157119-18-1Relevant academic research and scientific papers
Sequential Cu-Catalyzed Four- and Five-Component Syntheses of Luminescent 3-Triazolylquinoxalines
Merkt, Franziska K.,Pieper, Konstantin,Klopotowski, Maximilian,Janiak, Christoph,Müller, Thomas J. J.
, p. 9447 - 9455 (2019)
3-Triazolylquinoxalines can be readily synthesized by applying two complementary synthetic protocols starting from heterocyclic π nucleophiles or (hetero)aryl glyoxylic acids in a consecutive four- or five-component reaction. Conceptually, the sequential use of a single cuprous salt for alkynylation and Cu-catalyzed alkyne-azide cycloaddition (CuAAC) in a one-pot fashion sets the stage for activation-alkynylation-cyclocondensation-CuAAC or glyoxylation-alkynylation-cyclocondensation-CuAAC sequences in good yields. The diversity-oriented generation of differently substituted 3-triazolylquinoxalines is an excellent entry to tunable emission solvatorchromic fluorophores with triazole ligation. The electronic structure, corroborated by DFT and TD-DFT calculations, rationalizes the charge transfer character of relevant absorptions and large Stokes shifts as well as the electronic innocence of the triazole substituents.
Three-Component Activation/Alkynylation/Cyclocondensation (AACC) Synthesis of Enhanced Emission Solvatochromic 3-Ethynylquinoxalines
Merkt, Franziska K.,H?wedes, Simon P.,Gers-Panther, Charlotte F.,Gruber, Irina,Janiak, Christoph,Müller, Thomas J. J.
, p. 8114 - 8125 (2018/04/02)
2-Substituted 3-ethynylquinoxaline chromophores can be readily synthesized by a consecutive activation–alkynylation–cyclocondensation (AACC) one-pot sequence in a three-component manner. In comparison with the previously published four-component glyoxylation starting from electron-rich π-nucleophiles, the direct activation of (hetero)aryl glyoxylic acids allows the introduction of substituents that cannot be directly accessed by glyoxylation. By introducing N,N-dimethylaniline as a strong donor in the 2-position, the emission solvatochromicity of 3-ethynylquinoxalines can be considerably enhanced to cover the spectral range from blue–green to deep red–orange with a single chromophore in a relatively narrow polarity window. The diversity-oriented nature of the synthetic multicomponent reaction concept enables comprehensive investigations of structure–property relationships by Hammett correlations and Lippert–Mataga analysis, as well as the elucidation of the electronic structure of the emission solvatochromic π-conjugated donor–acceptor systems by DFT and time-dependent DFT calculations with the PBEh1PBE functional for a better reproduction of the dominant charge-transfer character of the longest wavelength absorption band.
