Copper -Schiff base

The catalytic asymmetric Henry reaction has been reviewed.42 Mild and efficient enantioselective nitroaldol reactions of nitromethane with various aldehydes have been catalysed by chiral copper Schiff-base complexes yielding the corresponding adducts with high yields and good enantiometric excess.43,44... 

Rong M, Liu C, Han J, Sheng W, Zhang Y, Wang H (2008) Catalytic oxidation of alcohols by a novel copper schiff base ligand derived from acetylacetonate and L-Leucine in ionic Uqttids. Catal Lett 125 52-56... 

Mixed 6),Af-donor ligands such as Schiff bases are of interest in that they provide examples not only of square-planar coordination but also, in the solid state, examples of square-pyramidal coordination by dimerization (Fig. 28.6(b)). A similar situation occurs in the bis-dimethylglyoximato complex, which dimerizes by sharing oxygen atoms, though the 4 coplanar donor atoms are all nitrogen atoms. Copper(II) carboxylates are easily obtained by crystallization from aqueous solution or, in the case of the higher carboxylates, by precipitation with the appropriate acid from ethanolic solutions... 

The major developments of catalytic enantioselective cycloaddition reactions of carbonyl compounds with conjugated dienes have been presented. A variety of chiral catalysts is available for the different types of carbonyl compound. For unactivated aldehydes chiral catalysts such as BINOL-aluminum(III), BINOL-tita-nium(IV), acyloxylborane(III), and tridentate Schiff base chromium(III) complexes can catalyze highly diastereo- and enantioselective cycloaddition reactions. The mechanism of these reactions can be a stepwise pathway via a Mukaiyama aldol intermediate or a concerted mechanism. For a-dicarbonyl compounds, which can coordinate to the chiral catalyst in a bidentate fashion, the chiral BOX-copper(II)... 

The conformation of Schiff-base complexes of copper(IT) a stereo-electronic view. H. S. Maslen and T. N. Waters, Coord. Chem. Rev., 1975,17,137-176 (127). 

The deamination of primary amines such as phenylethylamine by Escherichia coli (Cooper et al. 1992) and Klebsiella oxytoca (Flacisalihoglu et al. 1997) is carried out by an oxidase. This contains copper and topaquinone (TPQ), which is produced from tyrosine by dioxygenation. TPQ is reduced to an aminoquinol that in the form of a Cu(l) radical reacts with O2 to form H2O2, Cu(ll), and the imine. The mechanism has been elucidated (Wihnot et al. 1999), and involves formation of a Schiff base followed by hydrolysis in reactions that are formally analogous to those involved in pyridoxal-mediated transamination. 

In 2000, Gennaii et al. discovered a new family of chiral Schiff-base ligands, with the general structure, Af-alkyl-p-(A -salicylideneamino)alkanesulfonamide, depicted in Scheme 2.28. These ligands were successfully implicated in the copper-catalysed conjugate addition of ZnEt2 to cyclic enones (Scheme 2.28) and, less efficiently, to acyclic enones such as benzalacetone (50% ee) or chalcone... 

John E, Bott A, Green M. Preparation and biodistribution of copper-67 complexes with tetradentate Schiff-base ligands. J Pharm Sci 1994 83 587-590. 

Partial hydrolysis of a potentially heptadentate Schiff-base tripodal ligand derived from tris-(2-aminoethyl)amine and 2-hydroxyacetophenone, induced by copper(II) salts, was reported and the final copper(II) complex (377) was characterized.333 Using salicylaldehyde as a co-ligand, with a copper(II) complex (378), catalytic epoxidation was demonstrated 334... 

In 1966, Nozaki et al. reported that the decomposition of o-diazo-esters by a copper chiral Schiff base complex in the presence of olefins gave optically active cyclopropanes (Scheme 58).220 221 Following this seminal discovery, Aratani et al. commenced an extensive study of the chiral salicylaldimine ligand and developed highly enantioselective and industrially useful cyclopropanation.222-224 Since then, various complexes have been prepared and applied to asymmetric cyclo-propanation. In this section, however, only selected examples of cyclopropanations using diazo compounds are discussed. For a more detailed discussion of asymmetric cyclopropanation and related reactions, see reviews and books.17-21,225... 

In contrast to the flavin-dependent monoamine oxidases, SSAO/VAP-1 has evolved to hydroxylate a tyrosine residue in the active site which is further oxidized to the quinone state by oxygen in the presence of copper ion releasing hydrogen peroxide [28-30]. The primary amine in the substrate (R-NH2, Scheme 1) forms a Schiff-base with the quinone carbonyl group, which through a series of steps ultimately releases the aldehyde product. 

Asymmetric ring-opening of saturated epoxides by organocuprates has been studied, but only low enantioselectivities (< 15% ee) have so far been obtained [49, 50]. Muller et al., for example, have reported that the reaction between cyclohexene oxide and MeMgBr, catalyzed by 10% of a chiral Schiff base copper complex, gave trans-2-methylcyclohexanol in 50% yield and with 10% ee [50]. 

A number of structurally very different copper complexes were employed as catalysts. The copper complex of binaphthol-derived phosphoramidite 32 and the Schiff base complex 53 (derived from salicylaldehyde and phenylglycine) gave promising results in a screening reaction between 52 and MeMgBr, and 53 was chosen as the candidate for optimization. The effect of solvent (THF or Et20),... 

The i.r. and n.m.r. spectra of copper(ii) dithizonate together with other physicochemical data indicate that the complex is dimeric with structure (201). " The Schiff bases S-methyl-N-isopropylidenedithiocarbazate (NSH) and S-methyl-7V-(2-pyridyl)methylenedithiocarbazate (NNSH) form the square-... 

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