反应详情

温度

-20 °C

To a solution of (1,6-dihydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl)-acetic acid ethyl ester (2.55 g, 10.2 mmol) in anhydrous acetonitrile (150 mL) was added 2-bromo-5-nitro-[1,3,4]thiadiazole (3.0 g, 14.3 mmol) at 0° C. The reaction mixture was cooled to −20° C. and K2CO3 (9.87 g, 71.4 mmol) was added. After stirring at −20 to −25° C. for 3.5 days, the reaction mixture was acidified to pH 2 with dilute hydrochloric acid at 0° C. and extracted with EtOAc. The organic extracts were washed with brine, dried over sodium sulfate and concentrated in vacuo. The residue was purified by silica gel flash column chromatography (EtOAc/hexanes/AcOH=2:1:trace) followed by recrystallization from methanol to give pure product as a white powder after lyophilization (1.35 g, 34.9%). 1HNMR (400 MHz, DMSO-d6) δ9.41 (s, 1H), 7.54 (d, J=2.34 Hz, 1H), 7.41 (d, J=1.76 Hz, 1H), 5.58 (dd, J=8.64, 2.78 Hz, 1H), 4.02 (q, J=7.22 Hz, 2H), 3.14 (dd, J=15.52, 2.63 Hz, 1H), 2.23-2.43 (m, 4H), 1.12 (t, 3H). MS (ESI) m/z=378 [M−H]−.

1. extractionextracted with EtOAc
2. washThe organic extracts were washed with brine
3. dry with materialdried over sodium sulfate
4. concentrationconcentrated in vacuo
5. customThe residue was purified by silica gel flash column chromatography (EtOAc/hexanes/AcOH=2:1:trace)
6. customfollowed by recrystallization from methanol
7. customto give pure product as a white powder after lyophilization (1.35 g, 34.9%)