Peroxides cyclic, preparation

The platinum complexes have also been used in the presence of hydrogen peroxide to prepare cyclic lactones from cyclic ketones (Figure 2.31).91... 

Cyclic peroxides. Cyclic peroxides have been prepared by a variant of the peroxynierciiration of alkenes. The method is formulated for the synthesis of the dimethyl-1,2-dioxacyclohexane as a mixture of cis- and frfl s-isomers. 

The cyclic trimer ketone peroxides (eg, methyl ethyl ketone peroxide cyclic trimer [24748-23-0]) have been selectively prepared in dilute solution (in a safety solvent due to the shock sensitivity of the pure peroxide) for use as impromoted, thermal initiators (124,125). They have been shown to effectively modify polyolefins under certain conditions in a manner similar to dialkyl peroxides. 

Pyridazine-3,6-diones (diazaquinones) are prepared from cyclic hydrazides by oxidation with lead tetraacetate or other oxidizing agents, such as r-butyl hypochlorite, chlorine or nickel peroxide. 

The reductive elimination of a variety of )3-substituted sulfones for the preparation of di-and tri-substituted olefins (e.g. 75 to 76) and the use of allyl sulfones as synthetic equivalents of the allyl dianion CH=CH—CHj , has prompted considerable interest in the [1,3]rearrangements of allylic sulfones ". Kocienski has thus reported that while epoxidation of allylic sulfone 74 with MCPBA in CH2CI2 at room temperature afforded the expected product 75, epoxidation in the presence of two equivalents of NaHCOj afforded the isomeric j ,y-epoxysulfone 77. Similar results were obtained with other a-mono- or di-substituted sulfones. On the other hand, the reaction of y-substituted allylic sulfones results in the isomerization of the double bond, only. The following addition-elimination free radical chain mechanism has been suggested (equations 45, 46). In a closely related and simultaneously published investigation, Whitham and coworkers reported the 1,3-rearrangement of a number of acyclic and cyclic allylic p-tolyl sulfones on treatment with either benzoyl peroxide in CCI4 under reflux or with... 

An alternative method of preparing the saturated cyclic amines via cyclopolymerization of diallylamine or diallylammonium chloride was unsuccessful. Common free radical initiators such as 2,2 -azobisisobutyronitrile, ammonium persulfate, benzoyl peroxide were found to be ineffective. Several procedures reported in the literature were followed, and unfortunately all of them have resulted only a small amount of low molecular weight oligomers. Further research for polymerization conditions and types of initiation is still required. 

Most of the isolated diacyl (including sulfonyl) peroxides are solids with relatively low decomposition temperatures, and are explosive, sensitive to shock, heat or friction. Several, particularly the lower members, will detonate on the slightest disturbance. Autocatalytic (self-accelerating) decomposition, which is promoted by tertiary amines, is involved [1]. Solvents suitable for preparation of safe solutions of diacetyl, dipropionyl, diisobutyryl and di-2-phenylpropionyl peroxides are disclosed [2], The class is reviewed, including hazards and safety measures [3], Cyclic diacyl peroxides are more stable, but scarcely to be trusted. Individually indexed compounds are ... 

Finally, cyclic secondary alkyl peroxides have been prepared in high yield via the reaction of dienes with hydrogen peroxide and mercury(II) nitrate followed by hydrogen... 

Cyclic enones can be oxidatively cleaved by a range of reagents to yield keto acids. As ozonolysis can be quite hazardous for large-scale preparations with the build up of ozonides, the procedure has been modified using quaternary ammonium salts to catalyse the transfer of peroxide anion for a rapid oxidative work-up [32]. Two methods are available but, in the safer procedure (10.7.15.A), there is no effective build-up of the ozonide. 

For this reason, a reinvestigation of the cyclic ketene acetal, 2-methylene-l,3-dioxolane (I), that had been prepared by McElvain and Curry (14) was undertaken. Although McElvain and Beyerstedt (15) reported that benzoyl peroxide had no appreciable effect on diethyl ketene acetal, no such study was reported (14) for the 2-methylene-l,3-dioxolane (I). The synthesis was carried out as follows (6) ... 

For the preparation of cyclic peroxides from less electron-rich substrates, addition of some metal salts (MX) with non-nucleophilic anions that can support solvolysis, is beneficial (equation 8). 

DCA in such a photooxygenation Similar oxygenations of more electron-poor substrates 123 (e.g., Ar = Ar = Ph) give the cyclic peroxides 124 in poor yields (15-30%), and the corresponding benzophenones as the major product . Alternatively, 3,3,6,6-tetraphenyl-l,2-dioxane and related tetraaryl-analogues 124 can be effectively prepared in 80-90% yield by irradiation of pre-formed charge transfer complexes of 123 with SbCls in methylene chloride at —78°C in the presence of oxygen ... 

Cyclic peroxides can be prepared from hydroperoxides and their synthetic equivalents throngh processes involving intramolecular nucleophilic substitution at a carbon... 

The simple cyclic silyl peroxide, l,l,4,4-teteramethyl-l,4-disila-2,3-dioxane, 75, was prepared by classical synthetic methodology from its corresponding cyclic disilazane 74 and the urea complex of H2O2 (equation 85) . 

Although the parent formaldehyde-derived dioxirane (H2CO2) was the first of this intriguing class of cyclic peroxides to be prepared and spectrally characterized in 1976, the conversion of aldehydes into the corresponding dioxiranes by treatment with Caroate was deemed difficult because of the expectedly facile Baeyer-Villiger oxidation of the aldehydes to their carboxylic acids. Most gratifyingly, however, is that it was recently demonstrated that optically active aldehydes may also serve as promising catalysts for asymmetric epoxidations. For example, ee values up to 94% were obtained with the aldehyde 14 as dioxirane precursor. 

The preparation of acyclic allylic hydroperoxides has been described before (3, 7, 9), but it is not clear how the reactivities differ from the better known saturated hydroperoxides and cyclic allylic hydroperoxides. Dykstra and Mosher prepared allyl hydroperoxide by the reaction of allyl methanesulfonate with hydrogen peroxide and alcpholic potassium hydroxide and purified the hydroperoxide by gas chromatography. It detonated on heating and decomposed on exposure to light but was relatively stable in the cold and dark. The isomeric allylic hydroperoxides formed from the autoxidation of the branched olefin, 4-methyl-2-pentene, have also been isolated and were not abnormally reactive (3). In the present study, cis- and trans-2-butene were photooxidized in the presence of methylene blue as a sensitizer (14), and the product, l-butene-3-hydro-peroxide, was isolated by preparative chromatography. 1-Butene proved unreactive and 2-butene-l-hydroperoxide could be formed only by isomerization of the secondary hydroperoxide. 

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