N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium; ethylene dibromide 1.) cyclohexane, ether, -78 deg C, 1 h, 2.) cyclohexane, ether, a) -78 deg C, 30 min, b) 1 h; Yield given. Multistep reaction;

1: 81 percent / tetrahydrofuran / Ambient temperature 2: 1.) s-BuLi, TMEDA, 2.) BrCH2CH2Br / 1.) cyclohexane, ether, -78 deg C, 1 h, 2.) cyclohexane, ether, a) -78 deg C, 30 min, b) 1 h View Scheme

1: 81 percent / tetrahydrofuran / Ambient temperature 2: 1.) s-BuLi, TMEDA, 2.) BrCH2CH2Br / 1.) cyclohexane, ether, -78 deg C, 1 h, 2.) cyclohexane, ether, a) -78 deg C, 30 min, b) 1 h View Scheme

trifluoroacetic acid in dichloromethane

1: 95 percent / TFA / CH2Cl2 2: 99 percent / n-BuLi / tetrahydrofuran / -78 - 0 °C View Scheme