Facile syntheses of various per- or polyfluoroalkylated internal acetylene derivatives

Treatment of per- or polyfluoroalkylated vinyl iodides 5 with 2 equiv. of n-BuLi in THF produced the corresponding lithium acetylides in situ, which were transformed into zinc acetylides by the addition of ZnCl2.TMEDA complex into the reaction mixture. The in situ generated zinc acetylides were exposed to the cross-coupling conditions such as ArI/cat. Pd(PPh3)(4), reflux, 6-12 h, giving rise to the desired per- or polyfluoroalkylated acetylenes in high yields. In the case of trifluoromethylated acetylene, commercially available 2-bromo-3,3,3-trifluoropropene 6 could also be used instead of 5 as the starting material. In the acetylenes having a fluoroalkyl group and an aliphatic side chain, vinyl iodides 7, prepared by radical addition of perfluoroalkyl iodide to terminal acetylenes, were treated with t-BuOK at room temperature or at the reflux temperature of benzene, affording the desired compounds in good yields. (C) 2003 Elsevier Ltd. All rights reserved.