N-heterocyclic carbene (NHC)-metal complexes have become known as efficient catalysts for numerous transition metal catalyzed processes. An important application of many NHC-metal complexes is in the field of asymmetric catalysis, and this is achieved through the introduction of chiral information on the NHC ligands. Among the asymmetric transformations catalyzed by NHC-metal complexes is asymmetric hydrogenation, which is an attractive process for the synthesis of optically active compounds due to its high atom economy. However, to date, few chiral NHC-metal catalysts have been reported to be highly stereoselective for asymmetric hydrogenation. Over the past few years our group has made some significant breakthroughs within the field of asymmetric hydrogenation using chiral NHC catalysts. We have reported the NHC-Ru catalyzed asymmetric hydrogenation of a wide range of heterocyclic compounds with high regio-and enantioselectivity. The field of chiral NHC-metal complex catalyzed asymmetric hydrogenation is yet to be reviewed; this Perspective aims to provide a concise overview of NHCmetal catalyzed asymmetric hydrogenation to push the further development of this area of chemistry.

An efficient and highly asymmetric ruthenium-N-heterocyclic carbene-catalyzed hydrogenation of substituted thiophenes and benzothiophenes is described, providing a new strategy for the formation of valuable enantiomerically pure tetrahydrothiophenes and 2,3-dihydrobenzothiophenes.

This study describes the structural investigation of a highly versatile ruthenium-NHC (N-heterocyclic carbene) catalyst complex, which has been established for the asymmetric hydrogenation of various aromatic compounds. A complex containing an unusual doubly deprotonated NHC ligand was isolated and identified as the precatalyst to this complex. When its subsequent reactivity was monitored, two additional precatalysts, featuring partially hydrogenated naphthyl substituents, were characterized spectroscopically. Ligand hydrogenation appears to be a key activation process en route to the active catalyst.

The HOMO–LUMO energy gap of germylenes bearing CNHC ∧Namido chelate ligands has been calculated in order to find suitable candidates for the activation of small molecules. Identified as promising structures, intramolecularly NHC-stabilized three-coordinate germylenes and stannylenes of type [E­(CNHC ∧Namido)­Cl] (E = Ge and Sn) were synthesized and characterized by NMR spectroscopy and X-ray crystallography. Chlorido substitution at the EII center for tert-butoxido or hexamethyl disilazide ligands was also performed. Chlorido abstraction with NaBArF gave rise to cationic two-coordinate germylenes and stannylenes.

We report a method for the enantioselective hydrogenation of annulated arenes using 4H-pyrido[1,2-a]pyrimidinones as sub-strates. The method selectively generates multiple stereocenters in adjacent rings leading to architecturally complex motifs, which...

Small tablets for implantation into the subconjunctival space in the eye are being developed to inhibit scarring after glaucoma filtration surgery (GFS). There is a need to evaluate drug dissolution at the molecular level to determine how the chemical structure of the active may correlate with dissolution in the nonsink conditions of the conjunctival space. We conducted molecular dynamics simulations to study the dissolution process of tablets derived from two drugs that can inhibit fibrosis after GFS, 5-fluorouracil (5-FU) and the matrix metalloprotease inhibitor (MMPi), ilomastat. The dissolution was simulated in the presence of simple point charge (SPC) water molecules, and the liquid turnover of the aqueous humor in the subconjunctival space was simulated by removal of the dissolved drug molecules at regular intervals and replacement by new water molecules. At the end of the simulation, the total molecular solvent accessible surface area of 5-FU tablets increased by 60 times more than that of ilomastat as a result of tablet swelling and release of molecules into solution. The tablet dissolution pattern shown in our molecular dynamic simulations tends to correlate with experimental release profiles. This work indicates that a series of molecular dynamic simulations can be used to predict the influence of the molecular properties of a drug on its dissolution profile and could be useful during preformulation where sufficient amounts of the drug are not always available to perform dissolution studies.

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Various thiophene substrates are subjected to optimized conditions A), where high enantioselectivities are obtained in some cases.