The reaction of 2,7-diaminofluorene (I) with NaNO2 and tetrafluoroboric acid in THF-water gives the bisdiazonium tetrafluoroborate (II), which by decomposition in refluxing xylene yields 2,7-difluorofluorene (III). The oxidation of (III) with KMnO4 in pyridine affords 2,7-difluoro-9-fluorenone (IV), which is cyclized with KCN and ammonium carbonate in refluxing ethanol.

The reaction of 2,7-diaminofluorene (I) with NaNO2 and tetrafluoroboric acid in THF-water gives the bisdiazonium tetrafluoroborate (II), which by decomposition in refluxing xylene yields 2,7-difluorofluorene (III). The oxidation of (III) with KMnO4 in pyridine affords 2,7-difluoro-9-fluorenone (IV), which is cyclized with KCN and ammonium carbonate in refluxing ethanol.

The reaction of 2,7-diaminofluorene (I) with NaNO2 and tetrafluoroboric acid in THF-water gives the bisdiazonium tetrafluoroborate (II), which by decomposition in refluxing xylene yields 2,7-difluorofluorene (III). The oxidation of (III) with KMnO4 in pyridine affords 2,7-difluoro-9-fluorenone (IV), which is cyclized with KCN and ammonium carbonate in refluxing ethanol.