A new application of (polyfluoroorgano)trifluoroborate salts: the palladium-catalysed cross-coupling reaction with substituted benzenediazonium tetrafluoroborates

For the first time (polyfluoroorgano)trifluoroborate salts, namely K[C₆F₅BF₃], K[C₆HF₄BF₃] (all three isomers), K[3,4,5-C₆H₂F₃BF₃], and K[CF₂CFBF₃] were principally applied as reagents to Pd-catalysed cross-coupling reactions. A series of polyfluorinated biphenyls C₆H_5−nF_n-C₆H₄X-4′ were obtained from K[C₆H_5−nF_nBF₃] and the substrates [4-XC₆H₄N₂][BF₄] in the presence of Pd catalysts. The influence of the number and the position of the fluorine atoms in the (polyfluorophenyl)trifluoroborate salts on the reactivity in the coupling reaction was elucidated. In addition to (polyfluorophenyl)trifluoroborate salts, the cross-coupling was expanded to a first example of a perfluoroalkenyl reagent. K[CF₂CFBF₃] reacted with [4-FC₆H₄N₂][BF₄] and formed CF₂CF-C₆H₄F-4.