Conversion of Ketones into Blue-Emitting Electron-Deficient Benzofurans

A novel heavy metal-free and safe synthetic methodology enabling one-step conversion of ketones into corresponding 4,5,6,7-tetrafluorobenzofurans (F₄ BFs) has been developed. The presented approach has numerous advantageous qualities, including utilization of readily available substrates, broad scope, scalability, and good reaction yields. Importantly, some of the benzofurans prepared by this method were heretofore inaccessible by any other known transformation. Importantly, furo[2,3-b]pyrazines and heretofore unexplored difuro[2,3-c:3',2'-e]pyridazine can be prepared using this strategy. Spectroscopic studies reveal that for simple systems, absorption and fluorescence maxima fall within the UV spectral range, while π-electron system expansion red-shifts both spectra. Moreover, the good fluorescence quantum yields observed in solution, up to 96 %, are also maintained in the solid state. Experimental results are supported by density functional theory (DFT) calculations. The presented methodology, combined with the spectroscopic characteristics, suggest the possibility of using F₄ BFs in the optoelectronic industry (i. e., organic light emitting devices (OLED), organic field-effect transistors (OFET), organic photovoltaics (OPV)) as inexpensive and readily available emissive or semiconductor materials.