lithium; ethylene dibromide 1.) THF, -75 deg C, 3 h; 2.) THF, -75 deg C; Multistep reaction;

1: 1.) Na-K eutectic alloy / 1.) Et2O, reflux, 1 h; 2.) Et2O, -10 deg C then r.t., overnight 2: 1.) Cs-K-Na alloy; 2.) CO2; 3.) CH2N2 / 1.) THF, -75 deg C, 2 min; 2.) THF, -75 deg C View Scheme

potassium-sodium; hydrogen cation 1.) Et2O, reflux, 1 h; Multistep reaction;