Synthesis of enantiomerically pure substituted tetrahydrofurans from epoxides and phenylselenium reagents

Starting from the commercially available enantiomerically pure epoxides, enantiomerically pure substituted tetrahydrofurans were prepared using simple conversions promoted by organoselenium reagents. The first step consisted in the opening of the epoxides with phenylselenolate anions to afford hydroxyalkyl phenyl selenides. The PhSe group was then substituted by an allyl group by treatment with allyltributyltin and AIBN. The reaction of these allylic derivatives with electrophilic phenylselenium reagents afforded selenium containing tetrahydrofurans as the result of a stereospecific 5-exo-trig cyclization. The tetrahydrofuran derivatives thus obtained were finally deselenenylated with triphenyltin hydride and AIBN