Masking and demasking strategies for the BF2-BODIPYs as a tool for BODIPY fluorophores

An efficient and chemoselective route for transforming BF2-BODIPYs to Et2B-BODIPYs (masking) was developed using Et2AlCl. The Et groups can be easily replaced with F atoms using BF3·Et2O in moist CH2Cl2 to regenerate the BF2-BODIPYs (demasking). The masking-demasking strategy is very useful for synthesizing functionalized BODIPYs via nucleophilic and reductive reactions. The masking strategy was used to synthesize a BODIPY dimer by McMurry coupling of a formyl Et2B-BODIPY, while a new BODIPY with an asymmetrically substituted B-center was synthesized using the demasking strategy.