Oxolanes

Hydrogenolysis of open-chain ethers is also difficult whereas cyclic ethers are much more reactive. Cyclic ethers can be classified into two groups-strained three- and four-membered rings (oxiranes and oxetanes) are sufficiently reactive to be transformed even at room temperature whereas the five- and six-membered rings (oxolanes and oxanes) undergo transformation at higher temperatures only. 

Oxiranes can be hydrogenolyzed easily alcohols and oxo compounds are formed as the result of primary processes [11,20,21]. The less sterically hindered bond is cleaved on Pt and Pd whereas the more hindered bond is broken on Ni and Cu. The rates of transformation of dimethyloxirane stereoisomers were also different on these metals, c/5-2,3-Dimethyloxirane is transformed much more rapidly than the trans isomer on Pt and Pd catalysts, whereas on Ni the two isomers are converted at almost the same rate [22]. Solid-phase hydrogenolysis of oxiranes on supported palladium catalysts has also been reported [23]. 

Platinum, palladium, and nickel catalysts cleave the oxolanes in the sterically less hindered position Cu is inactive toward these molecules. On supported Pt the rupture of the secondary C-0 bond was also observed [24]. Ring-opening is much easier than the hydrogenolysis of open chain ethers, presumably because of the presence of specially bonded aySy-intermediates [25], Neither on Pt nor on Ni is any difference observed between the rates of transformation of the isomers among the dimethyl derivatives of oxolanes [26]. 

Acetals can also be hydrogenolyzed to ethers in acidic media. Vinyl ethers are assumed to be intermediates in this reaction [27]. 

These compounds, namely 2,5-anhydro- and 3,6-anhydro-aldoses may exist in bicyclic form, including the 2,5-dioxabicyclo[2.2.1]heptane (97), 2,6-dioxabicyclo[3.2.1]octane (98), and 2,6-dioxabicyclo[3.3.0]octane (99) basic skeletons, respectively, or as monocyclic oxolane derivatives possessing a free aldehyde group. In the latter case, a suitably oriented hydroxyl group is not disposed to form a furanose or pyranose ring with the free aldehyde group. 

Since the oxolane ring is relatively stable toward acids and bases, the reactivity of these anhydro sugars is predetermined mainly by the presence of a free or potential aldehyde group. 

The aforementioned anhydro sugars and their derivatives were prepared by  

Nevertheless, compound 81 was definitely obtained later by deamination of 2-amino-l,6-anhydro-2-deoxy-j6-D-mannopyranose (103) with nitrous acid, and was identified by reduction to 2,5-anhydro-D-glucitol.366 An analogous deamination was performed with 2-amino-l,6-anhydro-2-deoxy-3-0-tosyl-/l-D-altropyranose to give, after detosylation, 2,5-anhydro-D-allose.361 

In relation to these solvolyses is the formation of free 2,5-anhydro-L-idose upon attempted hydrolysis of 5,6-anhydro-1,2-O-isopropylidene-a-D-gluco-furanose.364 

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In each case the ring is numbered starting at the oxygen The lUPAC rules also permit oxirane (without substituents) to be called ethylene oxide Tetrahydrofuran and tetrahy dropyran are acceptable synonyms for oxolane and oxane respectively... 

Most frequent are oxidations of alkenes that can be converted to a series of compounds such as epoxides, halohydnns and their esters, ozonides (1,2,4 tri-oxolanes), a-hydroxyketones, a-hydroxyketone fluorosulfonates, ot-diketones, and carboxylic acids and their denvatives... 

Chemical Name 1 -Acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2(1 H-imidazol-1 -ylmethyl)-1,3-di-oxolan-4-yl 1 methoxy] phenyl ] piperazine... 

B) A mixture of 2.4 parts of 1 acetyl-4-(4-hydroxyphenyl)piperazine, 0.4 part of sodium hydride dispersion 78% 75 parts of dimethylsulfoxide and 22.5 parts of benzene is stirred for one hour at 40°C. Then there are added 4.2 parts of cis-2-(2,4-dichlorophenyl)-2-(1 H-imidazol-1 -ylmethyl)-1,3-dioxolan-4-ylmethyl methane sulfonate and stirring is continued overnight at 100°C. The reaction mixture Is cooled and diluted with water. The product is extracted with 1,1 -oxybisethane. The extract is dried, filtered and evaporated. The residue Is crystallized from 4-methyl-2-pentanone. The product is filtered off and dried, yielding 3.2 parts (59%) of cis-1-acetyl-4-[2-(2,4-dichlorophenyl)-2-(1 H-imidazol-1-ylmethyl)-13-di-oxolan-4-ylmethoxy] phenyl] piperazine MP 146°C. 

