Developing catalytic enantioselective fluorination

The background that led to the development of the first catalytic and enant ioselective carbon-fluorine bond-forming reaction is presented. Two differe nt approaches, i.e. the use of nucleophilic and electrophilic fluorinating agents, respectively, have been pursued. Well-defined Ru(II) 16-electron sy stems of the type [RuF(PP)(2)](+) (where PP is a chelating diphosphine), as well as analogous complexes containing tetradentate PNNP ligands, were fou nd to catalyze the halogen exchange reaction of activated alkyl chlorides, bromides, and iodides in the presence of TIF as the fluorine source. Isolab le crystalline [TiCl2(TADDOLato)] complexes are efficient catalysts in the enantioselective fluorination of 2-substituted 1,3-dicarbonyl compounds wit h Selectfluor((R)) (also called F-TEDA; 1-chloromethyl-4-fluoro-1,4-diazoni abicyclo[2.2.2]octane bis[tetrafluoroborate]). Levels of enantioselectivity up to 90% ee were obtained.