Chiral Oxovanadium Complexes Research Articles

ChemInform Abstract: Enantioselective Silylcyanation of Aldehydes Catalyzed by New Chiral Oxovanadium Complex.

Abstract Oxovanadium(V) complex 4 was prepared from VOSO 4 and tridentate Schiff base ligand, which was prepared from substituted salicylaldehyde and inexpensive ( S )-valine. Asymmetric silylcyanation of the aldehydes catalyzed by catalyst 4 afforded cyanohydrins with good enantioselectivities.

Enantioselective silylcyanation of aldehydes catalyzed by new chiral oxovanadium complex

Oxovanadium(V) complex 4 was prepared from VOSO 4 and tridentate Schiff base ligand, which was prepared from substituted salicylaldehyde and inexpensive ( S)-valine. Asymmetric silylcyanation of the aldehydes catalyzed by catalyst 4 afforded cyanohydrins with good enantioselectivities.

Novel Achiral Biphenol‐Derived Diastereomeric Oxovanadium(IV) Complexes for Highly Enantioselective Oxidative Coupling of 2‐Naphthols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic enantioselective coupling of 2-naphthols by new chiral oxovanadium complexes bearing a self accelerating functional group

New chiral oxovanadium complexes containing an extra phenolic hydroxyl group were found to enhance the catalytic enantioselective coupling of 2-naphthols in moderate to good enantioselectivity.

Novel achiral biphenol-derived diastereomeric oxovanadium(IV) complexes for highly enantioselective oxidative coupling of 2-naphthols.

Optically pure 1,1’-binaphthol and its derivatives have been evaluated as versatile chiral auxiliaries and ligands in asymmetric transformations. Research in this area has provided many efficient and useful methods for the preparation of key chiral building blocks, some of which have been used for the construction of complex natural products.[1] They have also been extensively applied to the preparation of chiral organic materials.[2] The wide-ranging and important applications of such compounds in organic synthesis have stimulated great interest in developing efficient methods for their preparation.[3] Compared to the well-established resolution of racemic binaphthol for the preparation of optically pure BINOL,[3a±f] catalytic asymmetric preparation of chiral binaphthols has developed much more slowly. The discovery of efficient catalysts for the highly enantioselective formation of optically active binaphthol and its derivatives is an attractive target. The oxidative coupling of 2-naphthols in the presence of a catalytic amount of a copper complex of a chiral amine has provided several promising results, but high enantioselectivity has been achieved only for the coupling of 3carboalkoxyl-2-naphthols (93% ee).[4] A photo-activated chiral [RuII(salen)(NO)] complex catalyzes the aerobic oxidative coupling of 2-naphthols with 33±71% ee.[5] Chen et al. and Uang et al. independently designed similar oxovanadium(iv) complexes of chiral Schiff bases for the asymmetric oxidative coupling of 2-naphthols with moderate enantioselectivities of up to 62% ee.[6] We developed the catalyst (R,S)-1c for the oxidative coupling of 2-naphthol with high enantioselectivity, and found that the chiral centers on the amino acid part and the axially chiral binaphthyl unit are both crucial to stereocontrol by the catalyst.[7] However, a drawback is that the chiral oxovanadium complex must be prepared from an optically pure 3,3’diformyl-2,2’-dihydroxy-1,1’-binaphthol and (S)-amino acid. The catalyst is only highly enantioselective when the two COMMUNICATIONS

ChemInform Abstract: Chiral Oxovanadium Complex Catalyzed Enantioselective Oxidative Coupling of 2‐Naphthols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chiral oxovanadium complex catalyzed enantioselective oxidative coupling of 2-naphthols

The enantioselective oxidative coupling of 2-naphthols using 2 mol% chiral oxovanadium complex under mild conditions afforded chiral BINOLs in moderate enantioselectivity.