A convenient access to thermodynamically nonstabilised spiroketal isomers: the first synthesis of (Z)-7-methyl-1,6-dioxaspiro[4.5]decane

Functionalised hydroxy α-alkynones were transformed to the corresponding spiroketals by a one-pot cascade consisting of palladium-catalysed hydrogenation of the triple bond, hydroxyl group deprotection and spirocyclisation under mild nonacidic conditions. The reaction does not rely upon thermodynamic control to set the configuration of the ketal stereocentre so that both the anomerically stabilised and nonstabilised isomers are similarly accessible.