Spiroketals: The synthesis of an olive fly pheromone component, 4-hydroxy-1,7-dioxaspiro[5,5]undecane, via a novle cation-olefin cyclisation step

An acid-catalysed rearrangement of the THP-ether of homoallylic alcohol gives ready access to an 0-protected derivative of 4-hydroxytetrahydropyran and thence by two further steps to provide a short and highly stereoselective route to the title spiroketal.