Tetrahydropyran (THP) is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom. It is named by reference to pyran, which contains two double bonds, and may be produced from it by adding four hydrogens. In 2013, its preferred IUPAC name was established as oxane. The compound is a colourless volatile liquid. Derivatives of tetrahydropyran are, however, more common. 2-Tetrahydropyranyl (THP-) ethers derived from the reaction of alcohols and 3,4-dihydropyran are commonly used as protecting groups in organic synthesis. Furthermore, a tetrahydropyran ring system, i.e., five carbon atoms and an oxygen, is the core of pyranose sugars, such as glucose.
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||86.134 g·mol−1|
|Melting point||−45 °C (−49 °F; 228 K)|
|Boiling point||88 °C (190 °F; 361 K)|
|Main hazards||Flammable, Causes skin irritation|
|NFPA 704 (fire diamond)|
|Flash point||−15.6 °C (3.9 °F; 257.5 K)|
|Lethal dose or concentration (LD, LC):|
LDLo (lowest published)
|3000 mg/kg (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure and preparationEdit
In gas phase, the THP exists in its lowest energy Cs symmetry chair conformation.
Although tetrahydropyran is an obscure compound, tetrahydropyranyl ethers are commonly used in organic synthesis. Specifically, the 2-tetrahydropyranyl (THP) group is a common protecting group for alcohols. Alcohols react with 3,4-dihydropyran to give 2-tetrahydropyranyl ethers. These ethers are resilient to a variety of reactions. The alcohol can later be restored by acid-catalyzed hydrolysis. This hydrolysis reforms the parent alcohol as well as 5-hydroxypentanal. THP ethers derived from chiral alcohols form diastereomers. Another undesirable feature is that the ethers display complex NMR spectra, which interfere with analysis.
Alternatively, the THP ether can be generated under the conditions akin to those for the Mitsunobu reaction. Thus the alcohol is treated with 2-hydroxytetrahydropyranyl, triphenylphosphine, and diethyl azodicarboxylate (DEAD) in tetrahydrofuran (THF).
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