A research team led by Professor Yoshikazu Hara, Assistant Professor Yusuke Kita, and Associate Professor Keigo Kamata at the Frontier Materials Research Laboratory, Innovative Research Institute, Tokyo Institute of Technology, is trying to extract ketones, which are often used as raw materials on for pharmaceuticals and agrochemicals, from alcohol, which is abundant in biomass We succeeded in developing a synthetic manganese catalyst.
Precious metal catalysts have traditionally been used to produce high value chemical products such as pyrroles and quinolines, and the development of alternative catalyst materials is underway.
In this study, we applied the accelerating effect of magnesium oxide on alcohol conversion reactions, explained in previous studies, to manganese catalysts. In this catalyst, by using nitrogen-containing raw materials in particular, we succeeded in synthesizing pyrrole, which is a raw material for drugs for the treatment of neoplastic diseases, and quinoline, which is a raw material for B vitamins sold as supplements. We are also investigating the reaction mechanism and catalytic effect of the developed manganese catalyst, and it can be said that the research results will contribute to the development of valuable metal-free catalysts in the future.
Towards the realization of a sustainable society, it is desired to develop catalysts that use “cheap and easily available elements”.
The results of this research were published in the Journal of the American Chemical SocietyACS Catalysis” was released on September 13th in the online bulletin version.
Pyrrole and quinoline, which are raw materials for pharmaceuticals, agricultural chemicals, and supplements, are high-value chemical products, and their market size exceeds 100 billion yen. These chemical products are produced using precious metals such as palladium and ruthenium as catalysts, which greatly increase manufacturing costs. In addition, reserves of precious metals are small, and the complexity of recent catalyst structures makes it difficult to recycle catalyst materials. Against this background, ubiquitous and cheap metals such as manganese and iron are attracting attention as alternatives to precious metals.
Professor Hara’s research group has reported in previous research that magnesium oxide (MgO) shows a remarkable acceleration effect in the conversion reaction of alcohol contained in biomass.[参考文献1]. In this study, we clarified that carbon-oxygen bonds in alcohols can be converted into carbon-carbon bonds by applying this promoting effect of MgO to manganese catalysts. Through this reaction, we have succeeded in synthesizing pyrroles and quinolines, which are used as synthetic intermediates for pharmaceuticals and synthetic dyes. This manganese catalyst was able to obtain higher activity than existing manganese catalysts and simple manganese oxides, but also noble metal catalysts prepared by the same method.
Investigation of this reaction mechanism revealed that the hydride species[用語1]It was found that the reaction proceeds through the In this reaction mechanism, we have confirmed that donating electrons from MgO to manganese lengthens the bond between manganese and hydride, increasing the reactivity of the hydride species (Fig. 1). Through this unique reaction pathway, it is possible to convert aliphatic alcohols, which are difficult to convert with common manganese catalysts.
For heterogeneous manganese catalysts, tetravalent manganese has been reported to form an active catalytic species. On the other hand, in the present study, divalent catalysts were mainly in highly active catalysts, and the catalytic performance decreased significantly as the oxidation number increased (Fig. 2). Since manganese with a high oxidation number is generally used as an oxidation catalyst, the performance of each catalyst was evaluated in an inert gas atmosphere and an oxygen atmosphere. As a result, it was found that the oxidation number of manganese has a great effect on the catalytic performance, it was found to progress along the reaction path (Fig. 3b). Therefore, a catalyst system whose catalytic performance changes greatly depending on the oxidation number of manganese is extremely rare. Furthermore, when the reactivity of the hydride species bonded to manganese was examined in detail, it was confirmed that electron donation from MgO to manganese oxide contributed to the promotion of the reaction.
The results of this research have achieved the ultimate goal of synthesizing useful organic compounds from readily available organic compounds in a small number of steps and at low cost by using abundant manganese, magnesium, and aluminum. their nature, as catalysts. related. In the future, it is expected to contribute to the sustainable development of mankind by providing useful organic compounds away from chemical synthesis that relies on metal catalysts, which has a high environmental impact.
.jpg?fit=300%2C300&ssl=1)
