Studies On The The Suzuki Reactions Catalyzed By Cyclopalladated Ferrocenylimines And The Enantioselective Aldol Condensation Catalyzed By Chiral Schiff Base-titanium Complexes

In this thesis, the catalytic activities of cyclopalladated ferrocenylimines in Suzuki reactions and the enantioselective aldol condensation catalyzed by chiral Schiff base-titanium complexes were studied in the following two aspects.I The catalytic activities of cyclopalladated ferrocenylimines in Suzuki reaction.1 The Suzuki reaction of phenylboronic acid with iodobenzene catalyzed by complex 1 was carried out to study in detail the influence of different solvents and bases. It was found that using DMF as solvent and potassium phosphate as base was the optimal reaction conditions.Scheme 12 We focused our studies on the coupling reactions of aryliodides with phenylboronic acid under the optimal conditions. The results obtained indicated that cyclopalladated ferrocenylimine 1 is an efficient catalyst for Suzuki reactions.Scheme 23 The thermal stability and applicability of catalyst 1 in the coupling of iodobenzene with phenylboronic acid were studied. The catalyst 1 could be reused at least five times with retention of its higher catalytic activites.Scheme 34 Six kinds of cyclopalladated ferrocenylimine dimers were synthesized and applied to the Suzuki reaction. All of them could catalyze the coupling reaction of 4-methoxyiodobenzene with phenylboronic acid. The yields were not significantly influenced by the substituent effects.Scheme 45 Comparison of the catalytic activities between the chlorine-bridged binuclear complex of palladium 1 and iodine-bridged binuclear complex of palladium 7 indicated that 7 was not as efficient as 1 for the Suzuki reaction, but it was still a good enough catalyst for the reaction with TON up to 9.3 103.Scheme 56 According to the characteristics of Suzuki reactions catalyzed by cyclopalladated ferrocenylimines, the possible mechanism was proposed.Scheme 6II The Mukaiyama aldol condensation catalyzed by chiral Schiff base-titanium complexes.1 Four p-chiral Schiff bases were synthesized and characterized by elemental analysis, IR and 1H spectra.Scheme 72 The reactions of 1-substituted-1-trimethylsilyloxyethene with benzaldehyde were carried out at room temperature catalyzed by chiral Schiff base-titanium complexes 1-5. It was found that the presence of different steric hindrance at 3 -carbon couldn't greatly improve the reaction yields. However, the yields could be improved by increasing the steric hindrance at a-carbon. The results obtained in different solvents showed that THF was the optimal solvent.