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

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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 (3.0 g, 12.0 mmol) in anhydrous DMF (20 mL) were added Cs2CO3 (23.45 g, 72 mmol) and methyl iodide (17.03 g, 120 mmol) at 0° C. After stirring at room temperature for 3 hours the reaction mixture was cooled to 0° C. and acidified to pH 2 with dilute hydrochloric acid. The mixture was extracted with ethyl acetate and 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=1:1:1) to give the product (1.24 g, 39.1%). 1HNMR (400 MHz, DMSO-d6) δ9.12 (s, 1H), 7.02 (d, J=2.34 Hz, 1H), 6.83 (d, J=2.34 Hz, 1H), 5.44 (dd, J=9.23, 2.49 Hz, 1H), 3.93-4.08 (m, 2H), 3.73 (s, 3H), 3.08 (dd, J=15.24, 2.64 Hz, 1H), 2.10-2.31 (m, 4H), 1.05-1.19 (m, 3H).

Provenance & Evidence