Pyridine, 2-chloro-5-nitro, reaction with

The order NO2 > Cl, which is known for the reactions of nitro-activated aromatic compounds, is also found for pyridine and quinoline derivatives. In the reaction of 2-chloro-4-nitroquinoline with methoxide ion, only the 4-methoxide derivative is formed, as shown by gas-chromatography, whereas 2,4-dichloroquinoline yields a mixture of the isomeric chloro-methoxy derivatives in comparable amounts. ... 

The 4- and 6-positions of pyrrolo[2,3-3]pyridines can be substituted via palladium-catalyzed cross-coupling reactions with the 4- or 6-halo-substituted derivatives (Scheme 3) <2001SL609>. Nucleophilic displacement of the 4-substituent of 6-chloro-4-nitro- and 4,6-dichloro-pyrrolo[2,3-/ ]pyridines takes place with phenols. Protection of the pyrrole nitrogen with a /3-trimethylsilylethoxymethyl (SEM) group affords good yields of the aryl ethers (Equation 3) <2006TL2069>. 

Since these early studies, numerous derivatives of 2-chloro- and 2-bromo ia, 672 and 4-chloro- and 4-bromo-pyridine 73 have been converted into amino- or alkylamino-pyridines under conditions differing little from those mentioned above. Modifications which have been used include the addition of copper sulphate as a catalyst a, 672a reaction in the presence of pyridine 64 and also, in the case of 4-chloropyridine, reaction with primary and secondary aliphatic amines in benzene 4 at 140-180 . The qualitative data from these numerous examples show the effect of other substituents upon 2- and 4-halogen atoms to be as expected. GarboxyM oa, 675, 9i8 and nitro-groups24ia markedly augment reactivity, and in a compound such as 2-chloro-3,5-dinitropyridine, much milder conditions than usual can be used for amination e ... 

In spite of the potential complexity of the general problem, even when restricted to the reagent family of amines, the nucleophilicities of such series as meta- and pom-substituted pyridines and anilines appear to correlate very closely with the expected substituent effects and with the basicities. This has been verified in the following cases (i) The reaction of pyridines (R = H, m- andp-CHs) with 2-chloro-3-nitro-, 2-chloro-5-nitro-, and 4-chloro-3-nitro-pyridines. ... 

The rate of amination and of alkoxylation increases 1.5-3-fold for a 10° rise in the temperature of reaction for naphthalenes (Table X, lines 1, 2, 7 and 8), quinolines, isoquinolines, l-halo-2-nitro-naphthalenes, and diazanaphthalenes. The relation of reactivity can vary or be reversed, depending on the temperature at which rates are mathematically or experimentally compared (cf. naphthalene discussion above and Section III,A, 1). For example, the rate ratio of piperidination of 4-chloroquinazoline to that of 1-chloroisoquino-line varies 100-fold over a relatively small temperature range 10 at 20°, and 10 at 100°. The ratio of rates of ethoxylation of 2-chloro-pyridine and 3-chloroisoquinoline is 9 at 140° and 180 at 20°. Comparison of 2-chloro-with 4-chloro-quinoline gives a ratio of 2.1 at 90° and 0.97 at 20° the ratio for 4-chloro-quinoline and -cinnoline is 3200 at 60° and 7300 at 20° and piperidination of 2-chloroquinoline vs. 1-chloroisoquinoline has a rate ratio of 1.0 at 110° and 1.7 at 20°. The change in the rate ratio with temperature will depend on the difference in the heats of activation of the two reactions (Section III,A,1). 

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