Substituted Butanolides and Butenolides: XVII. Substituted 3-(Furan-2-ylmethylidene)furan-2(3<Emphasis Type="Italic">H</Emphasis>)-ones and 3-(Furan-2-ylmethylidene)dihydrofuran-2(3<Emphasis Type="Italic">H</Emphasis>)-ones

A number of furan-2-ylmethylidene-substituted lactones were synthesized by condensation of 5-alkylfuran-2(3H)-ones and 4-alkyldihydrofuran-2(3H)-ones with 5-substituted furan-2-carbaldehydes. The reactivity of furan-2(3H)-ones was higher than that of furan-2(5H)-ones due to formation of intermediate conjugated anion. The condensation of 4-alkyldihydrofuran-2(3H)-ones with furan-2-carbaldehydes required more severe conditions than the condensation with furan-2(3H)-ones. The substituent in the furan ring affects the reaction time and yield.