Dioxolane solutions

Wang and coworkers first reported the use of these monomers as a novel elastomeric material for potential application in soft tissue engineering in 2002. The molar ratio of glycerol to sebacic acid they used was 1 1. The equimolar amounts of the two monomers were synthesized by polycondensation at 120°C for three days. The reaction scheme is shown in Scheme 8.1. To obtain the elastomers, they first synthesized a prepolymer and then poured an anhydrous 1,3-dioxolane solution of the prepolymer into a mold for curing and shaping under a high vacuum. 

Lithium phenolate is present as a mixture of tetramers and hexamers in 1,3-dioxolane solution. Crystallization of lithium phenolate from THF yields an LigAgSg aggregate, as determined by X-ray crystallography, although the predominant aggregate in solution is the tetramer. In the solid state the measured x value is 67 kHz with a r] value of 0.77, which translates to a QSC value of 73 kHz. This agrees with the QSC value of 72 kHz measured for the hexamer in dioxolane solution. 

This also proves an earlier conclusion on hyperconjugation in an 0CH20 fragment of the 1,3-dioxolane cation radical this conclusion was based on mass spectrometry (To-dres, Kukovitskii et al. 1981). As calculated, the carbon-hydrogen bonds corresponding to 0CH20 in the radical cation are weaker than those in the neutral molecule. For this reason, this site exhibits a maximal probability that deprotonation will result in the formation of the 2-yl radical (Belevskii et al. 1998). In experiments, photoirradiation of 1,3-dioxolane solutions in sulfur hexafluoride at 77 K really leads to formation of the cation radical of 1,3-dioxolane and the l,3-dioxolan-2-yl radical as a result of deprotonation. Consecutive ring... 

Tin-free photolytic conditions for addition of formyl radical equivalents to 3a have been reported by Alonso [53]. Photolysis of 1,3-dioxolane solutions of 3a in the presence of 1 equiv of benzophenone led to formation of the l,3-dioxalan-2-yl radical from solvent, followed by intermolecular radical addition in 87% yield (entry 6). A one-pot variant without isolation of 3a increased the yield and selectivity (entry 7). These conditions gave good yields across a range of chiral /V-acylhydrazones (not shown), but synthetically useful levels were restricted to aliphatic aldehyde precursors. 

An oven-dried, 1-L, three-neck round-bottom flask is equipped with a septum-sealed 125-mL pressure-equalizing addition funnel, a condenser fitted with a nitrogen inlet, and a glass stopper. Next, 2.96 g (0.122 mole) Mg turnings, a Teflon-coated stirring bar, and 200 mL anhydrous tetrahydrofuran (THF) are added to the flask. The addition funnel is charged with 27.8 g (0.121 mole) of the dioxolane. The reaction is initiated with a crystal of I2 and a few milliliters of the dioxolane solution. The remaining solution is added slowly in 3-mL aliquots from the addition funnel, and the reaction is then heated to reflux for 30 minutes. The clear, brownish solution is cooled in an ice bath while a solution of 22.4 mL (0.121 mole) redistilled chlorodiphenylphosphine (bp 110-120° at 0.1 torr) in 80 mL anhydrous THF is prepared in the addition funnel. 

Competition of solvation and association affects conductance strongly. Conductivity enhancements up to a factor of 300 were observed when DME, triglyme, DMSO, HMTT, PC, AN or 12-crown-4 ether were added to 1,3-dioxolane solutions of Lil, LiSCN and LiBPlv Increase of ion mobilities up to a factor of 5 is... 

Some remarkable results must be mentioned in connection with non-aqueous electrolyte solutions. The use of melts of Lil-glyme solvates as the electrolyte solution in the Li/TiSj cell prohibits its rechargeability in contrast to LiClO /dioxolane solutions The solvation of Li is supposed to be sufficiently strong to entail glyme co-interr ation. The cell of lithium/Iow temperature amotjriious molybdenum disulfide is highly reversible with LiQO /dioxolane as the electrolyte solution after 244 cycles the capacity still exceeds 50% of the second discharge step . Dioxolane/DME mixtures are the m< t favourable and THF/DME mixtures the... 

One of the most important factors affecting Qsei [75, 78, 86] is graphite-anode exfoliation as a result of intercalation of solvated lithium ions. Factors that are reported to decrease Qjr are increasing the EC content in organic carbonates or dioxolane solutions [101, 102], addition of CO2 [29, 86, 102] or crown ethers [8, 69, 78], and increasing the current density [71] (this also lowers Qse [12] as a result of decrease in Qsp). 

Treatment of the 6,11-diketo dioxolane (29) with methylmagnesium iodide in benzene-ether solution at room temperature gives the carbinol (30) in 70% yield. The 11-keto group is not attacked under these conditions. ... 

Cyclic ethylene carbonate and its halogeno derivatives are converted into 2 2 difluoro 1,3 dioxolanes, which are useful as inhalation anaesthetics by treatment with sulfur tetrafluonde m an anhydrous hydrogen fluoride solution at 100-150 °C [239] (equation 126)... 

NaB (C6H5 )4/l 8-crown-6/dioxolane systems the exchange was found to be slow on the nmr timescale two 23Na resonances were observed for solutions containing an excess of the sodium salt. 

The reason that OH does not attack the u-carbon in 63, in contrast to the reaction in Eq. (17), would be due to the stronger electron donation by the /3-carbon in 63, which increases the electron density at the a-carbon atom. Addition of ethylene glycol vinyl ether to the p-toluenesulfonate salt of 64 in CDC13 catalytically yields 2-methyl-1,3-dioxolane (Eq. (18)). The reaction proceeds almost instantaneously, and a 50-fold equivalent of the substrate is completely converted to 2-methyl-1,3-dioxolane, which was confirmed by -NMR. After the reaction, the Pt(III) dimer complex without alkyl ligand is left in the solution, which is still capable of catalysis. The reaction is shown as Eq. (18). 

Co-polymerizations and homo-polymerizations of monomers such as dienes or 4-methylene dioxolan, in which two or more types of ion may propagate simultaneously, are further examples of enieidic polymerizations. These dienes, of course, also provide examples of eniedic radical and anionic polymerizations. Indeed the idea of dieidic polymerization has been suggested by several authors in relation to anionic polymerizations it arose from the aggregation in solution of the lithium alkyls [135], and similar phenomena. 

The next structural study of polydioxolans of DP ranging from 7 to 70 by Plesch and Westermann [6] confirmed the regular structure of the polymer. It was also shown that when a polydioxolan was formed and then depolymerised in solution by perchloric acid, the only product was monomer. This is apparently in conflict with the findings of Miki, Higashimura, and Okamura [7] who reported that a reaction mixture, in which dioxolan had been polymerised for 3 hours at 35 °C by BF3-Et20, contained 1,3,5-trioxepan, 1,4-dioxane, trioxane, and other compounds. Most probably the difference is at least partly due to the long reaction time and the use of boronfluoride, which is well known to produce more side-reactions than protonic acids. 

Unsymmetrical vicinal diols can be prepared from a three-component reaction of aldehydes, CO, and aminotroponiminate-ligated titanium dialkyl complexes. Solutions of Me2TiL,2 (L = N -dimethylaminolroponiminalc) react rapidly with CO at room temperature. Double methyl migration to CO produces an 2-acclonc complex which inserts the aldehyde to afford a titana-dioxolane and releases the unsymmetrical diol upon hydrolysis [65]. 

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