Rh-catalysed asymmetric hydrogenations with a dynamic library of chiral tropos phosphorus-ligands

A library of 16 chiral tropos phosphorus-ligands, based on a chiral P-bound alcohol or secondary amine and a flexible (tropos) P-bound biphenol unit, was synthesised. This ligand library allowed the screening of 16 homocombinations and 115 heterocombinations for the rhodium catalysed asymmetric hydrogenation of methyl N-acetamido acrylate. The screening resulted in the identification of a phosphite/phosphoramidite heterocombination, which proved to be extremely effective and enantioselective (100% yield, 94% ee).