1.1: lithium 2,2,6,6-tetramethylpiperidine / tetrahydrofuran / 0.83 h / -90 °C 1.2: tetrahydrofuran / -90 - 20 °C 2.1: [O] 3.1: 74 percent / aq. HCl / tetrahydrofuran / 48 h / 50 - 55 °C View Scheme