Iyad Karamé

Tailored Ru‐NHC Heterogeneous Catalysts for Alkene Metathesis

The introduction of N-heterocyclic carbene ligands (NHC) has led to major breakthroughs in homogeneous catalysis. However, such homogeneous catalysts can still suffer from deactivation and problems related to catalyst cost and recovery, as well as metal separation from the organic substrates. In the case of the very challenging and promising reaction of alkene metathesis, these drawbacks have probably been delaying the development of economical industrial processes. One possible solution would be the development of an efficient heterogeneous catalysts that is highly active (TON and TOF), stable (minimum recycling and leaching) and tolerant to functional groups. Despite numerous efforts in this area (involving permanent grafting of Ru-NHC complexes on various supports or other immobilization strategies), heterogeneous catalysts has not fulfilled the aforementioned requirements. Recently, tailored made organic–inorganic materials have proved to be an alternative and advantageous route towards highly active and well-defined heterogeneous catalysts. In particular, fully characterized well-defined Ir-NHC materials displayed catalytic performances comparable to those of homogeneous homologues. This has been attributed to the careful control of the catalyst preparation: synthesis of materials containing regularly distributed NHC-moieties and subsequent selective functionalization into Ir-NHC species, leading to the “single-site” nature of these catalysts. Here, we describe the preparation of highly active and stable Ru-NHC alkene metathesis catalysts through surface organometallic chemistry on hybrid mesostructured materials (Scheme 1).

Iridium-catalyzed alternative of the Meinwald rearrangement

A novel and easy to handle procedure for the regioselective rearrangement of epoxides has been developed, based on an iridium catalyst.

N, N- and N, S-ligands for the enantioselective hydrosilylation of acetophenone with iridium catalysts

Abstract Enantiomerically pure C 2 -symmetric diamines and dithioureas as well as a series of monothioureas have been tested as chiral inducers for hydrosilylation of acetophenone with iridium catalysts. Some new N,S-ligands have been synthesized in good yields, one of them bearing four chiral centers. Enantioselectivities with dithioureas are better than the ones observed with analog diamine ligands. Up to 74% e.e. was reached for acetophenone hydrosilylation with a 10-fold excess of ligand versus iridium precursor.

Highly Enantioselective Hydrogenation of β‐Alkyl and β‐(ω‐Chloroalkyl) Substituted β‐Keto Esters

Abstract Highly enantioselective hydrogenation of β‐alkyl and β‐(ω‐chloroalkyl) substituted β‐keto esters was achieved with Ru catalysts based on chiral diphosphines in EtOH at 50°C under 50‐bar initial hydrogen pressure, affording the corresponding β‐hydroxy esters in >98% ee.

Diglycolamide-functionalized resorcinarene for rare earths extraction

A C-methylcalix(4)methylresorcinarene–DODGA ligand, derived from calix[4]methylresorcinarene functionalized with four diglycolamide (DGA) binding units, was synthesized and characterized by NMR and MS. The ligand was investigated with respect to the extraction of rare earth elements (REEs) from nitric acid solution. High sensitivity was observed, particularly toward heavy rare earth elements. The acidity effects, as well as the concentration of the extractant, were evaluated with regard to the extraction and separation efficiencies. The results showed that the distribution coefficient values increase with an increase in nitric acid concentration in the range from 0.1 to 5 mol L−1. A slope analysis method and spectrophotometric titrations showed clear complexation of the REEs with the ligand. An extraction mechanism is proposed from the estimation of the thermodynamic parameters (ΔH, ΔS, and ΔG). The extraction and stripping of REEs from a simulated leaching solution of a Nd/Fe/B/Dy magnet have been studied.

Highly Regioselective Synthesis of Ethyl 2-(N-Methylformate-1,4,5,6-tetrahydropyridin-2-yl) Acetate and Its Conversion into Corresponding (R)-Ethyl Homopepicolate by Asymmetric Hydrogenation

Abstract Ethyl 2-(N-methylformate-1,4,5,6-tetrahydropyridin-2-yl) acetate with endocyclic double bond was prepared with high regioselectivity and further reduced into (R)-N-protected homopipecolate with a good enantioselectivity using chiral ruthenium catalyst.

Structure and permanent electric dipole of para-fluoroaniline in gaseous phase

By coupling a matrix assisted laser desorption source to an electric beam deflection setup, we have measured the permanent electric dipole moment of the isolated para-fluroaniline PFAN (FC6H4NH2) molecule in the ground state. This measurement of the electric dipole of an isolated push-pull molecule is unique. The experimental value is compared to two different calculations and the structure of the system is discussed.Graphical abstract