[OH:1][B:2]1[C:6]2[CH:7]=[C:8]([C:11](=O)[CH3:12])[CH:9]=[CH:10][C:5]=2[C:4]([CH3:15])([CH3:14])[O:3]1.[NH2:16][OH:17].Cl.CC([O-])=O.[Na+].O>CO>[OH:1][B:2]1[C:6]2[CH:7]=[C:8](/[C:11](=[N:16]/[OH:17])/[CH3:12])[CH:9]=[CH:10][C:5]=2[C:4]([CH3:15])([CH3:14])[O:3]1
A mixture of 1-(1-hydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]-oxaborol-6-yl)ethanone (190 mg, 0.93 mmol), NH2OH HCl (77 mg, 1.12 mmol) and NaOAc (114 mg, 1.4 mmol) in MeOH (15 mL) was heated to 65° C. and stirred for 3 h. Water was added and the mixture was extracted with DCM. The organic layers were washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure to give (E)-1-(1-hydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]oxaborol-6-yl)ethanone oxime as a white solid. It was used in the next step without further purification. MS: m/z=220.1 (M+1, ESI+).
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