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.

Using the same organocatalyst for asymmetric synthesis of both enantiomers of glutamic acid-derived Ni(II) complexes via 1,4-additions of achiral glycine and dehydroalanine Schiff base Ni(II) complexes.

(S)- and (R)-BIMBOL were efficient PT catalysts of asymmetric Michael addition of prochiral Ni-PBP-Gly (1) to acrylic esters and malonic esters to Ni-PBP-Δ-Ala (2) correspondingly. The salient feature of the catalysis is opposite configurations of Glu prepared via the two paths with BIMBOL of the same configuration and a perspective novel catalytic procedure for the synthesis of Gla derivatives.

Asymmetric synthesis of enantiomerically and diastereoisomerically enriched 4-[F or Br]-substituted glutamic acids.

A novel simple synthetic protocol for the preparation of both (2S,4R)- and (2S,4S)-FGlu, applying Michael addition of methyl α-fluoroacrylate to a NiII complex of glycine Schiff base with BPB, was elaborated. In addition, same reaction of mentioned complex with ethyl α-bromoacrylate leads to the NiII complex of the Schiff base of BPB with (2S,4R)-4-bromo-glutamic acid monoester, that can be transformed into the corresponding complexes of 1-aminocyclopropane-1,2-dicarboxylic acid. The decomposition of the diastereoisomerically pure complexes leads to corresponding enantiomerically enriched (ee>98%) amino acids.

Catalytic asymmetric synthesis of O-acetyl cyanohydrins from KCN, Ac2O and aldehydes.

A (salen)titanium catalyst has been found to induce the asymmetric addition of potassium cyanide and acetic anhydride to aldehydes, giving enantiomerically enriched cyanohydrin esters with up to 92% enantiomeric excess using just 1 mol% of the catalyst. This is the first report of the asymmetric synthesis of cyanohydrin derivatives using a cyanide source which is non-volatile and inexpensive.