An efficient stereoselective synthesis of 4,5-trans-1,5-cis-3-oxabicyclo[3.1.0]hexan-2-ones through the iodolactonization of alkylidenecyclopropyl esters

A highly stereoselective iodolactonization of alkylidenecyclopropyl esters with iodine or N-iodosuccinimide (NIS) in aqueous CH3CN to afford 4,5-trans-1,5-cis-3-oxabicyclo[3.1.0]hexane-2-ones is described. The stereoselectivity might be controlled by the steric effects of the substituent group of the C=C bond.