Synthesis and Optical Properties of 2-(Benzo[b]thiophene-3-yl)pyrroles and a New BODIPY Fluorophore (BODIPY=4,4-Difluoro-4-bora-3a,4a-diaza-sindacene)

摘要

2-(Benzo[b]thiophene-3-yl)- 1-vinylpyrrole has been synthesized directly from 3-acetylbenzo[b]thiophene oxime and acetylene (flow system, KOH-DMSO, 120 8C, 5 h) in 68% yield. Devinylation of the synthesized pyrrole (HgACHTUNGTRENUNG(OAc)2, NaBH4, 508C) led to the corresponding 2-(benzo[b]thiophene- 3-yl)pyrrole in 63% yield. Trifluoroacetylation of both the pyrroles with trifluoroacetic anhydride (80 8C, 1 h) gave the corresponding 5-trifluoroacetyl pyrroles in 97% and 76% yields, respectively. 2-(Benzo[b]thiophene- 3-yl)pyrrole was reacted subsequently with mesityl aldehyde, 2,3-dichloro- 5,6-dicyano-1,4-benzoquinone (DDQ), and BF3·OEt2 to afford 4,4-difluoro- 3,5-diACHTUNGTRENUNG(benzo[b]thiophene-3-yl)- 8-mesityl-4-bora-3a,4a-diaza-s-indacene, a representative of the novel BODIPY fluorophore family (BODIPY=4,4-difluoro-4-bora-3a,4adiaza- s-indacene), in 34% overall yield. The synthesized pyrroles exhibit promising optical properties (absorption and emission spectra, nonlinear optical (NLO) features), superior to existing analogues. The BODIPY fluorophore displays an intense red-shifted fluorescence emission in CH2Cl2 (625 nm, 0.84 fluorescence quantum yield) that is fully preserved in the solid state.