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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 η2-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.