1: 1,2-difluoro-4-bromobenzene With magnesium; lithium chloride in tetrahydrofuran T=20°C; 2 h; Inert atmosphere; 2: With iron (III) acetylacetonate in tetrahydrofuran T=0°C; 0.0833333 h; Inert atmosphere; 3: ethylene,methyl acetate in tetrahydrofuran T=0°C; 0.75 h; Inert atmosphere;