反应详情

A solution of ethyl 4-bromo-5-(pyridin-2-yl)isoxazole-3-carboxylate (2-C) (170 mg, 0.572 mmol), tributyl(vinyl)tin (0.504 mL, 1.72 mmol), dichlorobis(triphenylphosphine)-palladium(II) (24.1 mg, 0.034 mmol), and 1-butyl-3-methylimidazolium hexafluorophosphate (0.012 mL, 0.057 mmol) in dioxane (3 mL) was heated to 170° C. via microwave for 120 minutes. The reaction mixture was diluted with ethyl acetate (50 mL), washed with water (10 mL), washed with brine (10 mL), and dried over anhydrous sodium sulfate. Concentration gave a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (4/1) to give ethyl 5-(pyridin-2-yl)-4-vinylisoxazole-3-carboxylate (60 mg, 2.37 mmol, 41% yield). The compound had an HPLC retention time=2.80 min.—Column: YMC S5 COMBISCREEN® 4.6×50 mm; Gradient time: 4 min; Flow rate=4 ml/min; Solvent A=10% MeOH—90% Water—0.2% H3PO4; Solvent B=90% MeOH—10% water—0.2% H3PO4; Start % B=0; Final % B=100. LC-MS: M+1=245.2. 1H NMR (400 MHz, MeOD) δ ppm 1.42 (t, 3H), 4.47 (q, J=7.19 Hz, 2H), 5.49 (dd, J=11.80, 1.25 Hz, 1H), 5.85 (dd, J=18.07, 1.51 Hz, 1H), 7.26 (dd, J=18.07, 11.80 Hz, 1H), 7.51 (ddd, J=7.03, 5.02, 1.76 Hz, 1H), 7.93-8.02 (m, 2H), and 8.72-8.75 (m, 1H).

1. washwashed with water (10 mL)
2. washwashed with brine (10 mL)
3. dry with materialdried over anhydrous sodium sulfate
4. concentrationConcentration
5. customgave a crude product which
6. customwas purified by silica gel chromatography with hexanes/ethyl acetate (4/1)