The present disclosure provides regioselective methods for synthesizing intermediates useful in making prostacyclin derivatives, such as treprostinil. Claimed is a method of producing a compound of formula III comprising heating a solution comprising a compound of formula II and an organic solvent, wherein said heating comprises irradiating said solution with microwave radiation and wherein X is hydrogen, an alkoxy group, or OR2, unsubstituted or substituted aryl, or unsubstituted or substituted benzyl. This method is suitable for regioselectively preparing intermediates useful in making prostacyclin derivatives, such as treprostinil.