GENERAL STEPS: CuCl (63.4 mg, 0.64 mmol, 1 mol%) was added to a solution of N,N'-diisopropylcarbodiimide (10.0 mL, 63.9 mmol, 1.0 equiv) in tert-butanol (6.97 mL, 73.5 mmol, 1.15 equiv). The reaction mixture was stirred at room temperature for 14 hours. After completion of the reaction, purification was carried out by distillation under reduced pressure (80°C, 25 mmHg). 2-tert-butyl-1,3-diisopropylisourea was obtained as a colorless oil (10.4 g, 51.9 mmol, 81% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 3.80-3.58 (1H, m, CH), 3.31-2.97 (1H, m, CH), 1.44 (9H, s, tBu), 1.19-1.01 (12H, m, Me2×2).
