Prins Cascade Cyclization for the Synthesis of 1,9-Dioxa-4-azaspiro[5.5]undecane Derivatives

A novel Prins cascade process for the synthesis of 1,9-dioxa-4- azaspiro[5.5]­undecane derivatives by the coupling of aldehydes with N-(4-hydroxy-2-methylenebutyl)-N-(2-hydroxyethyl)-4-methylbenzenesulfonamide has been developed. This is the first report of the synthesis of spiromorpholinotetrahydropyran derivatives through a Prins bicyclization.