Benjamin Willy, T. Müller
Aug 1, 2008
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Journal
European Journal of Organic Chemistry
Abstract
3,5-Disubstituted and 1,3,5-trisubstituted pyrazoles are readily synthesized from acyl chlorides, terminal alkynes, and hydrazines by a consecutive one-pot three-component Sonogashira coupling/Michael addition/cyclocondensation sequence in good to excellent yields. These pyrazoles are highly fluorescent, both in solution and in the solid state. Investigation of the electronic properties by UV/Vis and fluorescence spectroscopy and by DFT and ZINDO CI computations reveal that the excited state is highly polar and allows fine-tuning of the absorption and emission properties. X-ray structure analyses of 3,5-disubstituted pyrazoles reveal self-organization by hydrogen bonding and π-stacking. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)