1.3- Dioxolane derivatives

Dioxolane derivatives, which are obtained from methoxybutenone and glycols and used as antifungicides, and squalene synthetase inhibitors have been described (94MI1). The reactions of mono- and oligosaccharides with... 

The first step in the addition of alkoxides to Cgg is, consistently, the formation of the alkoxy Cgg anion. The subsequent process is strongly dependent on the presence of oxygen. In the presence of oxygen, 1,3-dioxolane derivatives of Cgg are formed [110]. In the absence of oxygen the oligo alkoxy fullerenide anions can be formed [111, 112]. Reaction of alkoxides with Cgg usually results in complex mixtures. This may be why only a few reactions of Cgg with alkoxides have been described [113]. Nevertheless, defined alkoxy fullerenes can be obtained by nucleophilic substitution reactions of alkoxides with halogenofullerenes (Chapter 9) [113]. 

One advantage of using a cleavable acetal surfactant instead of a conventional amphiphile has been elegantly demonstrated in a work by Bieniecki and WUk [51]. A cationic 1,3-dioxolane derivative was used as surfactant in a microemulsion formulation that was employed as a reaction medium for an organic synthesis. When the reaction was complete, the surfactant was decomposed by addition of acid and the reaction product easily recovered from the resulting two phase system. Through this procedure the problems of foaming and emulsion formation, frequently encountered with conventional surfactants, could be avoided. 

Dioxolane also pseudorotates essentially freely in the vapor phase. 2,2 -Bi-1,3-dioxolane (177) has been shown by X-ray crystallography to have a conformation midway between the half-chair and envelope forms. The related compound 2-oxo-1,3-dioxolane (178) shows a half-chair conformation. This result is confirmed by microwave spectroscopy and by 13C NMR data. Analysis of the AA BB NMR spectra of the ring hydrogen atoms in some 1,3-dioxolane derivatives is in agreement with a puckered ring. Some 2-alkoxy-l,3-dioxolanes (179) display anti and gauche forms about the exocyclic C(2)-0 bond. 

In sub-FC, a detailed study of the influence of mobile phase additives on the chiral resolution of isoxazoline-based Ilb/IIIb receptor antagonists was carried out by Blackwell [145] on Chiralcel OD-H CSPs. The different mobile phase additives used were acetic acid, trifluoroacetic acid, formic acid, water, triethylamine, triethanolamine, n-hexylamine, trimethyl phosphate, and tri-w-butyl phosphate. In general, n-hexylamine and tri-/ -butyl phosphate mobile phase additives resulted in better resolution. The chiral separation of four 1,3-dioxolane derivatives on an amylose-based column has been described [151]. The effects of mobile phase composition, temperature, and pressure have been investigated. The nature of the modifier is the main parameter it has the highest impact on chiral resolution and is more important than the polarity of the mobile phase. Therefore, the organic modifier that gave the best enantiomeric separation was different for each compound. 

Elemes, Y. et al. 1992 Reaction of C60 with dimethyldioxirane - formation of an epoxide and a 1,3-dioxolane derivative. Angew. Chem. Int. Edn. Engl. 31, 351-353. 

The action of strong base on 1,3-dioxolanes derived from /S,y-unsaturated ketones leads to unstable anions which ring open to enol ethers (80TL1515). This reaction is similar to the... 

Epoxyglycerides react with ketones in the presence of boron trifluoride to give 1,3-dioxolane derivatives. In this form they were analysed by GC on a column packed with 3% of OV-1 with temperature programming at 4°C/min from 260° C [649]. Cyclo-pentanone was recommended as the most suitable reagent, and acetone, methyl ethyl ketone, methyl isobutyl ketone and others can also be used. 

The major 1,3-dioxane could be separated by column chromatography but the diastereoisomeric 1,3-dioxolane derivatives could not be separated [Scheme 3.89],39 The strong preference for 1,3-dioxane formation is underscored in the benzylidenation of L-gulonolactone depicted in Scheme 3.90. Two different products formed depending on the reaction conditions, but in neither case was a 1,3-dioxolane ge tie rated.165... 

