N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium 1.) Et2O, cyclohexane, isopentane, -78 deg C, 4 h, 2.) Et2O, cyclohexane, isopentane, -78 deg C, 90 min; Yield given. Multistep reaction. Yields of byproduct given;

N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium 1.) Et2O, cyclohexane, isopentane, -78 deg C, 4 h, 2.) Et2O, cyclohexane, isopentane, -78 deg C, 90 min; Yield given. Multistep reaction. Yields of byproduct given;