1.1: hydrogen fluoride / tetrahydrofuran; water / 1 h / 20 °C 2.1: boron trifluoride diethyl etherate; 3-chloro-benzenecarboperoxoic acid / dichloromethane / 1 h / 20 °C 2.2: 0 - 20 °C 3.1: tetrabutyl ammonium fluoride / tetrahydrofuran; dichloromethane / 1 h / 20 °C View Scheme