The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Synthesis of several pyrazole and 1,2,3-triazole derivatives of ethylamine and alanine》. Authors are Huttel, Rudolf; Schneiderhan, Trudl; Hertwig, Hermann; Leuchs, Annemarie; Reincke, Vivian; Miller, Johannes.The article about the compound:1H-Pyrazole-5-carbaldehydecas:948552-36-1,SMILESS:O=CC1=CC=NN1).SDS of cas: 948552-36-1. Through the article, more information about this compound (cas:948552-36-1) is conveyed.
A mixture of 2 g. 4-formyl-1-phenyl-1,2,3-triazole (I), 2.5 g. hippuric acid (II), 1 g. NaOAc and 4 g. Ac2O was heated on the steam bath 40 min., the cooled mixture filtered and the precipitate triturated with 200 ml. H2O. Recrystallization from EtOAc yielded 2.8 g. 2-phenyl-4-(1-phenyl-1,2,3-triazol-4-yl)methyleneoxazolin-5-one (III), m. 190°. III (3 g.) was refluxed 3 hrs. with 2 g. red P, 15 ml. Ac2O, and 15 ml. HI, P filtered off and the concentrated filtrate extracted with ether to remove C6H5CO2H, the filtrate was then neutralized with NH3 and 64% crude 2-(1-phenyl-1,2,3-triazol-4-yl)alanine, m. 277°, was collected and purified by dissolving in aqueous NH3, removing the excess base and neutralizing with hot HCl. Similarly, condensation of 10 g. crude 3-formylpyrazole, m. 121-4°, with II yielded 15.3 g. 2-phenyl-4-(1-acetyl-3-pyrazolyl)methyleneoxazolin-5-one (IV), m. 177-8° (from EtOH). IV (15 g.) with HI yielded 4.2 g. 2-(3-pyrazolyl)alanine, m. 235°. 2-(3-methyl-5-pyrazolyl)alanine, m. 275-6°, was obtained by condensing 3-methyl-5-formylpyrazole with II and treating the azlactone, m. 160-2°, with HI. 1-Methyl-4-formyl-1,2,3-triazole and II yielded an azlactone, m. 215° (from CHCl3 or EtOAc), converted with HI to (1-methyl-1,2,3-triazol-4-yl)alanine, m. 288-90°. III, with hot dilute aqueous NaOH yielded 70% α-benzoylamino-β-(1-phenyl-1,2,3-triazol-4-yl)acrylic acid (V), m. 202-4°. Catalytic hydrogenation of V with PtO2 gave the corresponding propionic acid, m. 192.5° (decomposition). β-(1-phenyl-1,2,3-triazol-4-yl)-ethylamine oxalate, m. 197°, and the HCl salt, m. 197-8°, were prepared by the condensation of I with MeNO2 in the presence of HOAc and C5H10N, hydrogenation with Pd-C of the resulting nitroethylene derivative, m. 198-7°, to the oxime, m. 143°, followed by hydrogenation of PtO2 in the presence of (CO2H)2. A bis(piperidine) adduct of I, m. 131-2°, was obtained in 85% yield on storing I with piperidine in EtOH at room temperature for 1 day, evaporating the solvent and recrystallizing from petr. ether. I plus NH4Ac and HOAc yielded a compound (VI), m. 140° (from EtOAc) for which the structure RCH(OH)N:CHR (R = 1-phenyl-1,2,3-triazol-4-yl) was suggested. Addition of MeNO2 to VI yielded RCH(CH2NO2)N: CR (R as above), m. 170°. Using the rhodanine method of Sheehan and Robinson (C.A. 43, 6620c) β-(3-methyl-5-pyrazolyl)ethylamine and its oxalate, m. 168°, were prepared through the following intermediates: 5-(3-methyl-5-pyrazolyl)methylenerhodanine, m. approx. 318° (decomposition); 3-methyl-5-pyrazolylpyruvic acid, m. 178° (oxime, m. 196.5°); (N-acetyl-3-methyl-5-pyrazolyl)acetonitrile, m. 68°. Similarly, β-(1-methyl-1,2,3-triazol-4-yl)ethylamine and its oxalate, m. 156.5°, were prepared through the following intermediates: 5-(1-methyl-1,2,3-triazol-4-yl)methylenerhodanine, m. 315° (decomposition); (1-methyl-1,2,3-triazol-4-yl)pyruvic acid oxime, m. 155° (decomposition); (1-methyl-1,2,3-triazol-1-yl)acetonitrile, m. 73-73.5°; N-acetyl-2-(1-methyl-1,2,3-triazol-4-yl)ethylamine, m. 102-3°.
Different reactions of this compound(1H-Pyrazole-5-carbaldehyde)SDS of cas: 948552-36-1 require different conditions, so the reaction conditions are very important.