Hydrogenation of Esters to Alcohols with a Well-Defined Iron Complex

We present the first base‐free Fe‐catalyzed ester reduction applying molecular hydrogen. Without any additives, a variety of carboxylic acid esters and lactones were hydrogenated with high efficiency. Computations reveal an outer‐sphere mechanism involving simultaneous hydrogen transfer from the iron center and the ligand. This assumption is supported by NMR experiments. A brilliant progressIRON: A novel and efficient catalyst system based on iron complex 1 has been developed for the hydrogenation of various aromatic and aliphatic carboxylic acid esters as well as lactones towards the corresponding alcohols. The reaction is postulated to proceed by an outer‐sphere mechanism.