A research team led by Associate Professor Wei Han from the School of Chemistry and Materials Science of Nanjing Normal University found a new method of Wacker-type oxidation using an iron catalyst and ambient air. The results were entitled “Wacker-Type Oxidation Using an Iron Catalyst and Ambient Air: Application to Late-Stage Oxidation of Complex Molecules” and published in Angewandte Chemie International Edition, a top international chemical journal with current IF of 11.994 which is jointly published and issued by German Chemical Society and John Wiley & Sons, Inc.. It is the first time for NNU to publish a research paper on this journal as the only research unit.
Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst which is not consumed in the catalyzed reaction and can continue to act repeatedly. Catalysis plays a significant role in the process of human civilization and the global economic growth because it can help to transform raw materials into high value added chemical products and fuels in an efficient, green and economic way. It is widely used in fields including energy, chemical industry, food, medicine and electronics, existing in over 90% of chemical production in the world. Every major breakthrough in catalysis will greatly change the production and lifestyle of human. Catalysis is replaceable in dealing with energy crisis, resource shortage, climate change and environment pollution.
The palladium (II)-catalyzed oxidation of olefins into carbonyl compounds, a reaction best known as the Wacker–Tsujioxidation, has become one of the most straightforwardand convenient processes for the preparation of carbonylcompounds and found wide applications in the synthesis ofnatural products and chemical products. However, there are challenges in the field. First, the high cost andlow abundance of palladiumhave hastened the development of alternative catalysts basedon earth-abundant transition metals. Second, it’s hard to achievereactive and selective oxidation of internal alkenes, electron-deficient internal alkenes. In addition, styrene derivatives areproblematic substrates in classical Wacker oxidations owingto their facile polymerization and oxidative cleavage tobenzaldehydes and/or benzoic acids. Besides, the Wacker–Tsuji oxidation employscatalytic PdCl2, stoichiometric CuCl2, and O2 in a DMF/H2O solvent system. This process may leads to degradation of thepalladium catalyst, isomerization of the olefin, chlorinatedbyproducts, and copper waste.Although diverse oxidantshave been utilized to overcome these problems,they also cause high cost, chemical waste, and/or safetyconcerns.
Iron is an ideal candidate for catalysis since it is the second most earth-abundant metal and biocompatible.Based on the metabolizing process ofCytochrome P-450 in which ironas the active center, oxygen gas as the oxidant, and a reductantas the activator, the teamreportsthe first iron-catalyzed Wacker-type oxidations of olefins toketones using ambient air as the sole oxidant under mildreaction conditions. This catalytic system isgeneral, exceptionally functional-group tolerant, and highlyefficient even toward styrenes, internal olefins, and electrondeficient internal aryl olefins, as well as applicable for the late-stage oxidation of complex small molecules.
This research was highly praised by international expert: “I think this method is absolutely worth being published in AngewandteChemie International Edition”.
Co-first authors of this research are Binbin Liu and Fengli Jin, postgraduates from the School of Chemistry and Materials Science who are responsible for experiments. Tianjiao Wang and Xiaorong Yuan, as undergraduates in the same school and members of college student innovation program of Jiangsu province, also took part in the experiments. The only corresponding author of this paper is Associate Professor Wei Han, who designed the research idea and wrote the paper. Their work shows the great foundation and strength of NNU School of Chemistry and Materials Science, Organic Chemistry major in pursuit of international top-level research findings.
This research was financially supported by the National Natural Science Foundation of China, the Natural Science Foundation of Jiangsu Province, the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Qing Lan project.