The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Anomalous cyclization of diethyl 4,4-diethoxy-2-formylglutarate with ammonia》. Authors are Mangoni, Lorenzo.The article about the compound:5-Hydroxynicotinic acidcas:27828-71-3,SMILESS:O=C(O)C1=CN=CC(O)=C1).Related Products of 27828-71-3. Through the article, more information about this compound (cas:27828-71-3) is conveyed.
cf. CA 51, 6600i. The title ester (I) (3.0 g.) cyclized according to Jones (CA 50, 6429c) with NH3 and concentrated H2SO4, the mixture hydrolyzed by boiling 3 hrs. with alc. KOH, the solvent evaporated, the residue taken up in H2O, acidified with concentrated HCl and extracted repeatedly with Et2O gave 2,4-pyrroledicarboxylic acid (II). I (3.8 g.) in 10 ml. dry Et2O kept 10 min. with 5 ml. alc. containing 10% dry NH3, the solvent evaporated in vacuo, and the residue boiled 10 min. in 12 ml. AcOH with 1 g. (NH4)2CO3, the cooled mixture poured into excess ice and Na2CO3, the oily product extracted with Et2O, the washed and dried extract concentrated and the chilled concentrate diluted with petr. ether, filtered from the crystalline product and the filtrate evaporated gave 1.4 g. brown oil, containing II. The air-dried crystalline product (0.85 g.) sublimed at 150° in vacuo and crystallized from ligroine gave Et 3-ethoxy-2(1H)-pyridone-5-carboxylate (III), m. 109-10°, λ 280 mμ (log ε 4.03), giving no color with alc. FeCl3 and no Ehrlich reaction, evolving NH3 copiously on boiling with alc. KOH. III (0.40 g.) heated 20 min. at 130° with 0.25 ml. POCl3 and a trace of dry C5H5N, the cooled mixture treated with ice and filtered, the H2O-washed and dried product sublimed at 100° in vacuo gave Et 6-chloro-5-ethoxynicotinate (IV), m. 34-5°, reprecipitated from solution in concentrated HCl. IV (1.15 g.) in MeOH hydrogenated with 0.30 g. Pd-C 20 hrs. and the filtered solution evaporated gave 1.10 g. hygroscopic ester HCl salt, which refluxed 1.5 hrs. with 10 ml. 2N NaOH and 5 ml. alc., the alc. evaporated in vacuo and the residue acidified cautiously to Congo red gave 5-ethoxynicotinic acid, m. 191-2° (MeOH). The acid (0.15 g.) refluxed 3 hrs. with 3 ml. HBr (d. 1.48), the excess HBr evaporated in vacuo and the residue taken up in a min. of H2O, adjusted to pH 4.5-5.0 with 2N NaOH and the washed and dried precipitate crystallized from H2O gave 5-hydroxynicotinic acid monohydrate, m. 293-4° (decomposition), giving a reddish orange color with alc. FeCl3.
The article 《Anomalous cyclization of diethyl 4,4-diethoxy-2-formylglutarate with ammonia》 also mentions many details about this compound(27828-71-3)Related Products of 27828-71-3, you can pay attention to it, because details determine success or failure
Reference:
Chapter 1 An introduction to palladium catalysis,
Palladium/carbon catalyst regeneration and mechanical application method