Gold(I)-Catalyzed Cycloisomerization of 2-Fluoroalk-3-yn-1-ones: Synthesis of 2,5-Substituted 3-Fluorofurans

Fluorination of 1,4-disubstituted tert-butyldimethylsilyl but-1-en-3-yn-1-yl ethers with Selectfluor gives 2-mono-fluorobut-3-yn-1-ones. Subsequent 5-endo-dig cyclization in the presence of chlorotriphenylphosphine gold(I)/silver trifluoromethanesulfonate (both 5 mol%, dichloromethane) under ambient conditions, provides a facile method for the generation of mainly 2,5-diaryl-substituted 3-fluorofurans in high yields (89―96%). The structure of 2-(4-bromophenyl)-3-fluoro-5-(4-methylphenyl)furan was confirmed by X-ray crystallography.