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A new and highly convenient Au-catalyzed cyclization of alkyne-propargylic acetates leading to 2-acyl-3-arylnaphthalene derivatives is described; these are possible candidates for lightemitting materials.

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We report a new and highly-convenient Au-catalyzed cyclization of alkyne propargylic acetates leading to 2,3-bis(alkylidene)cyclohexanones and their cycloadditions with a pendant dienophile.

We discovered a new and highly convenient gold-catalyzed cyclization of alkyne-propargylic pivaloates leading to fused bicyclic compounds.Recent advances in gold-based alkyne activation led to develop new and efficient catalytic reactions applicable to the synthesis of complex molecules. 1 On the behalf of the excellent alkynophilicity of gold cations, terminal alkynes in the presence of a nucleophile could form gold-carbene complexes. 2 Internal alkynes are weakly activated enough to react with nucleophiles of alkenes or aldehydes. Phenyl-substituted alkynes, for example, might form weak pcomplexes which underwent [2+2+2] cycloaddition with a pendent double bond and one double bond in the phenyl ring. 3 We became interested in gold-catalyzed chemistry of triynes containing a terminal, an internal (propargylic ester), and a phenyl-conjugated triple bond in the same molecule.In this context, we recently reported gold-catalyzed cascade cyclization of the triyne 1 to the tricycle 3. 4 Mechanistically, the allene 2, the initial intermediate from 1 under the gold catalysis, would react with the terminal triple bond to form the gold-bound diene intermediate A, which would subsequently undergo [4+2] cycloaddition to B. The further conversion of B via demetalation (into C) and dehydrogenation afforded the tricycle 3 (Scheme 1). Yet its mechanism and the origin of hydrogen were not clear.The present conditions toward a triyne 4a, a homologue of 1a, did not afford the expected tricycle, but exhibited a different mode of reactions to give the [3.2.0]-bicyclic system 7a. Herein we wish to report our results on the scope and limitations of this new reaction leading to the [3.2.0] and [4.2.0] bicycles 7 (Scheme 2). 5 At first, we surveyed the reaction conditions including catalysts, solvent, and the reaction temperatures toward the substrate