The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Synthesis and protonation studies of a meso-unsubstituted surfactant porphyrin》. Authors are Ringuet, Michel; Gagnon, Jacques.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).Category: thiazolidine. Through the article, more information about this compound (cas:2199-44-2) is conveyed.
The surfactant porphyrin I was prepared Spectroscopic studies show that intermol. protonation occurs between the side-chain carboxyl groups and the inner N atoms of I, giving a porphyrin dication. In 5 × 10-5M CHCl3 solution, 27% of the porphyrin mols. are in the dicationic form and they are self-associated with some of the remaining mols. in the free base form.
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Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com