1: 97 percent / p-TsOH / benzene / 19 h / Heating 2: 1.) NaNH2, 2.) NH4Cl / 1.) NH3, Et2O 3: 1.) BuLi / 1.) THF, HMPA, hexane, -72 deg C, 15 min, 2.) THF, hexane, HMPA, , -55 - -50 deg C, 20 min; rt, 1 h 4: t-BuOK / dimethylsulfoxide; diethyl ether / -23 - 0 °C View Scheme