Gold Catalysed 1,4-Enyne Acetate Strategy for the Synthesis of 1H-Indenes and Partially Hydrogenated Methanonaphtho[1,2-c]furan-1,3(4H)-diones

A synthetic method to prepare 1H-indenes and partially hydrogenated methanonaphtho[1,2-c]furan-1,3(4H)-diones from gold(I)-catalysed 1,4-enyne acetate cycloisomerisation and oxidation or Diels-Alder reaction with maleic anhydride is described. The proposed mechanism involves Rautenstrauch rearrangement of the 1,4-enyne motif to give an in situ formed 1,3-cyclopentadiene intermediate. This is followed by 6-endo-dig cyclisation of the cyclic adduct and oxidation to give the aromatic carbocycle or Diels-Alder reaction with maleic anhydride to afford the bridged furan product.