{{about|tetrahydropyran, whose IUPAC name is oxane|ethylene oxide, which has occasionally been named as oxane|oxirane}}
{{chembox|verifiedrevid=470604410|Name=Tetrahydropyran|ImageFileL1_Ref={{chemboximage|correct|??}}|ImageFileL1=Tetrahydropyran.svg|ImageSizeL1=80px|ImageNameL1=Tetrahydropyran|ImageFileR1=Oxane-3D-vdW.png|ImageSizeR1=100px|ImageNameR1=THP|PIN=Oxane|OtherNames=Tetrahydropyran,<br>Oxacyclohexane, <br>1,5-epoxypentane|Section1={{Chembox Identifiers | PubChem = 8894 | InChI = 1/C5H10O/c1-2-4-6-5-3-1/h1-5H2 | InChIKey = DHXVGJBLRPWPCS-UHFFFAOYAV | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C5H10O/c1-2-4-6-5-3-1/h1-5H2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = DHXVGJBLRPWPCS-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 142-68-7 | Beilstein = 102436 | DrugBank_Ref = {{drugbankcite|correct|drugbank}} | DrugBank = DB02412 | EINECS = 205-552-8 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = V06I3ILG6B | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 46941 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = | SMILES = O1CCCCC1 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 8554 }}|Section2={{Chembox Properties | C = 5 | H = 10 | O = 1 | Appearance = Colourless liquid | Density = 0.880 g/cm<sup>3</sup> | MeltingPtC = -45 | BoilingPtC = 88 }} |Section3={{Chembox Hazards | MainHazards = Flammable, Causes skin irritation | NFPA-H = 2 | NFPA-F = 4 | NFPA-R = 1 | NFPA-S = | LDLo = 3000 mg/kg (oral, rat) | FlashPtC = -15.6 | AutoignitionPtC = }}}}
'''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'''.<ref>{{cite web|url=http://bulletin.acscinf.org/PDFs/247nm44.pdf|title=New IUPAC Organic Nomenclature - Chemical Information BULLETIN}}</ref> 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.<ref name = Greene /> Furthermore, a tetrahydropyran ''ring system'', i.e., five carbon atoms and an oxygen, is the core of pyranose sugars, such as glucose.
==Structure and preparation== In gas phase, the THP exists in its lowest energy C<sub>s</sub> symmetry chair conformation.<ref>{{Cite journal|title = A dynamical (e,2e) investigation of the structurally related cyclic ethers tetrahydrofuran, tetrahydropyran, and 1,4-dioxane|journal = Journal of Chemical Physics|date = 2013|pages = 034306|volume = 139|issue = 3|doi = 10.1063/1.4813237|first1 = J. D.|last1 = Builth-Williams|first2 = S. M.|last2 = Bellm|first3 = L.|last3 = Chiari|first4 = P. A.|last4 = Thorn|first5 = D. B.|last5 = Jones|first6 = H.|last6 = Chaluvadi|first7 = D. H.|last7 = Madison|first8 = C. G.|last8 = Ning|first9 = B.|last9 = Lohmann| pmid=23883026 | bibcode=2013JChPh.139c4306B |url = http://dspace.flinders.edu.au/xmlui/bitstream/2328/26887/1/Builth-Williams%20Dynamical.pdf|hdl = 2328/26887| s2cid=205181690 |hdl-access = free}}</ref>
One classic procedure for the organic synthesis of tetrahydropyran is by hydrogenation of the 3,4-isomer of dihydropyran with Raney nickel.<ref>{{OrgSynth | title = Tetrahydropyran | first1 = D. W. | last1 = Andrus | first2 = John R. | last2 = Johnson | collvol = 3 | collvolpages = 794 | year = 1943 | volume = 23 | pages = 90 | prep = cv3p0794 | doi = 10.15227/orgsyn.023.0090}}</ref>
==Tetrahydropyranyl derivatives== 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.<ref>{{OrgSynth | title = Methyl 4-Hydroxy-2-butynoate | first1 = R. A. | last1 = Earl | first2 = L. B. | last2 = Townsend | collvol = 7 | collvolpages = 334 | year = 1981 | volume = 60 | page = 81 | doi = 10.15227/orgsyn.060.0081 | prep = cv7p0334}}</ref><ref>{{OrgSynth | title =<nowiki>Diethyl [(2-Tetrahydropyranyloxy)methyl]phosphonate</nowiki> | first = Arthur F. | last = Kluge | collvol = 7 | collvolpages = 160 | year = 1986 | volume = 64 | page = 80 | doi = 10.15227/orgsyn.064.0080 | prep = cv7p0160}}</ref> 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.<ref name = Greene />
:thumb|center|320 px|Protection of alcohol as THP ether followed by deprotection. Both steps require acid catalysts.
In a typical procedure, the alcohol is treated with 3,4-dihydropyran and ''p''-toluenesulfonic acid in dichloromethane at ambient temperature.<ref name = Greene>{{cite book|title = Greene's Protective Groups in Organic Synthesis|chapter = Protection for the Hydroxyl Group, Including 1,2- and 1,3-Diols|pages = 16–366|edition = 4th|last1 = Wuts|first1 = Peter G. M.|last2 = Greene|first2 = Theodora W.|doi = 10.1002/9780470053485.ch2|year = 2006|isbn = 9780470053485}}</ref> [[File:THPProtection.png|center|thumb|610x610px|THP protection used in the total synthesis of solandelactone E<ref>{{Cite journal|last1=Robinson|first1=Anna|last2=Aggarwal|first2=Varinder K.|date=2010|title=Asymmetric Total Synthesis of Solandelactone E: Stereocontrolled Synthesis of the 2-ene-1,4-diol Core through a Lithiation–Borylation–Allylation Sequence|journal=Angewandte Chemie International Edition|volume=49|issue=37|pages=6673–6675|doi=10.1002/anie.201003236|pmid=20683835 }}</ref>]]
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).
Commonly, THP ethers are deprotected using acetic acid in a THF/water solution, ''p''-toluenesulfonic acid in water, or pyridinium ''p''-toluenesulfonate (PPTS) in ethanol.
==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.<ref>Ferenc Notheisz, Mihály Bartók, "Hydrogenolysis of C–O, C–N and C–X bonds", p. 416 in, R. A. Sheldon, Herman van Bekkum (eds), ''Fine Chemicals through Heterogeneous Catalysis'', John Wiley & Sons, 2008 {{ISBN|3527612971}}.</ref> The IUPAC preferred name for tetrahydropyran is now ''oxane''.<ref>{{cite web|url=http://bulletin.acscinf.org/PDFs/247nm44.pdf|title=New IUPAC Organic Nomenclature - Chemical Information BULLETIN}}</ref>
Oxane is also the brand name for ''cis''-2-methyl-4-propyl-1,3-oxathiane, a commercial fragrance.<ref>{{cite book |doi=10.1002/14356007.t11_t02 |chapter=Flavors and Fragrances, 3. Aromatic and Heterocyclic Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2016 |last1=Panten |first1=Johannes |last2=Surburg |first2=Horst |pages=1–45 |isbn=978-3-527-30673-2 }}</ref>
==See also== *Pyran *Dioxane and Trioxane, which have two and three oxygen atoms as part of their six-membered rings respectively
== References == <references/>
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Category:Protecting groups Category:Ether solvents Category:Tetrahydropyrans