Pyridine → Phthalimide

A mixture of N-hydroxyphthalimide (664 mg, 4.07 mmol), 4-chlorophenylboronic Acid (635 mg, 4.06 mmol) and powdered 4 Å molecular sieves (1.02 g) in dichloromethane (20 mL) was stirred open to the air. Pyridine (0.37 mL, 4.6 mmol) and Cu(OAc)2.H2O (812 mg, 4.07 mmol) were added, and stirring was continued for 18 h. Silica gel (10 g) was added, and the mixture was concentrated to dryness. The residue was added to the top of a silica gel chromatography column, and eluted with hexanes-EtOAc (4:1) to provide 2-4-chlorophenoxy)phthalimide as a white solid (820 mg). This was dissolved in chloroform (37 mL) and methanol (4 mL) and hydrazine hydrate (0.56 mL, 12 mmol) was added. The solution was stirred at room temperature for 24 h. Silica gel (10 g) was added, and the slurry was concentrated to dryness. The solid was added to the top of a silica gel chromatography column, and eluted with hexanes-EtOAc (4:1) to provide O-(4-chlorophenyl)hydroxylamine as a yellow oil (416 mg). This was dissolved in ethanol (5 mL) and treated with HCl/dioxane (4N, 1 mL), followed by gradual addition of EtOAc (50 mL) to precipitate the product. The mixture was filtered and dried under vacuum to provide the titled salt as an off-white crystalline solid (442 mg, 60%). 1H NMR (300 MHz, CD3OD) δ ppm 7.15-7.22 (m, 2H), 7.42-7.49 (m, 2H).