Of 1,3-dioxolane

Propanediol, THF, Amberlyst-15, 5 min, 50-70% yield. This method is also effective for the preparation of 1,3-dioxolanes. 

The section on the cleavage of 1,3-dioxolanes (Section 10, below) should be consulted. 

The irradiation of 1,3-dioxolane in the presence of alkenes and a photochemically activated initiator at 30°C leads to 2-alkyldioxolanes ... 

The synthesis of 1,3-dioxolanes in combined reaction-rectification process 98MI42. 

The monomer 2 can be regarded as a 2,4-disubstituted-1,3-dioxolane, and the thermodynamic parameters for the polymerization may be compared with those for the polymerization of 1,3-dioxolane in methylene chloride21. ... 

Fahey (16) suggests that intermediate 3 dissociates formaldehyde he finds supportive evidence in the rhodium-based system by observation of minor yields of 1,3-dioxolane, the ethylene glycol trapped acetal of formaldehyde. For reasons to be discussed later, we believe the formation of free formaldehyde is not on the principal reaction pathway. (c) We have also rejected two aspects of the reaction mechanism proposed by Keim, Berger, and Schlupp (15a) (i) the production of formates via alcoholysis of a formyl-cobalt bond, and (ii) the production of ethylene glycol via the cooperation of two cobalt centers. Neither of these proposals accords with the observed kinetic orders and the time invariant ratios of primary products. 

Two approaches that have been validated for HIV inhibitors, nucleoside 5 -phosphonates [48] and 1,3-dioxolane analogs [49] have proven unsuccessful when applied to HCV inhibitors. Phosphonodiphosphates have been synthesized and are incorporated by NS5B RdRp, but Vmax/Km for these chain terminators is 10-100-fold less than for ATP, and potency must be greatly improved for analogs of this type to have utility [50]. A small series of 1,3-dioxolanes also failed to afford active inhibitors of HCV, or HIV, despite the addition of a 5-methyl substituent to impose the desired conformational preference [51]. Ring expanded nucleobases [52,53] and AICAR analogs have also been synthesized as HCV inhibitors which provide only weak replicon activity [54]. 

Scheme 2.—Proposed Mechanism for Photochemically Initiated, Radical Addition of 1,3-Dioxolane to 5,6-Dideoxy-l,2-0-isopropylidene-a-D-xi//o-hex-5-enofuranose (3).

Scheme 3.—Proposed Mechanism for Photochemieally Initiated, Radical Addition of 1,3-Dioxolane to 3-Deoxy-l,2 5,6-di-0-isopropylidene-3-C-methylene-a-D-riho-hexo-furanose (5).

For the polymerisation of 1,3-dioxolan and 1,3-dioxepan by HC104 Plesch and Westermann [20] were able to show by conductivity measurement that Xxr = [HClO4]0 and hence obtained values of kp These values are probably composite, and the contributions from k v and k"p are not known, but is has been explained in Section 3 that they are unlikely to differ by more than one power of ten. 

The short-stop method of measuring [Pn ] was developed to produce an easily determinable end-group in systems in which the natural end-groups are unsuitable for accurate, quantitative determination. It was first used by Jaacks et al., (1968) to determine the concentration of tertiary oxonium ions during the polymerisation of 1,3-dioxolan, and by Saegusa et al., (1968) for similar studies on tetrahydrofuran. For the polymerisation of alkenes it has only been used on two occasions. 

Studies of the kinetics of the polymerisation of 1,3 dioxolan and of the depolymerisation of its polymer by perchloric acid in methylene dichloride have been accompanied by measurements of the electrical conductivity of the reaction mixtures [23]. These have shown that ions are present during the reactions and the evidence strongly suggests that they are essentially concerned in these. This is one of the very few direct demonstrations of the participation of ions. 

Figure 2a The dependence of k1 on [HC104] for the polymerisation of 1,3-dioxolane (1) at -22 °C. All calorimeter experiments except that at [HC104] = 0.5 x 10 3 M which was done in a dilatometer (PHW)...

The Polymerisation of 1,3-Dioxolan, Part I, Structure of the Polymer and Thermodynamics of its Formation, P.H. Plesch and P.H. Westermann, Journal of Polymer Science, Part C, 1968, 16, 3837-3843. 

