Acetic Anhydride → Ethyl 1H-indazole-5-carboxylate

関与物質

反応手順

Ethyl 4-amino-3-methylbenzoate (12.6 g, 70.0 mmol) prepared in the Step 4-1-1 and potassium acetate (7.20 g, 73.5 mmol) were suspended in chloroform (70 ml). Acetic anhydride (14.3 g, 140 mmol) was added to the suspension, and the mixture was stirred for one hour. To the mixture, 18-crown-6 (3.70 g, 14.0 mmol) and isoamyl nitrite (18.9 g, 161 mmol) were added, and the resulting mixture was heated under reflux for 21 hours. After being allowed to cool, under an ice cooling the mixture was rendered faintly alkaline with a saturated sodium bicarbonate solution and a 25% ammonia water. The faintly alkalified mixture was subjected to extraction with chloroform, and the extract was dried over anhydrous magnesium sulfate and then concentrated. The concentrate was purified by silica gel column chromatography (n-hexane:ethyl acetate=1:1) to give the title compound (4.06 g, 31%) as a light-brown powder and ethyl 1-acetyl-1H-indazole-5-carboxylate.

情報源と証拠