A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• less effective. The use of methanol as solvent helped suppress the formation of the undesired furan by-product. This study provides yet another example of the advantages of gold catalysis in the activation of alkyne π-systems. Keywords: alkynes; cyclocondensation; cycloisomerization; gold-catalyzed

• selectivity using the Utimoto conditions to prepare 6,6-spiroketals. Therefore, he suggested the preferred use of Ziese’s dimer, a platinum catalyst (Scheme 3, Reaction 2), for such cyclizations [9]. In an unrelated study that also bears on the current work, Aponick and co-workers described a gold-catalyzed

• methanol, as pre-mixing the gold(I) chloride with methanol and aging this mixture prior to adding the substrate results in a less efficient reaction. This is not the first time that we have observed the importance of the order of addition in a gold-catalyzed reaction in a protic solvent [38], but