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Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity
Xiao Xiao1, Brian P Woods1, Wen Xiu1
1Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota, 55455, USA.
Abstract:
The reaction of an aryne with an alkyne to generate a benzocyclobutadiene (BCB) intermediate is rare. We report here examples of this reaction, revealed by Diels-Alder trapping of the BCB by either pendant or external electron-deficient alkynes. Mechanistic delineation of the reaction course is supported by DFT calculations. A three-component process joining the benzyne first with an electron-rich and then with an electron-poor alkyne was uncovered. Reactions in which the BCB functions in a rarely observed role as a 4π diene component in Diels-Alder reactions are reported. The results also shed new light on aspects of the hexadehydro-Diels-Alder reaction used to generate the benzynes.
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