Phosphine-assisted annulation of 2,5-diarylfuran-3,4-dicarbaldehydes with maleimides provided the title isobenzofurans in satisfactory yields. An effect of the substituents at the para position of the aryl groups in these isobenzofurans was demonstrated clearly by a red shift in their UV-vis absorption and emission spectra. They were transformed into the corresponding naphthalene-2,3:6,7-bis(dicarboximide)s by Diels-Alder reaction with another maleimide and subsequent dehydration with the aid of trifluoromethanesulfonic acid. Emission behavior of the title bis(dicarboximide)s is also described.
Phosphine-assisted annulation of thiophene-2,3-dicarbaldehyde with N-substituted maleimides provided the N-substituted benzo[b]thiophene-5,6-dicarboximides in good to high yields. Introduction of cyano and aryl groups to the thiophene moiety of the N-cyclohexyl product was achieved by metal-catalyzed coupling reactions via its bromo derivative. Photophysical properties of the products were also reported.
The title arene-dicarboximides 8a-8d, having a benzo[k]fluoranthene skeleton, were synthesized in two steps from N-phenyl-1, 3-diarylisobenzofuran-5, 6-dicarboximides 4a-4d by the Diels-Alder reaction with acenaphthylene and subsequent dehydration with trifluoromethanesulfonic acid. Under photo-excitation these dicarboximides emit blue light, notably, with high quantum yields.
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