Planar-chiral arene ruthenium complexes: synthesis, separation of enantiomers, and application for catalytic C-H activation.

Heating tert-butyl-tetraline with [(p-cymene)RuCl2]2 produces the racemic complex [(arene)RuCl2]2, which can be separated into enantiomers by chromatography of its diastereomeric adducts with chiral phosphine ligand. The resolved chiral complex catalyzes C-H activation of N-methoxy-benzamides and their annulation with N-vinyl-pivaloyl amide giving dihydroisoquinolones in 50-80% yields and with 40-80% enantiomeric excess.

Streamlining the synthesis of amides using Nickel-based nanocatalysts.

The synthesis of amides is a key technology for the preparation of fine and bulk chemicals in industry, as well as the manufacture of a plethora of daily life products. Furthermore, it constitutes a central bond-forming methodology for organic synthesis and provides the basis for the preparation of numerous biomolecules. Here, we present a robust methodology for amide synthesis compared to traditional amidation reactions: the reductive amidation of esters with nitro compounds under additives-free conditions. In the presence of a specific heterogeneous nickel-based catalyst a wide range of amides bearing different functional groups can be selectively prepared in a more step-economy way compared to previous syntheses. The potential value of this protocol is highlighted by the synthesis of drugs, as well as late-stage modifications of bioactive compounds. Based on control experiments, material characterizations, and DFT computations, we suggest metallic nickel and low-valent Ti-species to be crucial factors that makes this direct amide synthesis possible.

Asymmetric cyclopropanation of electron-rich alkenes by the racemic diene rhodium catalyst: the chiral poisoning approach.

Asymmetric cyclopropanation of alkenes by aryldiazoacetates was achieved using the readily-available racemic (diene)rhodium complex in combination with the chiral oxazoline-phenol ligand, which acts as the chiral poison and selectively inhibits one of the enantiomers of the catalyst. This approach eliminates a common problematic step of the synthesis of chiral catalysts.

Synthesis of Rhodium Complexes with Chiral Diene Ligands via Diastereoselective Coordination and Their Application in the Asymmetric Insertion of Diazo Compounds into E-H Bonds.

A new method for the synthesis of chiral diene rhodium catalysts is introduced. The readily available racemic tetrafluorobenzobarrelene complexes [(R2 -TFB)RhCl]2 were separated into two enantiomers via selective coordination of one of them with the auxiliary S-salicyl-oxazoline ligand. One of the resulting chiral complexes with an exceptionally bulky diene ligand [(R,R-iPr2 -TFB)RhCl]2 was an efficient catalyst for the asymmetric insertion of diazoesters into B-H and Si-H bonds giving the functionalized organoboranes and silanes with high yields (79-97 %) and enantiomeric purity (87-98 % ee). The stereoselectivity of separation via auxiliary ligand and that of the catalytic reaction was predicted by DFT calculations.

A Planar-Chiral Rhodium(III) Catalyst with a Sterically Demanding Cyclopentadienyl Ligand and Its Application in the Enantioselective Synthesis of Dihydroisoquinolones.

The rapid development of enantioselective C-H activation reactions has created a demand for new types of catalysts. Herein, we report the synthesis of a novel planar-chiral rhodium catalyst [(C5 H2t Bu2 CH2t Bu)RhI2 ]2 in two steps from commercially available [(cod)RhCl]2 and tert-butylacetylene. Pure enantiomers of the catalyst were obtained through separation of its diastereomeric adducts with natural (S)-proline. The catalyst promoted enantioselective reactions of aryl hydroxamic acids with strained alkenes to give dihydroisoquinolones in high yields (up to 97 %) and with good stereoselectivity (up to 95 % ee).