1: 82 percent / 1,3-dicyclohexylcarbodiimide / tetrahydrofuran / 1 h 2: acetic acid; triethylamine / tetrahydrofuran / 1 h / Heating 3: 97 percent / triphenylphosphine; diethyl azodicarboxylate / tetrahydrofuran / 0.5 h / 0 - 5 °C 4: 65 percent / methylhydrazine / tetrahydrofuran / 0 - 20 °C View Scheme

1: 82 percent / 1,3-dicyclohexylcarbodiimide / tetrahydrofuran / 1 h 2: acetic acid; triethylamine / tetrahydrofuran / 1 h / Heating View Scheme