Shape-selective Oxidation Catalyzed by Sterically Controlled Metalloporphyrins

新型合成金属卟啉催化烯烃环氧化反应。该反应在二氯甲烷-水体系中以次氯酸盐为氧源进行。在阻转异构体卟啉锰催化苯乙烯氧化反应中<alpha><alpha><alpha><alpha>，反应发生在开放位优先于拥挤位。合成了几种邻位取代的四苯基卟啉：邻位被硝基、氟或氯取代。它们的配合物对催化剂的分解表现出很高的稳定性。利用这些铁（III）配合物，我们开发了铁卟啉-次氯酸盐体系作为高效催化剂。环氧化反应的初始速率表现出类似于酶促反应的底物饱和动力学。通过对这些金属卟啉催化环氧化反应的系统考察，发现催化剂的形状对Michaelis-Menten参数和产物选择性有很大的影响。此外，还指出锰和铁催化剂的环氧化反应机理不同。

New types of synthetic metalloporphyrin catalyzed epoxidation of olefins. The reaction was carried out in dichloromethane-water system by use of hypochlorite as an oxygen source. In the oxygenation of styrene catalyzed by an atropisomeric manganese porphyrin(<alpha><alpha> <alpha><alpha> isomer), the reaction took place in the preference for open site to the crowded one. Several orthosubstituted tetraphenylporphyrins were prepared:The ortho positions were substituted by nitro, fluoro or chloro groups. Their complexes showed high stability to the decomposition of catalyst. By use of these iron(III) complexes, we developed the iron porphyrin-hypochlorite system to efficient catalyst. The initial rate of the epoxidation exhibited the substrate saturation kinetics similar to the enzymatic process. From the systematic survey of epoxidation catalyzed by these metalloporphyrins, it is evident that Michaelis-Menten's parameters and and product selectivity are influenced by shape of catalysts. In addition it was indicated that the epoxidation mechanism is different between manganese and iron catalysts.