The cationic ring opening polymerization of oxolane (THF) or of N-substituted aziridines can be initiated by oxocarbenium salts [42]. The methacrylic ester unsaturation is insensitive to cationic sites, and polyoxolanes (poly-THF) macromonomers are obtained in good yields. 

High-valency metal fluoride fluorination of pyridine [82JFC(21)171], quinoline [82JFC(21)413], and 2-methylfurans [91 JFC(51)179] has been reported. With 2-methylfuran a complex mixture of stereoisomers of partially fluorinated oxolans was obtained. These can be dehydrofluorinated to fluorooxolens and no furans have been observed. Conformation and structural group were found to influence the direction and readiness toward dehydrofluorination [91 JFC(52) 165]. 

The system can prevent explosion, fire, and venting with fire under conditions of abuse. These batteries have a unique battery chemistry based on LiAsF6/l,3-di-oxolane/tributylamine electrolyte solutions which provide internal safety mechanism that protect the batteries from short-circuit, overcharge and thermal runaway upon heating to 135 °C. This behavior is due to the fact that the electrolyte solution is stable at low-to-medium temperatures but polymerizes at a temperature over 125 °C... 

It was reported that graphite can also be cycled with reasonable stability in di-oxolane-based electrolytes [81, 82], and in other high-molecular-weight ethers such as 2Me-THF, dimethyl THF, and 1-methoxybutane [83],... 

One of the most important factors affecting Qsei [76, 78, 87] is graphite-anode exfoliation, as a result of intercalation of solvated lithium ions. Factors that are reported to decrease (9lR are increasing the EC content in organic carbonates or di-oxolane solutions [98, 991 addition of C02 [31, 87, 99] or crown ethers [8, 71, 78] and increasing the current density [73] (this also lowers <2SE [14] as a result of decrease in (2s P ) ... 

This polymeric oxocarbenium salt readily initiates the cationic ring opening polymerization of oxolane to produce a polystyrene-polyTHF block copolymer. Molecular weight control is provided, polydispersity is narrow and compositional heterogeneity is small59). 

The simple hexaalkylditins, RsSnSnRs, do not disproportionate on heating, but, in oxolane (tetrahydrofuran) or acetonitrile in the presence of a base such as a Grignard reagent, or in the more strongly basic solvent hexamethylphosphoric triamide (HMPT), disproportionation readily occurs at room temperature, and, in HMPT, addition occurs to such alkynes as phenylacetylene and diphenylbutadiyne. The disproportionation is considered to proceed by nucleophilic attack upon tin (259, 260), e.g.,... 

Similarly, triphenyltin hydride reacts with diethylzinc or diethyl-cadmium in a strongly solvating solvent, such as oxolane (tetrahydro-furan) or 1,2-dimethoxyethane, to give the solvated, metal-metal-bonded products (272). 

The Noyori procedure was applied to a total synthesis of baiyunoside, a sweet principle, using 2,3,4-tri-<9-benzyl-D-xylopyranosyl fluoride (18 see Table 1), and a synthesis of glycotriosyl ceramide. A model experiment for the synthesis, using 18, showed a solvent dependence for the a ratio of the products. In this case, the use of acetonitrile, oxolane, or ether gave the a anomer (1,2-a.v), and the use of toluene or hexane gave the P anomer (1,2-trans), preponderantly. 

It has been found that furans undergo hydrogenolyses under very mild conditions. Such conditions are too mild to hydrogenolyze oxolanes (saturated furans). As concerns regioselectivity, the furan C-O bond rupture takes place in the sterically less hindered position, similar to the reaction in the oxolanes. The oxacycloalkene intermediate of an intramolecular Diels-Alder furan reaction was hydrogenolized over Pd/BaS04.27... 

Of the higher oxacycloalkanes, the four-membered oxetanes are similar to oxiranes whereas the higher rings are different. The Pt, Pd, and Ni catalysts cleave the oxolanes and oxanes in the sterically less hindered position (hydro-genolytic cleavage) (Scheme 4.66), whereas Cu is inactive toward these higher rings. 

The most studied area in this held is the dehydration of oxolanes to butadiene. This type of dehydration is catalyzed by various acidic heterogeneous catalysts. For example, 2,2,5,5-tetramethyloxolane can be dehydrated on Pt/Al203 to 2,5-dimethyl-2,4-hexadiene in good yield (Scheme 5.3).34... 

Oxobutanoic acid, a25 Oxolan-2-one, b617 3-Oxo-iV-phenylbutanamide, a24 2,2 -Oxybis(chloroethane), b 163... 

Polyalcohols do not generally interact noticeably with beryllium, probably on account of the low acidity of the alkyl-OH group. Two exceptions are known where solid compounds have been isolated. The complex anion [bis(meso-oxolane-3,4-diolato)Be]2 has been shown to contain two anionic diolato ligands (258). 

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