Sulfenes sulfide

The intermediate sulfides can be oxidized to the corresponding sulfoxides and sul-fones and then, liberated to give sulfenic and sulfinic acids. 

During the chain oxidation of hydrocarbons, sulfides and disulfides terminate chains by reacting with peroxyl radicals [40,42,44], which, as opposed to phenols, are weak inhibitors (see Table 17.6). The mechanism and stoichiometry of the termination reaction by sulfides remain yet unclear. Since sulfenic acid is an efficient scavenger of free radicals, the oxidation of tetralin in the presence of dialkylsulfoxide occurs only if the initiation rate v > vimin is proportional to the concentration of sulfoxide [5], so that the rate of oxidation is... 

The significant role of intermediates of conversion of sulfides and disulfides should be highlighted. Thus, sulfenic acid is formed by sulfoxide decomposition and terminates chains by reacting with R02 and, on the other hand, initiates chains by reacting with hydroperoxide. 

Peroxynitrite easily oxidizes nonprotein and protein thiyl groups. In 1991, Radi et al. [102] have shown that peroxynitrite efficiently oxidizes cysteine to its disulfide form and bovine serum albumin (BSA) to some derivative of sulfenic acid supposedly via the decomposition to nitric dioxide and hydroxyl radicals. Pryor et al. [124] suggested that the oxidation of methionine and its analog 2-keto-4-thiomethylbutanic acid occurred by two competing mechanisms, namely, the second-order reaction of sulfide formation and the one-electron... 

If an unsaturated trapping agent is not present, however, things get really complicated. First, the sulfenic acid RSOH formed in (57) can form thiolsulfinate RS(0)SR and water (24). If the initial thiolsulfinate is an un-symmetrical one, RS(0)SR, this will mean that the symmetrical thiolsulfinate RS(0)SR will begin to appear in the reaction mixture. Second, in some way, perhaps aided by reaction of some of the water formed in (24) with thiolsulfinate, traces of acid become present in the solution. This acid catalyzes a complex disproportionation of alkyl thiolsulfinates that parallels in a number of important aspects the mechanism of the acid- and sulfide-catalyzed disproportionation of aryl thiolsulfinates already discussed. The steps that are important in this disproportionation are shown in (61)—(66). 

Optically active iV-p-toluenesulfinyl piperidine 75 prepared in low optical purity by oxidation of iV-p-toluenesulfenyl piperidine with (+)-percamphoric acid represents the first example of a chiral sul-flnamide (105). As in the case of asymmetric oxidation of sulfides and sulfenates, the synthetic utility of this method is strongly limited by its low stereoselectivity. 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

The proposed metabolic pathway in strawberries is shown in Figure 3. Five compounds mixed disulfide, sulfide, sulfenic acid, thiophosgene and the GSH-re-action product have not been identified as a strawberry metabolite but their involvement is very likely based on the formation of bis-(fluorodichloromethyl)... 

Simple unsaturated sulfides cannot be used in place of enamines in cycloaddition reactions with sulfines leading to thietane dioxide derivatives. " Alkyl, vinyl, and cycloalkylvinyl sulfides, which carry a C=C double bond, are considerably less nucleophilic than the enamines and thus do not partake in cycloadditions to sulfene. But when the more electrophilic methylsulfonyl sulfene is used in association with an unsaturated sulfide substituted with a strong electron donating alkylamino group, the formation of thietane dioxides 72 is successful. 

Cycloaddition of sulfenes to a,)8-unsaturated sulfides that contain electron-donor substituents, such as alkyl and arylthio groups, has proved to be a valuable synthetic pathway for the production of thietane 1,1-dioxides. Methylsulfonylsulfene (84) is more reactive than the regular sulfenes because of the activating effect by the strong electron-acceptor properties of the sulfonyl group. If, in addition, a strong electron-donor group, such as the alkylamino function, is provided by the unsaturated sulfide molecule, the cycloaddition proceeds much more readily. 

In the case of the oxidation of methyl alkyl sulfides, enantioselectivity remains in the range of 50-60% ee (Table 6C.2). Disufides R-S-S-R, sulfenamides R-S-NR 2, and sulfenates R-S-O-R were oxidized to the corresponding chiral thiosulfinates, sulfinamides, and sulfinates, respectively (<52% ee, Table 6C.3) [21]. 

An AMI semiempirical method was used to investigate the Diels-Alder cycloaddition reactions of vinyl sulfenes with buta-1,3-dienes.156 The reactivity and stereoselectivity of vinyl boranes have been reviewed.157 Aromatic methyleneamines undergo reverse-electron-demand Diels-Alder reactions with cyclopentadiene, norbom-ene, and vinyl sulfides.158... 

Sulfenate ester (RO-SAr) (7) has a weak S-O bond, so the corresponding alkoxyl radical is formed under photolytic conditions with a mercury lamp, followed by 1,5-H shift where the formed carbon-centered radical reacts with the starting sulfenate ester to give 8-hydroxy sulfide (8) via a chain pathway, as shown in eq. 6.5 [9, 10]. 

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