Stereoselective catalytic oxidation

Stereoselective catalytic oxidation of Aryl methyl sulfides. 300... 

STEREOSELECTIVE CATALYTIC OXIDATION OF ARYL METHYL SULFIDES... 

Monzani E, Linati L, Casella L et al (1998) Synthesis, characterization and stereoselective catalytic oxidations of chelated deuterohaemin-glycyl-L-histidine complexes. Inorg Chim Acta 273 339-345... 

A convenient enantioselective catalytic oxidation of a variety of differently substituted, cyclic (E) and acyclic (Z)-enol phosphates with (salen)manganese(III) complex has been reported. The influence of electronic and steric effects of the enol phosphate substituents on the stereoselectivity of oxidation has been studied.50... 

Isomerization of alkenes is catalyzed by bis(j7 -allyl)(jj -cyclopentadienyl)vanadium(IV). Cyclohexene nndergoes catalytic stereoselective aerobic oxidation with CpV(CO)4. Reductive coupling (see Reductive Coupling) of aldehydes and aldimines is catalyzed by a Cp-substituted vanadium compound in the presence of a chlorosilane and zinc or aluminum. Vanadocene or bis( ] -cyclopentadienyl)dimethylvanadium(IV) catalyzes the synthesis of 1,2-diphenyldisilane and 1,2,3-triphenyltrisilane from phenylsilane. ... 

This procedure is primarily of industrial importance. It is sufficient to point out that oxirane, which is of great importance in industrial syntheses, is produced entirely by direct catalytic oxidation from ethylene. In the organic preparative laboratory, the direct epoxidation of olefins is carried out in the liquid phase. Independently of the reaction conditions employed, the reaction proceeds via a radical mechanism, generally with a poor yield, with low selectivity, and only rarely stereoselectively. 

Geier GR HI, Lybrand TP, Sasaki T (1999) On the absence of stereoselectivity in the catalytic oxidation of alkenes with a surface-bound metalloporphyrin-peptide conjugate. Tetrahedron 55 1871-1880... 

Abstract The catalytic oxidation is an area of the key technologies for converting petroleum-based feedstocks to useful chemicals such as diols, epoxides, alcohols, and carbonyl compounds. Many efficient homogeneous and heterogeneous oxidation systems based on polyoxometalates (POMs) with green oxidants such as H2O2 and O2 have been developed. This chapter summarizes the remarkable oxidation catalyses by POMs with multimetallic active sites. The multifunctionality of multimetallic active sites in POMs such as cooperative activation of oxidants, simultaneous activation of oxidants and substrates, stabilization of reaction intermediates, and multielectron transfer leads to their remarkable activities and selec-tivities in comparison with the conventional monometallic complexes. Finally, the future opportunities for the development of shape- and stereoselective oxidation by POM-based catalysts are described. 

Addition of the Cl-anion to aldehyde 30 gave compound 31 in good yield with high diastereoselective control at the new stereogenic center (10 1). Transformation of the Cl-substituted glycal to the C-cellobiose derivative 32 then required a three-step sequence involving reductive removal of the phenylsulfoxide with Raney nickel, a stereoselective hydroboration-oxidation step, and finally catalytic hydrogenation. 

In order to make these oxidative reactions of 1,3-dienes catalytic, several reoxidants are used. In general, a stoichiometric amount of benzoquinone is used. Furthermore, Fe-phthalocyanine complex or Co-salen complex is used to reoxidize hydroquinone to benzoquinone. Also, it was found that the reaction is faster and stereoselectivity is higher when (phenylsulflnyl)benzoquinone (383) is used owing to coordination of the sulfinyl group to Pd, Thus the reaction can be carried out using catalytic amounts of PdfOAcji and (arylsulfinyl)benzoquinone in the presence of the Fe or Co complex under an oxygen atmosphere[320]. Oxidative dicyanation of butadiene takes place to give l,4-dicyano-2-butene(384) (40%) and l,2-dicyano-3-butene (385)[32l]. 

Hydroboration-oxidation of a pinene (page 235) like catalytic IS stereoselective Addition takes place at the less hindered face and a single alcohol is produced in high yield (89%) Sug... 

The final stages of the successful drive towards amphotericin B (1) are presented in Scheme 19. Thus, compound 9 is obtained stereoselectively by sodium borohydride reduction of heptaenone 6a as previously described. The formation of the desired glycosida-tion product 81 could be achieved in dilute hexane solution in the presence of a catalytic amount PPTS. The by-product ortho ester 85 was also obtained in approximately an equimolar amount. Deacetylation of 81 at C-2, followed sequentially by oxidation and reduction leads, stereoselectively, to the desired hydroxy compound 83 via ketone 82. The configuration of each of the two hydroxylbearing stereocenters generated by reduction of carbonyls as shown in Scheme 19 (6—>9 and 82->83) were confirmed by conversion of 83 to amphotericin B derivative 5 and comparison with an... 

The enzyme-mediated Baeyer-Villiger oxidation to chiral lactone intermediates has received considerable attention in recent years as it offers several advantages in chemo-, regio-, and stereoselectivity compared to other catalytic strategies... 

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