PCN Pincer Pd Complexes: Synthesis And Application In Asymmetric Hydrophosphination Of Nitroalkenes

This thesis studies the synthesis and characterization of chiral PCN-pincer Pd(II)and explores their applications in asymmetric hydrophosphination of nitroalkenes.1. Synthesis and characterizaiton of chiral PCN-pincer Pd(II) complexes.(1) Chiral imidazolinyl m-phenol complexes 1a-e were synthesized in four steps from commercially available m-hydroxybenzoic acid. Then 1a-e can easily get 2a-e via one-pot phosphorylation/palladation reaction(Scheme 1). The new compounds1c-e and 2c-e were characterized by 1H NMR, 13 C NMR, 31 P NMR and elemental analysis(HR-MS for the new ligands 1c-e).(2) Complexes 3a and 4a-c were synthesized from optically pureα,α-Diphenyl-2-pyrrolidinemethanol via one-pot phosphorylation/palladation reaction(Scheme 2). The new compounds 3a and 4a-c were characterized by 1H NMR, 13 C NMR, 31 P NMR.2. Applications of PCN-pincer Pd(II) complexes in asymmetric hydrophos phination of nitroalkenes.The activities and enantioselectivities of 2a, 3a and 4a-c in asymmetric addition reaction of diarylphosphine to nitroalkenes(Scheme 3) were investigated. Complex4 a was proved to be the best catalyst. Under the condition of 5 mol% 4a, 10 mol%KOAc as base, and CHCl3 as solvent, at-20 o C for 12 h, the products were isolated after oxidation with up to 99% yield and 83% ee(Scheme 3).