The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Benzisoxazoles. VI. Friedel-Crafts acylation of benzisoxazoles》. Authors are Borsche, Walther; Hahn-Weinheimer, Paula.The article about the compound:1,2-Benzisoxazolecas:271-95-4,SMILESS:C12=CC=CC=C1ON=C2).COA of Formula: C7H5NO. Through the article, more information about this compound (cas:271-95-4) is conveyed.
cf. C.A. 35, 4378.1. 1,2-Benzisoxazole (I) (2.38 g.) in 5 cc. PhNO2 (II) reacting 24 h. with 3 g. AlCl3 suspended in 6.5 cc. II and 2 g. AcCl, treated with ice and 2 cc. concentrated HCl, steam-distilled, and the still residue extracted with Et2O, followed by extraction with 0.2 N NaOH and acidification, gave (impure) 5,2-Ac(HO)C6H3CN (III); 2,4-dinitrophenylhydrazone, red needles, m. 300° (from AcOH). Pure III, m. 78° (after distillation in vacuo), was formed from ο-HOC6H4CN (IV) by a very similar acylation. III heated with Ac2O gave the 2-acetate, b2 156°; dinitrophenylhydrazone, red, m. 272° (from MeOH). I in II warmed with AlCl3 and treated with HCl gave IV. I in II and AlCl3 on standing also gave IV. The 3-Me derivative (V) of I was prepared either from 2-BrC6H4COCl (cf. Borsche and Scriba, C.A. 34, 761.2) or by Lindemann’s method (C.A. 21, 91) from 2-HOC6H4Ac (formed from IV and MeMgI). V on acylation in II gave very small yields of a 4(?)-Ac derivative of V (isolated as the red 2,4-dinitrophenylhydrazone, m. 254°) and, as the main product 5,2-Ac(HO)C6H3CMe:NOH, brown oil, characterized as the dinitrophenylhydrazone, red leaflets, m. 314° (from AcOH). The 3-Ph derivative of I remained unchanged under various conditions of acetylation. Evidently the aromatic nucleus of benzisoxazole is not readily affected by the Friedel-Crafts reaction and acylation is effective only after fission of the isoxazole ring. 2,3-HO(MeO)C6H3CH:NOH, m. 124°, with Ac2O gave the O-acetyl derivative, C10H11O4N, m. 99°, 19.22 g. of which when heated at 40-50° and 2 mm. lost AcOH, and when heated further at 140-150° (at 2 mm.) gave a mixture of 12.2 g. 2,3-HO(MeO)C6H3CN (VI), b2 172-8°, yellow, m. 59°, and about 10% of the 7-MeO derivative (VII) of I, yellow oil, b2 155-60°. Friedel-Crafts acetylation of 2.98 g. VII gave about 0.95 g. of the alkali-soluble 5,2,3-Ac(HO)2C6H2CN (VIII), yellow, m. 44° [2,4-dinitrophenylhydrazone (IX), red needles, m. 316°], and (in the alkali-insoluble portion) the 4(?)-Ac-derivative of VII, brown oil (2,4-dinitrophenylhydrazone, bright red, m. 233°). Acetylation of VII with Ac2O gave 53% VIII. A Friedel-Crafts benzoylation of VII in II gave (in the alkali-insoluble portion) 2,3-BzO(MeO)C6H3CN (X), m. 80° (giving no color with FeCl3 and failing to react with (O2N)2C6H3NHNH2), and (in the alkali-soluble part) 2,3-BzO(HO)C6H3CN, m. 95-6° (giving a blue color with FeCl3 in MeOH and yielding no dinitrophenylhydrazone), and converted into X on methylation. Friedel-Crafts phenacetylation of VII in II gave (23%) 2,3-PhCH2CO(MeO)C6H3CN, m. 49-50° (from MeOH), also formed from PhCH2COCl and VI. CH2N2 and VI gave 2,3-(MeO)2C6H3CN, b2 195°, m. 45°. Br in AcOH and VI gave the 5-Br derivative of VI, m. 171° (from glacial AcOH). Acetylation of VI, however, yielded VIII, m. 44° (identified as IX). Benzoylation of VI gave a mixture of X and 2,3-BzO(HO)C6H3CN. VI (14.9 g.) in Et2O with MeMgI (from 35.5 g. MeI and 6.1 g. Mg) gave about 90% 2,3-HO(MeO)C6H3Ac, m. 53° (from petr. ether) (dinitrophenythydrazone, yellow leaflets, m. 222°), whose oxime (5.43 g.), m. 125°, with 20 cc. Ac2O gave 3 g. 3-Me derivative (XI) of VII, b2 185-90°. Friedel-Crafts acetylation of XI gave the alkali-insoluble 4(?)-Ac derivative of XI (dinitrophenylhydrazone, red, m. 146°) and, in the alkali-soluble part, 5,2,3-Ac(HO)(MeO)C6H2C(:NOH)Me, whose 2,4-dinitrophenylhydrazone, red needles, m. 233°. Analogously PhMgBr and VI gave the 2,3-HO(MeO)C6H3Bz, m. 59°, b3 220-25° (2,4-dinitrophenylhydrazone, red, m. 226°), whose oxime, m. 221°, with Ac2O, gave the 3-Ph derivative (XII) of VII, b2 230-40°, m. 58°. 4-Br derivative of XII m. 150°; 4-NO2 derivative of XII, pale yellow, m. 194° (from CHCl3-MeOH). Friedel-Crafts acetylation of XII in II gave 79% of the 4(?)-Ac derivative, m. 187° (dinitrophenylhydrazone, dark red, m. 278°). BzCl and XII gave a Bz derivative, C21H15O3N (yielding no dinitrophenylhydrazone).
Although many compounds look similar to this compound(271-95-4)COA of Formula: C7H5NO, numerous studies have shown that this compound(SMILES:C12=CC=CC=C1ON=C2), has unique advantages. If you want to know more about similar compounds, you can read my other articles.
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