methyllithium Yield given. Multistep reaction;

1: 2) Et3N / 1) Et2O, -40 deg C to 0 deg C, 2) HMPA 2: 1) MeLi, HMPA, (Me3Si)2NLi / 1) THF, -78 deg C to 25 deg C, 2) THF View Scheme

1: 1.) n-BuLi / 1.) 1 h, -78 deg C, 2.) a) 0.5 h, -78 deg C, b) 2 h to 0 deg C 2: 71 percent / tetrahydrofuran / 16 h / Ambient temperature 3: 53 percent / 2.5 h / -50 - -40 °C View Scheme