(S)-2-[(N-arylamino)methyl]pyrrolidines-Based Phosphoramidite P,N-Ligand Library for Asymmetric Metal-Catalyzed Allylic Substitution and Conjugate 1,4-Addition

A library of easy-to-prepare and modular chiral P,N-phosphoramidites based on [1,1′-biaryl]-2,2′-diols and C1-symmetric 1,2-diamines has been designed and developed. The structures of the novel ligands have been elucidated by means of 2D-NMR and confirmed in the solid state by X-ray diffraction analysis. Stereoselectors of this type exhibited high enantioselectivities in Pd-catalyzed allylic substitution reactions of (E)-1,3-diphenylallyl acetate with NaSO2pTol (up to 91 % ee), CH2(CO2Me)2 (up to 89 % ee), (C3H7)2NH (up to 94 % ee) and (EtO)2P(O)CH2NH2 as a novel nucleophile (up to 98 % ee). Ee values of up to 88 % and 72 % have been obtained in the Pd-catalyzed desymmetrization of N,N′-ditosyl-meso-cyclopent-4-ene-1,3-diol biscarbamate and in the Cu-catalyzed 1,4-conjugate addition of diethylzinc to chalcone, respectively. The reactions of P,N-bidentate ligands with [Pd(Cod)Cl2] at molar ratios of L/M=1 and 2 have been studied using 1H, 13C, 13C-1H HSQC, 13C-1H HMBC, 1H-1H COSY, 1H-1H ROESY, DOSY and 31P NMR spectroscopy as well as HR ESI mass spectrometry.