Synthesis of Dixanthones and Poly(dixanthone)s by Cyclization of 2-Aryloxybenzonitriles in Trifluoromethanesulfonic Acid
摘要:
[GRAPHICS]Condensation of 2-fluorobenzonitriles with phenoxides affords 2-aryloxybenzonitriles that cyclize cleanly in trifluoromethanesulfonic acid at room temperature to give xanthone-iminium triflates, The C=N bond in these compounds is remarkably resistant to hydrolysis, but prolonged reaction with strong aqueous acid under vigorous conditions affords xanthones in good yield. The synthesis is exemplified for a novel series of polynuclear dixanthones and for a high molar mass polyxanthone derived from the previously unreported monomer 3,3 ' -difluoro-4,4 ' biphenyldicarbonitrile.
Three dixanthones (1–3) and an unprecedented C3h‐symmetric trixanthone (4) were synthesized through a three‐step approach in overall yields above 63 %. These compounds possessed a planar π‐conjugated system and formed tight face‐to‐face columnar stacks, as confirmed by single‐crystal structural analysis. In comparison with xanthone, the fluorescence emissions of compounds 1–4 showed significant red‐shifts
Synthesis of Dixanthones and Poly(dixanthone)s by Cyclization of 2-Aryloxybenzonitriles in Trifluoromethanesulfonic Acid
作者:Howard M. Colquhoun、David F. Lewis、David J. Williams
DOI:10.1021/ol010097+
日期:2001.7.1
[GRAPHICS]Condensation of 2-fluorobenzonitriles with phenoxides affords 2-aryloxybenzonitriles that cyclize cleanly in trifluoromethanesulfonic acid at room temperature to give xanthone-iminium triflates, The C=N bond in these compounds is remarkably resistant to hydrolysis, but prolonged reaction with strong aqueous acid under vigorous conditions affords xanthones in good yield. The synthesis is exemplified for a novel series of polynuclear dixanthones and for a high molar mass polyxanthone derived from the previously unreported monomer 3,3 ' -difluoro-4,4 ' biphenyldicarbonitrile.