Source:http://linkedlifedata.com/resource/pubmed/id/18357587
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| Predicate | Object |
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| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
14
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| pubmed:dateCreated |
2008-5-5
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| pubmed:abstractText |
With the aid of computations and experiments, the detailed mechanism of the phosphine-catalyzed [3+2] cycloaddition reactions of allenoates and electron-deficient alkenes has been investigated. It was found that this reaction includes four consecutive processes: 1) In situ generation of a 1,3-dipole from allenoate and phosphine, 2) stepwise [3+2] cycloaddition, 3) a water-catalyzed [1,2]-hydrogen shift, and 4) elimination of the phosphine catalyst. In situ generation of the 1,3-dipole is key to all nucleophilic phosphine-catalyzed reactions. Through a kinetic study we have shown that the generation of the 1,3-dipole is the rate-determining step of the phosphine-catalyzed [3+2] cycloaddition reaction of allenoates and electron-deficient alkenes. DFT calculations and FMO analysis revealed that an electron-withdrawing group is required in the allene to ensure the generation of the 1,3-dipole kinetically and thermodynamically. Atoms-in-molecules (AIM) theory was used to analyze the stability of the 1,3-dipole. The regioselectivity of the [3+2] cycloaddition can be rationalized very well by FMO and AIM theories. Isotopic labeling experiments combined with DFT calculations showed that the commonly accepted intramolecular [1,2]-proton shift should be corrected to a water-catalyzed [1,2]-proton shift. Additional isotopic labeling experiments of the hetero-[3+2] cycloaddition of allenoates and electron-deficient imines further support this finding. This investigation has also been extended to the study of the phosphine-catalyzed [3+2] cycloaddition reaction of alkynoates as the three-carbon synthon, which showed that the generation of the 1,3-dipole in this reaction also occurs by a water-catalyzed process.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:issn |
0947-6539
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| pubmed:author | |
| pubmed:issnType |
Print
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| pubmed:volume |
14
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
4361-73
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| pubmed:dateRevised |
2009-8-4
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| pubmed:year |
2008
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| pubmed:articleTitle |
Mechanism, regioselectivity, and the kinetics of phosphine-catalyzed [3+2] cycloaddition reactions of allenoates and electron-deficient alkenes.
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| pubmed:affiliation |
Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
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| pubmed:publicationType |
Journal Article
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