1: (9R)-1-[3,5-bis(trifluoromethyl)benzyl]cinchonan-1-ium-9-ol bromide; tetramethyl-ammonium fluoride / dichloromethane; toluene / 2 h / -40 °C / Inert atmosphere 2: tetrabutyl ammonium fluoride / tetrahydrofuran / 1 h / 20 °C / Inert atmosphere 3: iron; acetic acid / tetrahydrofuran; methanol / 5 h / 20 °C / Inert atmosphere View Scheme

1.1: (9R)-1-[3,5-bis(trifluoromethyl)benzyl]cinchonan-1-ium-9-ol bromide; tetramethyl-ammonium fluoride / dichloromethane; toluene / 2 h / -40 °C / Inert atmosphere 2.1: tetrabutyl ammonium fluoride / tetrahydrofuran / 1 h / 20 °C / Inert atmosphere 3.1: iron; acetic acid / tetrahydrofuran; methanol / 5 h / 20 °C / Inert atmosphere 4.1: potassium hydrogencarbonate / tert-butyl methyl ether; water / 1 h / 20 °C / Inert atmosphere 4.2: pH 12 / Inert atmosphere View Scheme