Synthesis of Dihydropyrans via Pd-catalyzed Cyclization of 2-allyl-1,3-dicarbonyl Compounds and Vinylic Triflates Or Halides

The palladium-catalyzed reaction of 2-allyl-1,3-dicarbonyl compounds with vinylic triflates or halides affords dihydropyran derivatives, most probably through the intermediacy of η 3-allylpalladium complexes that undergo an intramolecular nucleophilic attack by the oxygen