Source:http://linkedlifedata.com/resource/pubmed/id/18373345
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| Predicate | Object |
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| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
16
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| pubmed:dateCreated |
2008-4-18
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| pubmed:abstractText |
The detailed mechanism for the diboration of aldehydes catalyzed by (NHC)Cu(boryl) complexes (NHC = N-heterocyclic carbene) was studied with the aid of DFT by calculating the relevant intermediates and transition states. The results show that the catalyzed diboration occurs through aldehyde insertion into Cu-B to give a Cu-O-C(boryl) species followed by sigma-bond metathesis with a diboron reagent. It is the "electron-richness", that is, the nucleophilicity of the Cu-boryl bond, which gives rise to a small insertion barrier and determines the direction of insertion. The results of our calculations also explain the formation of the product, observed experimentally, from the stoichiometric reaction of (IPr)Cu-Bpin (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with mesitylaldehyde. In the absence of a diboron reagent, the insertion intermediate having a Cu-O-C(boryl) linkage isomerizes to the thermodynamically preferred Cu-C-O(boryl) isomer via a boryl migration to the metal-bonded oxygen through an S(E)2-like transition state. We have also studied the catalyzed diboration of 2-pyridinecarboxaldehyde, which gives the unexpected reductive coupling product 1,2-di-2-pyridyl-1,2-bis(pinacolboroxy)ethane. The insertion intermediate, which contains a coordinated pyridyl group, isomerizes easily to a 1,2-dihydropyridine form, preventing its metathesis with a diboron reagent to give the expected diboration product as observed for other aldehyde substrates.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Apr
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| pubmed:issn |
1520-5126
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| pubmed:author | |
| pubmed:issnType |
Electronic
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| pubmed:day |
23
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| pubmed:volume |
130
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| pubmed:owner |
NLM
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| pubmed:authorsComplete |
Y
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| pubmed:pagination |
5586-94
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| pubmed:year |
2008
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| pubmed:articleTitle |
DFT studies on the mechanism of the diboration of aldehydes catalyzed by copper(I) boryl complexes.
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| pubmed:affiliation |
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
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| pubmed:publicationType |
Journal Article
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