Facile generation method for conjugated allenyl esters based on retro-Dieckmann-type ring-opening reactions

α-Alkynyl-α-ethoxycarbonyl cyclopentanones 1a–c and cyclohexanones 2a–c were readily synthesized by the reaction of ethyl 2-oxocyclopentanonecarboxylate 6 and ethyl 2-oxocyclohexanonecarboxylate 7 with alkynyllead triacetates 5a–c obtained from lithium acetylides 4a–c and lead tetraacetate. Treatment of 1a–c and 2a–c with 1 N KOH in THF or with n-Bu4N+OEt− in EtOH and THF gave the corresponding conjugated allenyl esters 8a–c, 9a–c, 10a–c, and 11a–c in good to excellent yields, respectively.