Expanding the Catalytic Scope of (Cyclopentadienone)iron Complexes to the Hydrogenation of Activated Esters to Alcohols

Article abstract of DOI:10.1002/cctc.201600972

Herein, we report the application of easy-to-make and bench-stable (cyclopentadienone)iron complexes (such as 1) as precatalysts for the hydrogenation of esters. After optimization of the reaction conditions (i.e., solvent, temperature, pressure), complex 1 was tested in the hydrogenation of a range of esters. With most of the activated trifluoroacetate esters, quantitative formation of 2,2,2-trifluoroethanol was obtained at low catalyst loadings. For nonactivated esters, no reaction was observed. Trifluoroacetic acid, a common impurity in hydrolytically labile trifluoroacetate esters, was shown to act as a poison for the catalyst. However, the simple addition of Et₃N allowed the catalyst activity to be restored. Our study constitutes the first examples of ester hydrogenation with an Fe complex based on a non-pincer ligand.