Organic Letters 2001-07-26

Synthesis of dixanthones and poly(dixanthone)s by cyclization of 2-aryloxybenzonitriles in trifluoromethanesulfonic acid.

H M Colquhoun, D F Lewis, D J Williams

Index: Org. Lett. 3(15) , 2337-40, (2001)

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Abstract

[reaction: see text] 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.