1: 72 percent / p-TsOH / benzene / 1 h / Heating 2: 62 percent / K2CO3 / ethanol / 15 h / Heating 3: KtBuO / tetrahydrofuran / 0.5 h / 0 °C 4: 69 percent / tetrahydrofuran / 0.5 h / Ambient temperature; pH 4 (aq. buffer solution citric acid - sodium acetate) 5: 65 percent / aq. 50percent HOAc / 15 h / Ambient temperature View Scheme

1: 72 percent / p-TsOH / benzene / 1 h / Heating 2: 62 percent / K2CO3 / ethanol / 15 h / Heating 3: KtBuO / tetrahydrofuran / 0.5 h / 0 °C 4: 69 percent / tetrahydrofuran / 0.5 h / Ambient temperature; pH 4 (aq. buffer solution citric acid - sodium acetate) 5: 65 percent / aq. 50percent HOAc / 15 h / Ambient temperature View Scheme