BODIPYS in Multicomponent Reactions. Synthesis of BODIPY-4H-Pyran Hybrids

The Liebeskind-Srogl (LSCC) and Suzuki cross-coupling reactions were employed to prepare 10 formyl-substituted BODIPY dyes in high yields (64-98%). These derivatives were reacted with malononitrile, ethyl acetoacetate and ammonium hydroxide in a multicomponent reaction (MCR) to furnish highly substituted 4H-pyranes. In Method A, conventional heating was employed to prepare nine such derivatives in yields that range from 25 to 72%. In Method B, six derivatives were prepared under ultrasound-activation in 35-64% isolated yields and reduced reaction times. The photophysical properties of the 4H-pyranes thus prepared were measured. A rather low fluorescence quantum yield (Φ_F = 0.61-5.67%) of the products was observed. Moreover, absorption and emission are in accordance with typical for BODIPY green-yellow region. Finally, it was observed excellent chromophore behavior (log ε_max = 3.94-4.91 M^-1 cm^-1) and moderate Stokes shift values for the product series (599-728 cm^-1), and finally 2,3,5,6-tetraarylBODIPY product with absorption and emission displaced to red (627 and 718 nm, respectively).