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(Il)-salen complex the yields and diastereoselectivities were greatly enhanced and the scope of the reaction could also be enlarged.