Synthese chiraler Kobalt‐Komplexe mit planoid‐tetradentatem Ligand‐System

Härter, Ralph; Wegmuth, Christophe; Scheffold, Rolf; Engel, Peter; Linden, Anthony

doi:10.1002/hlca.19930760120

Cited by 8 publications

(1 citation statement)

References 14 publications

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“…The ring-opening reactions of 1,2-dioxines 1 with Fe(II), , Ru(II), Pd(0), − and Co(II) − have been previously studied. In the case of bicyclic 1,2-dioxines, the reaction usually yields bisepoxides as a result of the inability of the intermediate oxy radicals to undergo 1,5-hydrogen abstraction.…”

Section: Introductionmentioning

confidence: 99%

Ring-Opening of Unsymmetrical 1,2-Dioxines Using Cobalt(II) Salen Complexes

Greatrex

Taylor

2004

J. Org. Chem.

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The regioselectivity of the metal-catalyzed ring opening of unsymmetrical 1,2-dioxines to cis-gamma-hydroxyenones was investigated using two different Co(II) salen complexes. Regioselectivity was determined by direct examination of the enone ratios and by derivitization with a stabilized phosphorus ylide. The steric influence of the substituents on the 1,2-dioxine was the primary influence on regioselectivity. Temperature played little role; however, solvent and selection of Co(II) complex could be used to mildly influence the outcome of the rearrangement for selected substrates. The origins of the selectivity for the reaction are discussed.

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Section: Introductionmentioning

confidence: 99%

Ring-Opening of Unsymmetrical 1,2-Dioxines Using Cobalt(II) Salen Complexes

Greatrex

Taylor

2004

J. Org. Chem.

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Preparation of Achiral and of Enantiopure Geminally Disubstituted β-Amino Acids for β-Peptide Synthesis

2000

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ChemInform Abstract: Synthesis of Chiral Cobalt Complexes with Planoid‐Tetradentate Ligand System.

et al. 1993

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1993 stereochemistry stereochemistry (general, optical resolution) O 0030 24 -066 Synthesis of Chiral Cobalt Complexes with Planoid-Tetradentate Ligand System.-Cobalamins and related derivatives are versatile, enantioselective catalysts for electron transfer induced reactions. Since cobalamins can act in the reaction of achiral educts only in the direction of one enantiomorphous form, synthetic B12-analogous metal complexes are needed, which are accessible in both enantiomorphous forms. As model compounds Co complexes (I) and (II) are chosen which contain a chiral tetradentate-planoid ligand system consisting of two different parts. A study on the catalytic properties of (I) in the isomerization of the achiral 1,4-epiperoxide (III) shows a high activity, but (IV) is obtained only as a racemic mixture. When using (II) as the catalyst, the change in the ligand periphery causes the generation of (IV) with an excess of the (S) enantiomer. The catalytic activity is comparable to that of vitamin B12. -(HAERTER, R.; WEYMUTH, C.; SCHEFFOLD, R.; ENGEL, P.; LINDEN, A.; Helv. Chim. Acta 76 (1993) 1, 353-371; Inst. Org. Chem., Univ. Bern, CH-3012 Bern, Switz.; DE)

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Synthese chiraler Kobalt‐Komplexe mit planoid‐tetradentatem Ligand‐System

Cited by 8 publications

References 14 publications

Ring-Opening of Unsymmetrical 1,2-Dioxines Using Cobalt(II) Salen Complexes

Ring-Opening of Unsymmetrical 1,2-Dioxines Using Cobalt(II) Salen Complexes

Preparation of Achiral and of Enantiopure Geminally Disubstituted β-Amino Acids for β-Peptide Synthesis

ChemInform Abstract: Synthesis of Chiral Cobalt Complexes with Planoid‐Tetradentate Ligand System.

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