Studies On Asymmetric Reactions Catalyzed By Supported Rulbenium Porphyrin, BINOL And Their Derivatives And The Interaction Of N₂S₂ Compounds With DNA

Metalloporphyrins have been applied to catalyze the epoxidation of unfunctionalized alkenes. In recent years emphasis has been put on the stability and reuse of the metalloporphyrins. Therefore, many supported metalloporphyrins have been synthesized with high stability. The ruthenium(â…¡) 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin(tfpp) carbonyl complex has been covalently attached to a 3-aminoporpyl functionalized silica gel(APS).Steroid epoxides are an important class of oxysterols (derivatives of cholesterol) that regulate cell proliferation and cholesterol homeostasis in organism. They are also versatile intermediates for steroid synthesis, playing increasingly important roles in the biochemical studies of enzymes, this supported ruthenium porphyrin(APS-Ru(â…¡)(tfpp)CO) was applied to catalyze the epoxidation ofΔ⁵- andΔ⁴-unsaturated steroids, and the encouraging results are obtained. Firstly, the epoxidation ofΔ⁵-steroids obtained high yield (up to 99%) andβ-selectivity(up to 99%). Secondly, this supported metalloporphyrin could also catalyzeΔ⁴- steroids and the catalytic reactions obtained 99%β-selectivity, though the yields were low. Thirdly, this supported metalloporphyrin had high stability, and the activity didn't decrease after being reused five times. Finally, the analysis of the reaction results was simple by ¹H-NMR, and the catalyst can easily be reused. Ligands with N₂S₂ structures, especially 2, 9- dimethyl-4, 7-diazadecane-2, 9-dithiol (DDD), have been studied in recent years. DDD is a strong chelating agent and can form stable lipophilic chelate complex with technetium or rhenium in high yields. The derivatives of N₂S₂ ligands have been employed in diagnostic imaging, radiopharmaceuticals, nuclear medicine and so on. Five N₂S₂ piperidine derivatives, NEPDDD, NEMPDDD, NEMMPDDD, NNEPDDD, NNEMPDDD, were synthesized. Three derivatives(NEPDDD, NEMPDDD, NEMMPDDD) were selected to catalyze DNA cleavage, and obtained a series of encouraging results. First, the three free ligands could cleave plasmid DNA(pUC 19) efficiently, especially NEMPDDD. Second, for the cleavage reaction catalyzed by NEMPDMDD, Formâ… DNA could convert to Formâ…¡completely in 24 h at 37℃under physiological condition(pH 7.0). Third, the DNA-cleavage mechanism involved an oxidative pathway. Eventually, the free N₂S₂ piperidine derivatives were employed in DNA cleavage for the first time. The results show that these free ligands have the same catalysis activity as restriction enzymes.Diets-Alder reaction is one of the important reactions in organic chemistry for the construction of six-membered rings and the formation of carbon-carbon bonds. Asymmetric Hetero-Diets-Alder reaction (HDA) between electron-rich diene with aldehydes can provide a series of dihydropyrans and dihydropyranones which are among the most important intermediates in the synthesis of many natural products. The Hetero-Diels-Alder reactions of trans-4-methoxy-2-trimethylsiloxy-penta-1,3-diene with aromatic aldehyde were studied and the encouraging results were obtained. Firstly, optically active 2,6-disubstituted dihydropyrones were available by hetero-Diels-Alder (HDA) reaction of aldehydes and diene in presence of MCl₄ (M=Wi⁴⁺, Sn⁴⁺) and (R)-BINOL with sodium alcoholates as additives under mild reaction conditions. Secondly, all the reaction products catalyzed by TiCl₄ and BINOL with NaOCH -(CH₃)CH₂CH₃ as an additive were obtained up to 88% yield and 94% ee. Finally, the substituent positions of aromatic ring affected the yield and enantioselectivity of HAD reactions, but the electric effects of substituent were not significant.At the same time, the 3- and 3,3'-BINOL imidazonium were synthesized successfully, and were used to catalyze direct Aldol reaction, HDA reaction and the hydroacylation of a-keto ester with aldehyde. Although the catalytic reactions has no results, this imidazonium will be employed in some reaction under capable conditions.