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Tetrahydropyran (THP) is the
In a typical procedure, the alcohol is treated with 3,4-dihydropyran and ''p''-toluenesulfonic acid in 
Alternatively, the THP ether can be generated under the conditions akin to those for the
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
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, or oxine, 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 ...
, 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 special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. Furthermore, a tetrahydropyran ''ring system'', i.e., five carbon atoms and an oxygen, is the core of pyranose 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. There may be other carbons external to the ring. The name derives from its similarity ...
sugars, such as glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
.
Structure and preparation
In gas phase, the THP exists in its lowest energy Cs symmetry chair conformation. One classic procedure for theorganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
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 Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...
of the 3,4-isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
Iso ...
of dihydropyran In organic chemistry, dihydropyran refers to two heterocyclic compounds with the formula C5H8O:
* 3,4-Dihydro-2''H''-pyran
*3,6-dihydro-2''H''-pyran
Nomenclature
In IUPAC names, "dihydro" refers to the two added hydrogen atoms needed to remove o ...
with Raney nickel.
Tetrahydropyranyl derivatives
Although tetrahydropyran is an obscure compound, tetrahydropyranyl ethers are commonly used inorganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. 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 many ...
for alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
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.
:
In a typical procedure, the alcohol is treated with 3,4-dihydropyran and ''p''-toluenesulfonic acid in dichloromethane
Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...
at ambient temperature.
Alternatively, the THP ether can be generated under the conditions akin to those for the Mitsunobu reaction
The Mitsunobu reaction is an organic reaction that converts an alcohol into a variety of functional groups, such as an ester, using triphenylphosphine and an azodicarboxylate such as diethyl azodicarboxylate (DEAD) or diisopropyl azodicarboxylat ...
. Thus the alcohol is treated with 2-hydroxytetrahydropyranyl, triphenylphosphine
Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists a ...
, and diethyl azodicarboxylate
Diethyl azodicarboxylate, conventionally abbreviated as DEAD and sometimes as DEADCAT, is an organic compound with the structural formula CH3CH2O2CN=NCO2CH2CH3. Its molecular structure consists of a central azo functional group, RN=NR, flanked ...
(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 ma ...
(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 component ...
in a THF/water solution, ''p''-toluenesulfonic acid in water, or Pyridinium ''p''-toluenesulfonate (PPTS) in ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
.
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''.See also
*Pyran
In chemistry, pyran, or oxine, 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 ...
*Dioxane
1,4-Dioxane () is a heterocyclic organic compound, classified as an ether. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane because the other dioxane isomers ( 1,2- ...
and Trioxane
Trioxane refers to any of three isomeric organic compounds composed of a six-membered ring with three carbon atoms and three oxygen atoms, having the molecular formula C3H6O3.
The three isomers are:
* 1,2,3-trioxane, a hypothetical compound rela ...
, which have two and three oxygen atoms as part of their six-membered rings respectively
References