[CH2:1]([C:3]1([CH2:15][CH3:16])[O:7][B:6]([OH:8])[C:5]2[CH:9]=[CH:10][C:11]([CH:13]=O)=[CH:12][C:4]1=2)[CH3:2].[NH2:17][OH:18].Cl.CC([O-])=O.[Na+].CC(=O)OCC>C1COCC1.O>[CH2:1]([C:3]1([CH2:15][CH3:16])[O:7][B:6]([OH:8])[C:5]2[CH:9]=[CH:10][C:11]([CH:13]=[N:17][OH:18])=[CH:12][C:4]1=2)[CH3:2]
To a mixture of 3,3-diethyl-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbaldehyde (1.1 g, 5.04 mmol) and NH2OH.HCl (420 mg, 6.05 mmol) in THF (20 ml) and H2O (5 ml) at rt was added NaOAc (578 mg, 7.06 mmol). The mixture was stirred at rt for 16 h, diluted with H2O and extracted with EA (20 ml×2). The combined organic layers were washed with aqueous NaHCO3 and brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was purified by column chromatography over silica gel eluted with PE:EA (10:1 to 1:1) to give the product (600 mg, yield 51%) as white solid: MS: m/z=234 [M+1]+.
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