Acetaldehyde → alpha-Methyl-N-phenyl-1H-benzotriazole-1-methanamine

Benzotriazole (5.0 g, 4.20 mmol) and aniline (3.91 g, 4.20 mmol) were dissolved in diethyl ether (85 ml), and acetaldehyde (2.03 g, 4.62 mmol) was added dropwise thereto on ice. The reaction mixture was stirred at room temperature for 15 minutes and then allowed to stand overnight at −20° C. The crystallized product was collected by filtration, washed with diethyl ether and then dried to give α-methyl-N-phenyl-1H-benzotriazole-1-methanamine (8.7 g) as a white crystal. The resulting α-methyl-N-phenyl-1H-benzotriazole-1-methanamine (2.86 g, 12 mmol) and vinylphthalimide (2860 mg, 12.0 mmol) were suspended in chloroform (10 ml), to which p-toluenesulfonic acid monohydrate (190 mg, 1.0 mmol) was then added and stirred at room temperature for 10 hours. After addition of water, the reaction mixture was extracted with chloroform. The organic layer was washed with saturated aqueous sodium carbonate and water, and then concentrated. The residue was applied to silica gel column chromatography to give the titled compound (1.03 g, yield over 2 steps: 25%) as a white crystal.