3,4-Dihydropyran
3,4-Dihydropyran is a heterocyclic compound with the formula C5H8O. The six-membered C5O ring has the unsaturation adjacent to oxygen. The isomeric 3,6-dihydropyran has a methylene separating the double bond and oxygen. DHP is used for protecting group for alcohols. It is a colorless liquid.Preparation
Dihydropyran is prepared by the dehydration of tetrahydrofurfuryl alcohol over alumina at 300–400 °C. THFA is itself prepared from tetrahydro-2-furoic acid.Reactions
In organic synthesis, the 2-tetrahydropyranyl group is used as a protecting group for alcohols. Reaction of the alcohol with DHP forms a THP ether, protecting the alcohol from a variety of reactions. The alcohol can later be restored by acidic hydrolysis, concomitant with formation of 5-hydroxypentanal.
