Au-catalyzed cyclization of monopropargylic triols: an expedient synthesis of monounsaturated spiroketals.

The gold-catalyzed cyclization of monopropargylic triols to form olefin-containing spiroketals is reported. The reactions are rapid and high yielding when 2 mol % of the catalyst generated in situ from Au[P(t-Bu)(2)(o-biphenyl)]Cl and AgOTf is employed in THF at 0 degrees C. A range of differentially substituted triols leading to substituted 5- and 6-membered ring spiroketals were prepared and function well in the reaction.