title: Synthesis of dixanthones and poly(dixanthone)s by cyclization of 2-aryloxybenzonitriles in trifluoromethanesulfonic acid.
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.
authors.affiliation: Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK. h.m.colquhoun@rdg.ac.uk
authors.forename: H M
authors.initials: HM
authors.lastname: Colquhoun
authors.forename: D F
authors.initials: DF
authors.lastname: Lewis
authors.forename: D J
authors.initials: DJ
authors.lastname: Williams