Treatment with TMS chloride in acetonitrile generates the Lewis acid phenylboron difluoride in situ, avoiding the need to handle boron trihalides: J. Org. Chem., 60, 3020 (1995). Aryltrifluoroborate salts are more nucleophilic than the corresponding arylboronic acids and undergo ligand-free Pd-catalyzed cross-coupling reactions with arenediazonium tetrafluoroborates to give good yields of biaryls: Tetrahedron Lett., 38, 4393 (1997); Eur. J. Org. Chem., 1875 (1999). Cross-coupling with aryl or heteroaryl halides and triflates, under ligand-free conditions, has subsequently been reported: Org. Lett., 4, 1867 (2002). Coupling with diaryliodonium salts has also been reported: Synth. Commun., 29, 2457 (1999). The method has been extended to the synthesis of benzophenones by carbonylative cross-coupling in the presence of CO: J. Chem. Res. (Synop.), 400 (1999). In the presence of Dicarbonyl-(2,4-pentanedionato)-rhodium(I)-, K aryl- and alkenyltrifluoroborates add to aldehydes and enones to give secondary alcohols and saturated ketones, respectively: Org. Lett., 1, 1683 (1999). Asymmetric Rh-catalyzed additions to enones in the presence of a chiral BINAP catalyst give the corresponding saturated ketones in high yield and ee: Eur. J. Org. Chem., 3552 (2002).
