Hydroperoxides with dimethyl sulfide

Photochemical decomposition of malonic acid by irradiation in solution has been reported. Some of the radical species produced by this treatment are identical to those formed by the Ce decomposition of malonic acid in the Belousov-Zhabotinsky reaction. The (2 + 2)-cycloadducts (172) can be readily prepared by irradiation of mixtures of the corresponding enone and alkene, and these adducts can conveniently be converted into the hydroperoxide (173) by irradiation at 366 nm in the presence of air and acridine in toluene.The decarboxylation occurs by a free radical pathway and treatment of the hydroperoxide with dimethyl sulfide brings about formation of the ring-expanded ketones or lactones (174),... 

When ozonolysis is done in alcoholic solvents, the carbonyl oxide fragmentation product can be trapped as an a-hydroperoxy ether.146 Recombination to the ozonide is then prevented, and the carbonyl compound formed in the fragmentation step can also be isolated. If the reaction mixture is treated with dimethyl sulfide, the hydroperoxide is reduced and the second carbonyl compound is also formed in good yield.147 This procedure prevents oxidation of the aldehyde by the peroxidic compounds present at the conclusion of ozonolysis. 

An olefin of type (1) is conveniently converted into an aldehyde (3) by ozon-ization in methanol to produce the methoxy hydroperoxide (2) and reduction of this with dimethyl sulfide.1 This. reducing agent has a number of virtues. It is highly... 

Synthetic methods for preparation of 1,2,4,5-tetroxanes have been reviewed recently <2001COR601, 2002RMC113>. The most general method involves acid-catalyzed addition of hydrogen peroxide to carbonyl compounds and subsequent cyclization of the hydroperoxide intermediates. The direct synthesis is carried out normally in the presence of either sulfuric, perchloric, or methanesulfonic acids and affords symmetrically substituted tetroxanes (Equation 26). In many cases, for example, where the carbonyl compound is unsubstituted in the a-position, tetroxanes are contaminated with hexaoxonanes and open-chain hydroperoxides. Selective removal of the more reactive hydroperoxides can be achieved with dimethyl sulfide or potassium iodide. Recrystallization usually removes residual hexaoxonanes but, failing that, heating the mixture with perchloric acid in acetic acid can convert hexaoxonanes to tetroxanes or convert the thermodynamically less stable hexaoxonanes to more water-soluble lactones, which may facilitate the purification process <2002RMC113>. 

There was further study of indole-2,3-epoxides and indole-2,3-dioxetanes. Dioxetanes can be isolated from 1-acyl indoles by photo-oxygenation and are accompanied by more stable hydroperoxides. The oxetanes can be converted to indole-2,3-epoxides by deoxygenation with dimethyl sulfide. <94J0C2733, 94JCS(P2)1503> The epoxides can also be prepared by oxidation of 1-acyl-indoles by dimethyldioxirane. The indole-2,3-epoxides... 

Despite the complexities in the mechanism of ozonolysis, the reaction constitutes a high-yield method for cleavage of carbon-carbon double bonds. The oxidation states of the products that are actually isolated depend on the conditions used in processing the reaction mixture. If the carbonyl products are desired, it is advantageous to carry out ozonolysis in methanol, resulting in the formation of a-methoxyalkyl hydroperoxides. The reaction mixture is then treated with dimethyl sulfide, which reduces the hydroperoxide and permits isolation of the carbonyl compounds in good yield. This procedure prevents oxidation of the carbonyl products, especially aldehydes, by the peroxidic compounds present at the conclusion of ozonolysis. 

It was shown from decomposition kinetics and by treatment with dimethyl sulfide that peroxides consist of two types a fast-decomposing one composed of peradds, and a slowly decomposing one consisting of hydroperoxides and hydro-peresters. During the induction period, the slowly decomposing hydroperoxides accumulate and the oxidation rate is controlled by the rate of decomposition, which may be finally catalyzed by metal ion residues. The autoacceleration stage is controlled by the fast-decomposing peracids [22]. 

Usually, organoboranes are sensitive to oxygen. Simple trialkylboranes are spontaneously flammable in contact with air. Nevertheless, under carefully controlled conditions the reaction of organoboranes with oxygen can be used for the preparation of alcohols or alkyl hydroperoxides (228,229). Aldehydes are produced by oxidation of primary alkylboranes with pyridinium chi orochrom ate (188). Chromic acid at pH < 3 transforms secondary alkyl and cycloalkylboranes into ketones pyridinium chi orochrom ate can also be used (230,231). A convenient procedure for the direct conversion of terminal alkenes into carboxyUc acids employs hydroboration with dibromoborane—dimethyl sulfide and oxidation of the intermediate alkyldibromoborane with chromium trioxide in 90% aqueous acetic acid (232,233). 

