Substitution of hydroxide by fluoride at the boron center of a BODIPY dye

4-Chloro-4-phenyl-1,3,5,7,8-pentamethyl-3a,4a-diaza-4-bora-s-indacene (2) has been synthesized, structurally characterized and converted into the corresponding hydroxide derivative 4-hydroxo-4-phenyl-1,3,5,7,8-pentamethyl-3a,4a-diaza-4-bora-s-indacene (3). This boron hydroxide derivative reacts with fluoride anions under acidic conditions to afford the corresponding fluoride derivative 4-fluoro-4-phenyl-1,3,5,7,8-pentamethyl-3a,4a-diaza-4-bora-s-indacene (4). This simple reaction may become useful for the incorporation of [18F]-fluoride and may serve for the preparation of radiolabeled BODIPY derivatives.