Source:http://linkedlifedata.com/resource/pubmed/id/15578710
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
2
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| pubmed:dateCreated |
2005-1-10
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| pubmed:abstractText |
The mechanism of Pt(II)-catalyzed intramolecular cycloisomerization of allenyne systems has been extensively investigated by DFT calculations. Different mechanistic schemes have been proposed and discussed, including the Alder-ene reaction. The free energy results suggest that the kinetically preferred reaction pathway for precursors that are tri- and tetrasubstituted on the allene moiety should proceed by a five-step mechanism. This would involve formation of a platina(IV)cyclopentene intermediate by selective engagement of the external pi bond of the allene, which would undergo regioselective beta-H elimination from the equatorially disposed methyl group. A metal-induced H migration leads to a second octahedral Pt(IV)-chelate complex, which would yield the expected bicyclic system through an intramolecular migratory insertion step. Therefore, depending on the conformation of the initial eta(4)-reactant complex for trisubstituted patterns, two possible intermediates can be formed that would evolve through different paths. In these cases, the regio- and stereochemical outcomes predicted by the mechanistic scheme proposed agree with experimental data. Substituted precursors on the alkyne moiety follow a distinct, four-step, mechanism also involving an oxidative cyclometalation process to an octahedral Pt(IV) intermediate complex. Theoretical results reveal the kinetic preference for beta-H elimination from the allylic group rather than from the gem-dimethyl group, which should account for the observed regioselectivity.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Jan
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| pubmed:issn |
0947-6539
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:day |
7
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| pubmed:volume |
11
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
521-33
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| pubmed:dateRevised |
2009-8-4
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| pubmed:year |
2005
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| pubmed:articleTitle |
A DFT-based theoretical investigation of the mechanism of the PtCl2-mediated cycloisomerization of allenynes.
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| pubmed:affiliation |
Sección de Síntesis Orgánica e Imagen Molecular por Resonancia Magnética, Instituto Universitario de Investigación, UNED, Facultad de Ciencias, 28040 Madrid, Spain. esoriano@arrakis.es
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| pubmed:publicationType |
Journal Article
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