potassium carbonate in N,N-dimethyl-formamide T=20°C;

1: NEt3 2: 70 percent / 2,4,6-triisopropylbenzenesulfonyl azide / hexamethylphosphoric acid triamide / -78 °C 4: H2O / 20 °C 5: 65 percent / Et3N / CH2Cl2 / 20 °C 6: 95 percent / NaOH / tetrahydrofuran / 20 °C 7: 95 percent / Br2 / acetic acid / 20 °C 8: 85 percent / K2CO3 / dimethylformamide / 20 °C View Scheme

1: NEt3 2: 70 percent / 2,4,6-triisopropylbenzenesulfonyl azide / hexamethylphosphoric acid triamide / -78 °C 4: H2O / 20 °C 5: 65 percent / Et3N / CH2Cl2 / 20 °C 6: 95 percent / NaOH / tetrahydrofuran / 20 °C 7: 95 percent / Br2 / acetic acid / 20 °C 8: 85 percent / K2CO3 / dimethylformamide / 20 °C View Scheme

1: 70 percent / 2,4,6-triisopropylbenzenesulfonyl azide / hexamethylphosphoric acid triamide / -78 °C 3: H2O / 20 °C 4: 65 percent / Et3N / CH2Cl2 / 20 °C 5: 95 percent / NaOH / tetrahydrofuran / 20 °C 6: 95 percent / Br2 / acetic acid / 20 °C 7: 85 percent / K2CO3 / dimethylformamide / 20 °C View Scheme

2: H2O / 20 °C 3: 65 percent / Et3N / CH2Cl2 / 20 °C 4: 95 percent / NaOH / tetrahydrofuran / 20 °C 5: 95 percent / Br2 / acetic acid / 20 °C 6: 85 percent / K2CO3 / dimethylformamide / 20 °C View Scheme

1: 95 percent / Br2 / acetic acid / 20 °C 2: 85 percent / K2CO3 / dimethylformamide / 20 °C View Scheme