Copper-catalyzed ?-selective cross-dehydrogenative coupling of BODIPY dyes with aldehydes: A new route to acylated BODIPYs and dipyrromethenes

A novel copper-catalyzed direct acylation of BODIPYs with aldehydes via C-H bond activation was developed, in which acyl radicals were formed from aldehydes in the presence of TBHP as radical initiator, and selectively reacted with BODIPYs at the alpha-positions. This radical oxidative dehydrogenative cross-coupling reaction showed excellent functional group tolerance, and both heteroaromatic and aliphatic aldehydes could be effectively reacted to BODIPYs. Comparing with those of the corresponding starting BODIPYs, those alpha-acylated BODIPYs showed red-shifted absorption and emission, as well as decreased both HOMO and LUMO energies due to the installation of electron-deficient carbonyl groups. Furthermore, the alpha-acylated BODIPY provided an efficient access to alpha-acylated dipyrrin by removal of the BF2 protecting groups, which showed sensitive and selective "turn-on" fluorescence response toward Zn2+ ion in aqueous buffer solution and living cells.