Derivatives of Octaethynylphenazine and Hexaethynylquinoxaline

摘要

In 1986, hexaethynylbenzene, the first peralkynylated perimeter, was obtained by Vollhardt and co-workers.[1] Since then, peralkynylated cyclobutadiene complexes, cymantrenes, ferrocenes, cylcopentadienyl radicals, thiophenes, and extended systems derived from tetraethynylethylenes and hexaethynylbenzenes have been reported.[2]-[7] Peralkynylated N-heterocycles are scarce, and only recently peralkynylpyrazinophorphyrazine and triethynyltriazine were reported.[8], [9] Dialkynylated pentacenes, hexacenes, and heptacenes play a significant role in materials science and are fairly easily accessible.[10] Peralkynylated acenes as a class, however, are entirely unknown; the peri interactions in acenes would result in steric crowding of the alkynes and their all-too-close spacing would lead to Bergman-type reactions. If the peri interactions could be removed in naphthalene, anthracene, or the larger acenes, peralkynylation should be possible: Hexaethynylquinoxaline and octaethynylphenazine are attractive synthetic targets that might show promise as n-type semiconductors and as unusual sensory platforms for metal cations.[11] Herein, we report the synthesis of the first representatives of the heteroacenes, namely, hexaethynylquinoxaline and octaethynylphenazine.