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

Abstract

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-(1H)-one (1), derived from o-iodobenzoic acid. The palladium dichloride complex of this ligand (10) shows the P(CF3)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.