Gold and Brønsted Acid Catalyzed Hydride Shift onto Allenes: Divergence in Product Selectivity

A series of allenyl ethers can be transformed into various fused or spiro tetrahydrofurans and tetrahydropyrans following a hydride shift/cyclization sequence. A divergence in product selectivity, which depends on the nature of the catalyst used (Au(I) complex or Brønsted acid), was observed.