Knölker type iron complexes, used directly or generated in situ, are suitable
catalysts for (de)hydrogenation reactions enabling the synthesis of carbonyl
derivatives, amines and alcohols of industrial and academic interest. Enantioselective
hydrogenation of prochiral C=X double bonds (X: O, N) was achieved with up to 94%
e.e. using iron-complexes bearing chiral ligands or Knölker’ complex in combination
with a chiral additive. Knölker type complexes were also competent catalysts for
sequential reactions based on temporary dehydrogenative alcohol activation including
dynamic kinetic resolution of racemic secondary alcohols (99% e.e.) and borrowing
hydrogen methodology. The latter method was applied to synthesize N-alkyl
substituted amines, α-alkylated ketones and oxygen- or nitrogen-heterocycles.
Keywords: Alcohol, Amine, Asymmetric hydrogenation, Bifunctional catalyst,
Borrowing hydrogen, Carbonyl compound, Dehydrogenation, Direct
hydrogenation, Dynamic kinetic resolution, Heterocycle, Iron, Knölker’s
complex, Metal-ligand cooperation, Transfer hydrogenation, Water-gas-shift
reaction.
