The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Preliminary work to the ring syntheses of porphyrins, etc. III. Several pyrrole compounds with amino groups and unsaturated side chains》. Authors are Fischer, H.; Zeile, Karl.The article about the compound:Ethyl 3,5-Dimethyl-2-pyrrolecarboxylatecas:2199-44-2,SMILESS:O=C(C1=C(C)C=C(C)N1)OCC).Formula: C9H13NO2. Through the article, more information about this compound (cas:2199-44-2) is conveyed.
cf. C. A. 24, 5302. 2,4-Dimethyl-3-amino-5-carbethoxypyrrole (I) yields an Ac derivative, m. 201° (60% yield). With iso-AmNO2, I gives 90% of the diazonium chloride, decomposes at 173°; it is not completely decomposed by boiling with H2O for 1 hr.; continued boiling, especially with Cu powder, gives 2,4-dimethyl-5-carbethoxypyrrole, m. 125°. Hydrolysis of I with 10% NaOH gives 2,4-dimethyl-3-amino-5 carboxypyrrole (II), which begins to split off CO2 at 75°; Ac derivative, m. 203° (decomposition). 2,4-Dimethyl-3-aminopyrrole, m. 127°, results in about 50% yield by warming the moist II at 75°; Ac derivative, m. 205°. The bromination product of the Ac derivative of I, heated with H2O, gives nearly quant. bis(3-acetylamino-4-methyl-5-carbethoxy-2-dipyrryl)methane, m. 251°, crystallizing in different forms from EtOH, Ac2O and dilute AcOH. With HCO2H and Fe powder, this yields an amorphous 1,4,5,8-tetramethyl-2,3,6,7 tetraacetylaminoporphin. II, HCO2H and HBr, heated 2-3 min., give (2,4-di-methyl-3-aminopyrryl)-2′,4′-dimethyl-3′-aminopyrrolenyl)methene tri-HBr salt, decomps over 280°; from H2O it seps. as violet crystals, from HBr in yellow-red prisms; AcONa gives the mono-HBr salt, dark violet needles, m. 234°. 2,4-Dimethyl-3-(β-carboxy-vinyl)-5-carbethoxypyrrole (III) and NaOH with a little H2O, heated over a free flame for 2 hrs. and then dry-distilled, give dimethylpyrrole and (2,4-dimethylpyrryl)(2′,4′-dimethylpyrrolenyl)methene. MeNO2 adds to 2,4-dimethyl-3-(β-nitrovinyl)-5-carbethoxypyrrole, giving the compound C12H17O6N3, m. 180°. 2,4-Dimethyl-3-(β-dicyano-vinyl)-5-carbethoxypyrrole (IV) and Br give a perbromide, golden yellow, decomposed by H2O to a 2-bromomethyl derivative, m. 258°. IV, MeOH and Br give the 2-carbomethoxy derivative, m. 187°; saponification with 0.1 N NaOH by heating 12 hrs. at 85° gives 2.5-dicarboxy-3-formyl-4-methylpyrrole, does not m. 360°; the di-Me ester m. 180° (oxime, m. 221°; semicarbazone, m. 247°). IV and SO2Cl2 in Et2O, followed by hydrolysis with H2O, give the 2-carboxy derivative, does not m. 360°; similarly III gives the 2-carboxy derivative, m. 241°; the free acid has no m. p. The Me ester of III m. 150°. 2,4-Dimethyl-3-formyl-5-carbethoxypyrrole and SO2Cl2 give the 2-carboxy-3-chloro derivative, m. 260°. 2,4-Di-methyl-3,5-diformylpyrrole (V) and 2,4-dimethyl-3-acetylpyrrole with HBr-EtOH give (2,4-dimethyl-3-formylpyrryl)(2′,4′-dimethyl-3′-acetylpyrrolenyl)methene, m. 210°. V and cryptopyrrole give with HBr 5,5′,3,3′-tetramethyl-4-ethyl-4′-formylpyrromethene-HBr, thick prisms. 2,4-Dimethyl-5-carbethoxy-3-thioformylpyrrole, for which a method of preparation is given, gives with SO2Cl2 and H2O 4-methyl-3-formyl-2-carbethoxy-5-carboxylic acid-pyrrole, m. 169°; phenylhydrazone, yellow, m. 235°.
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Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com