Charcoal, as catalyst

Q. CO. C(COaEt). N(CO. Ph). CH. CHj. CHPr. CH, was hydrolysed and decarboxylated and the unstable keto-amine hydrogenated in methyl alcohol with palladised charcoal as catalyst to the... 

Under similar conditions, but with palladised charcoal as catalyst, solasodine forms a dihydro-derivative, C27H45O2N, m.p. 208-5-210-5°, [a] ° — 63-5° (CHCI3), and in presence of platinic oxide, a tetrahydro-derivative, C27H4,02N, which is dimorphic, m.p. 292-5°, and 285-291°, [air - 4-94° (CHCI3). 

Scheme 6/1.58. Domino reaction with palladium on charcoal as catalyst.

Oxazines are prone to hydrogenolysis since the relatively weak N-O bond is easily cleaved. This reaction has often been employed for the transformation of this cycle (generally obtained from nitrones) into amino alcohols in a stereocontrolled manner. For example, reaction of 57 with hydrogen and palladium on charcoal as catalyst (Equation 1) furnished the expected substituted pyrrolidine 58 in moderate yields <2003EJ01153>. 

Better yields may be obtained from vinylpyridines and alkyl propiolates, as can be seen from the conversion of 36 to the cycl[3,2,2]-azine (lw).41 Reaction of a-(bismethylthio)methylene-2-pyridineaceto-nitrile and ethyl bromoacetate using triethylamine afforded the indolizine derivative (37). Dimethyl l-carbamoyl-2-methylthiocycl-[3,2,2]azine-3,4-dicarboxylate (Iz) was synthesized by allowing dimethyl acetylenedicarboxylate to react with indolizine derivative 38, which was obtained by decarboxylation of 37 using sulfuric acid in presence of palladium-on-charcoal as catalyst [Eq. (6)].42... 

The oxidation of aqueous solutions of cobalt(II) salts in the presence of ligands may give a variety of products depending on the conditions. Air oxidation of Co(en)2(H20)22+ in the presence of charcoal as catalyst yields Co(en)33 +, and without charcoal catalyst the reaction gives either the peroxo-bridged dicobalt(III) complex (en)2Co(0H)(02)-Co(en)23+ or the tetranuclear complex Co (OH)2Co(en)2 36+, depending on the conditions. 

These products (42) may be dehydrogenated using palladium on charcoal as catalyst. In some cases, the 2,3-dihydro intermediates have been isolated. Analogous products are formed from quaternary salts of quinoline and isoquinoline. 

Hydrocarbons. The reaction of isoprene with toluene, ethylbenzene, or isopropylbenzene is catalyzed by sodium or potassium (72). The reactions are carried out at 125°C in a pressure autoclave by adding the isoprene slowly to the alkylarene in which the alkali metal is dispersed along with a trace quantity of 0-chlorotoluene which is used as a chain initiator. The products are chiefly monopentenylated in the side chain, and no information can be obtained on whether the addition is 1,4- or 1,2- since under these conditions the double bond migrates. The alkene products subsequently are reduced to alkanes by hydrogenation using 5% palladium on charcoal as catalyst. 

Finally the benzyl group is removed by hydrogenolysis using 10 % palladium on charcoal as catalyst. The reaction proceeds in MeOH at atmospheric pressure and is completed after 3 h reaction time. To remove the catalyst the reaction mixture is filtered through celite. Finishing with basic aqueous work-up and silica gel chromatography (MeOH/CHCl3 1 10), enantiomerically pure (+)-paniculatine (15) is afforded in 65 % yield. 

Hydroxylamine can be made by reduction of NO in dilute solution by H2 using platinized charcoal as catalyst or by reduction of nitrates electrolytically or with S02. The solid (mp 33°C) decomposes above ca. 0°C and the amine is normally encountered as stable, water soluble salts of NH3OH+. 

Another example for the coordinative behaviour of phenoxy functionalised carbene ligands comes from the Bielawski group [76]. They synthesised a phenoxy functionalised benzimi-dazolium salt starting from o-fluoro-nitrobenzene, which they reacted with o-hydroxyaniline. Reductive ring closure reaction with formic acid/formate and palladium/charcoal as catalyst... 

When 7V-bromosuccinimide was used instead of l,3-dibromo-5,5-dimethylhydantoin, similar yields were achieved. Lilectron-rich aromatic rings undergo bromination. Thus, the desired products are obtained by dehalogcnation of the brominated products using palladium on charcoal as catalyst. 

