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.
从取代炔酮出发,通过乙基氰乙酸酯的Michael加成-环缩合反应生成α-吡喃酮和/或1H-吡啶。独特的产物形成取决于反应条件以及炔酮的电子取代模式。虽然电子给予基团提供α-吡喃酮作为主要产物,但电子提取基团主要给出相应的1H-吡啶。这两类杂环在溶液和固态中均发出荧光。特别是二甲氨基取代的α-吡喃酮作为给体-受体系统,显示出显著的光物理性质,如强烈的红移吸收和发射最大值,具有日光荧光和溶液中高达99%的荧光量子产率,固态中约为11%,以及明显的发射溶剂致色变。此外,给体取代的α-吡喃酮显示出明显的聚集诱导发射增强。