A novel one-pot synthesis of ferrocenyl-substituted 1,2,4-oxadiazoles

One-pot synthesis of 5-ferrocenyl-1,2,4-oxadiazoles via the reaction between 3-ferrocenylpropynal and amidoximes is described. 3-Ferrocenylpropynal reacts with a variety of amidoximes in the presence of KOH in refluxing dioxane to afford a broad range of 5-ferrocenyl-1,2,4-oxadiazole derivatives. The reaction first produces the corresponding conjugate addition product which, upon cyclization and rearrangement, yields the targeted 1,2,4-oxadiazole. The reaction appears to be general for a diversity of amidoximes and tolerates the presence of aryl groups with electron-withdrawing and electron-donating substituents.