Methyl iodide → [4-(4-Carbamimidoylphenyl)butyl]carbamic acid tert-butyl ester

[4-(4-Thiocarbamoylphenyl)butyl]carbamic acid tert-butyl ester (58) (500 mg, 1.6 mmol) and iodomethane (4 mL, 64 mmol) were combined in methylene chloride (8 mL). The solution was stirred at reflux for 3 h, and allowed to stand overnight. The volatiles were removed by evaporation, and the residue was dried under vacuum for 3 h. The resulting crystalline solid was dissolved in ethanol (5 mL), and ammonium acetate (1.1 g, 14.4 mmol) was added. The resulting solution was stirred at reflux for 2 h, and the solvent was evaporated. The residue was taken up in a mixture of methanol and concentrated ammonium hydroxide (20 mL, 10:1), and the solvent was then evaporated. To this residue were added water (20 mL) and concentrated ammonium hydroxide (3 mL). The resulting mixture was stirred for 1 h, cooled in an ice bath, and suction filtered to collect a solid. The solid was dried under vacuum overnight to afford the product 59 (137 mg, 29%). 1H NMR (300 MHz, DMSO-d6) δ 1.37 (s, 9H), 1.38 (m, 2H), 1.55 (m, 2H), 2.64 (t, 2H), 2.93 (m, 2H), 6.80 (br s, 1H), 7.35 (d, 2H), 7.70 (d, 2H), 9.62 (br s, 3H).