Thiophenols oxidation—

Stability. Diesel fuel can undergo unwanted oxidation reactions leading to insoluble gums and also to highly colored by-products. Discoloration is beheved to be caused by oxidation of pyrroles, phenols, and thiophenols to form quiaoid stmctures (75). Eventually, these colored bodies may increase in molecular weight to form insoluble sludge. 

Make acid yields coumaUc acid when treated with fuming sulfuric acid (19). Similar treatment of malic acid in the presence of phenol and substituted phenols is a facile method of synthesi2ing coumarins that are substituted in the aromatic nucleus (20,21) (see Coumarin). Similar reactions take place with thiophenol and substituted thiophenols, yielding, among other compounds, a red dye (22) (see Dyes and dye intermediates). Oxidation of an aqueous solution of malic acid with hydrogen peroxide (qv) cataly2ed by ferrous ions yields oxalacetic acid (23). If this oxidation is performed in the presence of chromium, ferric, or titanium ions, or mixtures of these, the product is tartaric acid (24). Chlorals react with malic acid in the presence of sulfuric acid or other acidic catalysts to produce 4-ketodioxolones (25,26). 

With hydrogen sulfide at 500—600°C, monochlorotoluenes form the corresponding thiophenol derivatives (30). In the presence of palladium catalysts and carbon monoxide, monochlorotoluenes undergo carbonylation at 150—300°C and 0.1—20 MPa (1—200 atm) to give carboxyHc acids (31). Oxidative coupling of -chlorotoluene to form 4,4 -dimethylbiphenyl can be achieved in the presence of an organonickel catalyst, generated in situ, and zinc in dipolar aprotic solvents such as dimethyl acetamide (32,33). An example is shown in equation 4. 

The action of sulfur nucleophiles like sodium bisulfite and thiophenols causes even pteridines that are unreactive towards water or alcohols to undergo covalent addition reactions. Thus, pteridin-7-one smoothly adds the named S-nucleophiles in a 1 1 ratio to C-6 (65JCS6930). Similarly, pteridin-4-one (73) yields adducts (74) in a 2 1 ratio at C-6 and C-7 exclusively (equation 14), as do 4-aminopteridine and lumazine with sodium bisulfite. Xanthopterin forms a 7,8-adduct and 7,8-dihydropterin can easily be converted to sodium 5,6,7,8-tetrahydropterin-6-sulfonate (66JCS(C)285), which leads to pterin-6-sulfonic acid on oxidation (59HCA1854). 

Butyroin has been prepared by reductive condensation of ethyl butyrate with sodium in xylene, or with sodium in the presence of chloro-trimethylsilane. and by reduction of 4,5-octanedlone with sodium l-benzyl-3-carbamoyl-l,4-dihydropyridine-4-sulfinate in the presence of magnesium chloride or with thiophenol in the presence of iron polyphthalocyanine as electron transfer agent.This acyloin has also been obtained by oxidation of (E)-4-octene with potassium permanganate and by reaction of... 

In an attempt to protect thiophenols during electrophilic substitution reactions on the aromatic ring, the three substituted thioethers were prepared. After acetylation of the aromatic ring (with moderate yields), the protective group was converted to the disulfide in moderate yields, 50-60%, by oxidation with hydrogen peroxide/boiling mineral acid, nitric acid, or acidic potassium permanganate. ... 

The reaction of 1,2,4-triazine 4-oxides 55 with thiophenols proceeds in the same manner, resulting in the corresponding 5-arylmercapto-1,2,4-triazines 80 in high yields. Thiophenols in this case react as S-nucleophiles, in spite of the relative phenols—the C-nucleophiles (01RCB1068). 

Peroxide decomposers—These function by reacting with the initiating peroxides to form nonradical products. Presumably mercaptans, thiophenols, and other organic sulfin compounds function in this way [19]. It has been suggested that zinc dialkyldithiocarbamates function as peroxide decomposers, thus giving mbber compounds good initial oxidative stability. 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

An extraordinary way of stabilizing RUO2-coated CdS colloids for H2 generation was chosen by Fendler and co-workers The colloidal particles were generated in situ in surfactant vesicles of dioctadecyldimethylammonium chloride and dihexa-decyl phosphate. Thiophenol as a membrane permeable electron donor acted as a sacrificial additive. Later, a surface active re-usable electron donor (n-C,gH3,)2N — (CHj)—CH2—CHj—SH, Br was incorporated into the vesicles. Its R—SS—R oxidation product could be chemically reduced by NaBH to regenerate the active electron donor. The H2 yields in these systems were only 0.5 %. However, yields up to 10% were later reported for a system in which CdS was incorporated into a polymerizable styrene moiety, (n-C,jH3jC02(CH2)2) N (CH3) (CH2CgH4CH=CH2>, CP, and benzyl alcohol was used as the electron donor. 

