CONVERSION OF ARYLBORONIC ACIDS INTO POTASSIUM ARYLTRIFLUOROBORATES - CONVENIENT PRECURSORS OF ARYLBORON DIFLUORIDE LEWIS-ACIDS

Reaction of ArB(OH)(2) (3) with KHF2 affords crystalline salts KArBF3 (2). In the presence of TMSCl in acetonitrile, 2a reacts to give NMR signals typical of PhBF(2) in acetonitrile solution. When the reaction of 2 + TMSCl is performed in the presence of potential Lewis bases, the trivalent borane 1 is intercepted, resulting in organoboron complexes. Thus, the oxazaborolidinones 7-10 have been prepared from amino acid-derived amidine carboxylates NaO2CCH(R)N = CHNMe(2) (R = H or phenyl). Complexes 11 and 12 derived from 1,3-diketones are also easily prepared. The KHF2 fluoride exchange coupled with the TMSCl activation method allows in situ generation of ArBF2 without having to handle corrosive trivalent boron halides.