Source:http://linkedlifedata.com/resource/pubmed/id/17474744
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pubmed-article:17474744 | rdf:type | pubmed:Citation | lld:pubmed |
pubmed-article:17474744 | lifeskim:mentions | umls-concept:C0439659 | lld:lifeskim |
pubmed-article:17474744 | lifeskim:mentions | umls-concept:C0441712 | lld:lifeskim |
pubmed-article:17474744 | lifeskim:mentions | umls-concept:C1710028 | lld:lifeskim |
pubmed-article:17474744 | lifeskim:mentions | umls-concept:C0332514 | lld:lifeskim |
pubmed-article:17474744 | pubmed:issue | 21 | lld:pubmed |
pubmed-article:17474744 | pubmed:dateCreated | 2007-5-23 | lld:pubmed |
pubmed-article:17474744 | pubmed:abstractText | Asymmetric cross-coupling of aryl iodides (ArI) with secondary arylphosphines (PHMe(Ar'), Ar' = (2,4,6)-R3C6H2; R = i-Pr (Is), Me (Mes), Ph (Phes)) in the presence of the base NaOSiMe3 and a chiral Pd catalyst precursor, such as Pd((R,R)-Me-Duphos)(trans-stilbene), gave the tertiary phosphines PMe(Ar')(Ar) in enantioenriched form. Sterically demanding secondary phosphine substituents (Ar') and aryl iodides with electron-donating para substituents resulted in the highest enantiomeric excess, up to 88%. Phosphination of ortho-substituted aryl iodides required a Pd(Et-FerroTANE) catalyst but gave low enantioselectivity. Observations during catalysis and stoichiometric studies of the individual steps suggested a mechanism for the cross-coupling of PhI and PHMe(Is) (1) initiated by oxidative addition to Pd(0) yielding Pd((R,R)-Me-Duphos)(Ph)(I) (3). Reversible displacement of iodide by PHMe(Is) gave the cation [Pd((R,R)-Me-Duphos)(Ph)(PHMe(Is))][I] (4), which was isolated as the triflate salt and crystallographically characterized. Deprotonation of 4-OTf with NaOSiMe3 gave the phosphido complex Pd((R,R)-Me-Duphos)(Ph)(PMeIs) (5); an equilibrium between its diastereomers was observed by low-temperature NMR spectroscopy. Reductive elimination of 5 yielded different products depending on the conditions. In the absence of a trap, the unstable three-coordinate phosphine complex Pd((R,R)-Me-Duphos)(PMeIs(Ph)) (6) was formed. Decomposition of 5 in the presence of PhI gave PMeIs(Ph) (2) and regenerated 3, while trapping with phosphine 1 during catalysis gave Pd((R,R)-Me-Duphos)(PHMe(Is))2 (7), which reacted with PhI to give 3. Deprotonation of 1:1 or 1.4:1 mixtures of cations 4-OTf gave the same 6:1 ratio of enantiomers of PMeIs(Ph) (2), suggesting that the rate of P inversion in 5 was greater than or equal to the rate of reductive elimination. Kinetic studies of the first-order reductive elimination of 5 were consistent with a Curtin-Hammett-Winstein-Holness (CHWH) scheme, in which pyramidal inversion at the phosphido ligand was much faster than P-C bond formation. The absolute configuration of the phosphine (SP)-PMeIs(p-MeOC6H4) was determined crystallographically; NMR studies and comparison to the stable complex 5-Pt were consistent with an RP-phosphido ligand in the major diastereomer of the intermediate Pd((R,R)-Me-Duphos)(Ph)(PMeIs) (5). Therefore, the favored enantiomer of phosphine 2 appeared to be formed from the major diastereomer of phosphido intermediate 5, although the minor intermediate diastereomer underwent P-C bond formation about three times more rapidly. The effects of the diphosphine ligand, the phosphido substituents, and the aryl group on the ratio of diastereomers of the phosphido intermediates Pd(diphos*)(Ar)(PMeAr'), their rates of reductive elimination, and the formation of three-coordinate complexes were probed by low-temperature 31P NMR spectroscopy; the results were also consistent with the CHWH scheme. | lld:pubmed |
pubmed-article:17474744 | pubmed:language | eng | lld:pubmed |
pubmed-article:17474744 | pubmed:journal | http://linkedlifedata.com/r... | lld:pubmed |
pubmed-article:17474744 | pubmed:status | PubMed-not-MEDLINE | lld:pubmed |
pubmed-article:17474744 | pubmed:month | May | lld:pubmed |
pubmed-article:17474744 | pubmed:issn | 0002-7863 | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:RheingoldArno... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:IncarvitoChri... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:AndersonBrian... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:BrunkerTim... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:ZakharovLev... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:MoncarzJillia... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:GlueckDavid... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:GolenJames... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:ScribanCorina... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:BlankNatalia... | lld:pubmed |
pubmed-article:17474744 | pubmed:author | pubmed-author:AmirOmarO | lld:pubmed |
pubmed-article:17474744 | pubmed:issnType | lld:pubmed | |
pubmed-article:17474744 | pubmed:day | 30 | lld:pubmed |
pubmed-article:17474744 | pubmed:volume | 129 | lld:pubmed |
pubmed-article:17474744 | pubmed:owner | NLM | lld:pubmed |
pubmed-article:17474744 | pubmed:authorsComplete | Y | lld:pubmed |
pubmed-article:17474744 | pubmed:pagination | 6847-58 | lld:pubmed |
pubmed-article:17474744 | pubmed:year | 2007 | lld:pubmed |
pubmed-article:17474744 | pubmed:articleTitle | Palladium-catalyzed asymmetric phosphination. Scope, mechanism, and origin of enantioselectivity. | lld:pubmed |
pubmed-article:17474744 | pubmed:affiliation | Contribution from the 6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA. | lld:pubmed |
pubmed-article:17474744 | pubmed:publicationType | Journal Article | lld:pubmed |
http://linkedlifedata.com/r... | pubmed:referesTo | pubmed-article:17474744 | lld:pubmed |