Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• hydroxy(methoxy)-functionalized dihydronaphthalene derivatives is highly remarkable in the context of the observed reaction pathways for the cycloisomerizations of 1,6-enynes bearing a trisubstituted olefin. Keywords: catalysis; dihydronaphthalenes; gold; gold catalysis; hydroxycyclization; selectivity

• cyclization should be noted and only minor amounts (10–15%) of 3a were also formed. Due to the unexpected 6-endo-favored pathway found for substrate 1a [39], we attempted to further improve this selectivity in the hydroxycyclization process (Table 1). Switching the ligand from Ph3P to XPhos or N-heterocyclic

• significant influence on the selectivity but led to the formation of minor amounts of alcohol 8a, derived from a 5-exo hydroxycyclization reaction. With a 1:1 mixture of CH2Cl2/dioxane the effect of the selected catalytic systems was checked (Table 1, entries 7–10). We found that the use of JohnPhos as a