FIGURE 33. Transition structures [B3LYP/6-31+G(d,p)] for the oxidation of dimethyl sulfide with (a) monomeric CH3O—OH and (b) dimeric methyl hydroperoxide... 

Birch reduction, followed by acid treatment and addition of diazomethane leads to the A9(11)-enone 159 in 41% yield. Then, the double bond is hydrogenated and, by using PhSeCl and hydrogen hydroperoxide, the double bond A13 is formed. Treatment of the enone with lithium disopropylcuprate-dimethyl sulfide complex gives an intermediate enolate that is trapped again using PhSeCl. Enone 160 is obtained via oxidative elimination (62%). 

Computational studies showed that the nature of the reactive species in the oxidation of trimethylamine, iodide ion, and dimethyl sulfide with lumiflavin is a C4 a-hydroperoxide complexed with water. The other two species, C4 a-hydroperoxide and C4 a-peroxide, yielded higher activation energies.237 Kinetic and spectroscopic studies on the effect of basic solvents, ethers, esters, and amides, on the oxidation of thianthrene-5-oxide with substituted peroxybenzoic acids indicated the involvement of the basic solvent in the transition state of the reactions. A solvent parameter, Xtc, based on the ratio of the trans to the cis form of thianthrene-5,10-dioxide, has been introduced.238... 

Treatment of a-iodo lactone (45) with triethylborane under oxygen atmosphere gives the corresponding a-hydroxy lactone (46), via a-lactone radical species. This reaction comprises of SH2 reaction by Ef on the iodine atom of a-iodo lactones, reaction of the formed a-lactone radical with molecular oxygen, and subsequent hydrogen-atom abstraction from the solvent to form alkyl hydroperoxide (ROOH). Finally, by the addition of dimethyl sulfide for the reduction of the peroxide, the corresponding a-hydroxy lactone is obtained (eq. 2.24) [58]. 

The detoxification of catalysts poisoned by Group V or VI compounds can be accomplished by reactions in which these inhibitors are converted to substances that do not have unshared electron pairs. For instance, bivalent sulfur compounds can be oxidized to sulfones or sulfonic acids by treatment with hypochlorite or hydroperoxides. "2,108 Thiophene, dimethyl sulfide and other sulfur and metal ion poisons as well as phosphorous"" and arsenic compounds " can be removed from platinum by washing the catalyst with acetic acid. This method for the reactivation of the catalyst is simpler than the oxidation techniques. Acidic or basic inhibitors are removed by the addition of an appropriate amount of base or acid, respectively. The effect of a small amount of inhibitor can frequently be overcome by the use of a larger amount of catalyst. 

Barton has devised such a pathway for converting carboxylic acids to hydroperoxides via A -hydroxypyridine-2-thione esters [16a,b] (Scheme 5). The yields of hydroperoxides are 45-89% [16]. Reduction of the crude products with trimethyl phosphite (rt) or dimethyl sulfide (80 °C) readily provides the corresponding alcohols. On the other hand, tosylation and ensuing Kornblum-De La Mare type fragmentation [17] leads to carbonyl compounds [16b] (Scheme 5). 

Chemical derivatization can also be used for structure elucidation in complex mixtures. For instance, dimethyl sulfide has been used to differentiate peracids from other peroxy compounds. The rate of conversion of dimethyl sulfide into dimethyl sulfoxide is almost instantaneous with peracids [Eq. (25)], whereas it is slow with sec- and tert-hydroperoxides [Eq. (26)]. 

Diethyl tartrate is the best tartaric acid derivative for enantioselective oxidation of thioethers. This finding was established for the asymmetric oxidation of methyl p-tolyl sulfide with cumene hydroperoxide, that is, 96% ee (DET) 87% ee (diisopropyl tartrate) 62% ee (dimethyl tartrate) [24] and 1.5% ee (bis A, V-dimethy I tart rami de, r-BuOOH as the oxidant) [17]. 

Cotton etal. [14] described an asymmetric synthesis of esomeprazole. Esomeprazole, the (S)-enantiomer of omeprazole, was synthesized via asymmetric oxidation of prochiral sulfide 5-methoxy-2-[[(4-methoxy-3,5-dimethyl pyridin-2-yl)methyl]thio]-lH-benzimidazole 1. The asymmetric oxidation was achieved by titanium-mediated oxidation with cumene hydroperoxide in the presence of (S,S)-diethyl tartarate (DET). The enan-tioselectivity was provided by preparing the titanium complex in the presence of sulfide 1 at an elevated temperature and/or during a prolonged preparation time and by performing the oxidation of sulfide 1 in the presence of amine. An enantioselectivity of 94% ee was obtained using this method. 

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