Electrophilic Cyclizations of 2-Fluoroalk-3-yn-1-ones: Room-Temperature Synthesis of Diversely 2,5-Disubstituted 3,4-Fluorohalofurans

A 5-endo-dig halocyclization of 2-fluoroalk-3-yn-1-ones with the use of N-iodo- and N-bromosuccinimide, in the presence of gold chloride/zinc bromide (5:20 mol-%, dichloromethane), under ambient conditions, provides a facile method for the synthesis of 2,5-disubstituted 3-bromo-4-fluoro- and 3-fluoro-4-iodofurans. The sequential procedure starts at monofluorination of the alk-1-en-3-yn-1-yl silyl ethers with Selectfluor and proceeds with good overall yields (62-78%).