dihydropyran

Dihydropyran is a heterocyclic organic compound in the pyran family. It consists of a six-membered ring with five carbons and one oxygen, with the ring partially saturated. The empirical formula is C5H8O and the molecular weight is about 84.1 g/mol. The compound exists as isomers depending on which bond remains unsaturated; the most common commercially relevant form is 3,4-dihydropyran. Dihydropyran can be prepared by hydrogenation of pyran or by dehydrogenation of tetrahydropyran; it is also sold as a reagent for organic synthesis.

In organic synthesis, dihydropyran is best known as the precursor to the tetrahydropyranyl (THP) protecting group. In the presence of acid, dihydropyran reacts with alcohols to form THP ethers, temporarily protecting hydroxyl groups during multi-step syntheses. It also participates in acetal formation with carbonyl compounds, yielding THP acetals that protect aldehydes and ketones. The THP protecting group is valued for its stability under a wide range of conditions and for its relatively mild, acid-labile removal.

Safety considerations include that dihydropyran is a flammable liquid and should be handled in a well-ventilated area with appropriate protective equipment, away from sources of ignition.