反应详情

A solution of (4-methylpent-1-ynyl)benzene (0.247 g, 1.56 mmol), dimethyl 2-nitromalonate (0.421 mL, 3.12 mmol), 1-butyl-3-methylimidazoliumhexafluorophosphate (0.032 mL, 0.156 mmol) in toluene (5 mL) was subjected to the microwave at 170° C. for 150 min. By HPLC, the reaction was ˜40-50% complete and resubjected to the microwave conditions for 360 min. (170° C.). The toluene was decanted off leaving a dark gum which was triturated several times with ethyl acetate. The combined organic layers were concentrated under reduced pressure. The residue was purified by flash silica gel chromatography using 5% ethyl acetate in hexane to give methyl 4-isobutyl-5-phenylisoxazole-3-carboxylate (0.122 g, 0.470 mmol, 30.2% yield) as a clear, colorless oil. The compound had an HPLC ret. time=2.96 min.−Column: CHROMOLITH® SpeedROD 4.6×50 mm (4 min.); Solvent A=10% MeOH, 90% H2O, 0.1% TFA; Solvent B=90% MeOH, 10% H2O, 0.1% TFA. LC/MS M+1=259.9. 1H NMR (500 MHz, chloroform-d) δ ppm 0.88 (s, 3H), 0.89 (s, 3H), 1.89 (dt, J=13.75, 6.87 Hz, 1H), 2.80 (d, J=7.15 Hz, 2H), 4.00 (s, 3H), 7.45-7.53 (m, 3H), 7.73 (d, J=6.60 Hz, 2H).

1. custom(170° C.)
2. customThe toluene was decanted off
3. customleaving a dark gum which
4. customwas triturated several times with ethyl acetate
5. concentrationThe combined organic layers were concentrated under reduced pressure
6. customThe residue was purified by flash silica gel chromatography