1: With oxalyl dichloride; dimethyl sulfoxide in dichloromethane T=-78°C; Swern oxidation; 0.25 h; Inert atmosphere; 2: With triethylamine in dichloromethane T=-78 - -40°C; Swern oxidation; 2 h; Inert atmosphere;

sulfuric acid 10 h; Ambient temperature;

1.1: tetrabutyl ammonium fluoride / tetrahydrofuran / 0 - 25 °C / Inert atmosphere 2.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 2.2: 2 h / -78 - -40 °C / Inert atmosphere View Scheme

1.1: 1H-imidazole / dichloromethane / 12 h / 25 °C / Inert atmosphere 2.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 2.2: 2 h / -78 - -40 °C / Inert atmosphere 3.1: tetrahydrofuran / 1 h / 0 °C / Inert atmosphere 4.1: tetrabutyl ammonium fluoride / tetrahydrofuran / 0 - 25 °C / Inert atmosphere 5.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 5.2: 2 h / -78 - -40 °C / Inert atmosphere View Scheme

1.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 1.2: 2 h / -78 - -40 °C / Inert atmosphere 2.1: tetrahydrofuran / 1 h / 0 °C / Inert atmosphere 3.1: tetrabutyl ammonium fluoride / tetrahydrofuran / 0 - 25 °C / Inert atmosphere 4.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 4.2: 2 h / -78 - -40 °C / Inert atmosphere View Scheme

1.1: tetrahydrofuran / 1 h / 0 °C / Inert atmosphere 2.1: tetrabutyl ammonium fluoride / tetrahydrofuran / 0 - 25 °C / Inert atmosphere 3.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.25 h / -78 °C / Inert atmosphere 3.2: 2 h / -78 - -40 °C / Inert atmosphere View Scheme