2.6- dichloroisonicotinic acid

When nicotinic acid is heated for 8 hours at 180° with thionyl chloride, a low yield of 5-chloronicotiriic acid is obtained.182 The orientation observed in this case suggests an electrophilic attack, perhaps on a complexed nicotinic acid chloride molecule (which would thus behave somewhat like a pyridine A-oxide). If the reaction is carried out at 150° and the reaction time lengthened to 50 hours, a 30% yield of 5,6-dichloronicotinic acid is obtained.182 Both mechanistic pathways may be involved here. Isonicotinic acid reacts with thionyl chloride at 180-220°, presumably by, way of an electrophilic attack since 3-chloro-and 3,5-dichloroisonicotinic acid are formed.182 Nicotinoyl chloride (from nicotinic acid and thionyl chloride—probably in the complexed form) gives an 87% yield of 5-bromonicotinic acid on reaction with bromine for 10 hours at 150-1700.185... 

Durner, J., and Klessig, D. F., 1995, Inhibition of ascorbate peroxidase by salicylic acid and 2,6-dichloroisonicotinic acid, two inducers of plant defense responses, Proc. Natl. Acad. Set USA 92 11312nll316. 

Fig. 1. Salicylic acid and its synthetic functional analogs. Salicylic acid and its derivative acetyl salicylic acid (aspirin) induce expression of the PR genes and enhance resistance to pathogens. The two synthetic compounds, 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole S-methyl ester (BTH) show structural similarities to salicylic acid and like salicylic acid induce expression of the PR genes and enhance resistance to pathogens.

Resistance inductors. R. i. are compounds which initiate the biosynthesis of phytoalexins or, respectively, of PR proteins. Besides certain synthetic compounds some low-molecular weight natural compounds such as salicylic acid , fatty acids methyl jasmonate as well as the peptide systemin act as resistance inductors in plants and initiate the plant s defensive mechanism against phytopathogens. lit. Mdtraux et al.. Induced Resistance in Cucumber in Response to 2,6-Dichloroisonicotinic Acid and Pathogens, in Hennecke Verma (eds.), Adv. Mol. Genet. Plant-Microb. Inter. vol. 1, p. 432-439, Dordrecht Kluwer 1991. J. Pesticide Sci. 15, 199-203 (1990). Plant Physiol. 106, 1269-1277 (1994). Science 250, lOOdff. (1990). Plant Physiol. 99, 799-803 (1992). Science 212, 67Jf. (1981). Trends Cell Biol. 2,236-241 (1992). Plant Physiol. 44,569-589 (1993). Science 255, 1570-1573 (1992). 

Dichloropyridine-4-carhoxylic acid (2,6-dichloroisonicotinic acid) [5398-44-7] M 192.0, in 210 , 209-212 , pK st(i) -1. Purify the acid by crystallisation from H2O, and it forms needles or platelets from EtOH. The methyl ester crystallises from aqueous MeOH with m 82 , the ethyl ester from aqueous EtOH has m 66 , and the amide from H2O has m 207-208 . [Meyer et al. Monatsh Chem 36 731 1915, Levelt Wibaut Rec Trav Chim Pays Bas 48 469 1929.]... 

Citrazinic acid can be converted in high yield to 2,6-dichloroisonicotinic acid (X-3, X = Cl) with POCI3. The latter is easily reduced catalytically to isonicotinic acid (X-3, X = H). ... 

Reduction of 2,6-dichloroisonicotinic acid with hydrazine hydrate in presence of palladium on charcoal is claimed to yield isonicotinic acid. ... 

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