One‐Pot Synthesis of Ferrocene Thioamides from Ferrocenecarboxaldehyde via the Willgerodt–Kindler Reaction

Ferrocene thioamides are potential alternatives for classical oxoamide‐type ferrocene ligands with broad applications in metal‐catalyzed transformations as well as substrates for CH activations and applications in other fields. A reaction of ferrocenecarboxaldehyde with various amines and sulfur promoted by sodium sulfide furnishes a wide range of ferrocene thioamides via the Willgerodt–Kindler multicomponent reaction. The detailed solvent screening reveals that amide‐type solvents are highly beneficial for the reaction. The steric hindrance of bulky amine substrates limits the reaction. While secondary amines require only conventional heating, primary amines yield better results with microwave irradiation at higher temperatures. The mechanism is investigated using nuclear magnetic resonance kinetic measurements, which show that Na 2 S acts as a promoter, rather than a catalyst, of the reaction.