1: pyridine; 4-(N,N-dimethlyamino)pyridine / 4 h / 0 °C / Inert atmosphere 2: sodium azide / N,N-dimethyl-formamide / 4 h / 0 °C / Inert atmosphere 3: tetrabutyl ammonium fluoride; acetic acid / tetrahydrofuran View Scheme

1: (COCl)2; DMSO; Et3N / CH2Cl2 / -78 °C 2: PPh3 / CH2Cl2 / 20 °C 3: n-BuLi / tetrahydrofuran / 0 °C 4: aq. HCl / methanol / 20 °C View Scheme

1: (COCl)2; DMSO; Et3N / CH2Cl2 / -78 °C 2: PPh3 / CH2Cl2 / 20 °C 3: n-BuLi / tetrahydrofuran / 0 °C 4: aq. HCl / methanol / 20 °C 5: (COCl)2; DMSO; Et3N / CH2Cl2 / -78 °C View Scheme