Dimethyl nitromalonate → Methyl 4-isobutyl-5-phenylisoxazole-3-carboxylate

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Reaktionsschritte

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).

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