Six diphenylacetylene fluorophores were synthesized for potential fluorescence detection of amyloid ß protein plaques, which are one of the most important biomarkers of Alzheimer disease. From commercial 4-ethynyl-N,N-dimethylaniline and
4'-bromoacetophenone, ketone was obtained by Sonogashira coupling, which served as a substrate for all further transformations. The following compounds were prepared by various types of condensations and intramolecular cyclizations through reactions of the starting ketone with malononitrile, DMF-DMA, cyanoacetic acid, ethyl acetate and 2-cyano-3,3-bis(methylthio)acrylate. The prepared compounds were fully characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry (HRMS), and for solid compounds melting point was determined. The purity of the compound was verified by high performance liquid chromatography (HPLC). Absorption, emission, and excitation spectra were compared to determine how the presence of different electron-withdrawing groups affects the optical properties of the prepared molecules. The quantum yield and molar absorptivity were calculated. The results of the optical measurements were interpreted in the context of the applicability of the new compounds as potential molecular probes for the diagnosis of Alzheimer disease.
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