Four- and Five-Component Syntheses and Photophysical Properties of Emission Solvatochromic 3‑Aminovinylquinoxalines

3-Aminovinylquinoxalines
are readily accessible from (hetero)­aryl
glyoxylic acids or heterocyclic π-nucleophiles by consecutive
four- and five-component syntheses in the sense of an activation-alkynylation-cyclocondensation-addition
sequence or glyoxylation-alkynylation-cyclocondensation-addition sequence
in good yields. The title compounds are highly fluorescent with pronounced
emission solvatochromicity and protochromic fluorescence quenching.
Time-resolved fluorescence spectroscopy furnishes radiative and nonradiative
fluorescence decay rates in various solvent polarities. The electronic
structure is corroborated by DFT and TD-DFT calculations rationalizing
the observed spectroscopic effects.