Novel Monodentate Phosphoramidites By Chiral Pool Synthesis Starting fromD-Mannitol, and Their PdII and RhI Complexes

Abstract

The new monodentate phosphoramidites 6a−e were prepared in an ex-chiral-pool synthesis from readily available D-mannitol in high yields. A ring opening of 1,2;5,6-dianhydro-3,4-O-isopropylidene-D-mannitol (4) with nucleophiles provides the chiral diols 5a−e with different steric demand as key intermediates. The ligands 6a−e are synthesized by refluxing 5a−e with hexamethyltriaminophosphane (HMTAP) and lead, after treatment with [PdCl2(COD)] or [Rh(COD)2][SO3CF3], to the corresponding Pd complex 8a and rhodium(I) complexes 7a−e, respectively. The cis-arrangement of the ligands and the C2-symmetry of the complexes in the solid state is demonstrated by an X-ray structure investigation performed on 8a. In addition, variable temperature NMR experiments show that 8a keeps its C2-symmetric coordination geometry even at temperatures up to 90 °C (decomposition).