Oxalamide-based bisdiamidophosphites: synthesis, coordination, and application in asymmetric metallocatalysis

A series of easy-to-prepare and modular chiral bisdiamidophosphites with oxalamide linkers were synthesized. The structures of the novel ligands were elucidated by means of 2D-NMR and confirmed by single-crystal X-ray diffraction. The reactions of such ligands with [Pd(Cod)Cl2] at molar ratios of L/Pd = 1 and 0.5 were studied by 1H, 13C, 13C DEPT, 31P, 1H–13C HSQC, 1H–13C HMBC, 1H–1H COSY, 1H–1H ROESY, 1H–15N HMBC and DOSY spectroscopy, as well as by DFT calculations. Stereoselectors of this type exhibited high enantioselectivities in the Pd-catalyzed allylic substitution reactions of (E)-1,3-diphenylallyl acetate with pTolSO2Na (up to 92% ee), CH2(CO2Me)2 (up to 97% ee), (CH2)4NH (up to 96% ee), (EtO)2P(O)CH2NH2 (up to 96% ee) and (CH2)4N(CCH(CH2)4) (up to 92% ee). ee values of up to 90%, 97% and 83% were obtained in the Pd-mediated allylic alkylation of cinnamyl acetate with ethyl 2-oxocyclohexane-1-carboxylate, allylic amination of cyclohex-2-en-1-yl ethyl carbonate with dibenzylamine and desymmetrization of N,N’-ditosyl-meso-cyclopent-4-ene-1,3-diol biscarbamate, respectively. In addition, ee values of up to >99% were achieved in the Rh-catalyzed asymmetric hydrogenation of methyl esters of unsaturated acids.