Tetrahydropyran Oxane

Tetrahydropyran (oxane) [142-68-7] M 86.1, b 88.0°, d 0.885, ng 1.4202, pK -2.79 (aqueous H2SO4). Dry oxane with CaH2, then pass it through a column of silica gel to remove olefinic impurities and fractionally distil it. Free it from peroxides and moisture by refluxing with sodium, then distil it from LiAlH4. Alternatively, peroxides can be removed by treatment with aqueous ferrous sulfate and sodium bisulfate, followed by solid KOH, and fractional distillation from sodium. [Beilstein 17 H 12, 17 I 6, 17 n 18, 17 III/IV 51, 17/1 V 64.]... 

Ethylene oxide (oxirane) Trimethylene oxide (oxetane) Tetrahydrofuran (oxolane) Tetrahydropyran (oxane)... 

This article deals with the conformational analysis of substituted oxanes (tetrahydropyranes) and derivatives in which ring methylenes are replaced by further oxygen atoms (di-, tri-, tetroxanes, pentoxanes, and O ) or by carbonyl group(s) (oxanones, Meidrum s acid derivatives) and, if conforma-tionally of interest, systems incorporating these rings in polycyclic structures... 

Cyclic ethers can be named simply as oxacycloalkanes, such as oxacyclopropane, oxacyclo-butane, oxacyclopentane, and oxacyclohexane, where the prefix oxa indicates the replacement of CH2 by O in corresponding cycloalkanes. Most cyclic ethers, however, are known by other names. The 3-, 4-, 5-, and 6-membered rings are oxirane, oxetane, oxolane, and oxane, respectively, or ethylene oxide (or epoxide), trimethylene oxide, tetrahydrofuran, and tetrahydropyran. 

Pyrans (Oxanes) The six-membered cyclic ethers are commonly named as derivatives of pyran, an unsaturated ether. The saturated compound has four more hydrogen atoms, so it is called tetrahydropyran (THP). The systematic term oxane is also used for a six-membered ring containing an oxygen atom. 

One recognizes an oxane ring (tetrahydropyran) substituted by three secondary alcohol functions in an equatorial orientation, a side chain carrying a primary alcohol function and finally a hemiacetal hydroxyl carried by carbon 1. This intramolecular hemiacetal is derived from the addition of the oxygen carried by C-5 to an aldehyde function. 

The most frequently used measure of the anomeric effect is based on the comparison of the stabihty of 2-substituted oxane (tetrahydropyran THP) and cyclohexane. In general, conformational properties of the oxane ring are similar to those of cyclohexane, with dominance of a chair conformation. It is further presumed that steric interactions in oxane are the same as in cyclohexane, with preference for equatorial positions of bulky substituents. The Gibbs energy of the anomeric effect, AG(AEl), can be expressed as the... 

Various other 1,6-anhydro sugars have been polymerized to relatively high-mole-cular-weight polysaccharides. All of them contain fused 1,3-dioxolane (0,1,0,5,6), oxane (tetrahydropyran (0,1,2,3,4,5) and oxepane (0,1,2,3,4,5,6) rings and differ only by the configuration on carbons 2,3 and 4 ... 

The tetrahydopyran nucleus is found in many classes of secondary metabolites, and a variety of methods are now available for the synthesis of this saturated heterocycle.As one might expect, cyclization strategies to oxanes are manifold. However, relatively few of these approaches are able to generate heavily substituted tetrahydropyrans with complete stereocontrol. 

In this category, there are no multiple bonds between the ring atoms. The compounds react largely like their aliphatic analogues, e.g. oxane (tetrahydropyran) and dioxane behave like dialkyl ethers, thiane and 1,4-dithiane like dialkyl sulfides, and piperidine and piperazine like secondary aliphatic amines. 

The third method of polymer preparation involves a ring-opening polymerization (ROP) of cyclic monomers to polymeric chains. Thus, monomers such as ethylene oxide, propylene oxide or even tetrahydrofu-ran can be used as monomers for ROP. Cyclic amides (lactams) and cyclic esters (lactones) can also be polymerized. It is important to note that all cyclic organic compounds cannot be converted into linear chains. For example, well-known organic molecules such as benzene, cyclohexane, di-oxane, tetrahydropyran etc., cannot be polymerized to the corresponding... 

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