A short route to access oxaspiro[,3,3]propellanes

Novel access to oxaspiro[ n ,3,3]propellanes has been developed from bicyclic lactones directly prepared by a photochemical hydroxymethylation or alternatively by a three-step sequence. Thanks to the presence of additional hydroxy- and propargylic groups, a second cyclization catalyzed by silver or bismuth salts, led to the propellane structure which was finally transformed into spiranic derivatives by a Simmons-Smith reaction or condensation with α-ketoesters. Two different oxapropellane derivatives have been prepared from a common α-propargyl-β-ketoester.