sodium hydroxide in dimethyl sulfoxide T=55°C; 1 h;

hydrogenchloride in ethanol 2 h; Heating;

1: 74 percent / tetrahydrofuran / 30 min, -65 deg C, then room temperature 2: 1.) potassium t-butoxide / tetrahydrofuran, 1.) 30 min, 2.) 30 min 3: 11 percent / 5percent aqueous HCl / ethanol / 2 h / Heating View Scheme