The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Cinnolines. III. Synthesis of bz-substituted 3-nitro- and 3-aminocinnolines》. Authors are Baumgarten, Henry E.; Pedersen, Donald L.; Hunt, Mack W..The article about the compound:2-Amino-5-chlorobenzaldehydecas:20028-53-9,SMILESS:NC1=CC=C(Cl)C=C1C=O).Reference of 2-Amino-5-chlorobenzaldehyde. Through the article, more information about this compound (cas:20028-53-9) is conveyed.
cf. C.A. 50, 8672d. Crude, moist 4,2-Cl(H2N)C6H3CHO (7 g.), 2.9 g. NaNO2, and 75 g. crushed ice slurried in a Waring blender, treated with 9 cc. concentrated HCl and 50 g. crushed ice in 1 portion, blended 5 min. while adding periodically crushed ice, 4.3 cc. MeNO2 in 5 cc. EtOH added slowly with stirring to 5.7 g. KOH in 3.5 l. iced H2O, the solution treated with 3.3 g. NaOAc, the diazonium salt solution added slowly, the mixture allowed to stand 20 min. and filtered, the residue blended about 5-10 min. with 1.3 g. KOH in 50 cc. H2O, the mixture poured into a beaker, allowed to stand 2.5 hrs., and filtered, and the residue dried overnight (1.51 g.) and recrystallized from Me2CO or EtOAc yielded 1.1 g. 7-chloro-3-nitrocinnoline (I), yellow needles, m. 165.6-66° (all m.ps. are corrected). A similar run with a 4-fold larger amount of each reagent was carried out, the resulting yellow solid blended about 10 min. with 5.2 g. KOH in 200 cc. H2O, kept 2.5 hrs., and filtered, the brown residue refluxed 2 hrs. with 300 cc. Me2CO and filtered, and the filtrate treated with C, concentrated to about 75 cc., and cooled, giving 5.5-14.0 g. 5,2-Cl(AcCH:CH)C6H3NHN:CHNO2, yellow-orange needles, m. 234-5° (Me2CO). 5,2-Cl(O2N)C6H3CHO (15.6 g.) in 360 cc. hot EtOH added to 180 g. FeSO4.7H2O in 600 cc. H2O at 90°, the mixture treated slowly during 10 min. with 600 cc. concentrated NH4OH and steam-distilled, the 1st 300-500 cc. distillate discarded, and the following 2 l. distillate cooled to 5°, saturated with NaCl, and filtered yielded 6.5-7.0 g. crude 5,2-Cl(H2N)C6H3CHO (II), m. 73.5-4.5°. Crude moist II (7.0 g.) was converted as described for the preparation of I to 5.1 g. (crude) 6-Cl isomer of I, yellow plates, m. 227-8° (EtOAc). 6-Aminopiperonal (9.0 g.) was converted in the usual manner to nitroformaldehyde 4,5-methylenedioxy-2-formylphenylhydrazone and this to 1.96 g. (crude) 6,7-methylenedioxy-3-nitrocinnoline, cream-colored needles, m. 255-310° (indefinite). 3-Nitrocinnoline (13.8 g.) in 110 cc. AcOH and 55 cc. H2O treated during about 5 min. with 11 g. Fe powder, refluxed 1 hr., poured into 300 g. cold 33% aqueous KOH, kept overnight, and filtered through Celite, the filter cake washed with H2O, suspended in 150 cc. absolute EtOH, heated to boiling, filtered, and again extracted with 150 cc. and 100 cc. absolute EtOH, the combined filtrates evaporated, and the residue recrystallized from 250 cc. C6H6 gave 8.0 g. 3-aminocinnoline (III), m. 165-6°; 2nd crop, 1.1 g. I (3.0 g.) reduced similarly gave 2.2 g. 7-Cl derivative of III, bright yellow plates, m. 202° (decomposition). II (3.0 g.) gave similarly 1.91 g. 6-Cl derivative of III, bright yellow needles, m. 215° (decomposition). ο-O2NC6H4CHO (IV) (10 g.) in 50 cc. absolute MeOH treated with 2 drops concentrated HCl and 0.75 g. CaCl2, the mixture kept 6 days in a desiccator over CaCl2, filtered, neutralized with NaOMe in MeOH, and evaporated, and the oily residue distilled gave 11.4 g. ο-O2NC6H4CH(OMe)2 (V), b27 146-9°, n25D 1.5265. IV (100 g.) in 750 cc. C6H6 and 50 cc. absolute MeOH refluxed 28 hrs. with 2 g. p-MeC6H4SO3H with the azeotropic removal of H2O, concentrated by removing 500 cc. distillate, neutralized with NaOMe, and worked up in the usual manner yielded 116 g. V. IV (15 g.) in 250 cc. C6H6 and 35 cc. absolute MeOH refluxed 35 hrs. with 2 g. Amberlite IR-120 with the azeotropic removal of H2O, filtered, and distilled gave 18.4 g. V. IV (10 g.) in 250 cc. C6H6 and 25 cc. (CH2OH)2 refluxed 30 hrs. with 0.25 g. p-MeC6H4SO3H with the azeotropic removal of H2O, concentrated by removal of about 150 cc. distillate, basified with NaOMe to litmus, and fractionated gave 10.3 g. ethylene acetal (VI) of IV, pale yellow oil, b0.7 120.7°, n20D 1.5487. IV (15 g.) in 250 cc. C6H6 and 10 cc. (CH2OH)2, refluxed 30 hrs. with 2 g. Amberlite IR-120 with the azeotropic removal of H2O, filtered, and distilled gave 18.4 g. VI, b0.7 120°. V (5.0 g.), 100 cc. absolute MeOH, and about 1 g. Raney Ni hydrogenated about 1 hr. at 45 lb., filtered, slurried in a Waring blender with 50 cc. H2O, 3.5 g. NaNO2, and 300 g. crushed ice, treated with 25 cc. 6N HCl, and slurried again 20 min. while adding periodically crushed ice, the mixture added dropwise with stirring during 20 min. to a solution of 3.0 g. MeNO2, 10 cc. EtOH, and 5.7 g. KOH in 400 cc. H2O, and the precipitate recrystallized from 1:3 Me2CO-H2O gave 4.3 g. ο-O2NCH:NNHC6H4CH(OMe)2 (VII), bright orange needles, m. 80-1°. VI (4.3 g.), 50 cc. absolute MeOH, and about 0.5 g. Raney Ni hydrogenated, filtered, diazotized in a blender with 3 g. NaNO2, 100 cc. H2O, 300 g. ice, and 22 cc. 6N HCl, added to a solution of 4 g. MeNO2, 10 cc. EtOH, and 7.5 g. KOH in 400 cc. iced H2O, adjusted with cold 1% HCl to pH 3, stirred 20 min. at 5°, and filtered gave 2.5 g. ethylene acetal (VIII) of ο-O2NCH:NNHC6H4CHO (IX), golden yellow plates, m. 83.6-85° (aqueous Me2CO); the filtrate warmed to room temperature and extracted with Et2O, and the extract evaporated gave 1.8 g. IX, m. 156-8°. VII (0.87 g.) added at 95° to 3 cc. concentrated HCl in 200 cc. H2O in a Waring blender, the solution blended 0.5 hr., cooled to 10°, and extracted with Et2O, and the extract worked up gave 0.66 g. IX, m. 157-8°. VIII (0.65 g.) hydrolyzed similarly with 2 cc. concentrated HCl in 150 cc. hot H2O yielded 0.49 g. IX. IX (2.0 g.) in 300 cc. tetrahydrofuran circulated 18 hrs. at 55° through 6 g. dry Amberlite IRA-400, filtered, and evaporated gave 1.0 g. 3-nitrocinnoline, m. 204-5° (aqueous Me2CO).
The article 《Cinnolines. III. Synthesis of bz-substituted 3-nitro- and 3-aminocinnolines》 also mentions many details about this compound(20028-53-9)Reference of 2-Amino-5-chlorobenzaldehyde, you can pay attention to it, because details determine success or failure
Reference:
Tetrahydrofuran – Wikipedia,
Tetrahydrofuran | (CH2)3CH2O – PubChem