Provided herein are improved processes for converting C7-amino-substituted tetracyclines to C7-fluoro-substituted tetracyclines, as well as intermediates produced by or used in these processes. In one embodiment, a thermal fluorination method is provided in which a suspension comprising a non-polar organic solvent and a C7-diazo-substituted tetracycline hexafluorophosphate, hexafluoroarsenate or hexafluorosilicate salt, or a salt, solvate or combination thereof, is heated to provide a C7-fluoro-substituted tetracycline, or salt, solvate or combination thereof. In another embodiment, a photolytic fluorination is provided in which a solution comprising an ionic liquid and a C7-diazo-substituted tetracycline tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate or hexafluorosilicate salt, or a salt, solvate or combination thereof, is irradiated to provide a C7-fluoro-substituted tetracycline, or salt, solvate or combination thereof.