LITHIATION AND PHOSPHORYLATION OF CHIRAL 1,1'-BIS(OXAZOLINYL)FERROCENES

Two chiral 1,1'-bis[(S)-2-(4-R-oxazolinyl)]ferrocenes (3) were prepared by condensation of 1,1'-bis(chlorocarbonyl)ferrocene with (S)-valinol and (S)-tert-leucinol, respectively. Lithiation of 3 with n-BuLi followed by coupling with ClPPh(2) gave the diphosphorylated product 5 of C-2 symmetry as a minor product and the monophosphorylated product 4 as the major product even with using more than 2 equiv of n-BuLi. Use of t-BuLi led to the non-C-2 symmetric diphosphorylated product 6, which acted as an N,P-chelating ligand in the palladium complex 7.