1.1: n-butyllithium / tetrahydrofuran; hexane / 0.17 h / -70 °C 1.2: tetrahydrofuran; hexane / -70 - 20 °C 2.1: p-toluenesulfonic acid / benzene / 2 h / Heating 3.1: 91 percent / trifluoroacetic acid / H2O / Heating View Scheme

1.1: n-butyllithium / tetrahydrofuran; hexane / 0.17 h / -70 °C 1.2: tetrahydrofuran; hexane / -70 - 20 °C 2.1: p-toluenesulfonic acid / benzene / 2 h / Heating View Scheme