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Synthesis of Dixanthones and Poly(dixanthone)s by Cyclization of 2-Aryloxybenzonitriles in Trifluoromethanesulfonic Acid

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journal contribution
posted on 06.07.2001, 00:00 authored by Howard M. Colquhoun, David F. Lewis, David J. Williams
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.