Chiral Lewis Acid. These chiral titanium reagents are widely used as chiral Lewis acid catalysts. The Diels-Alder reaction of methyl acrylate and cyclopentadiene affords the endo adduct in moderate enantioselectivity when a stoichiometric amount of the chiral titanium reagent (5) is employed (eq 6). Use of 3-(2-alkenoyl)-l,3-oxazolidin-2-ones as dienophiles greatly improves the optical purity of the cycloadduct when the 2-phenyl-2-methyl-1,3-dioxolane derivative (6) is used as a chiral ligand. Most importantly, the reaction proceeds with the same high enantioselectivity for the combination of various dienophiles and dienes even when 5-10 mol % of the chiral titanium reagent is employed in the presence of molecular sieves 4A (eqs 7 and 8). ... 

By electrochemical oxidation in alcoholic solution, e.g. in the presence of alkoxides, of aldehyde acetals or 1,3-dioxolanes derived from aldehydes orthoesters, e.g. (400 equation 185), can be obtained. " Orthobenzoates (401 equation 186) are accessible by electrolysis of substituted toluenes in the presence of triarylamines in solvents such as methanol/meAylene chloride. Decarboxylation and subsequent electrochemical oxidation of the dicarbonic acid (402 equation 187) in methanol affords cyclic orthoesters (403). ... 

The 3R stereochemistry of the most potent isomers (121) and (122) is consistent with that of other potent 1,3-dioxolane derivatives. Extension of these studies (157) led to a racemic 1,2,4-oxadiazole derivative (123) that has high affinity and efficacy at central muscarinic receptors. 

Table 2 H NMR data for ring protons of 1,3-dioxolane derivatives.

Table 5 Melting and boiling points of simple 1,3-dioxolane derivatives.

It is well known that the condensation of aldehydes with polyalcohols may produce diastereoisomeric 1,3-dioxolane derivatives, as the difference in energy between the endo and exo isomers is small. 

On elaboration of l,5-hexadiene-3,4-diol through a 1,3-dioxolane derivative, the RCM delivers a precursor of either exo-brevicomin or endo-brevicomin. A route to (+)-malyngolide also exploits the RCM process. A successful cyclization-fragmentation approach to medium-sized rings is based on the RCM reaction of 2-hydroxycycloalkanones that are substituted with proper alkenyl groups at both a- and a -positions.- ... 

Special methods exist for the simultaneous derivatization of two hydroxyl groups, particularly when located on adjacent carbon atoms. Ketal formation — reaction of a diol with an aldehyde or ketone to form a 1,3-dioxolane derivative — is the most obvious approach for example, 20,21-dihydroxycorticosteroids have been converted to acetonides [203]. 

The 1,3-dioxolane derivatives XCIII undergo ring opening with phenols, and Mukaiyama and his co-workers have used this reaction sequence to prepare polymers from the corresponding difunctional materials. 

All characteristic last steps in the synthesis of EDOT, i.e. the ring closure to the dioxane structure, are also sufficient for the formation of the analogous seven-membered rings (1,3-dioxepanes), the 3,4-propylenedioxythiophenes (ProDOTs) Williamson ether synthesis [13], transetherification [30] and Mitsunobu reaction [25]. The analogous basic five-membered ring compound 3,4-methylenedioxythiophene (MDOT, a 1,3-dioxolane derivative) is also accessible by Williamson ether synthesis using bro-mochloromethane [31]. 

Alcohols add reversibly to aldehydes and ketones to give a transient hemiacetal or hemiketal, which then reacts with more alcohol to give an acetal or a ketal. Acetal and ketal formation is reversible. An excess of alcohol drives the reaction toward the acetal or ketal, but an excess of water will convert the acetal or ketal back to the aldehyde or ketone. 1,2-Diols react with aldehydes and ketones to give 1,3-dioxolane derivatives and 1,3-diols react to give 1,3-dioxane derivatives. 

The same carbocationic intermediates are postulated in the reactivity of fuUerene epoxide with ketones and aldehydes to afford 1,3-dioxolane derivatives 12 in the presence of various Lewis acids (10P7671219,08JOC2518). In the same reaction conditions, anilines and phenols react with fiillerene oxide to afford indolino[2, 3 l,2][60]fuUerenes 13 and benzo[lt]furano[2, 3 l,2] [60]fullerenes 14, respectively (08CL1018,09ECST33). 

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