oxalyl dichloride; dimethyl sulfoxide; triethylamine in dichloromethane T=-78 - 20°C; Swern oxidation;

1: TBAF; HOAc / tetrahydrofuran 2: Dess-Martin reagent View Scheme

1.1: n-BuLi / diethyl ether; hexane / 0.33 h / -78 °C 1.2: 73 percent / diethyl ether; hexane / -78 - 20 °C 2.1: 81 percent / TBAF / tetrahydrofuran / 5 h / 20 °C 3.1: 68 percent / oxalyl chloride; Et3N; DMSO / CH2Cl2 / -78 - 20 °C View Scheme

1.1: Cp2ZrCl2 / toluene / 2 h / 20 °C 1.2: CH2Cl2; toluene / -20 - 20 °C 1.3: 98 percent / I2 / CH2Cl2; toluene; tetrahydrofuran / -40 - 20 °C 2.1: 99 percent / imidazole; DMAP / dimethylformamide / 0.5 h 3.1: n-BuLi / diethyl ether; hexane / 0.33 h / -78 °C 3.2: 73 percent / diethyl ether; hexane / -78 - 20 °C 4.1: 81 percent / TBAF / tetrahydrofuran / 5 h / 20 °C 5.1: 68 percent / oxalyl chloride; Et3N; DMSO / CH2Cl2 / -78 - 20 °C View Scheme

1.1: 99 percent / imidazole; DMAP / dimethylformamide / 0.5 h 2.1: n-BuLi / diethyl ether; hexane / 0.33 h / -78 °C 2.2: 73 percent / diethyl ether; hexane / -78 - 20 °C 3.1: 81 percent / TBAF / tetrahydrofuran / 5 h / 20 °C 4.1: 68 percent / oxalyl chloride; Et3N; DMSO / CH2Cl2 / -78 - 20 °C View Scheme

1: TBAF; HOAc / tetrahydrofuran 2: Dess-Martin reagent View Scheme