Copper-catalyzed α-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 α-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 α-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 α-acylated BODIPY provided an efficient access to α-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.