1: 1.) PhN=C=NPh, 2.) N,N-dimethylaniline / 1.) CH2Cl2, 18 h, 0 deg C, 2.) CH2Cl2 2: 56 percent / CF3COOH / various solvent(s) / 1.) -30 deg C, 2.) -20 deg C, 20 min, 3.) -10 deg C, 20 min View Scheme

N,N'-diphenylcarbodiimide in dichloromethane T=0°C; 18 h;