Iron‐Salen Complexes as Efficient Catalysts in Ring Expansion Reactions of Epoxyalkenes

The optimisation of the iron‐catalysed ring expansion reaction of epoxyalkenes was considerably improved when the original phosphine ligand system [FeCl2(dppe)] was altered to include nitrogen‐containing ligand systems. Especially, the very potent class of salen ligands gave the best results in inter‐ and intramolecular ring expansion reactions. With a preformed iron(II)‐salen complex the yields and diastereoselectivities were greatly enhanced and the scope of the reaction could also be enlarged.