n-butyllithium in diethyl ether 1.) -78, 1 h, 2.) RT, 1 h;

1: 56 percent / n-BuLi / diethyl ether / 1.) -78, 1 h, 2.) RT, 1 h 2: 73 percent / CuCl, N,N,N',N'-tetramethylethylenediamine, air / 1,2-dimethoxy-ethane / 1 h / 30 - 35 °C 3: 100 percent / Na2S*9H2O / methanol / Heating View Scheme