Pyridines, 2,4-diamino-, synthesis from

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... 

The synthesis of the poly-(o-chlorophenyl)-imides was accomplished in two steps involving low-temperature reaction between the diamines and bis(phthalic anhydrides) in NMP followed by catalytic imidisation of the PCA directly in the reaction solutions using the catalytic complex pyridine acetic anhydride. The synthesis of polyimides from l,l-dichloro-2,2-di-(3-amino-4-aminophenyl)-ethylene proceeded homogeneously throughout the course of the reaction, as did reactions of 3,3 -diamino-4,4 -dichlorobenzophenone with the dianhydride of diphenyloxide-3,3, 4,4 -tetracarboxylic acid. As to reactions of 3,3 -diamino-4,4 -dichlorobenzophenone with the dianhydrides of pyromellitic and diphenylsulfone-3,3, 4,4 -tetracarboxylic acids, these were homogeneous at the PCA formation step but heterogeneous at the polyimide formation step. Some properties of these polyimides are given in Tables 3.3 and 3.4. 

If, on the other hand, an amino group can be introduced ortho to the nitro group, reduction of 202 or 203 makes available the starting materials for fused heterocycles. One example is the synthesis of imidazo[4,5-c]pyridines 205 from diamino pyridines such as 204. 

The following example has been described by Ogata et al. in the synthesis of a copolyamide [15b] A solution was prepared from terephthalic acid (2 mmol) and triphenylphosphine (4.8 mmol) in pyridine (5 mft this was then added to a 5 ml pyridine solution containing p-phenylenediamine (2 mmol), 4,4 -diamino-diphenykther (2 mmol) and C2CI6 (6 mmol) at room temperature. The reaction... 

Monofluoropyridines were obtained also from polyfluoropyiidines, using reactions of nucleophilic substitution. N-Ethyl-2,6-diamino-4-fluQropyridinium Inflate (108) was synthesized from N-ethyl-2,4,6-trifluoropyridinium triflate (107) by interaction anhydrous ammonia gas in MeCN at 0 °C during 5-10 min. in 72 % yield [95] (Scheme 42). Compound 108 is used for synthesis biologically active 8-fluoro-4-ethyl-4H-bis[l,2,3]dithiazolo[4,5-b 5, 4 -e]pyridine-3-yl [95]. 

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