1.1: 51 percent / (EtO)3CH; H2SO4 / tetrahydrofuran / 48 h / 20 °C 2.1: pyrrolidine; BuLi / tetrahydrofuran; hexane / 2 h / -30 °C 2.2: tetrahydrofuran / 2.5 h / -30 - -10 °C 2.3: 85 percent / H2O / tetrahydrofuran / 0.33 h / 0 °C 3.1: 92 percent / aq. HCl / tetrahydrofuran / 3 h / 20 °C View Scheme