Hydrogen activities, lead oxides

A heterocyclic ring may be used in place of one of the benzene rings without loss of biologic activity. The first step in the synthesis of such an agent starts by Friedel-Crafts-like acylation rather than displacement. Thus, reaction of sulfenyl chloride, 222, with 2-aminothiazole (223) in the presence of acetic anhydride affords the sulfide, 224. The amine is then protected as the amide (225). Oxidation with hydrogen peroxide leads to the corresponding sulfone (226) hydrolysis followed by reduction of the nitro group then affords thiazosulfone (227). ... 

The results confirm that the novel metal nitrate conversion method using nitric oxide in place of air advocated by Sietsma et al. in patent applications WO 2008029177 and WO 2007071899 leads to, after activation in H2, catalysts with smaller cobalt crystallites, as measured by EXAFS and hydrogen chemisorption/ pulse reoxidation. In spite of the lower extent of cobalt reduction for H2-activated nitric oxide calcined catalysts, which was recorded by TPR, XANES, EXAFS,... 

The addition of a phenylsulfoxide moiety to the end of the side chain markedly changes the activity of this class of compounds. This product, sulfinpyrazone (97-11), stimulates uric acid excretion, making it a valuable dmg for dealing with the elevated serum uric acid levels associated with gout. The compound is stiU one of the more important uricosuric agents available today. The starting ester (96-9) is available by alkylation of the dianion from ethyl malonate with 2-chloroethylphenyl thioether. Condensation with diphenylhydrazine (97-3) in the presence of a base then affords the pyrrazolodione (97-10). Oxidation of sulfur with a controlled amount of hydrogen peroxide leads to the sulfoxide and thus sulfinpyrazone (97-11) [107]. 

Catalysts Catalysts are widely used for PU manufacture. Sometimes a combination of two or three catalysts is required to obtain the desired balance of reaction rates between compounds of differing active hydrogen activity. Metal compounds, especially organotin compounds, are much more efficient catalysts than tertiary amines for the -OH/NCO reaction. In addition to more commonly used dibutyltin(IV) dilaurate, dibutyltin(IV) diacetate, dialkyltin(IV) oxide or salts of divalent fin with a variety of carboxylic acids such as stannous octoate, hexoate and naphthenate etc. are available for this purpose. Combination of tin catalysts with tertiary amines has been reported to lead to a synergistic increase in catalytic activity. 

Liquefaction catalysts, such as sulfides, lose their catalytic activity, especially hydrogenation activity when they are transformed into sulfate or oxide. Even reduction of the extent of sulfiding leads to a significant loss in catalyst activity. The crystalline form of the catalyst may also influence the catalytic activity. Thus, the level of sulfur during coal liquefaction is critical. This can be controlled by the addition of sulfur additives. 

Heterolytic cleavage. This leads to formation of a metal hydride with release of a proton (equation 1). The formal oxidation state of the metal does not change. This mode of hydrogen activation is common in hydrogenation by complexes of ruthenium(II). 

Kinetic studies have shown that the product formed in the reaction of the fully oxidized enzyme with hydrogen peroxide is catalytically inactive. Reaction of the half-reduced enzyme with hydrogen peroxide leads to an enzymatically active compound, in which the Fe" heme is oxidized to Fe, and the FeIU heme is oxidized to the FeIV ferryl species. No stoichiometric formation of a radical species is observed, unlike the case for other peroxidases. The peroxide-oxidized enzyme will then oxidize two molecules of reduced cytochrome c. Mechanistic details are still unclear, particularly with regard to the interaction between the two heme groups, a phenomenon revealed by ESR studies.1373... 

Ruthenium(O) complexes such as Ru(COD)(COT) catalyze the dehydrohalo-genative coupling of vinyl halides with olefins to give substituted conjugated dienes in a Heck-type reaction [11]. Thus, alkenyl halides readily react with activated olefins to produce dienes 16 (Eq. 7). Oxidative addition of vinyl halide, followed by regioselective insertion of an electron-deficient olefin and by -hydrogen elimination leads to the diene. 

Many compounds, especially various metallic oxides, also induce very rapid decomposition of hydrogen peroxide without themselves being permanently changed.4 In addition to the solutions of the alkali hydroxides already,mentioned, manganese dioxide, cobalt oxide, and lead oxide (massicot) are remarkably active, and as might be expected a colloidal solution of manganese dioxide 5 is also able to exert powerful catalytic influence.6 The effect in such cases may be partly a surface effect, but is also probably due in part to the intermediate formation and decomposition of unstable highly oxidised derivatives. 

---