C–N Coupling of Amides with Alcohols Catalyzed by N‑Heterocyclic Carbene–Phosphine Iridium Complexes

N-Heterocyclic carbene–phosphine iridium complexes (NHC–Ir) were developed/found to be a highly reactive catalyst for N-monoalkylation of amides with alcohols via hydrogen transfer. The reaction produced the desired product in high isolated yields using a wide range of substrates with low catalyst loading and short reaction times

Enantioselective Synthesis of Chiral Sulfones by Ir-Catalyzed Asymmetric Hydrogenation: A Facile Approach to the Preparation of Chiral Allylic and Homoallylic Compounds

A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg–Bäcklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%)

An Enantioselective Approach to the Preparation of Chiral Sulfones by Ir-Catalyzed Asymmetric Hydrogenation

Several chiral sulfonyl compounds were prepared using the iridium catalyzed asymmetric hydrogenation reaction. Vinylic, allylic and homoallylic sulfone substitutions were investigated, and high enantioselectivity is maintained regardless of the location of the olefin with respect to the sulfone. Impressive stereoselectivity was obtained for dialkyl substitutions, which typically are challenging substrates in the hydrogenation. As expected, the more bulky <i>Z</i>-substrates were hydrogenated slower than the corresponding <i>E</i> isomers, and in slightly lower enantioselectivity

Catalytic Water Oxidation by a Molecular Ruthenium Complex: Unexpected Generation of a Single-Site Water Oxidation Catalyst

The increasing energy demand calls for the development of sustainable energy conversion processes. Here, the splitting of H₂O to O₂ and H₂, or related fuels, constitutes an excellent example of solar-to-fuel conversion schemes. The critical component in such schemes has proven to be the catalyst responsible for mediating the four-electron oxidation of H₂O to O₂. Herein, we report on the unexpected formation of a single-site Ru complex from a ligand envisioned to accommodate two metal centers. Surprising N–N bond cleavage of the designed dinuclear ligand during metal complexation resulted in a single-site Ru complex carrying a carboxylate–amide motif. This ligand lowered the redox potential of the Ru complex sufficiently to permit H₂O oxidation to be carried out by the mild one-electron oxidant [Ru­(bpy)₃]³⁺ (bpy = 2,2′-bipyridine). The work thus highlights that strongly electron-donating ligands are important elements in the design of novel, efficient H₂O oxidation catalysts