Task: Translation
Input (Spanish): 5,5'-diformyl-2,2'-difuran is prepared in excellent yield by photochemically irradiating furfural or a mixture of furfural and 5-bromo-2-furfural.
Output (English): ?-difurano, con excelentes rendimientos, por irradiar fotoquimicamente el furfural o una mezcla del furfural y un 5-bromo-2-furfural.