The hydrofluorination of propene to give 2 can be carried out in the liquid phase with hydrogen fluoride or with hydrogen fluoride/pyridine, or in the vapor phase with activated charcoal as catalyst. ... 

Selective reduction to hydroxylamine can be achieved in a variety of ways the most widely applicable systems utilize zinc and ammonium chloride in an aqueous or alcoholic medium. The overreduction to amines can be prevented by using a two-phase solvent system. Hydroxylamines have also been obtained from nitro compounds using molecular hydrogen and iridium catalysts. A rapid metal-catalyzed transfer reduction of aromatic nitroarenes to N-substituted hydroxylamines has also been developed the method employs palladium and rhodium on charcoal as catalyst and a variety of hydrogen donors such as cyclohexene, hydrazine, formic acid and phosphinic acid. The reduction of nitroarenes to arylhydroxyl-amines can also be achieved using hydrazine in the presence of Raney nickel or iron(III) oxide. ... 

Hydrazides are hydrogenated by a substantial excess of Raney nickel. Phenylhydrazides are reduc-tively cleaved over palladium/charcoal as catalyst, and the corresponding amides are obtained in good... 

Schaffer and his collaborators examined the tris[(+)-trans-1,2-diaminocyclohexane]cobalt(III) system (22). Equilibrium between the isomers was established by the presence of charcoal as catalyst at 393K. The equilibrium mixture was separated by column chromatography on a Sephadex ion exchange column and the formation ratios were determined. On the other hand, equilibrium geometries of the four conformers, lei, lel-ob, lelot>2 and ob, were calculated by Boyd s procedure (29, 307. The strain energies are shown in Table IV. The values do not differ very much from those for... 

Another elegant demonstration of the cis addition processes using platinum on charcoal as catalyst has been reported by Brook and coworkers (191) and is described in Scheme 45. Cis addition to diphenylacetylene affords the silylstil-benes 117. Their geometry was established by photochemical cyclization to the 9-silylphenanthrenes 118 as well as by comparison with the coupling product of chlorosilanes 116 and cis-stilbenyllithium. 

Dehalogenation of 5,8-dichloropyrazino[2,3-with hydrogen using palladium on charcoal as catalyst and concentrated ammonium hydroxide at room temperature.86... 

Reduction of 8-chloropyrazino[2,3-rf]pyridazin-5-ol with hydrogen and palladium on charcoal as catalyst in a mixture of methanol and concentrated ammonium hydroxide furnishes 1,2,3,4-tetrahydropyrazino[2,3-c/]pyridazin-5-ol with loss of the chlorine atom in a yield of 33 % mp 223 °C (EtOH/CHClj).27... 

Although hydrogenation of the 5,6-olefins has been used in the preparation of 5,6-dideoxy-D-X2/Zo-hexose> and 5,6-dideoxy-L-ara6mo-hexose, hydrogenation of compound (114), in the presence of palladium-charcoal as catalyst, gave rise to two products in approximately equal... 

Hydroxylamine is prepared by reduction of nitrates or nitrites either elec-trolytically or with S02, under very closely controlled conditions. It is also made, in 70% yield, by H2 reduction of N02 in HC1 solution with platinized active charcoal as catalyst. Free hydroxylamine is a white solid (m.p. 33°) which must be kept at 0°C to avoid decomposition. It is normally encountered as an aqueous solution and as salts, e.g., [NH3OH]Cl, [NH30H]N03 and [NH30H]2S04, which are stable, water-soluble, white solids. Although... 

Catalytic hydrogenation of nitrosamines to A, A-di substituted hydrazines is effected in water or aqueous alcohol with 10% palladium-charcoal, 10% platinum-charcoal, or 5% rhodium-charcoal as catalyst,132 in the presence of a salt (e.g., calcium chloride, ammonium acetate, or lithium chloride) at temperatures between 25° and 60° for example, 0.2 mole of 4-nitrosomorpholine in a solution of 30 g of calcium chloride in 150 ml of water is stirred with 2 g of 10% palladium-charcoal under a hydrogen pressure of 3-4 atm for 22 hours at 60°, thereby affording an 82.7% yield of 4-aminomorpholine. 

Oxiranes can also be cleaved by mercaptanes, this yielding -hydroxy sulfides. This reaction has been carried out386 with oxirane, 7-oxabicyclo[4.2.1]heptane, and epichlorohydrin [(chloromethyl)oxirane] and, as sulfur components, ethane-, 1-propane-, benzene-, and a>toluene-thiol in the presence of a little active charcoal as catalyst. 

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