The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Synthetic sympatholytic substances in the ergotamine series. V. Some derivatives of 1,2,3,4-tetrahydroquinoline》. Authors are Chiavarelli, Stefano; Marini-Bettol, G. B..The article about the compound:1,2,3,4-Tetrahydroquinoline-3-carboxylic acidcas:114527-53-6,SMILESS:OC(=O)C1CNC2=CC=CC=C2C1).Reference of 1,2,3,4-Tetrahydroquinoline-3-carboxylic acid. Through the article, more information about this compound (cas:114527-53-6) is conveyed.
cf. C.A. 46, 5602g. In connection with investigations aimed at establishing the relations between the chem. structure and biol. activity of compounds of the type of the alkaloids of Segale cornuta, it seemed of interest to study some 3-substituted derivatives of 1,2,3,4-tetrahydroquinoline (I), particularly since the structure of I is found in the lysergic acid mol. By a modification of the method of Gilman and Spatz (C.A. 35, 5495.2), 83 g. 3-quinolinecarboxylic acid (II), m. 275-6°, was obtained by refluxing 108 g. 3-cyanoquinoline (III) and 20% aqueous NaOH 2 hrs. The Na salt of II (25 g.) in 200 cc. water and 5 g. Raney Ni, hydrogenated 2 hrs. at 150° and 120 atm., filtered, the filtrate concentrated, acidified with HCl (d. 1.17) (to Congo red), and the precipitate purified by dilute EtOH yield 14 g. 1,2,3,4-tetrahydro-3-quinolinecarboxylic acid-HCl (IV), m. 236°, which with NH4OH yields the free acid, m. 145-6° (from EtOH). IV (0.2 g.) in 3 cc. anhydrous C5H5N and 1.6 g. Ac2O, refluxed 10 min., poured when cool into 10 cc. water + 6 cc. HCl, allowed to stand, and the precipitate purified by EtOH, yield the 1-Ac derivative, C12H14O2N, straw-colored, m. 152°. A suspension of 100 g. III in 1400 cc. MeOH refluxed 10 hrs. in a current of HCl gas (III.HCl forms first), most of the MeOH distilled, the residue poured into 3 l. ice-water, made alk. with K2CO3, kept ice-cold several hrs., and the precipitate purified by MeOH, yields 82 g. of Me 3-quinolinecarboxylate (V), m. 73-4°. V (36 g.) in 300 cc. MeOH with 5 g. Pd-C, hydrogenated at 60-65° under 90 atm., filtered, concentrated in vacuo, and allowed to stand, yields Me dihydro-3-quinolinecarboxylate (VI), m. 134-5°, is strongly fluorescent in Wood light (both solid and in solution), reduces neutral AgNO3 solution, is oxidized by dilute KMnO4; picrate, m. 187-9°. V (2 g.) in 50 cc. MeOH with 2 g. Raney Ni, hydrogenated 3 hrs. at 110° under 100 atm., filtered, and distilled at 115° (0.1 mm.); or 5 g. VI in 100 cc. MeOH with 4 g. Raney Ni and 1 g. 10% Pd-C, hydrogenated at 100° under 100 atm., and the product filtered, concentrated, and distilled in vacuo, yields the 1,2,3,4-tetrahydro derivative (VII), of VI, viscous oil, b0.3 124°. With HCl, it forms an HCl salt, m. 181-4°, and with picric acid a picrate, m. 151-3°. VII (1 g.) and 5-8 cc. concentrated HCl, heated in a sealed tube 3 hrs. at 100°, and the product purified by dilute EtOH, yield 1,2,3,4-tetrahydro-3-quinolinecarboxylic acid-HCl (VIII), m. 234°. N,N-Diethyl-3-quinolinecarboxamide (IX) (10 g.) in 100 cc. MeOH with 3 g. 10% Pd-C, hydrogenated 3 hrs. at 60° under 90 atm., filtered, concentrated, and the precipitate purified by EtOH, yields 1,2,3,4-tetrahydro derivative (X), m. 132-3°, forming with HCl a HCl salt, m. 160-1°. Hydrolyzed like VII, X yields VIII, m. 235-6°. 3-Aminoquinoline (XI) (144 g.) in 400 cc. tetrahydronaphthalene with 15 g. Raney Ni, hydrogenated at 55° under 90 atm., filtered, distilled in vacuo, and the residue rectified in vacuo, yields 127 g. crude product, b8 160-6°, which, fractionated and the fractions b. above 164° distilled in vacuo (0.8 mm.) at 250°, yields the 1,2,3,4-tetrahydro derivative (XII), m. 57°; picrate (from anhydrous EtOH), m. 205-6°; HCl salt (from EtOH by addition of Et2O), sinters 240°, m. 250°, turns violet by oxidation in air. XII oxidizes easily on exposure to air and light, and shows triboluminescence when rubbed with a wooden spatula. Benzoylated by the Schotten-Bauman method, XII gives a di-Bz derivative, C23H20O2N2, m. 201° (from EtOH). The distillation residue of XII (a fraction, b0.8 250°), fractionated further, gives a fraction, b0.4 234°, 3,3′-iminobis(1,2,3,4-tetrahydroquinoline) (XIII), very viscous resinous oil. With HCl, it forms a HCl salt (XIV), m. 254°, and with picric acid a picrate, m. 190-2°. In aqueous HCl solution, XIV gives with aqueous NaNO2 a yellow precipitate, which, purified by EtOH, yields the nitroso derivative, C18H18O3N6, m. 156°. Et2SO4 (9 cc.), added during 1 hr. to 15 g. XII in 200 cc. anhydrous Me2CO and 16 g. K2CO3, the mixture refluxed 6 hrs., filtered, evaporated, excess 20% aqueous NaOH added, the solution extracted with Et2O, the extract dried by K2CO3, evaporated, and the residue distilled in vacuo, yields 3-ethylamino-1,2,3,4-tetrahydroquinoline, b0.1 110-13°; picrate (from anhydrous EtOH), m. 198°. Et2SO4 (28 cc.), added during 1 hr. to 15 g. XII in 300 cc. anhydrous Me2CO and 48 g. K2CO3, the mixture refluxed 8 hrs., and the foregoing procedure followed, yields 3-diethylamino-1-ethyl-1,2,3,4-tetrahydroquinoline, b0.4 116°; picrate, m. 103-4°; HCl salt, very hygroscopic. The ultraviolet absorption spectra of II, IV, V, VI, VII, IX, X, XI, and XII are reproduced.
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Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com