A kinetic-controlled photocatalyst-free visible-light-induced stereoselective synthesis of α,α-gem-difluoro-Z-allyl esters was succeeded at room temperature in moderate to excellent yields with up to Z-isomer-only stereoselectivities through a reductive radical ethoxycarbonyldifluoromethylation of terminal aryl alkynes with blue LED (465 nm)-excited Hantzsch ester. The geometry optimizations obtained by the DFT/B3LYP calculation with a standard 6-31G(d,p) basis set were also employed for the mechanism study on the formation of a key α,α-difluoroallyl ester radical intermediate, which was generated from the addition of the ethoxycarbonyldifluoromethyl radical to aryl alkyne substrates and the stabilization effect of the neighboring group. Subsequent steric hindrance-determined hydrogen generated from the Hantzsch ester radical cation led to the formation of final aryl-substituted Z-difluoroallyl esters. This methodology provided convenient access to the synthetically important Z-configured gem-difluoroallylic building blocks.

The 0.2μm ultrathin fluoroacrylic emulsion coating wrapped effective microporous non-woven air filtration membranes were made for the PPE masks with up to 99.9% filtration efficiencies for both 0.3μm NaCl aerosol...