A highly efficient, one-pot synthesis of benzo[b]fluoren-10-ones

5,11-Dioxa- and 5-oxa-11-thiabenzo[b]fluoren-10-ones were prepared via a one-pot procedure initiated by the reaction of salicylates or thiasalicylates with ortho fluoro-α-bromoacetophenones in the presence of cesium carbonate. The reactions proceeded in good yield and the final products were obtained without chromatography. The reaction presumably proceeds via a sequential intermolecular alkylation, intramolecular acylation sequence concluded by an intramolecular, ipso-fluoro substitution.