A simple and expeditious synthesis of 2,3,6-trisubstituted tetrahydropyrans through (3,5)-oxonium-ene cyclization using molecular iodine

A variety of aldehydes undergo a smooth coupling with 6-methylhept-5-en-2ol in the presence of molecular iodine to afford the 2,3,6-trisubstituted tetrahydropyrans in good yields through 3,5-oxonium-ene cyclization under mild and neutral conditions. This method is simple, convenient, and cost-effective.