1,2,4,5-tetroxane

PEROXIDES AND PEROXIDE COMPOUNDS - ORGANIC PEROXIDES] (Vol 18) cis-3,6-Diethyl-3,6-dimethyll,2,4,5-tetroxane [33817-91-3]... 

DFT molecular dynamics simulations were used to investigate the kinetics of the chemical reactions that occur during the induction phase of acid-catalyzed polymerization of 205 [97JA7218]. These calculations support the experimental finding that the induction phase is characterized by the protolysis of 205 followed by a rapid decomposition into two formaldehyde molecules plus a methylenic carbocation (Scheme 135). For the second phase of the polymerization process, a reaction of the protonated 1,3,5-trioxane 208 with formaldehyde yielding 1,3,5,7-tetroxane 209 is discussed (Scheme 136). 

Trioxane 210 has been used as a model system by Gu and coworkers to study the antimalarial drug artemisinin 211 (Scheme 137) [97CPL234, 99JST103]. It is the boat/twist form rather than the chair conformer of 210 that describes the subunit in 211. Moreover, geometric parameters and vibrational frequencies can only reliably be computed at the DFT level and by post-Hartree-Fock methods. B3-LYP/6-31G calculations on the conformers of 3,3,6,6-tetramethyl-1,2,4,5-tetroxane show that the chair conformer is stabilized with respect to the twisted conformer by about -2.8 kcal/mol [00JST85]. No corresponding boat conformer was found. 

The thermolysis of a variety of 1,2,4-trioxanes in methanol has been followed by mass spectrometry and provided evidence of the corresponding products. A smdy of the thermal decomposition of 3,6-diphenyl-1,2,4,5-tetroxane in toluene and methanol revealed a significant solvent effect that supported a homolytic stepwise mechanism instead of a concerted process. ... 

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... 

Other cyclic acetals that have been studied are 1,3,5-trioxane, 1,3,5-trioxepane, 1,3,6,9-tetraoxacycloundecane, and 1,3,5,7-tetroxocane (also referred to as 1,3,5,7-tetroxane) [Kawakami and Yamashita, 1979 Munoz-Escalona, 1978 Schulz et al., 1984 Szwarc and Perrin, 1979]. Polymerization of bicyclic acetals has been of interest for synthesizing polysaccharides [Good and Schuerch, 1985 Hirasawa et al., 1988 Okada, 1991 Okada et al., 1989 Sumitomo and Okada, 1984]. 

O NMR resonances for several 1,2,4-trioxolanes have been reported <91CC816> (Table 6). The ether and peroxide signals are very distinct proving the value of O NMR as an analytical tool for characterization of ozonides. It can be used to determine unequivocally whether a compound is an ozonide (peroxide 6 295-327 ppm) or tetroxane ((26), for example d = 256 ppm). This is often a competing product from the ozonolysis reaction of alkenes (Section 4.16.8.2). 

Recently, the enthalpies of combustion and sublimation were measured for formaldehyde diperoxide, i.e. 1,2,4,5-tetroxane , from which the enthalpies of formation could be derived. These results were shown to be in good agreement with quantum chemical... 

A related study of 3,6-diphenyl-l,2,4,5-tetroxane resulted in enthalpies of formation of the sohd and gaseous species of 134.0 1.3 and 99.7 1.3 kJmor. Again, while computational theory and experiment are in good agreement, the sublimation enthalpy of 34.3 kJmoU seems too low. We would have suggested a lower bound of ca 71 kJmoU based on our enthalpy of vaporization estimation approach given above. 

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. 

An important paper by Salomon, Clennan and coworkers on dialkyl peroxides , where also one ozonide was reported, appeared in 1985. In this paper, a correlation among and 0 chemical shifts was established, and the influence of several factors like concentration, temperature, solvent and, naturally, chemical structure was thoroughly studied but confined to dialkyl peroxides. There was a gap of several years before the appearance of a further note reporting data of seven 1,2,4-trioxolanes (ozonides), 1-4, and of the 1,2,4,5-tetroxane 5. Their 0 NMR data are given in Table 2. Spectra were obtained at natural isotopic abundance, in toluene at 27 °C. 

In 2001, Albrecht Berkessel and Nadine Vogl reported on the Baeyer-Villiger oxidation with hydrogen peroxide in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as solvent in the presence of Brpnsted acid catalysts such as para-toluenesulfonic acid (equation 85) . Under these conditions cyclohexanone could be selectively transformed into the corresponding lactone within 40 min at 60 °C with a yield of 92%. Mechanistic investigations of Berkessel and coworkers revealed that this reaction in HFIP proceeds by a new mechanism, via spiro-bisperoxide 234 as intermediate, which then rearranges to form the lactone. The study illustrates the importance of HFIP as solvent for the reaction, which presumably allows the cationic rearrangement of the tetroxane intermediates. 

The 1,2,4,5-tetroxane products 199a and 199b in Scheme 7 were identified and their transformation to other products could be followed by H NMR spectroscopy . 

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