1: pyridine / dichloromethane / 2 h / 4 °C 2: sodium azide / N,N-dimethyl-formamide / 60 °C 3: triphenylphosphine / tetrahydrofuran / 4 h / 22 °C 4: water / tetrahydrofuran View Scheme

1: 24 percent / CBr4; tris(dimethylamino)phosphine / CH2Cl2 / 16 h / 20 °C 2: 31 percent / NaH / dimethylformamide / 0.58 h / 0 - 20 °C View Scheme

carbon tetrabromide; tris-(dimethylamino)-phosphine in dichloromethane T=20°C; 16 h;