2.4- dichloro-6-aminopyridine

Picrasma quassioides (D. Don) Benn. P quassioides (D. Don) Benn. f. dasycarpa Kitag. Ku Shu (stem bark) 2.4- dichloro-6-aminopyridine, 4.5- dimethoxycanthin-6-one, 2.6- dimethoxy-p-benzo-quinone, methyl nigakinone, picrasmin, nigakihemiacetal A, nigakilactone A, nigakinone, quassin.50 Treat fever, stomachache. 

Katritzky et al.508 have measured rates of deuteration of aminopyridine by deuterated sulphuric acid (Table 146), and for the 4-amino and 2-amino-5-methyl compounds, the general increase in rate with increasing acidity, dlogkjd (—H0) 0.6, shows reaction to be occurring on the conjugate acids. For the latter compound this is only true at acidities > —H0 = 4.0, below which rates are relatively independent of acidity indicating reaction on the free base. For the 2,6-dichloro... 

Stable 3,5-dichloro-2,4,6-trimethylbenzonitrile oxide reacts with 2- and 4-aminopyridines in their imino forms, if acids are present to promote the formation of imine, to give cycloadducts such as 168 (337). 

For exchange in dibasic compounds, such as aminopyridines, ideally if both equilibrium and kinetic protonations follow H0, a rate profile of the type in Figure 3 should be expected (67JCS(B)1219>. Rate profiles obtained for 4-amino, 4-amino-2,6-dichloro- and 2-amino-5-methyl-pyridine correspond to the portions b-c, c-d and d-e respectively of Figure 3. 

By reacting 2-aminopyridine and epichlorohydrin, Knunjanz187 obtained the hydrochloride of 3-hydroxy-3,4-dihydro-2H-pyrido[l,2-a]pyrimidine (131 R = OH). Analogous products from 4-methyl-, 5-methyl-, 5-halo- and 3,5-dibromo-substituted 2-aminopyridines have been prepared by Soviet workers.188,189 The same products arose from the reaction of 2-aminopyridines and l,3-dichloro-2-propanol.188 189 Klusis and Kuthevicius190 reacted 2-aminopyridine with 3-chloro-1,2-propanediol (127) or 2,3-... 

Chlorination of 2-aminopyridine gives 5-chloro and 3,5-dichloro derivatives in equal amounts when the medium is 17 wt% H2S04, but 98 and 6%, respectively, in 72 wt% H2S04. This selectivity was ascribed to differences in rates of chlorination of protonated versus nonprotonated species (76JOC93). For the more basic 2-aminopyridine chlorination presumably occurs on the monocation throughout the acidity region but the less basic 5-chloro derivative chlorinates via the free base at low acidity. 

Dichloro-3-methylisoxazolo[4,5-c]pyridine 300 underwent nucleophilic substitution with 2-(aminomethyl)ani-line to give the corresponding aminopyridine intermediate 301 in good yield. 

Tetracyclic quinone 206 was obtained from 2,3-dichloro-1,4-naphthoquinone and 2-aminopyridine in an unexpected manner (63JOC1019). 

Fig. 11-1. Intramolecular electronic effects in the adsorption of meta- and para-% ih-stituted pyridines on (a) alumina and (b) silica (15,24). 1, 4-amino 2, 3, 4-dimethyl 3, 4-methyl 4, 4-ethyl 5, 3-methyl 6, pyridine 7, 3-hydroxy 8, 4-chloro 9. 4-aldehyde 10,3-acetyl 11,3-iodo 12,3-aldehyde 13, 3-chloro 14, 3-bromo 15. 4-cyano 16, 3-cyano 17, 3,5-dichloro. [The plots do not include points for the compound 3-aminopyridine see discussion of Ref (/5).]...

The preparation of fluazinam is shown in Scheme 11.10. The key intermediate that is used to produce fluazifop-butyl, 2-chloro-5-trifluoromethylpyridine (4) (see Scheme 11.1), is used as a starting material for the synthesis of fluazinam as well. Further chlorination of pyridine 4 with chlorine gas in the presence of a catalyst such as acetic acid followed by amination with ammonia gives aminopyridine 34. The synthesis of fluazinam is completed by nucleophilic reaction of 34 with 2,4-dichloro-3,5 -dinitrobenzotrifluoride. 

Analogously, a satisfactory yield of IbP was obtained by treating 2,6-dichloro-5-fluoro-3-aminopyridine with substituted acetamide in the presence of oxalyl chloride to give an amidine followed by reaction with potassium carbonate (94HCA1057). 

Condensation of 4,5-dichloro-l, 2,3-dithiazolium chloride 23 (Appel s salt) with various ort/zo-halogenated anilines and aminopyridines 22 gives the... 

Dichlorothiophene-5-carboxaldehyde condenses with 2-aminopyridine to yield 2-(4,S-dichloro-2-thienylidene)aminopyridine (IX-71). °... 

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