反应详情

To a mixture of 1-ethynyl-1-methylcyclopropane (Preparation 4B, 5.0 g, 62.4 mmol) and (Z)-ethyl 2-chloro-2-(hydroxyimino)acetate (4.73 g, 31.2 mmol) in diethyl ether (80 mL) was added a solution of triethylamine (8.67 mL, 62.4 mmol) in diethyl ether (20 mL) dropwise over 75 min. After complete addition, the reaction mixture was stirred at room temperature for 2 h. The reaction mixture was filtered, and the filtrate was concentrated under reduced pressure. The crude product was purified by flash silica gel chromatography using a 10% mixture of ethyl acetate in hexane to give ethyl-5-(1-methylcyclopropyl)isoxazole-3-carboxylate (3.54 g, 65% yield) as a yellow liquid. The product had an HPLC ret. time=2.23 min.-(condition B); LC/MS M+1=196.07. 1H NMR (400 MHz, CDCl3) δ ppm 0.79 (m, 2H), 1.13 (m, 2H), 1.26 (t, J=7.15 Hz, 3H), 1.35 (s, 3H), 4.31 (q, J=7.12 Hz, 2H), and 6.23 (s, 1H).

1. additionAfter complete addition
2. filtrationThe reaction mixture was filtered
3. concentrationthe filtrate was concentrated under reduced pressure
4. customThe crude product was purified by flash silica gel chromatography