Hydrochloric Acid → Ethyl 2-(1-hydroxy-4-methyl-6-(5-nitro-1,3,4-thiadiazol-2-yloxy)-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate

Participants

Reaction Conditions

Reaction Steps

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]−.

Provenance & Evidence