Oxidation of Sulfides and Amines

Ti(IV) alkylperoxides oxidize sulfides to sulfoxides. Kagan found that, although the standard Shaipless conditions for epoxidation of allylic al- 

Imaginary asymmetric catalyst surface A mnemonic device for predicting enantioface selection 

Model of a chirally modified dinuclear osmium complex reacting with olefins at 0 +. 

SCHEME 40. Reactive species and origin of asymmetric induction. [K. B. Sharpless,. Amberg, M. Beller, H. Chen, J. Hartung, Y. Kawanami, D Lubben, E. Manoury, Ogino, T. Shibata, and T. Ukita, J. Org. Chem., 56, 4585 (1991) E. J. Corey and I. Lotto, Tetrahedron Lett., 31, 2665 (1990) Y.-D. Wu, Y. Wang, and K. N. Houk, J. Org. Chem., 57, 1362 (1992). Reproduced by permission of the American Chemical Society and Pergamon Press.] 

X-ray structure of the major osmate derived from iranT-stilbene and the Os04-Tomioka diamine ligand complex 

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The selective oxidation of sulfides and amines to sulfoxide and amine oxides, respectively, can be obtained with a variety of oxidants. In particular, catalytic... 

The selective oxidation of sulfides and amines to sulfoxide and amine oxides can be obtained with a variety of oxidants. In particular, catalytic oxidations employing environmentally benign oxidants such as hydrogen peroxide and molecular oxygen have attracted considerable interest recently. A number of catalytic methods that give highly selective and mildly selective oxidations with the latter oxidants are known today. Organocatalysts (e. g., flavins), biocatalysts and metal catalysts have been used for these transformations. 

Lang X, Leow WR, Zhao J, Chen X (2015) Synergistic photocatalytic aerobic oxidation of sulfides and amines on Ti02 under visible-light irradiation. Chem Sci 6(2) 1075-1082... 

Spiro-linked CMPs functionalized with metal phthalocyanine units show enhanced catalytic activity towards different reactions." The Co-phthalocyanine-incorporated CMP acts as a catalyst with improved activity for cyclohexene oxidation, hydroquinone oxidation and H2O2 decomposition, whereas the spiro-linked Fe-porphyrin network shows increased catalytic activity for hydroquinone oxidation. The spiro linkages in these networks open up a lot of free space around the catalytic sites to enhance the accessibility of substrates to reach more catalytic sites. More functionalization in this vray of conjugated networks by various metals improves the scope of these networks in heterogeneous catalysis. Oxidation of sulfides, reductive aminations and photocatalyzed aza-Heniy reactions are reactions effectively catalyzed by different metal-incorporated CMPs" (Figure 10.6). 

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... 

The oxidation of sulfides to sulfoxides (1 eq. of oxidant) and sulfones (2 eq. of oxidant) is possible in the absence of a catalyst by employing the perhydrate prepared from hexafluoroacetone or 2-hydroperoxy-l,l,l-trifluoropropan-2-ol as reported by Ganeshpure and Adam (Scheme 99 f°. The reaction is highly chemoselective and sulfoxidation occurs in the presence of double bonds and amine functions, which were not oxidized. With one equivalent of the a-hydroxyhydroperoxide, diphenyl sulfide was selectively transformed to the sulfoxide in quantitative yield and with two equivalents of oxidant the corresponding sulfone was quantitatively obtained. 2-Hydroperoxy-l,l,l-fluoropropan-2-ol as an electrophilic oxidant oxidizes thianthrene-5-oxide almost exclusively to the corresponding cw-disulfoxide, although low conversions were observed (15%) (Scheme 99). Deprotonation of this oxidant with sodium carbonate in methanol leads to a peroxo anion, which is a nucleophilic oxidant and oxidizes thianthrene-5-oxide preferentially to the sulfone. 

The research work of recent years includes predominantly the epoxidation of alkenes9,200, asymmetric hydroxylations209,224-228 and the asymmetric oxidation of sulfides to sulfoxides205,209,229,230. Optical yields of practical significance were obtained (>90%). A detailed review published in 1991231 reports about the versatile use of oxaziridines in the field of the electrophilic amination. 

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. 

The oxidation of selenides to selenium oxides (Figure 17.35) is faster than the oxidation of sulfides to sulfoxides. The former reaction also succeeds in the presence of C=C double bonds, and even a sulfide group that might be present in the substrate will not react. Tertiary amines yield amine IV-oxides in a similar fashion (Figure 17.36). 

It has been shown in the previous sections that at least the polymerization of cyclic ethers, sulfides and amines proceeds via onium ions. The large majority of authors have agreed on this point (the mechanism of propagation of disubstituted cyclic ethers like isobutylene oxide is, however, still in dispute) . ... 

Sodium perborate, NaBOa dlljO (mp 60 °C dec), is used for oxidations of primary aromatic amines to azo compounds [795] or nitro compounds [194] and of sulfides to sulfoxides and sulfones [794]. This reagent does not affect alcohols and only slightly affects alkenes [794]. 

High-valent d transition metal complexes, e.g. complexes of Mo , V and Ti, catalyze numerous oxidations of organic substrates by alkyl hydroperoxides, such as epoxidation of alkenes, oxidation of tertiary amines to the corresponding N-oxides, of sulfides to sulfoxides. 

See [6]. The following reaction types have been listed (a) Geometric isomerization of alkenes (b) Allylic [1,3] hydrogen shift (c) Cycloaddition of alkenes. Dimerization, Tri-merization. Polymerization (d) Skeletal rearrangments of alkenes and methathesis (e) Hydrogenation of alkenes (f) Additions to alkenes (g) Additions to C = X (h) Aliphatic substitutions (i) Aromatic substitution (j) Vinyl substitution (k) Oxidation of alkenes (1) Oxidation of alcohols (m) Oxidation of arenes (n) Oxidative decarboxylation (o) Oxidation of amines (p) Oxidation of vinylsilanes and sulfides (q) Oxidation of benzal-dehyde (r) Dehydrogenations. 

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