Source:http://linkedlifedata.com/resource/pubmed/id/15352102
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
17
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| pubmed:dateCreated |
2004-9-7
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| pubmed:abstractText |
Iridium(I) complexes containing a (5H-dibenzo[a,d]cyclohepten-5-yl)-phosphane (tropp(R); R = phosphorus-bound substituent = Ph, Cyc) as a rigid, concave-shaped, mixed phosphane olefin ligand were prepared and tested as catalyst precursors in the hydrogenation of imines. With the complex [Ir(tropp(Cyc))(cod)]OTf, turnover frequencies (TOFs) of >6000 h(-1) were reached in the hydrogenation of N-phenyl-benzylidenamine, PhN==CHPh. Lower activities (TOF>80 h(-1)) are observed with N-phenyl-(1-phenylethylidene)amine, PhN==CMePh. Chiral tropp-type ligands were prepared in few simple steps. Monosubstitution of the olefinic unit in the dibenzo[a,d]cycloheptenyl moiety with (R)- or (S)-mentholate gave mixtures of diastereomers that could be separated and isolated in enantiomerically pure form. Iridium(I) complexes with these ligands are rare examples of side-on bonded enolether complexes. In catalytic imine hydrogenations, complete conversion (>98 %) was reached in all cases (conditions: p[H(2)] = 50 bar, T = 50 degrees C, t = 2 h, substrate/catalyst 100:1). The best enantiomeric excess (ee = 86 % S isomer) was reached with PhN==CMePh as substrate and the R,R form of the (10-menthyloxy-5H-dibenzo[a,d]cyclohepten-5-yl)diphenylphosphane ligand. The iridium(I) complex containing the same phosphane gave a 60 % ee (S isomer) with the enamide N-(1-phenylvinyl)acetamide as substrate (conditions: p[H(2)] = 4 bar, T = 50 degrees C, t = 18 h, substrate/catalyst = 50:1). These reactions constitute the first examples in which chiral olefins have been used as steering ligands in catalytic enantioselective hydrogenations.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Sep
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| pubmed:issn |
0947-6539
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:day |
6
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| pubmed:volume |
10
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
4198-205
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| pubmed:dateRevised |
2009-8-4
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| pubmed:year |
2004
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| pubmed:articleTitle |
Olefins as steering ligands for homogeneously catalyzed hydrogenations.
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| pubmed:affiliation |
Department of Chemistry and Applied Biosciences, ETH-Hönggerberg, Wolfgang-Pauli-Strasse, 8093 Zürich, Switzerland.
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| pubmed:publicationType |
Journal Article
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