A　Knoevenagel-type　reaction　of　1,3-diketone　substrates　with　trifluoroacetic　anhydride　is　described.　The　electrophilic　species　of　trifluoroacetaldehyde　is　easily　generated　in　situ　by　the　reaction　of　trifluoroacetic　anhydride/difluoroacetic　anhydride　with　triethylamine.　By　this　efficient　and　simple　approach,　a　library　of　2-(2,2,2-trifluoroethylidene)-1,3-dicarbonyl　compounds　that　contain　a　wide　range　of　functional　groups　were　synthesized　in　good　yields.　Moreover,　the　reaction　with　difluoroacetic　anhydride　affords　the　corresponding　(2,2-difluoroethyl)-1,3-dicarbonyls.　Some　of　these　compounds　exhibited　promising　fungicidal　activities.　©　the　Partner　Organisations.