1,1′-Binaphthyl-2,2′-diamine-Based Chiral Phosphorous Triamides: Synthesis and Application in Asymmetric Catalysis

A set of chiral monodentate phosphorous triamides (PTA) comprising 1,1'-binaphthyl-2,2'-diamine as the common moiety have been synthesised. Electronic and steric tuning of the ligands was achieved by variation of the substituents at the diamine nitrogen atoms by incorporating methyl, p-tolyl and tosyl groups. Both chiral and achiral building blocks were used as monoamine components. Notably, (11bR)-3,5dimethyl-N,N-bis[(S)-1-phenylethyl]-3,5-dihydro-4H-di- naphtho[2,1-d:1',2'-f][1,3,2]diazaphosphepin-4-amine, which is the PTA most closely related to the Feringa phosphoramidite ligand, was synthesised and characterised by NMR spectroscopy and X-ray diffraction. This PTA displays increased conformational rigidity in comparison with the corresponding phosphoramidite and adopts a Cl-symmetric structure both in the solid state and in solution, even at room temperature. The new PTA ligands were used in the copper-catalysed conjugate addition of diethylzinc to cyclohex-2-enone and the nickel-catalysed hydrovinylation of styrene giving good activities and chemoselectivities at moderate enantioselectivities in both reactions. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)