(Fluoroorgano)fluoroboranes and -borates.: 14.: Preparation of potassium ((perfluoroorgano)ethynyl)trifluoroborates K[RFC=CBF3]

Despite the remarkable progress in organoboron chemistry, (alkynyl)fluoroborates remained unknown until 1999, when Darses et al. reported the preparation of the first two potassium (alkynyl)trifluoroborates, K[RC equivalent to CBF3] (R = Bu, Et3Si).(1) Later Molander et al. extended this series of salts with R = C8H17, C6H5, C6H5-CH(2)CH2, CClH2CH2CH2, CH2=C(CH3) Me3Si, and t-BuMe2SiOCH2CH2.(2) Both groups introduced (alkynyl)trifluoroborates successfully into Pd-catalyzed cross-coupling reactions and demonstrated impressively the application potential of alkynyltrifluoroborate salts. It is well-known that the replacement of all or the majority of hydrogen atoms by fluorine atoms in hydrocarbons or in their organoelement derivatives caused significant changes of their physical and chemical properties. 3 In this regard the chemistry of organoboron compounds is no exception. A recently published review presented a number of peculiarities which were derived from the combination of the specific properties of both roots, organofluorine and organoboron chemistry, and their co-action.(4) sWe have continued our systematic studies in the field of polyfluorinated organofluoroborates and -boranes investigated approaches to the synthesis of ((perfluoro-organo)ethynyl)trifluoroborate salts K[RFC equivalent to CBF3]. We have included perfluorinated alkyl, alkenyl, and aryl groups R-F attached to C-2 of the ethynyl unit.(5)