Table 13 Deng s (DHQD)2AQN catalyzed DKR of 1,3-dioxolane-2,4-diones [219]...

Finally, it should be mentioned that there exist two other routes for the synthesis of copolymers. First the partial chemical conversion of homopolymers (see Sect. 5.1), for example, the partial hydrolysis of poly(vinyl acetate). Secondly, by homopolymerization of correspondingly built monomers. An example for these macromolecular compounds, sometimes called pseudo-copolymers, is the alternating copolymer of formaldehyde and ethylene oxide synthesized by ringopening polymerization of 1,3-dioxolane. 

An additional problem with the enthalpies of formation of the two tetroxane species is irreconcilable. The —288 kJmoU difference between the enthalpies of formation of the parent and diphenylated species is much too large. After all, the difference between the enthalpies of formation of 1,3-dioxolane and its 2-phenyl derivative is —93 kJmoU and doubling this value for two substituents is but —186 kJmor. No explanation for this discrepancy is apparent. 

Fig.13 Preparation of 1,3-dioxolane surfactant (a) and 1,3-dioxane surfactant (b) from a long-chain aldehyde and a 1,2-and a 1,3-diol, respectively...

When a strong electrophile, such as a triphenyl methylium ion, abstracts a hydride ion from the 2-position of 1,3-dioxolan, the product is the 1,3-dioxolan-2-ylium or (for short) dioxolenium ion as shown in Equation (5.3) ... 

The possible intermediacy of formaldehyde in CO hydrogenation has been addressed above with regard to the cobalt catalytic system. Fahey has observed a small amount of 1,3-dioxolane (the ethylene glycol acetal of formaldehyde) as a product of the rhodium system (43). Thus, there is evidence that formaldehyde or a complexed form of this molecule could be an intermediate in the CO reduction process by this system. Rhodium catalysts are indeed found to be useful for the hydroformylation of formaldehyde to glycolaldehyde (159-161) methanol is a by-product in these reactions. 

All attempts to isolate 2-halogeno-l,3-dioxolanes or -1,3-dioxanes were unsuccessful. For instance, 2-chloro-l,3-dioxolane was detected only by photochlorination of 1,3-dioxolane (Ref. 118) at low temperature and 2-chloro-2-methyl-l,3-dioxolane was prepared by treatment of 2-methyl-l,3-dioxolane-2-carboxylic acid with phosphorus pentachloride at —60°, and shown119 to rearrange to 2-chloroethyl acetate on warming to 0°. For other examples of such problems, see especially, references 120 and 121. 

The observation of ring cleavage of 1,3-dioxolanes and 1,3-dioxanes by Grignard reagents was first reported for isosafrole treated with... 

Experimental results are found to be in very good agreement with theoretical results based on an RIS model which assumed perfect alternation of 1,3-dioxolane and 1,3-dithiolane, rather than a more irregular distribution which could conceivably occur in the type of ring-opening polymerization used to prepare the polymer. 

Other ethers suggested as plasticizers are the oligomers of epoxides—for instance, the polymers of glycerol allyl ethers and the polymers of 1,3-dioxolane. These products do not seem to have practical importance. 

The photosensitized addition of 1,3-dioxolane and 1,3,5-trioxane to, alkenes was developed a number of years ago as a route to a-alkylated ethers (68JOC805). It has now been shown that 2-methyl-l,3-dioxolane will undergo a photochemically induced conjugate addition reaction to cyclohexenone to afford an adduct (327) in 54% yield which can be hydrolyzed to the diketone (328) (77CJC3986). Functionalized dioxolane (330) was also... 

Both stable oxonium ion (118,119) and carbocation salts (23,54,151) have been used in the study of 1,3-dioxolan polymerisations in methylene chloride solvent. Some confusion still surrounds the complex mechanism involved though the work of Penczek and his co-workers (54) has gone far towards clarifying the situation. 

Methyl-l,3,5-trioxazepanium cation was generated on treatment of 1,3-dioxolane with methoxymethyl cation in S02 <1982MMC1587>. 

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