Synthesis of modified binol-phosphoramidites

A number of chiral phosphoramidite ligands containing electronically different N-heterocycles at the 3,3′-positions of the binol scaffold were synthesized. The nucleophilicity of the pendant heterocycles correlated with the propensity of the P(III) centre to undergo aerobic oxidation to P(V). Due to an unexpected Staudinger-type reaction between the product phosphoramidites, the order in which the individual synthetic transformations were conducted was found to be important. The synthesis of a phosphoramidite ligand containing flanking groups at the 3,3′-positions of the binol scaffold in addition to a stereogenic phosphorus atom was also undertaken.