Hydrogen platinum

The above base is catalytically hydrogenated (platinum oxide seems to work the best) to 1-(p-methoxybenzyl)-2-methyl-l,2,3,4,5,6,7,8-octahydro-isoquinoline. This is separated from the... 

In order to increase the contact of a catalyst with hydrogen and the compounds to be hydrogenated platinum (or other metals) is (are) precipitated on materials having large surface areas such as activated charcoal, silica gel, alumina, calcium carbonate, barium sulfate and others. Such supported catalysts are prepared by hydrogenation of solutions of the metal salts, e.g. chloroplatinic acid, in aqueous suspensions of activated charcoal or other solid substrates [28. Supported catalysts which usually contain 5, 10 or 30 weight percent of platinum are very active, and frequently pyrophoric. 

Adams cat. pre-hydrogenated platinum dioxide A boiling solvent ( reflux ), heat... 

The von Braun degradation (85, 67) was reinvestigated and fully worked out by Boit (86). The reaction of strychnine with cyanogen bromide in hot benzene leads to the formation of two products, the amorphous bromocyanamide-I (LXXX) and the crystalline bromo-cyanamide-II (LXXXI). Dihydrostrychnine, on the other hand, gives only one product (LXXXII), which is identical with the product of catalytic hydrogenation (platinum in ethyl acetate) of bromocyan-amide-II. The corresponding brucine compounds behave analogously. 

Analysis.—Decomposition in aqueous alkali proved to be unsuitable analytical procedure for dioxygenyl hexafiuoroplatinate(v), giving consistently low values for fluorine. Platinum analysis required two determinations, one of the mixture of metallic platinum and hydrated platinum oxides, the other of the solution of hexafluoroplatinate(iv). The precipitate was reduced to the metal in hydrogen. Platinum in the solution was precipitated by zinc. The total-platinum figures were not very concordant and always higher than that required... 

Palladium in the form of Pd black or Pd/C is the most effective catalyst. Although Raney nickel has been used, there is doubt that it serves only as a hydrogen transfer catalyst because it contains a considerable amount of adsorbed hydrogen. Platinum and rhodium have been found to be ineffective. Both alkenes and alkynes have been hydrogenated and syn addition to 1,2-diphenylacetylene has been demonstrated. ... 

Cinchonidine modified catalysts, though, have been effectively used for several other enantioselective hydrogenations. Platinum-cinchonidine catalysts have been used for the hydrogenation of the a ketolactone, 36, to D-pantolactone (37) in 35% ee at complete conversion (Eqn. 14.26) while palladium-cinchonidine catalysts have been used for the enantioselective dehydrohalogenation of a,a-dichloro-2-benazapinone (38) (Eqn. 14.27) and the hydrogenation of (E) a phenylcinnamic acid (39) to (S) 2, 3-diphenylpropionic acid (40) in a 44% ee (Eqn. 14.28). ... 

The bishydrazones of DHA and related compounds have been studied and used to synthesize a number of nitrogen derivatives of DHA (18-23), Thus the bisphenylhydrazone of DHA is reduced by hydrogen/platinum to 2,3-diamino-2,3-dideoxyascorbic acid, which in turn can be converted to a variety of acyl derivatives. The structure of DHA phenylosazone is a hexenonelactone (24),... 

Several surface oxygen species have been postulated based on kinetic parameters, stable intermediates, and in situ observations during oxygen reduction or evolution. As in the case of hydrogen, platinum is the most well-studied electrocatalyst. Optical measurements (122-126) show that a freshly developed oxygen layer on platinum behaves reversibly up to 0.95 V. However, rapid aging yields an irreversibly bound layer. Chemisorption of OH is assumed to occur in this potential region (123,124,127,128) formed by z. + + H- + e (27)... 

Pseudovmcadifformine (680), prepared from catharanthine by reduction (sodium borohydride, then hydrogen-platinum oxide) followed by oxidation (mercuric acetate), undergoes the same rearrangement as vincadifformine (76) when oxidized, then treated with triphenylphosphine and acetic acid. The products are pseudovincamine (681) and its C-16 epimer 682 (Scheme 96), and it is of interest that these compounds were prepared by this transformation well before this ring system was found in Nature (5S5). 

L.4 Heterogeneous (Bromate-Hydrogen-Platinum-Acid) System. .. 104... 

In the iodate-hydrogen-platinum-acid system the oscillatory range was found to be narrow and sensitive to physical parameters. Under similar conditions, with anions such as Cr207 and Mn04 no oscillations were recorded. 

IIIL) Orban, M., Epstein, I. R. Oscillations and Bistability in Hydrogen-Platinum-Oxyhalogen 1981 Systems. J. Am. Chem. Soc., 103, 3723-3727... 

Besides the composition of the sample, the electronic population density in each state will also depend on the geometric distribution of each of the components. The changes in the electronic distribution at the local density of the states due to a second metal was certainly expected because the presence of the hydrogen on the clean platinum (involved in the formation of the hydrogen platinum bond) affects the vacant states of the platinum atoms that are arranged in the second layer [45]. In particular, the hydrogen adsorption state is assumed to occupy the hollow sites of the single crystal surface. 

Nevertheless, despite the strong hydrogenation platinum activity, the butene fraction remained higher over the Pt/Ga-silicate. 

As the cinchona alkaloids contain a nucleophilic nitrogen center, they can be alkylated at this position. Thus, cinchonidine reacts with benzyl chlorides to form quaternary salts, e.g., 9 and 108, which are useful as chiral phase-transfer catalysts (see Section D.1.5.2.4. for enantioselec-tive additions to azaenolates, and D.4.1. for the oxidation of enolates). Further modification by catalytic reduction of the double bond (hydrogen/platinum) leads to the corresponding dihydrocinchonidine derivatives. 

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