Highly Convergent Synthesis of Intensively Blue Emissive Furo[2,3-c]isoquinolines by a Palladium-catalyzed Cyclization Cascade of Unsaturated Ugi Products

reserved5siA convergent and diversity-oriented approach to the unusual furo[2,3-c]isoquinoline scaffold is presented. This serendipity-driven approach is characterized by an Ugi multicomponent reaction, which gives the substrate for a palladium-catalyzed insertion-alkynylation-cycloisomerization cascade to provide the furo[2,3-c]isoquinolines in moderate to high yield. Upon UV excitation, all representatives are intensively blue luminescent, as observed by the naked eye, and quantitative fluorescence spectroscopy reveals a considerable effect of the substitution pattern on the quantum yields. The electronic structure is semiquantitatively rationalized by DFT and time-dependent DFT calculations.mixedMoni, L.; Gers-Panther, C.; Anselmo, M.; Müller, T. J. J.; Riva, R.Moni, Lisa; Gers Panther, C.; Anselmo, Manuel; Müller, T. J. J.; Riva, Renat

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