Facile access to cyclooctanoid ring systems via microwave-assisted tandem 6-exo dig cyclization-rearrangement sequence

Appropriately substituted 5-alkyn-1-ol systems bearing a nitrile moiety at the triple bond serve as versatile precursors to a variety of cyclooctenone derivatives via a 'one-pot' base-catalyzed oxyanionic 6-exo dig cyclization/Claisen rearrangement sequence under microwave irradiation. It was found that the initially formed cyclic intermediate consists of a mixture of endo and exocyclic isomers, which appear to be in equilibrium under the reaction conditions. However, the only observed products from these reactions are α-cyano-substituted cyclooctenones, derived from the exocyclic dihydrofuran intermediates.