Synthesis and catalytic reactivity of orgamometaeeics possessing cavity

点击翻译按钮获取中文摘要

This research has been focused on to develop new synthetic catalysts, which would mimic the high reactivity and selectivity in enzymatic reactions. The catalysts have been so designed to have a metal-center as an active site and a cavity as a recognition site, that they would catalyze cationic carbon-carbon formation reactions, such as polyene cyclization reactions and glycosylation reactions. We have also investigated a new synthetic methodology for the effective synthesis of the cavity molecules. We find followings.1. New metal ligands, which possess optically active binaphtol moiety as a metal chelating site and dendritic branch moiety as a recognition site, have been successfully synthesized. Complexation of the ligand with Lewis acidic metals gives corresponding optically active metal catalysts, which catalyze asymmetric carbon-carbon bond formation reactions.2. A new glycosylation reaction has been developed. The telluroglycosids are activated under mild oxidative conditions, and give α-and β-anomers selectively depending on the reaction conditions.3. Development of new synthetic methodologies for the synthesis of cavity molecules has been examined by using radical reaction. Telluroglycosides undergo stereochemical isomerization under photochemical and thermal conditions. The isomerization involves reversible generation of glycosyl radicals which are formed by the hemolytic C-Te bond cleavage.4. The radicals described above react with alkynes and isonitriles to give the corresponding group-transfer products. The C-Te bond of the product also undergoes the reversible hemolytic cleavage and the recombination of the resulting radicals.