NOBIN-based phosphoramidite and phosphorodiamiditeligands and their use in asymmetric nickel-catalysed hydrovinylation

Phosphoramidite and P-stereogenic phosphorodiamidite ligands derived from (Sa)-2-phenylamino-2′-hydroxy-1,1′-binaphthyl (N-Ph-NOBIN) and bis(1-phenyl-ethyl)amine were synthesised, fully characterised, and the absolute configuration of the stereogenic phosphorus atoms was assigned. The phosphoramidite ligand L2 features three non-bridged substituents at phosphorus comprising the bis(1-phenylethyl)amine and two NOBIN moieties. The NOBIN units are bound to the phosphorus through the oxygen atoms with two pendant nitrogen atoms. In the Ni-catalysed hydrovinylation of styrene no conversion was observed with the phosphorodiamidites, while the phosphoramidite ligands led to active catalysts with a marked co-operative effect on selectivities. Whereas the racemic product was obtained with the (Sa,Sa,SC,SC) diastereomer, the (Sa,Sa,RC,RC) diastereomer proved to be one of the best ligands for this reaction, leading to almost perfect selectivity and ees of up to 91%.