Electrophilic Trifluoromethylation of Primary Phosphines: Synthesis of a P-Bis(trifluoromethyl) Derivative of BINAP

The new chiral diphosphine ligand ( R )-(2′-(bis(trifluoromethyl)phosphino)-1,1′-binaphthyl-2-yl)diphenylphosphine ( 2 ), which contains a bis(trifluoromethyl)phosphine group, was prepared in five steps from ( R )-BINOL ( 5 ). As a key transformation, the unprecedented electrophilic double trifluoromethylation of the primary phosphine 8 was achieved using the hypervalent iodine trifluoromethylation reagent 1-trifluoromethyl-1,2-benziodoxol-3-(1 H )-one ( 1 ), derived from o -iodobenzoic acid. The palladium dichloride complex of this ligand ( 10 ) shows the P(CF 3 ) 2 group with a high degree of pyramidalization at the P atom and a relatively short Pd−P bond (2.2230(4) Å), both features being indicative of the strong s-character of the phosphorus lone pair.