Pd/C catalysts

Hydrogenation of 2- (4-oxo-4//-pyrido[l, 2-n]pyrimidin-2-yl)oxymethyl -4-isopropyl-6-alkoxysaccharins 134 over 10% Pd/C catalyst at 50 psi Parr hydrogenator yielded 6,7,8,9-tetrahydro derivatives 135... 

Catalytic debenzylation of 10-(dibenzylamino)-6-(4-rerr-butylphenyl)-3,4-dihydro-2//-pyrimido[2,l-n]isoquinoline 421 (R = PhCH2) over a 5% Pd/C catalyst under hydrogen at atmospheric pressure in acidified EtOH at ambient temperature afforded the 10-amino derivative 421 (R = H) (98JMC1050). 

A different set of tautomeric tetrahydropyridines was obtained on partial hydrogenation of 2-alkoxy-3-acylpyridines 25 on PtOa or Pd/C catalyst (Scheme 9) (79JHC939). The tetrahydropyridines 26 formed exist exclusively as single tautomers, the type of tautomer, however, being determined by the substitution in the pyridine ring. 

Hydrogenation of 2,4u,5,6,7,8-hexahydropyrido[l,2-A][l,2]oxazin-8-onei 14 over 10% Pd/C catalyst gave perhydro derivatives 15 (96JCS(P1)1113, OOOL2955, 01JOC3338). 

Under the circumstance of catalytic hydrogenation of piperidine derivatives 190 in MeOH over Pd/C catalyst afforded an isomeric mixture of perhydropyrido[l,2-c]pyrimidines 174-177 (98TL7021, 00JA5017). The main product was 174 (66%). 

Reduction of 8-nitro-l,3,4,6,l 1,1 la-hexahydro[l,4]oxazino[4,3-/)]isoqui-nolin-4-one with BH3 in THF afforded 8-nitro-1,3,4,6,11,1 la-hexahydro [l,4]oxazino[4,3-/)]isoquinoline (97MIP4). Then the nitro group was reduced by catalytic hydrogenation over 5% Pd/C catalyst in acidified MeOH to yield 8-amino derivative. Catalytic hydrogenation of 3-nitro-6,6a,7,... 

A side-chain COOH group in 5//-pyrido[l,2,3- 7e]-l,4-benzoxazin-5-one was reduced into a HOCH2 group with NaBH4 in a 1 1 mixture of MeOH and THE at 5°C (98MIP13). Ethyl 7-oxo-2,3,6,7-tetrahydro-5//-pyr-ido[l,2,3- 7e]-l,4-benzoxazine-2-carboxylate was prepared by the catalytic hydrogenation of the l-oxo-5H derivative over 10% Pd/C catalysts in EtOH (99EUP894796). 

Oxo-2,3,6,7-tetrahydro-5//-pyrido[l,2,3- /e]-l,4-benzoxazine-2-carbox-ylates (291, X = H2) were obtained by hydrogenation of 4-substituted 3, 4-dihydro-2//-1,4-benzoxazine-2-carboxylates (290, X = H2) over 10% Pd/C catalyst, then by the treatment of free acids with (CF3C0)20 (99EUP894796). 5,7-Dioxo-2,3,6,7-tetrahydro derivatives 291 (X = 0) were prepared similarly from 290 (X = O). The products 291 (X = O) exist in 7-hydroxy-5-oxo-2,3-dihydro-5// tautomeric form. 

Methyl 2-substituted perhydropyrido[l,2-u]pyrazine-8-acetates were obtained by catalytic hydrogenation of 2-substituted 8-(methoxycarbonyl-methylene)perhydropyrido[l,2-a]pyrazines over 10% Pd/C catalysts (00JAP(K)00/86659). A side chain 4-pyridyl group was hydrogenated over Pt02 catalysts to yield a 4-piperidyl derivative. 

The side chain C=C double bond of 2,3,4,6,ll,lln-hexahydro-l//-pyrazino[l,2-i]isoquinoline-l,4-diones 354 was saturated by catalytic hydrogenation over Pd/C catalysts in EtOH to give 355 (98MIP7). 7-(2-Pyridylmethyl)amino derivative was obtained by reduction of 7-[(2-pyridylmethylene)amino]-2,3,11,11 n-tetrahydro-6//-pyrazino[l, 2-i]isoqui-noline-l,4-dione (356) with NaBH4 in EtOH at ambient temperature for 24 h. 

Substituted perhydropyrido[l,2-a]pyrazine-l,4-diones were obtained when methyl A-[2-(benzyloxycarbonylamino)acetyl]-4-substituted pipecoli-nates were hydrogenated over 10% Pd/C catalyst in MeOH, and then the methanolic solutions were refluxed (00JAP(K)00/86659). 

The. synthesis starts with the Stobbe condensation of diethylsuccinate and 3,4-dichloroben-zophenone (13). The product (14) is hydrolyzed and decarboxylated to a cis-trans mixture of olefins (15). This last is reduced using a Pd/C catalyst and then undergoes unidirectional Friedel-Crafts intramolecular acylation into the more reactive ring to produce substituted tetralone 16. 

Hydrocarbon A has the formula C9HI2 and absorbs 3 equivalents of H to yield B, C9H]g, when hydrogenated over a Pd/C catalyst. On treatment of A with aqueous H2S04 in the presence of mercury(d), two isomeric ketones, C and D, are produced. Oxidation of A with KMn04 gives a mixture of acetic acid (CH3C02H) and the tricarboxylic acid E. Propose structures for compounds A-D, and write the reactions. 

Functional biaryl derivatives are important industrial chemicals. They are used as monomers for the production of high performance and other polymers, as well as dyes, pharmaceuticals and agrochemical intermediates. We have developed an improved method for the dehalogeno-dimerization of aryl bromides to yield biaryl derivatives under mild conditions (temperature < 100°C, atmospheric pressure) using a common base, a 5 % Pd/C catalyst (0.1 - 10 % w/w, based on the starting material) in an aqueous medium and formyl hydrazine as the reducing agent. Several examples of biaryl derivatives are discussed. 

As has been elucidated, 4-CBA rmdergoes complex reactions in the comse of purification, during which the hydrogenation inevitably competes with the decarbonylation. At the same time, although the BA is easy to be washed out, the concomitant CO during decarbonylation is a poison to Pd/C catalyst. 

In this study, commercial catalysts were used. As the cathode catalyst Pt black was used. Different amounts of Pt black, Pt-Ru black, 10wt% Pt-Pd/C and 20wt% Pt-Pd/C catalysts were used for the anode. 

Powdered palladium combusts spontaneously in air. The combustion is even stronger with the Pd/C catalyst. The interaction of palladium with the O2/H2... 

A dry Pd/C catalyst was incorporated in sodium borohydride. The hydrogen which was released combust spontaneously in contact with air and the catalyst. The interaction between the catalyst and borohydride would not represent any danger if borohydride was incorporated into the aqueous phase onto the Pd/C and not the other way round. 

In Table 14.3 the reaction times (until complete conversion) and relative rate values for the repeated use of four catalysts are collected. It was obvious that the two 10% Pd/C catalysts (Heraeus-10, SQ-6) were more stable. 

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