Poly-salen Ligands: Design, Synthesis And Their Applications In Asymmetric Catalytic Reactions

In this thesis, linear and crosslinked polymeric salen ligands were prepared, and their Mn(III) complexes, Ti(IV) complexes and Co(III) complexes were used in the asymmetric epoxidation of unfunctionalized olefins, the asymmetric trimethylsilylcyanation of aromatic aldehydes and the hydrolytic kinetic resolution (HKR) of terminal epoxides.1. Synthesis of poly-salenMn(III) complex and its application in the asymmetric epoxidation of unfunctionalized olefinsBegin from 2-f-Butyl-phenol, a novel chiral poly-salen ligand L-l was synthesized in four steps, whose Mn(III) complex C-l was employed in the asymmetric epoxidation of unfunctionalized olefins. In the NaCIO / 4-PPNO or W2-CPBA / NMO systems, using styrene, (Z)-p-methylstyrene and substituted 2,2-dimethylchromenes as substrates, catalyst C-l exhibited the same activities and enantioselectivities as its parent monomer catalyst. In the w-CPBA / NMO system, 6-Br-2,2-dimethylchromene as the substrate, up to 92 % isolated yield and 97 % ee were obtained with 4 mol % polymeric catalyst in 30min. Furthermore, the polymeric catalyst could be easily recovered and recycled efficiently for several times in the NaCIO / 4-PPNO svstem. after five reactions. 95 % ee and 63 %isolated yield of epoxide were obtained using 2,2-dimethylchromene as the substrate. Compared with the polymeric catalysts 2-31, 2-32 we reported before, the new polymeric catalyst have the best enantioselectivities because of the introduction of two geminal methyl groups on the linking carbon atom. In the recycling experiments, the new polymeric catalyst kept its enantioselectivities.2 Asymmetric trimethylsilylcyanation of aromatic aldehydes catalyzed by poly-salenTi(IV) complexA poly-salen-Ti complex C-2 derived from L-l was used as catalyst for the catalytic asymmetric trimethylsilylcyanation of aromatic aldehydes. At -40℃, with 1 mol % of polymeric catalyst C-2, the adduct of 4-CH3-C6H4CHO was obtained in 82 % ee and 98 % yield. The polymeric catalyst could be recycled for six times with the same enantioselectivity.3 The HKR of terminal epoxides catalyzed by chiral poly-salenCo(III) complexesPoly-salen.Co(III) complexes C-3, C-4 were employed in the HKR of terminal epoxides. As that observed in the asymmetric epoxidation of olefins, polymeric catalyst C-3 showed better enantioselectivities, the ees were 98 %, 97 % and 98 % respectively for 1,2-propane diol, epichlorohydrin and phenyl glycidyl ether with 0.5 mol, % mol of C-3. In the HKR of epichlorohydrin, we found that the polymeric catalysts reacted with the substrate to form hydrophilic ends, which simplified the separation and the recovery of the polymeric catalysts. The recovered catalyst showed better enantioselectivities in some conditions.4 The design, synthesis of crosslinked poly-salenCo(III) complexes and theirapplication in the HKR of terminal epoxidesDi-salicylaldehydes and tri-salicylaldehydes S-3, S-4, S-5 were synthesized from some easily prepared acids. The crosslinked polymeric ligands could be prepared by condensation of (R,R)-1,2-cyclohexanediamine stoichiometrically with a mixture of S-3 and S-4 in different proportions, polymeric catalysts were obtained by inserting the Co atoms to the ligands. These catalysts were employed in the HKR of epichlorohydrin, styrene oxide and phenyl glycidyl ether. The results showed that the crosslinked polymeric catalysts had better activities in a proper range of crosslinker's proportions, up to 99 % ee were obtained, using only 0.02-0.16 mol % of polymeric catalysts (based on catalytic unit).