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Alkane desaturation by concerted double hydrogen atom transfer to benzyne
Benzynes are capable of concerted removal of two vicinal hydrogen atoms from a hydrocarbon, a discovery enabled by the thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates. A new route for C–H activation This paper...
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Published in: | Nature (London) 2013-09, Vol.501 (7468), p.531-534 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Benzynes are capable of concerted removal of two vicinal hydrogen atoms from a hydrocarbon, a discovery enabled by the thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates.
A new route for C–H activation
This paper reports a new route for the dehydrogenation of an alkane to an alkene — a reaction of long-standing interest to synthetic chemists. The authors show that benzynes are capable of concerted, bimolecular removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this chemical transformation was enabled by the thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates. This appears to be the first report of a single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane.
The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists
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,
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. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids
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, eicosanoids, gibberellins
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and carotenoids
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. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or σ-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels–Alder cycloisomerization reaction of triyne substrates
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. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C–H bonds in the alkane donor. |
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ISSN: | 0028-0836 1476-4687 |
DOI: | 10.1038/nature12492 |