Rylander oxidation

DJERASSI RYLANDER Oxidation Ru04 in oxidative cleavage ot phenols or alkenes oxidation ol aromatics to quinones oxidation ol alkyl amides to irmdes or ol ethers lo esters... 

R2CHOH—>J 2C=0. In a preliminary experiment Berkowitz and Rylander oxidized tra/ -cyclohexane-12-Uiol in water as solvent and isolated in 15% yield a product characterized as probably cyclohexane-l -dione. Nakata oxidized several steroid secondary alcohols to ketones in very high yield. For example a... 

Olefins, see also Catalytic method (p. 989). Djerassi and Engle report one experiment on the oxidation of phenanthrene with ruthenium tetroxide in carbon tetrachloride the reaction mixture contained considerable starting material and a small amount of phenanthrenequinone. Berkowitz and Rylander oxidized cyclohexene in the same way and obtained adipaldehyde in low yield as the only isolated product they regard the method as unsatisfactory for the production of aldehydes and acids because these substances are strongly adsorbed on the ruthenium dioxide formed. 

DIELS - ALDER Cyclohexene synthesis 95 DtMROTH Rearrangement 96 DJERASSI - RYLANDER Oxidation 97 Doebner 205... 

DJERASSI RYLANDER Oxidation R11O4 in oxidative cleavage of phenols or alkenes oxidation of aromatics to qumones oxidation ot alkyl amides to irmdes or of ethers to esters... 

Platinum, especially platinum oxide, has been used by many investigators (5), Platinum oxide, when used with aldehydes is apt to be deactivated before reduction is completed. Deactivation is inhibited by small amounts of ferrous or stannous chlorides (59,82). This type of promoter can also sharply curtail hydrogenolysis if it is a troublesome reaction (Rylander and Starrick, 1966). Deactivated systems can often be regenerated by shaking the reaction mixture with air (2,8,21 J3,96). The usefulness of this regenerative technique transcends aldehyde reductions it frequently is worth resorting to. 

Isolated proximal tubules have been utilized to study the mechanisms of nephrotoxicity induced by antibiotics (Sina et al., 1985, 1986), radiocontrast dyes (Humes et al., 1987), metals (Rylander et al., 1985), anoxia (Weinberg, 1985 Weinberg et al., 1987), cellular oxidants (Messana et al., 1988), cysteine conjugates (Rylander et al., 1985 Schnellman et al., 1987 Zhang and Stevens, 1989), and a variety of nephrotoxic bromobenzene metabolites (Schnellman and Mandel, 1986 Schnellman et al., 1987). 

The first oxidation by a Ru complex of an amide was carried out by Berkowitz and Rylander in 1958, using stoich. RuOyCCl to convert y-butyrolactam to suc-cinimide [52]. 

Rylander and Rakoncza compared the rates of hydrogenation of pyridine V-oxide over 5% palladium-, platinum-, rhodium-, and ruthenium-on-carbon in methanol, water, and acetic acid.224 Rhodium was always the most active, although the pyridine ring was hydrogenated concomitantly with the reduction of the V-oxide group. 

Rylander and Kilroy studied the formation of cyclohexyl phenyl ether intermediate in the hydrogenation of phenyl ether over binary platinum-rhodium oxide catalysts in cyclohexane at room temperature and atmospheric hydrogen pressure. The yield of the intermediate varied greatly with the catalyst composition. The highest yield (48%) was obtained over the catalyst consisting of 30% Pt-70% Rh.149... 

Most of the metallic oxidants which have been used for the oxidation of ethers have been based on oxides of the transition metals chromium, manganese and ruthenium, the latter being of greatest synthetic importance. The first reported example of the application of ruthoiium tetroxide in the oxidation of ethers tqipeared over 30 years ago in 1958, although an indication of its reactivity towards ethers had been obt ed some years before. In a systematic study which revealed the powerful oxidizing properties of the reagent, Berkowitz and Rylander demonstrated the quantitative conversion of tetrahydrofuran and R-butyl ether into y-butyrolactone and butyl butyrate, respectively. Significantly, no overoxidation was observed. Apart f m an unsuccessful attempt to oxidize ethylene oxide, no fitter attempts were made by the authors to examine further the scope of this novel transformation. In a series of subsequent publications and a patent, Wolf and his coworkers went on to exploit the reaction in the preparation of aldosterone and relr steroids (equation 1). 

The physical properties, preparation and reactions of ruthenium tetroxide have been reviewed by Lee and van den Engh, Rylander," Haines and Hetuy and Lange. A more vigorous oxidant than osmium tetroxide, its reaction with double bonds produces only cleavage products. " Under neutral conditions aldehydes are formed from unsaturated secondary carbons while carboxylic acids are obtained under alkaline or acidic conditions. For example, Shalon and Elliott" found that ruthenium tetroxide reacted with compound (11) to give the corresponding aldehyde under neutral conditions, but that a carboxylic acid was formed in acidic or alkaline solvents (equation 23). 

Oxidation of ethers. Berkowitz and Rylander found that, after a brief induction period, di-n-butyl ether is oxidized rapidly by RUO4 in CCl4 at room temperature. Infrared analysis of the reaction product indicated an essentially quantitative yield. of h-butyl n-butyrate. 

There are many other methods of preparing active synthetic silica-alumina catalysts. A fair catalyst can be made by impregnating dried silica gel with an aluminum compound which is easily converted to the oxide by calcination, e.g., A1(NC>3)3. A preferred impregnation technique is to soak a sodium-free silica hydrogel in a solution of an aluminum salt and to follow this with an aqueous ammonia treatment to precipitate the hydrous alumina on the silica (Thomas, 16 Ryland and Tamele, 17). It should be noted that silica hydrogel can easily be freed of sodium ions by water washing, since it is not a zeolite. Exceptionally pure silica-alumina composites can also be prepared by the hydrolysis of mixtures of ethyl orthosilicate and aluminum alkoxides (Thomas, 18). 

USE Oxidizing agent, particularly for converting olefins to glycols. Catalyzes chlorate, peroxide, periodate, and other oxidations P. N. Rylander. Organic Syntheses with Noble... 

Chem. 136, 49 (1924) Grube in Handbook of Preparative Inorganic Chemistry vol, 2, G, Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) p 1599. Crystal structure Tr6-houx et al., Campt. Rend. Ser. C 268, 246 (1969). Review of use as oxidizing agent P. N. Rylander, Organic Syntheses with Noble Metal Catalysts (Academic Press, New York, 1973) pp 134-144. 

Ryland BL, Stahl SS. Practical aerobic oxidations of alcohols and amines with homogeneous copper/TEMPO and related catalyst systems. Angew Chem Int Ed Engl. 

Hoover JM, Ryland BL, Stahl SS. Copper/TEMPO-catalyzed aerobic alcohol oxidation mechanistic assessment of different catalyst systems. CS Catd. 2013 3 2599-2605. 

Another example of induction period is hydrogenation of nitrobenzene on supported gold catalysts (Fig. 9.37), when the induction period was su ested to be related with the creation of active sites, namely metaUic Au sites required to chemisorb hydrogen. The earher work of P.N. Rylander in the 1960s with metal oxides already showed that the oxide is first reduced to the metal before hydrogenation of nitrobenzene begins. 

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