sulfuric acid T=80 - 100°C; 4 h;

sulfuric acid T=100 - 120°C; 3 h;

1: 1.) 70percent H2SO4, 2.) NaNO2 / 1.) 80 to 100 deg C, 2.) 2h 2: 87 percent / dicyclohexylcarbodiimide / tetrahydrofuran / 39 h / Ambient temperature 3: 86 percent / lithium hexamethyldisilazide / tetrahydrofuran / 96 h / Heating View Scheme

sulfuric acid; sodium nitrite 1.) 80 to 100 deg C, 2.) 2h; Multistep reaction;