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DOI: 10.1055/s-2008-1042714
End-Substituted Pentacenes
Contributor(s):Timothy M. Swager, Jeewoo LimUniversity of Oxford, UK
Three-Step Synthesis of End-Substituted Pentacenes
J. Org. Chem. 2007, 72: 9776-9778
Publication History
Publication Date:
21 February 2008 (online)
Key words
pentacenes - organic semiconductors - Negishi’s reagent
Significance
Pentacenes constitute a class of compounds with potential applications as organic semiconductors. In order to overcome the low stability and solubility of unsubstituted pentacenes, various derivatives have been studied. This synthesis represents a homologation approach to pentacenes first developed by Takahashi and co-workers (J. Am. Chem. Soc. 2000, 122, 12876). The novelty of this approach reported by the authors is that it is symmetric and requires fewer steps.
Comment
In the oxidation of tetrahydropentacenes (2a-c) by DDQ to pentacenes (1a-c), the authors report formation of incompletely oxidized byproducts. In cases where R = Me or Ph, these byproducts could be separated by precipitation in methanol. For R = TMS, where byproducts were also soluble in methanol, excess of DDQ was used to ensure full oxidation. This led to the formation of 3, which was transformed to 1c via reverse Diels-Alder reaction driven by 1,3-cyclohexadiene.