Tetrahydropyran (THP) is the

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom. It is named by reference to

pyran In chemistry, pyran is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C5H6O. There are two isomers of pyran that differ by the location ...

, 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 Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

. Furthermore, a tetrahydropyran ''ring system'', i.e., five carbon atoms and an oxygen, is the core of

pyranose In organic chemistry, pyranose is a collective term for saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom (a heterocycle). There may be other carbons external to the ...

sugars, such as

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

Structure and preparation

In gas phase, the THP exists in its lowest energy C_s symmetry chair conformation. One classic procedure for the

of tetrahydropyran is by

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...

of the 3,4-

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

of dihydropyran with

Raney nickel Raney nickel , also called spongy nickel, is a fine-grained solid composed mostly of nickel derived from a nickel–aluminium alloy. Several grades are known, of which most are gray solids. Some are pyrophoric, but most are used as air-stable s ...

Tetrahydropyranyl derivatives

Although tetrahydropyran is an obscure compound, tetrahydropyranyl ethers are commonly used in

. Specifically, the 2-tetrahydropyranyl (THP) group is a common

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In man ...

for

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

s. 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 Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

. 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. : THPmeth

In a typical procedure, the alcohol is treated with 3,4-dihydropyran and ''p''-toluenesulfonic acid in dichloromethane at ambient temperature. THPProtection

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 Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

(THF). Commonly, THP ethers are deprotected using

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

in a THF/water solution, ''p''-toluenesulfonic acid in water, or Pyridinium ''p''-toluenesulfonate (PPTS) in

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

Oxanes

Oxanes are the class of hexic cyclic ether rings with tetrahydropyran as the root chemical. Oxanes have one or more carbon atoms replaced with an oxygen atom. The IUPAC preferred name for tetrahydropyran is now ''oxane''. Oxane is also the brand name for ''cis''-2-methyl-4-propyl-1,3-oxathiane, a commercial fragrance.

References

{{Authority control Protecting groups Ether solvents

Structure and preparation

Tetrahydropyranyl derivatives

Oxanes

See also

References