105837-04-5Relevant articles and documents
Solvent-Free FeCl3-Assisted Electrophilic Fluorine-Catalyzed Knoevenagel Condensation to Yield α,β-Unsaturated Dicarbonyl Compounds and Coumarins
Yang, Lu,Zhu, Jiang,Xie, Fukai,Peng, Xiaoshi,Lin, Bin,Liu, Yongxiang,Cheng, Maosheng
, p. 1053 - 1060 (2019)
A highly environmentally friendly procedure was developed for the Knoevenagel condensation of aromatic aldehydes with diethyl malonate in the presence of FeCl3 and N-fluorobenzenesulfonimide as a source of electrophilic fluorine under solvent-free conditions. The scope of the reaction was explored using commercially available substrates. The reaction with substituted salicylaldehydes afforded the corresponding coumarin derivatives which attract interest due to their potential medicinal importance.
A General Strategy to Enhance Donor-Acceptor Molecules Using Solvent-Excluding Substituents
Asbury, John B.,Hoelzel, Conner A.,Hu, Hang,Jung, Kwan Ho,Karim, Basel A.,Li, Xiaosong,Liu, Yu,Munson, Kyle T.,Wolstenholme, Charles H.,Yennawar, Hemant P.,Zhang, Han,Zhang, Xin
supporting information, p. 4785 - 4792 (2020/02/11)
While organic donor-acceptor (D-A) molecules are widely employed in multiple areas, the application of more D-A molecules could be limited because of an inherent polarity sensitivity that inhibits photochemical processes. Presented here is a facile chemical modification to attenuate solvent-dependent mechanisms of excited-state quenching through addition of a β-carbonyl-based polar substituent. The results reveal a mechanism wherein the β-carbonyl substituent creates a structural buffer between the donor and the surrounding solvent. Through computational and experimental analyses, it is demonstrated that the β-carbonyl simultaneously attenuates two distinct solvent-dependent quenching mechanisms. Using the β-carbonyl substituent, improvements in the photophysical properties of commonly used D-A fluorophores and their enhanced performance in biological imaging are shown.
A versatile long-wavelength-absorbing scaffold for Eu-based responsive probes
Szijjarto, Csongor,Pershagen, Elias,Ilchenko, Nadia O.,Borbas, K. Eszter
supporting information, p. 3100 - 3109 (2013/04/23)
Coumarin-sensitized, long-wavelength-absorbing luminescent Eu III-complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen-based chelating framework that is attached through a short linker to a 7-hydroxycoumarin, a 7-B(OH)2-coumarin, a 7-O-(4-pinacolatoboronbenzyl)-coumarin or a 7-O-(4-methoxybenzyl)-coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high-yielding steps. The sensitivity of coumarin photophysics to the 7-substituent enables modulation of the antenna-absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate-based functionalities (cages) with H2O 2 yielded the corresponding 7-hydroxycoumarin species. The same species was produced with peroxynitrite in a ×106-10 7-fold faster reaction. Both reactions resulted in the emergence of a strong ≈407 nm excitation band, with concomitant decrease of the 366 nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu-complex was quenched by ONOO-. We have shown that preliminary screening of simple coumarin-based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in EuIII-excitation profile in the fully elaborated complex. Taken together, our results show that the 7-hydroxycoumarin antenna is a viable scaffold for the construction of turn-on and ratiometric luminescent probes. A visible change: Eu complexes can be rendered analyte responsive by exploiting the sensitivity of a coumarin antenna to the nature of the 7-substituent (see figure). A boronate switch installed in the 7-position afforded complexes that responded rapidly to μM concentrations of peroxynitrite; the product of this reaction being the corresponding phenol. The analogous reaction with H 2O2 proceeds at a significantly lower rate. As the reaction shifts the absorption to longer wavelengths, the construction of ratiometric probes is possible. Copyright
