Palladized strontium carbonate

D. 2,3-Diamino pyridine (Note 12). In an apparatus for catalytic hydrogenation (Note 13) 56.4 g. (0.3 mole) of 2,3-diamino-5-bromopyridine suspended in 300 ml. of 4% sodium hydroxide solution is shaken with hydrogen in the presence of 1.0 g. of 5% palladized strontium carbonate (Note 14). When absorption of hydrogen is completed, the catalyst is removed by filtration, and, after saturation with potassium carbonate (about 330 g. is required), the resulting slushy mixture is extracted continuously with ether until all the precipitate completely disappears (usually about 18 hours, but this depends on the efficiency of the extraction apparatus). The ether is removed by distillation, and the residue of crude 2,3-diaminopyridine is recrystallized from benzene (about 600 ml. is required) using 3 g. of activated charcoal and filtering rapidly through a preheated Buchner funnel. The yield of 2,3-diaminopyridine, obtained as colorless needles, m.p. 115-116°, pKa 6.84, is 25.5-28.0 g. (78-86%) (Note 15). 

Palladized strontium carbonate, 44, 37 2.2]Paracyclophane. 42, 83 Paraformaldehyde, condensation with nitromethane, 41, 67... 

The palladized strontium carbonate is prepared as follows. Suspend 33 g. of strontium carbonate in 350 ml. of water at 70°. Add 2 g. of palladium chloride dissolved in 10 ml. of concentrated hydrochloric acid, and stir the mixture at 70° for 15 minutes. Filter the mixture, wash the product thoroughly with hot water, and dry the product at 110°. 

Hydrogenolysis of 7-bromopyrido[2,3-fc]pyrazine over palladized strontium carbonate gave the parent heterocycle. Similar treatment provided the 2-methyl-3-oxo compound from its 7-bromo derivative, without reduction of the pyrazine ring. A variety of other 7-bromo compounds have also been dehalogenated by this technique. On the other hand, catalytic hydrogenation has also been used to reduce 2- and 3-0x0 compounds to the tetrahydro derivatives 117 and 118. Reduction of the... 

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See also in sourсe #XX -- [ , ]

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