Vladimir A. Larionov

Chiral Cobalt(III) Complexes as Bifunctional Brønsted Acid–Lewis Base Catalysts for the Preparation of Cyclic Organic Carbonates

Stereochemically inert cationic cobalt(III) complexes were shown to be one-component catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa carbon dioxide pressure. The optimal catalyst possessed an iodide counter anion and could be recycled. A catalytic cycle is proposed in which the ligand of the cobalt complexes acts as a hydrogen-bond donor, activating the epoxide towards ring opening by the halide anion and activating the carbon dioxide for subsequent reaction with the halo-alkoxide. No kinetic resolution was observed when terminal epoxides were used as substrates, but chalcone oxide underwent kinetic resolution.

Chiral octahedral complexes of Co(III) as catalysts for asymmetric epoxidation of chalcones under phase transfer conditions

Stereochemically inert and positively charged chiral complexes of Co(III) were shown to catalyze the asymmetric epoxidation of chalcones with H2O2 under phase transfer conditions. The reaction products had enantiomeric purities of up to 55%. It was also shown that complex 1a I− catalyzed the coupling reaction of a resulting epoxide with CO2 (conversion 72%).

A novel type of catalysts for the asymmetric C-C bond formation based on chiral stereochemically inert cationic Co-III complexes

Schiff bases derived from (1R,2R)-1,2-diaminocyclohexane and 1 eq. of salycylic (or substituted salycylic) aldehyde form stereochemically inert positively charged chiral octahedral Coiii complexes of Δ-configuration with the stereoselectivity approaching 100%. To evaluate the calatylic activity and stereoinduction of the resulting complexes with various counteranions in the outer sphere, a model reaction of trimethylsilyl cyanide addition to benzaldehyde was used. O-trimethylsilylmandelonitrile formed in the process had an enantiomeric purity up to 27%. Complexes with F− counterion showed high catalytic activity.

A novel type of catalysts for asymmetric oxidative coupling of 2-naphthol

Stereochemically inert, positively charged chiral octahedral complexes of CoIII and CrIII were used as catalysts for asymmetric oxidative coupling of 2-naphthol. The reaction product 1,1´-bi-2-naphthol was produced with a yield of up to 74% and enantiomeric excess of up to 22%. The reduction and oxidation potentials of a series of CoIII and CrIII cationic complexes were measured.

Kinetic Resolution of Epoxides with CO2 Catalyzed by a Chiral-at-Iridium Complex

Chiral-at-metal bis-cyclometalated iridium(III) complexes are introduced as a new class of chiral catalysts for the reaction of epoxides with CO2 to form cyclic carbonates under conditions of kinetic resolution. Reactions are typically performed at room temperature in the presence of 1 mol % of iridium catalyst and 1.5 mol % of tetraethylammonium bromide as the nucleophilic cocatalyst to provide selectivity factors of up to 16.6. A variety of monosubstituted epoxides, including styrene epoxide, epoxides with aliphatic side chains, glycidyl ethers, and a glycidyl ester, are found to be suitable substrates. No polymerization side reaction is observed for any of the investigated substrates.

Self-Assembled Ionic Composites of Negatively Charged Zn(salen) Complexes and Triphenylmethane Derived Polycations as Recyclable Catalysts for the Addition of Carbon Dioxide to Epoxides

The design and synthesis of a novel type of self‐assembled ionic composite composed of negatively charged Zn(salen) complexes and triphenylmethane derived polycations is reported. These composites were applied as easily recyclable catalysts for carbon dioxide addition to epoxides. The composites functioned as bifunctional catalysts which could be easily separated and recycled by precipitation from the reaction mixture upon addition of tetrachloromethane. The same batch of the catalyst could be employed for, at least, five runs with its catalytic properties improving as it was reused. A fully heterogeneous system was also prepared by cross‐linking leuco dye with para‐dibromoxylene and adding to it calculated amounts of Zn(salen) complex. The heterogeneous system was catalytically competent in the reaction between styrene oxide and carbon dioxide and its activity also increased on its reuse.