Cesium carbonate → 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 stirred solution of ethyl 2-(1,6-dihydroxy-4-methyl-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate (43 g, 0.17 mol) in anhydrous acetonitrile (2000 mL) at −20° C. was added a solution of 2-bromo-5-nitro-1,3,4-thiadiazole (70 g, 0.33 mol.) in acetonitrile (1000 mL). Then Cs2CO3 (166 g, 0.51 mol, 3 eq.) as added portionwise at this temperature. The mixture was stirred at −20 to −30° C. for 20 hrs. Then, the reaction mixture was allowed to warm to r.t. and stirred at this temperature for 15 h. After filtration, the filtrate was concentrated and acidified to pH=2 at 0° C. with diluted hydrochloric acid. The mixture was extracted with EtOAc and the organic extracts were washed with brine, dried over sodium sulfate and concentrated in vacuo The residue was purified by chromatography on silica gel column (petroleum ether/EtOAc/AcOH, gradient elution) to give the 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 as a yellow solid (23 g, 36% yield).

Provenance & Evidence