1-B. Preparation of N-hydroxybenzimidoyl chloride: refer to the method of Liu, K.C. et al. (J. Org. Chem., 45: 3916-1918, 1980). N-chlorosuccinimide (26.9 g, 201 mmol) was added to a solution of (E)-benzaldehyde oxime (24.4 g, 201 mmol) in N,N-dimethylformamide (60 mL) in batches at room temperature. After each addition, the reaction mixture first turns yellow and then gradually returns to nearly colorless. Note that the reaction is exothermic and batch addition of N-chlorosuccinimide is required to ensure smooth initiation of the reaction. If necessary, the reaction temperature can be controlled with an ice bath. After addition, the reaction mixture was stirred at room temperature overnight. After completion of the reaction, dilute with 250 mL of water and extract with ether (3 x 100 mL). The organic layers were combined and washed sequentially with water (2 x 100 mL), 10% aqueous lithium chloride (2 x 100 mL) and brine (100 mL). The aqueous layer was then back-extracted with ether (100 mL), and all organic layers were combined (about 400 mL) and dried over anhydrous sodium sulfate. Concentration under reduced pressure afforded (Z)-N-hydroxybenzenecarbamoyl chloride (30.84 g, 198 mmol, 98% yield) as a fluffy light yellow solid. The product was analyzed by HPLC (column: CHROMOLITH? SpeedROD 4.6×50 mm; mobile phase A: 10% MeOH, 90% H2O, 0.1% TFA; mobile phase B: 90% MeOH, 10% H2O, 0.1% TFA; run time: 4 min) with a retention time of 1.57 min. LC/MS (M+1) = 155.8. 1H NMR (500 MHz, DMSO-d6) δ 7.30-7.64 (m, 3H), 7.73-7.87 (m, 2H), 12.42 (s, 1H).
