4-Pyridinecarboxylic acid, rhodium

Phenyl, platinum complex, 26 136 QH,N, Pyridine, osmium complex, 26 291 OH,NO, 4-Pyridinecarboxylic acid, rhodium complex, 27 292... 

NOCgHj, Benzoyl isocyanide, chromium complex, 26 32,34,35 N0C,3H,3, Formanide, N-(l-(l-naphthal-enyl)ethyll-, rhenium complex, 29 217 NOPCjsHjj, Benzamide. 2-(diphenylphos-phino)-N-phenyl-, 27 324 NOPCjjHjj, Benzamide, Af-[2-(diphenyl-phosphino)phenyl]-, 27 323 NO2CH3, Methane, nitro-, antimony complex, 29 113 cobalt complex, 29 114 NOjCjHj, 4-Pyridinecarboxylic acid, rhodium complex, 27 292 NO2P2C3JH33, Phosphorus(l-t-), p-nitrido-bis(triphenyl-, acetate, 27 296 NO2SC3H7, L-Cysteine, molybdenum complex, 29 255,258... 

NOC11H5, Benzoyl isocyanide, chromium complex, 26 32, 34, 35 NOPC25H2, Benzamide, 2-(diphenylphos-phino)-A/-phenyl-, 27 324 NOPCjjHji, Benzamide, N-(2-(diphenyl-phosphino)phenyl -, 27 323 N02C H5, 4-Pyridinecarboxylic acid, rhodium complex, 27 292... 

Hydrogenation of 3-pyridinecarboxylic acids is apt to be accompanied by extensive decarboxylation (2S), but this unwanted reaction can be prevented by carrying out the reaction in the presence of one equivalent of base (33,79). Ruthenium (33), rhodium (29), platinum oxide (2S,59), and palladium (30) have all proved effective catalysts for reduction of pyridinecarboxylic acids to the saturated acid. 

The hydrogenation of 2- and 4-pyridinecarboxylic acids proceeded best in water over a platinum catalyst at room temperature and 3-4 atmospheres of hydrogen. Nicotinic acid (3-pyridinecarboxylic acid) was, however, decarboxylated under these conditions. 25 This compound, as well as the pyridine alkanoic acids (except 2-pyridine acetic acid which is easily decarboxylated), was hydrogenated at room temperature and 3-4 atmospheres of hydrogen over a rhodium catalyst in water to which had been added a slight excess of ammonium hydroxide. Product isolation merely involved the removal... 

Rhodium (5%) on carbon is a better catalyst for the reduction of the isomeric pyridinecarboxylic acids, their esters, and amides to the corresponding piperidine analogues than is rhodium on alumina. Reductions are generally slow, but yields are very satisfactory. Catalytic reductions of pyridylalkane... 

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