Synthesis of BODIPY Derivatives

In a three-necked
100 mL round-bottom flask, BODIPY derivatives
(4–6) (1 eqv.) and compound 1 (2.4 eqv.) were dissolved in 40 mL of benzene. Piperidine
(0.3 mL) and glacial acetic acid (0.3 mL) were added. The solution
was refluxed using a Dean–Stark apparatus. When the solution
was concentrated, the reaction was followed by TLC until the starting
compound (4–6) was consumed. The
reaction mixture was extracted with dichloromethane/water (200 mL,
three times), and the organic layer was dried over anhydrous Na₂SO₄ and concentrated on a rotary evaporator until
the solvent was removed. Compounds 7–9 were isolated by column chromatography on silica gel (230–400
mesh).