1: With n-butyllithium; N,N,N',N,-tetramethylethylenediamine in tetrahydrofuran; hexane T=-80 - -20°C; 2: With 1,2-dibromo-1,1,2,2-tetrafluoroethane in tetrahydrofuran; hexane T=-80 - 20°C; Further stages.;