1.1: 70 percent / 3 h / 140 °C 2.1: 90 percent / aq. acetic acid / 4 h / Heating 3.1: potassium tert-butoxide; tetrabutylammonium iodide / tetrahydrofuran / 0 °C 3.2: 51 percent / tetrahydrofuran / 20 °C View Scheme

1.1: 70 percent / 3 h / 140 °C 2.1: 90 percent / aq. acetic acid / 4 h / Heating 3.1: potassium tert-butoxide; tetrabutylammonium iodide / tetrahydrofuran / 0.25 h / 0 °C 3.2: 99 percent / tetrahydrofuran / 20 °C 4.1: 93 percent / Na2S2O4; NaHCO3; tetrabutylammonium iodide / toluene; H2O / 90 °C View Scheme