovered that the dienones generated from the Morita-Baylis-Hillman carbonates of 2-cyclopentenone under Pd(0) catalysis could be umpolunged by regioselectively forming η 2 -Pd(0) complexes via π-Lewis base activation, and underwent asymmetric inverse-electron-demand oxa-Diels-Alder reaction with α-cyano chalcones. An array of fused pyran frameworks with dense substitutions was constructed with excellent stereoselectivity (up to 99% ee, >19:1 dr), which could be elaborated to access enantioenriched architectures with higher molecular complexity.