Oxidative Photochemical Cyclisations to Access Spiroketals

The spiroketal moiety is an important substructure within many biological natural products. One method to access them is via the oxidative cyclisation of a pendant hydroxyl group on to a pre‐formed pyran. However applications of this methodology have been severely limited by requiring the use of toxic oxidants, such as lead (IV) tetraacetate or mercuric oxide. Herein we report a high yielding photochemical route to prepare complex spiroketals using an oxidative photochemical approach employing iodine monochloride and sodium acetate and demonstrate the methodology to the synthesis of a number of insect pheromones.