1: tetrahydrofuran / 12 h / 0 - 20 °C 2: TBAF / tetrahydrofuran / 6 h View Scheme

1: tetrahydrofuran / 12 h / 0 - 20 °C 2: TBAF / tetrahydrofuran / 6 h 3: Et3N / CH2Cl2 / 0 - 20 °C 4: 18-crown-6 / CH2Cl2 / 6 h / Heating View Scheme

1.1: tetrahydrofuran / 12 h / 0 - 20 °C 2.1: TBAF / tetrahydrofuran / 6 h 3.1: Et3N / CH2Cl2 / 0 - 20 °C 4.1: 18-crown-6 / CH2Cl2 / 6 h / Heating 5.1: diethyl ether / -78 - 0 °C 5.2: aq. NH4Cl / diethyl ether / 0.17 h / 0 °C View Scheme