Copper-catalyzed cascade radical cyclization of alkynoates: construction of aryldifluoromethylated coumarins.

A mild and simple method is reported for the construction of 3-difluoroarylmethylated coumarins using α,α-difluoroarylacetic acids as an easily handled difluoromethyl source in reaction with ester 3-arylpropiolates under the promotion of copper. The reaction involves a proposed radical-triggered domino decarboxylative aryldifluoromethylation/5-exo cyclization/ester migration process that directly forms Csp2-CF2Ar and C-C bonds with good functional group tolerance.

Efficiently Improved Photoluminescence in Cesium Lead Halide Perovskite Nanocrystals by Using Bis(trifluoromethane)sulfonimide.

Cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (NCs) have attracted enormous attention because of their great potential for optoelectronic applications, such as light-emitting diodes (LEDs). However, the photoluminescence and surface ligands of CsPbX3 NCs have a great impact on their device applications. Herein, we report a molecular superacid of bis(trifluoromethane)sulfonimide (TFSI), which could boost the photoluminescence in the metal halide perovskite nanocrystals. In particular, the photoluminescence quantum yield (PLQY) of CsPbI3 nanocrystals could be greatly improved from 28.6% to near 100% with the superacid treatment. The improved PLQY in CsPbX3 nanocrystals is mainly contributed from the surface passivation based on the characterizations. The CsPbX3 nanocrystals were further modified with PMMA, which could greatly improve their stability while preserving high photoluminescence and good dispersion. The use of superacid combined with a polymer for improving the photoluminescence and stability in CsPbX3 provides an alternative strategy for optoelectronics.