Hydrochloric Acid → [1-Hydroxy-4-methyl-6-(pyrazin-2-yloxy)-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid ethyl ester

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 (0.5 g, 2.0 mmol) in anhydrous DMF (5 mL) were added Cs2CO3 (1.629 g, 5.0 mmol) and 2-chloro-pyrazine (0.275 g, 2.4 mmol) at room temperature. The reaction mixture was heated to 90° C. for 3 hours then poured into ice-water (10 mL). The mixture was acidified to pH 2 using dilute hydrochloric acid and extracted with ethyl acetate. The organic extracts were dried over sodium sulfate and concentrated in vacuo. The residue was purified by silica gel flash column chromatography (EtOAc/hexane/AcOH=3:2:trace) to give the product as an oil (0.250 g, 38.1%). 1HNMR (400 MHz, DMSO-d6) δ9.22 (s, 1H), 8.53 (d, J=1.17 Hz, 1H), 8.35 (d, J=2.64 Hz, 1H), 8.18 (dd, J=2.78, 1.32 Hz, 1H), 7.25 (d, J=2.05 Hz, 1H), 7.10 (d, J=1.46 Hz, 1H), 5.53 (dd, J=9.08, 2.34 Hz, 1H), 3.94-4.11 (m, 2H), 3.13 (dd, J=15.52, 2.63 Hz, 1H), 2.20-2.40 (m, 4H), 1.06-1.26 (m, 3H). MS (ESI) m/z=329 [M+H]+.

Provenance & Evidence