Substituent effects on the regiochemical and stereochemical course of the nussbaumer-frater variation of the prins cyclization

Eleven vinylogous carbonates were examined in the Nussbaumer-Frater variation of the Prins cyclization to provide 2,3,4,6-tetrasubstituted tetrahydropyrans. Results indicate that substrate olefin geometry is a more reliable control element than preset substrate vicinal stereochemistry for establishing C 2 -C 3 vicinal stereochemistry in tetrahydropyran products.