1: diethyl malonate With sodium ethanolate in ethanol; toluene T=20°C; 0.5 h; 2: (E)-1,4-ditosyloxybut-2-ene in ethanol; toluene T=20°C; 23 h; 3: With sodium hydroxide in water; toluene T=20°C; 1 h; Product distribution / selectivity;