Rhodium-catalyzed [2+2+2] cycloaddition of various fluorine-containing alkynes--novel synthesis of multi-substituted fluoroalkylated aromatic compounds.

Treatment of various fluorinated internal alkynes with 10 mol% of RhCl(3).H(2)O and 30 mol% of i-Pr(2)NEt in toluene at the reflux temperature for 18 h gave the corresponding trimerization products as an isomeric mixture in high yields. Cycloaddition using 1.0 equiv. of fluorinated alkynes and 2.0 equiv. of non-fluorinated alkynes under the same reaction conditions as in the trimerization led to mono- and bis-fluoroalkylated benzene derivatives in high yields, together with small amounts of trimerization products. The reaction of fluorine-containing bispropargyl ether with non-fluorinated alkynes took place smoothly to afford the corresponding bicyclic molecules in good to high yields.