1: 93 percent / t-BuOK / 2-methyl-propan-2-ol; diethyl ether / 0.33 h / 25 °C 2: 87 percent / K2CO3 / dimethylformamide / 0.5 h / 25 °C 3: 99 percent / NaH / tetrahydrofuran; hexamethylphosphoric acid triamide / 1.) 25 deg C, 2 h 2.) reflux 16 h 4: O3 / CH2Cl2 / -78 °C 5: 89 percent / diethylamine / CHCl3 / Heating View Scheme