Yield: 85%

Reaction Conditions:

with sulfuric acid;nitric acid in water at 0; for 20 h;

Steps:

65.2
The compound (20.91 g, 0.11 mol) obtained in Step 1 was dissolved in concentrated sulfuric acid (63 ml), nitric acid (5.2 ml, 0.12 mol) was added under ice-cooling, and the mixture was stirred for 20 hr. The reaction mixture was gently poured into ice water and the mixture was stirred. The precipitated solid was filtered and washed with water. The obtained solid was dissolved in ethyl acetate, and the solution was washed with saturated aqueous sodium hydrogencarbonate solution and saturated brine, and dried over magnesium sulfate. After filtration, the filtrate was concentrated under reduced pressure to give the object product as a pale-yellow solid (21.97 g, yield 85%). ¹H NMR(CDCl₃ 400 MHz) (δ) ppm: 4.01 (3H, s), 7.68 (1H, d, J=1.6 Hz), 8.16 (1H, d, J=1.9 Hz)

References:

Satoh, Motohide;Aramaki, Hisateru;Nakamura, Hiroshi;Inoue, Masafumi;Kawakami, Hiroshi;Shinkai, Hisashi;Matsuzaki, Yuji;Yamataka, Kazunobu US2006/84665, 2006, A1 Location in patent:Page/Page column 70