ORGANIC SPECTROSCOPY INTERNATIONAL: 5-methoxyisatin

5-methoxyisatin

To a stirred solution of 12.6 g (75.6 mmol) of chloral hydrate in 168 mL water was added the following: 180 g (1.27 mole) sodium sulfate; 7.67 g (62.4 mmol) 4-methoxyaniline in 6 mL of concentrated HC1 and 42 mL of water; and 15.4 g (224 mmol) of hydroxylamine hydrochlori.de in 70 mL of water. The mixture was heated slowly to 100°C and kept at that temperature for 1 h. The mixture was cooled to room temperature, filtered and the precipitate washed with water and dried to give 81% yield of the anilide: Η MR (300 MHz, DMSO-d₆) δ 12.15 (s, IH) 10.1 (s, IH) 7.65 (s, IH) 7.6 (d, 2H) 6.95 (d, 2H) 3.75 (s, 3H). The crude anilide (10.8 g, 61 mmol) was added to 27 mL of concentrated sulfuric acid at 50°C, heated at 65°C for 1 h, cooled to room temperature, and poured into 300 mL of ice. The solids were filtered and dried in vacuo over P₂O₅. The crude isatin was dissolved in boiling CH₂C1₂ with 2% N-methylpyrrolidone and applied to a silica gel column. The product was eluted using a CH₂Cl₂:MeOH gradient 100% CH₂C1₂ to (9:1) CH₂Cl₂:MeOH. 5-Methoxyisatin was obtained in 12% yield overall: mp 168-172°C;

*H NMR (300 MHz, DMSO-d₆) δ 10.85 (s, IH) 7.17-7.24 (m, IH) 7.1 (d, IH) 6.87 (d, IH) 3.75 (s, 3H);

MS (M+CH₄CN)⁺ 158.

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