1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / 2 h / -20 - -10 °C 2: at -75 deg C to room temperature 3: 94 percent / deketalization 4: 0 °C 5: 86 percent / CsF / acetonitrile / 1.5 h / Heating View Scheme

1: 83 percent 2: t-Bu4NF / acetonitrile / 1 h / Ambient temperature View Scheme