反应详情

To a water bath-cooled solution of 2,6-dichlorobenzaldehyde oxime (2.20 g, 11.6 mmol) in N,N-dimethylformamide (7 mL) was added solid N-chlorosuccinimide (1.55 g, 11.6 mmol). The solution was stirred while in the water bath for approximately 20 min and outside the bath for approximately 1 hr. The solution was poured into water and extracted twice with ether. The combined organic layers containing the crude imidoyl chloride were dried over magnesium sulfate and then concentrated. To a separate solution of ethyl 3-cyclobutyl-3-oxopropanoate (2.37 g, 13.9 mmol) in THF (3 mL) at 0° C. was added sodium ethoxide (25 wt % in ethanol, 4.36 mL, 13.9 mmol). The solution was stirred for a few minutes and then the above imidoyl chloride was added. The solution was stirred at 0° C. for 10 minutes and then at ambient temperature overnight. The solution was poured into water and extracted three times with ethyl acetate. The combined organic layers were dried over magnesium sulfate, concentrated and purified by chromatography (silica gel, 0-5% ethyl acetate in hexanes gradient elution) to afford ethyl 5-cyclobutyl-3-(2,6-dichlorophenyl)-4-isoxazolecarboxylate (1.52 g, 38%). 1H-NMR (400 MHz, DMSO-d6) δ 7.63-7.53 (m, 3H), 4.29-4.20 (m, 1H), 4.02 (q, J=7 Hz, 2H), 2.43-2.36 (m, 4H), 2.15-2.06 (m, 1H), 1.97-1.89 (m, 1H), 0.94 (t, J=7 Hz, 3H).

1. extractionextracted twice with ether
2. additionThe combined organic layers containing the crude imidoyl chloride
3. dry with materialwere dried over magnesium sulfate
4. concentrationconcentrated
5. stirringThe solution was stirred at 0° C. for 10 minutes
6. customat ambient temperature
7. customovernight
8. extractionextracted three times with ethyl acetate
9. dry with materialThe combined organic layers were dried over magnesium sulfate
10. concentrationconcentrated
11. custompurified by chromatography (silica gel, 0-5% ethyl acetate in hexanes gradient elution)