Fractional separation of tin compounds used as stabilisers in PVC was based on substoichiometric isotope dilution analysis [446]. The tin compounds were isolated by extraction and complexed with salicylideneamino-2-thiophenol, followed by controlled addition of y-irradiated tributyl tin oxide and measurement of the y-activity. PVC containing a nominal 0.63% (Bu Sn analysed 0.614 0.016% in nine determinations. 

A versatile approach for the solid-phase synthesis of aminopyr-idazines used the anchoring of 3,6-dichloropyridazine to resin-bound thiophenol 59 (Scheme 28) [68]. Treatment with nucleophilic amines released the aminopyridazine products from the solid support without further oxidation. 

Combining, in tandem, the nitro-aldol reaction with the Michael addition using thiophenol is a good method for the preparation of P-nitro sulfides as shown in Eqs. 4.2 and 4.3. This reaction is applied to a total synthesis of tuberine. Tuberine is a simple enamide isolated from Streptomyces amakusaensis and has some structural resemblance to erbastatin, an enamide which has received much attention in recent years as an inhibitor of tyrosine-specific kinases. The reaction of p-anisaldehyde and nitromethane in the presence of thiophenol yields the requisite P-nitro sulfide, which is converted into tuberine via reduction, formylation, oxidation, and thermal elimination of... 

The oxidative properties of ditelluronium and diselenonium dications are similar to S-S dications. For instance, interaction of thiophenol or 1,2-diphenylhydrazine with either the diselenonium dication 113 or the ditelluronium dication 114 leads to almost quantitative formation of diphenyldisulfide or azobenzene and reduced bis-chalcogenides.113,114,124 Reduction of 113 and 114 with NaBH4 gives the same products as above but proceeds quantitatively via direct electron transfer (Scheme 47).128... 

The chemical properties of trichalcogen dications are, in many ways, analogous to the properties of dichalcogen dications, but are considerably less studied. Hydrolysis of chalcogenurane dications occurs preferentially at the onium chalcogen atom. Similar to the usual dichalcogen dications, trichalcogen dications also display oxidative properties. For example, reduction of selenu-rane dication 135 (X = Y = Se) is observed in reactions with Sm(II) salts, triphenylphosphine or thiophenol (Scheme 54).135... 

Another example of a mononuclear complex is the dicationic Cr(III) complex [CrinH2L19(OAc)]2+ (47). This complex is obtained when (L19)2 is treated with CrCl2 and NaOAc in methanol followed by oxidation in air (226). The Cr ion in 47 is coordinated to three N and two S atoms of (L19)2 and an O atom of a monodentate acetate coligand in an octahedral manner as shown in Fig. 33. To our knowledge, mononuclear complexes of macrocyclic thiophenolate Schifif-bases have not yet been documented in the literature (227). 

These reactions produce free radicals, as follows from the fact of consumption of free radical acceptor [42]. The oxidation of ethylbenzene in the presence of thiophenol is accompanied by CL induced by peroxyl radicals of ethylbenzene [43]. Dilauryl dithiopropionate induces the pro-oxidative effect in the oxidation of cumene in the presence of cumyl hydroperoxide [44] provided that the latter is added at a sufficiently high proportion ([sulfide]/[ROOH] > 2). By analogy with similar systems, it can be suggested that sulfide should react with ROOH both heterolytically (the major reaction) and homolytically producing free radicals. When dilauryl dithiopropionate reacts with cumyl hydroperoxide in chlorobenzene, the rate constants of these reactions (molecular m and homolytic i) in chlorobenzene are [42]... 

Related (diisopropoxyphosphoryl)- and (diisobutoxyphosphoryl)formonitrile oxides (114), generated in basic media from the corresponding oximes react in situ with alcohols, phenols, alkanethiols, thiophenols, aliphatic and aromatic primary amines, hydrazines and hydrazides as well as 4-aminoantipyryne to give hydroxymates, thiohydroxymates, and amidoximes, respectively. It is important to note that the addition is stereoselective and gives E-adducts with the exception of (i-Pr0)2P(0)C( N0H)0Me, which is formed as a 1 1 mixture of E and Z isomers. 

Homolytic hydrostannation can also be initiated at room temperature by thiophenols, when a trace of oxygen may oxidize the thiol to the ArS radical, which abstracts hydrogen from the stannane to give the stannyl radical (Equation (15)).93 With azoisobutyronitrile (AIBN) initiation, alkynes undergo only monohydrostannation, but with the thiol, simple alkynes show bis(hydrostannation) or bis(stannation). 

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