1: 1.) n-BuLi, 2.) HMPA / 1.) THF, hexane, -78 deg C, 20 min, 2.) -78 deg C, 3 h 2: 69.6 percent / NaI / butan-2-one / 40 h / 4 °C 3: 1.) n-BuLi / 1.) THF, hexane, -23 deg C, 20 min, 2.) -23 deg C, 20 min 4: MeLi, TMEDA / tetrahydrofuran; diethyl ether / 6 h / 4 °C View Scheme

methyllithium in tetrahydrofuran; diethyl ether 1.) -78 deg C, 1 h, 2.) room temp., 24 h; Product distributionMechanism;