反应详情

A solution of 2-(pent-1-ynyl)pyridine (150 mg, 1.03 mmol), dimethyl nitromalonate (0.35 mL, 2.58 mmol), and 1-butyl-3-methylimidazolium hexafluorophosphate (0.021 mL, 0.103 mmol) in toluene (3 mL) was heated to 170° C. for 120 minutes under microwave. The reaction mixture was concentrated to yield a crude product which was purified by silica gel chromatography with hexanes/ethyl acetate (10/1) to afford methyl 4-propyl-5-(pyridine-2-yl)isoxazole-3-carboxylate (14.3 mg, 0.052 mmol). The compound had an HPLC retention time=3.05 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=247.1. 1H NMR (500 MHz, CDCl3) δ ppm 0.97 (t, 3H), 1.66 (sxt, J=7.48 Hz, 2H), 3.15-3.20 (m, 2H), 4.01 (s, 3H), 7.33 (ddd, J=7.56, 4.81, 1.10 Hz, 1H), 7.83 (td, J=7.77, 1.79 Hz, 1H), 7.91 (d, J=7.97 Hz, 1H), and 8.72 (d, J=4.12 Hz, 1H).

1. concentrationThe reaction mixture was concentrated
2. customto yield a crude product which
3. customwas purified by silica gel chromatography with hexanes/ethyl acetate (10/1)