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

Abstract

AbstractA 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)‐3,5‐dimethyl‐N,N‐bis[(S)‐1‐phenylethyl]‐3,5‐dihydro‐4H‐dinaphtho[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 C1‐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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)