A series of new sulfur heteroarenes, isoelectronic with dibenzo[g,p]chrysene, have been prepared by double photocyclization of the corresponding tetraaryl substituted ethenes. The first step proceeds efficiently in each case, and the corresponding intermediate sulfur heteroarenes, isoelectronic with phenanthrene, have been isolated. The second ring closure is only efficient when one of the participating aryl substituents is thienyl, which thus manifests a higher electron density on the carbon atom involved in the excited singlet state reaction. Most of the new compounds are of minimal solubility in common solvents and do not display improved electron donor properties otherwise commonly found among heteroaromatics.
Synthesis of New Sulfur Heteroaromatics Isoelectronic with Dibenzo(g,p) chrysene by Photocyclization of Thienyl-and Phenyl-Substituted Ethenes.-The photocyclization of sulfur-containing tetraaryl substituted ethenes proceeds for the first step efficiently in each case forming sulfur heteroarenes isoelectronic with phenanthrene. The second photolytic ring closure to give the title compounds is only efficient when one of the participating aryl substituents is thienyl. The new compounds are minimal soluble and do not display improved electron donor properties. -(FISCHER, E.; LARSEN, J.; CHRISTENSEN, J. B.; FOURMIGUE, M.; MADSEN, H. G.; HARRIT, N.; J. Org. Chem. 61 (1996) 20, 6997-7005; Dep. Chem., Univ. Copenhagen, DK-2100 Copenhagen, Den.; EN)
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