Vinylogous Elimination/C-H Functionalization/Allylation Cascade Reaction of Allenoate Adducts: Synthesis of Ring-Fused Dihydropyridinones.

A palladium-catalyzed cascade reaction of β'-allenoate adducts with aryl/heteroaryl carboxamides through a vinylogous elimination/C-H functionalization/intramolecular allylation reaction sequence has been developed with high Z stereoselectivity. Various ring-fused dihydropyridinones bearing an α,β-unsaturated ester substituent are obtained. It is the first example of application of the allenoate adducts to C-H functionalization annulations as practical precursors of hard-to-get functionalized electron-deficient 1,3-butadienes. Using air as the terminal oxidant also shows a great advantage in environmental friendliness.