A synthetic methodology for the preparation of a water-soluble quaternized amino phosphine oxide ligand

After several unsuccessful attempts to synthesize quaternized aniline-derived phosphanes, we succeeded to develop a synthetic methodology for the preparation of a water-soluble amino phosphine oxide ligand containing a quaternary ammonium ion by insertion of a second amino moiety on the aniline derivative before the insertion of the phosphino group. The methodology involves insertion of an amino moiety on the alkyl chain of the aniline derivative via its mesylate, subsequent insertion of the phosphino group via ortho-lithiation of the aromatic ring, oxidation to the corresponding phosphine oxide and finally quaternization of the alkyl chain amino moiety.