Oxidation of sulfides catalyzed

As an extension, this type of reagent can also be used to oxidize sulfides. Scheme 4-43 depicts the asymmetric oxidation of sulfides catalyzed by salen Mn(III) complexes. 

Figure 25 Stereoselective oxidation of sulfides catalyzed by SN37.4-Ru(ToCPP) and 3A3-MP8 complexes and regioselective nitration of phenol catalyzed by 3A3-MP8.

Colonna S, Gaggero N, Manfredi A, Casella L, Gullotti M, Carrea G, Pasta P (1990) Enantioselective Oxidations of Sulfides Catalyzed by Chloroperoxidase. Biochemistry 29 10465... 

Optimization of asymmetric oxidation of sulfides catalyzed by a Fe(salan) complex has been carried out. ° Using alkyl hydroperoxide as oxidant for sulfides, a Ti(IV) chelate of... 

Enantiosclcctivc Oxidation of Sulfides Catalyzed by Fe" (Salcn) Complexes... 

Table 6. Catalytic oxidation of sulfides catalyzed by iron complexes 14,15...

Rhodanese. A product of animal metabolism is thiosulfate, SjOa . Two mechanisms have been shown to produce thiosulfate. One is a nonspecific oxidation of sulfide catalyzed by various hemins no protein is required. Another mechanism was found to employ liver enzymes, which form thiosulfate from jS-mercaptopyruvate - - sulfite. Thiosulfate is metabolized by an enzyme named rhodanese, to indicate that the enzyme synthesizes, rather than degrades, rhodanate (thiocyanate). Rhodanese, which was recently crystallized by Sorbo, catalyzes the reaction ... 

A method for mild and efficient aerobic oxidation of sulfides catalyzed by HAuCl4/AgN03 was reported by Hill [58]. The active catalyst is thought to be Au(III)Cl2N03(thioether). A very high selectivity for sulfoxide was observed in these oxidations and no sulfone was detected. Isotope labeling studies with H2 0 shows that water and not Og is the source of oxygen in the sulfoxide product. 

Oxidation of sulfides catalyzed by haloperoxidases has been reviewed [74]. The natural biological role of haloperoxidases is to catalyze oxidation of chloride, bromide, or iodide by hydrogen peroxide. Three classes of haloperoxidases have been identified (i) those without a prosthetic group, found in bacteria, (ii) heme-containing peroxidases such as chloroperoxidase (CPO), and (iii) vanadium-containing peroxidases. 

The flow-cell design was introduced by Stieg and Nieman [166] in 1978 for analytical uses of CL. Burguera and Townshend [167] used the CL emission produced by the oxidation of alkylamines by benzoyl peroxide to determine aliphatic secondary and tertiary amines in chloroform or acetone. They tested various coiled flow cells for monitoring the CL emission produced by the cobalt-catalyzed oxidation of luminol by hydrogen peroxide and the fluorescein-sensitized oxidation of sulfide by sodium hypochlorite [168], Rule and Seitz [169] reported one of the first applications of flow injection analysis (FTA) in the CL detection of peroxide with luminol in the presence of a copper ion catalyst. They... 

TABLE 26. CPO-catalyzed oxidations of sulfides using H2O2 or TBHP as oxidants producing sulfoxides (ff)-23 (yields are given and ee values are given in parentheses)... 

SCHEME 111. Titanium-catalyzed asymmetric oxidation of sulfides with carbohydrate hydroperoxides... 

Optically active Schiff-base oxovana-dium(IV) complexes catalyze the asymmetric oxidation of sulfides to sulfoxides by peroxides [86]. The catalytically active species is VO(V) rather than VO(IV) and is formed in situ under the reaction conditions. A series of related complexes based on the optically active ligand shown in Eig. 15 shows linear dependence of their oxidation Ef values on the Hammett parameters of functional group X. These values ranged from 0.18 V versus Cp2Ee/DMSO for X = NO2 to —0.18 V for X = OCH3 [87]. A few complexes of planar tetradentate non-Schiff base ligands have also been investigated [88]. 

Table 9.1 Oxidation of sulfides ArSR to sulfones catalyzed by LDH-OSO4 using molecular oxygen as oxidant.

BENZYL-4,6-O-ISOPROPYLIDENE-a-D-GLUCOPYRANOSIDE, 2-DEOXY-2-[[(2-HYDROXY-3,5-di-lerl-BUTYLPHENYL)METHYLENE]IMINE] AS A LIGAND FOR VANADIUM-CATALYZED ASYMMETRIC OXIDATION OF SULFIDES... 

In combination with H2O2 (salen)Mn(III) complexes 173a, b, i-n have also been employed by Jacobsen and coworkers as catalysts for the asymmetric oxidation of sulfides to sulfoxides, without a need for additives. From the structurally and electronically different Mn-salen catalysts screened, 173i turned out to be the most active and selective one (equation 58)389. While dialkyl sulfides underwent uncatalyzed oxidation with H2O2, aryl alkyl sulfides were oxidized only slowly compared with the catalyzed pathway. Using... 

Asymmetric reactions also occur via oxo metal intermediates 101, 104). Thus, chiral poiphyrin-Fe complexes catalyze oxidation of sulfides with iodosylbenzene in the presence of 1-methylimidazole with high turnover numbers to give optically active sulfoxides in moderate ee (Scheme 45) 105). 

All measured profiles of sulfate reduction in sediments indicate that much sulfide production and, by inference, oxidation occurs in permanently anaerobic sediments (78, 73, 90,101). The two most likely electron acceptors for anaerobic sulfide oxidation are manganese and iron oxides. Burdige and Nealson (151) demonstrated rapid chemical as well as microbially catalyzed oxidation of sulfide by crystalline manganese oxide (8-Mn02), although elemental S was the inferred end product. Aller and Rude (146) documented microbial oxidation of sulfide to sulfate accompanied by reductive dissolution... 

Oxo-metal species participate in a wide range of biological and chemical oxidation reactions. Representative oxidizing enzyme, cytochrome P-450, which carries iron(III)-porphyrin complex as its active site, catalyzes various O-atom transfer reactions such as epoxidation, hydroxy-lation of C-H bond, and oxidation of sulfides. These reactions have been proven to proceed through cationic oxoiron(IV)-porphyrin species, which are generated by the oxidation of Fe(III) complex with molecular oxygen. This conversion from Fe(III) to 0=Fe(IV) species is a... 

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