FeCl3·6H2O-catalyzed synthesis of substituted cis-2,6-tetrahydropyrans from ζ-hydroxy allylic derivatives

A highly diastereoselective iron-catalyzed synthesis of substituted cis-2,6-tetrahydropyrans from ζ-hydroxy allylic derivatives is described. The FeCl3·6H2O-induced epimerization of the formed 2-alkenyl 6-substituted tetrahydropyrans is the key reaction to account for the high diastereoselectivities observed.