Gold(I)-catalyzed benzannulation of 3-hydroxy-1,5-enynes: an efficient synthesis of substituted tetrahydronaphthalenes and related compounds

We report a novel gold(I)-catalyzed benzannulation of 3-hydroxy-1,5-enynes to prepare tetrahydronaphthalenes. The reaction is catalyzed by 2.5 mol % Ph3PAuCl and 2.5 mol % AgOTf in dichloromethane. We discovered that this process can be also catalyzed by 1 mol % Ph3PAuCl and 1 mol % TfOH. To the best of our knowledge, this constitutes the first report of an active gold catalyst generated from Au(PPh3)Cl and triflic acid. This mild process is compatible with a variety of functional groups and proves to be an effective method to synthesize various meta-substituted aromatic rings in good yields.