[OH:1][B:2]1[C:6]2[CH:7]=[C:8]([CH:11]=O)[CH:9]=[CH:10][C:5]=2[C:4]([CH3:14])([CH3:13])[O:3]1.[NH2:15][OH:16].Cl.CC([O-])=O.[Na+]>C1COCC1.O>[OH:1][B:2]1[C:6]2[CH:7]=[C:8](/[CH:11]=[N:15]/[OH:16])[CH:9]=[CH:10][C:5]=2[C:4]([CH3:14])([CH3:13])[O:3]1To a solution of 1-hydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbaldehyde (9.0 g, 47.4 mmol) and NH2OH.HCl (3.92 g, 56.9 mmol) in THF (100 mL) and H2O (25 mL) at rt was added NaOAc (5.83 g, 71.1 mmol). The reaction mixture was stirred for 2 h and diluted with H2O. The mixture was extracted with EA and the organic layer was separated. The organic solution was washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure to give crude compound (E)-1-hydroxy-3,3-dimethyl-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbaldehyde oxime as a light yellow solid. It was used in next step without further purification.
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