Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

Abstract

Starting from substituted alkynones, α-pyrones and/or 1H-pyridines were generated in a Michael addition–cyclocondensation with ethyl cyanoacetate. The peculiar product formation depends on the reaction conditions as well as on the electronic substitution pattern of the alkynone. While electron-donating groups furnish α-pyrones as main products, electron-withdrawing groups predominantly give the corresponding 1H-pyridines. Both heterocycle classes fluoresce in solution and in the solid state. In particular, dimethylamino-substituted α-pyrones, as donor–acceptor systems, display remarkable photophysical properties, such as strongly red-shifted absorption and emission maxima with daylight fluorescence and fluorescence quantum yields up to 99% in solution and around 11% in the solid state, as well as pronounced emission solvatochromism. Also a donor-substituted α-pyrone shows pronounced aggregation-induced emission enhancement.

Heterocycles by Consecutive Multicomponent Syntheses via Catalytically Generated Alkynoyl Intermediates

“…Moreover, a consecutive four-component alkynylation-Michael addition-cyclocondensation-ammonolysis sequence has been conceived by adding an excess of ammonia in the final step. After reaction at 90 • C for 4 h a mixture of α-pyridones with and without ester functionality were obtained in moderate yields, while the ester separated α-pyridones were in the majority because of the concomitant acyl cleavage [96].…”