Pyridine, 2,5-Diamino

Trivalent hydrogen-bonding systems have been used very extensively for guiding and influencing the structuring of polymers. As mentioned in Sect. 1, Fig. 5, the most important triple-hydrogen bonds derive from 2,6-diamino-pyridines, 2,6-diamino-1,3,5-triazines and their complexes with flavine- and... 

Beilstein Handbook Reference) AI3-18054 BRN 0108513 CCRIS 6682 DAP DAP (amine) 2,6-Diaminopyridine EINECS 205-507-2 NSC 1921 2,6-F ridinediamine Pyridine, 2,6-diamino- Pyridine-2,6-diyldiamine. Used as a chemical intermediate. Crystals mp = 121.5 bp = 285 , bps = 148 Am = 244, 308 nm (MeOH) slightly soluble in H2O, MezCO, Cilag-Chemie Ltd. Janssen Chimica Lancaster Synthesis Co. Reilly Ind. 

The residue in the flask is said to contain 4-amino- and 2 6-diamino-pyridine, YY dipyridyl and aa -dipyridylamine in varying amounts. 

Other indications of the template effect have been offered as well. Fenton, Cook and Nowell reported that the condensation of pyridine-2,6-dicarbaldehyde with 1,11-diamino-3,6,9-trioxaundecane in 1 1 molar ratio in butanol leads only to resinous gums . In the presence of equimolar amounts of Pb(SCN)2, the macrocycle illustrated in Eq. (2.5) was obtained in good yield . 

Diazotized 3,6-diamino-4-phenylpyrazolo[3,4-6]pyridine-5-carbonitrile 373 reacted with 2-naphthol to give 374 and with active methylene com-... 

Lithiumboranat10 N atriumboranat11 Kaliumboranat12 tert.-Butylamin-Boran13 Dimethylamin-Boran13 1,2-Diamino-athan-Boran 4 Pyridin-Boran15... 

The asymmetric synthesis of 2,3-diamino acids can be accomplished by the addition of chiral enolates to prochiral imines. For example, reaction of morpholine-2-one 103, derived from (S)-phenylglycinol, with N-benzyl ben-zaldimine in the presence of pyridine and para-toluenesulfonic acid at high... 

Synthetic Method 7 l,9-dimethyl-4-acetarnido-8-diethylaminoimidazo-phenoxazine (31) (procedure from U.S. Patent 4,604,462). 12 A mixture of 10 g of l,3-diamino-7-diethylamino-8-methylphenoxazin-5-ium chloride (Brilliant Cresyl Blue), 50 ml of acetic anhydride, 10 g of zinc dust, and 10 ml of pyridine was maintained at 85 to 90°C for approximately 1 h. After cooling to room temperature, the reaction mixture was poured into a mixture of water and toluene and the resulting aqueous layer was discarded. The toluene solution was washed twice, first with water and then with... 

Diamino-2,l,3-benzothiadiazole 82 affords [l,2,5]selenodiazolo[3,4-i ]-2,l,3-benzothiadiazole 83 quantitatively on treatment with selenium oxychloride in refluxing chloroform-pyridine <2004JHC955>. This was an improvement of the previous method using selenium dioxide (62% yield) <1984ZNB485>. 6-Isoprenyl-477-imidazo[4,5-< ]-benzothiadiazolone 84 was obtained when 4,5-diaminobenzothiadiazole was reacted with methyl acetoacetate in xylene at reflux (Scheme 10) <1997H(45)19>. 

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). 

C. 2,3-Diamino-5-bronto pyridine (Note 8). A 100-ml. flask fitted with a reflux condenser is charged with 10.9 g. (0.05 mole) of 2-amino-5-bromo-3-nitropyridine, 30 g. of reduced iron, 40 ml. of 95% ethanol, 10 ml. of water, and 0.5 ml. of concentrated hydrochloric acid (Notes 9 and 10). The mixture is heated on a steam bath (Note 11) for 1 hour, and at the end of this period the iron is removed by filtration and is washed three times with 10-ml. portions of hot 95% ethanol. The filtrate and washings are evaporated to dryness, and the dark residue is recrystallized from 50 ml. of water, 1 g. of activated carbon being used and the mixture being filtered while hot. The charcoal is washed with hot ethanol to avoid losses. 2,3-Diamino-5-bromopyridine crystallizes as colorless needles, m.p. 163°. The yield is 6.5-7.1 g. (69-76%). 

Both amino groups of 3,5-diamino-4-phenylpyrazole reacted with EMME during 2 min. at reflux [83JCS(P1)11], The amino group at position 3 underwent a cyclocondensation reaction to form the bicyclic pyraz-olo[l,5-a]pyrimidine, while the amino group at position 5 participated in an addition reaction to give a (2,2-diethoxycarbonyl-l-ethoxyethyl)amino side-chain. Pyrazolo[l,5-a]pyridine (25) was obtained in 27% yield. 

Diamino-6-[(2,4,6-trimethylphenyl)methylamino]pyridine was reacted with EMME in boiling dioxane for 30 min to give 3-pyridylamino-methylenemalonate (169) in 73% yield (79CZ387). 

The reactions of 5-methylthio-3-amino- or 3,5-diamino-l,2,4-triazole and diethyl 1-ethoxyethylidenemalonate in boiling ethanol in the presence of sodium ethylate for 1.5-3.5 hr gave l,2,4-triazolo[l,5-a]pyrimidin-7-ones (1123, R = MeS, NH2, R1 = Me) in 44% and 20% yields, respectively. The reaction of 5-methylthio-3-amino-l, 2,4-triazole (R = MeS) and 2-ethoxyethylidenemalonate in boiling pyridine for 4 hr gave 1,2,4-tria-zolo[l,5-a]pyrimidin-5-one (1122, R = MeS, R1 = Me) in 12% yield (61JCS3046). 

Similar studies have recently been extended to aminopyridones and thiones and to aminopyrimidones (Barlin jmd Pfleiderer, 1971 Barlin, 1972). Protonation of 3- and 5-amino-2-hydroxypyridine and 3,4-diamino-2-hydroxypyridine occurs first at the 3- (or 5-) amino-group, but 4- and 6-amino-2-hydroxypyridine and 2- and 3-amino-4-hydroxypyridine first protonate at the oxygen atom, because the amino-group is involved in conjugation with the partially positively charged ring nitrogen. Similar results are found for the amino-pyridine-2(and 4)-thiones (Barlin, 1972). 

Pyrazine and pyrimidine heterocycles, like pyridine, are electron deficient and need the presence of an activating/electron-releasing group to allow efficient electrophilic nitration to occur. An example of this strategy is seen during the synthesis of 2,6-diamino-3,5-dinitropyrazine (ANPz) (183) where one of the chloro groups of 2,6-dichloropyrazine (180) is substituted for a... 

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