Visible Light Catalytic Trifluoromethylation/Cyclization Cascade Reaction Of β,γ-unsaturated Hydrazones And Oximes

Fluorine has the maximum electronegativity in the periodic table. Introduction of one or more fluorine atoms into a molecule alters the charge distribution and sterically structure, futher affecting the physical and chemical properties, and also the bioactivity, metabolic stability, lipophilicity and membrane permeability. Thus, the fluorine-containing compound has found its wide application in the pharmaceuticals, agrochemicals and materials science. Therefore, the efficiently and greenly introduction of the fluorine or fluorine-containing groups, such as trifluoromethyl, into the organic compounds especially carbon-ring or heterocyclic compounds has become a significant topic, obtained many chemists’ attention.As a clean, green and abundant energy resource, visible light has gain chemists’ attention for a long time. In recent years, due to the application of photocatalyst of metal complex or some large organic molecules, the visible light has been widely used in the organic transformation for construting of carbon-carbon or carbon-heteratom bonds. In this thesis, we have introduced the application of visible light catalytic strategies in the field of trifluoromethylation. Based on the the key intermediate, P-CF3 carbon cation, via the photocatalytic trifluoromethylation, we disclosed an efficient approach to synthesis of CF3-containg pyrazolines and isoxazolines.Pyrazolines and Isoxazolines are two important classes five-membered nitrogen hetercycles, and have good biological activities including anti-cancer, anti-viral, anti-fungal and antihypertensive, etc., as well as have wide apllications in material science. Thus, synthesis and study of these two classes of compounds are of great significance. Based on the literature and our group’s previous works, here, with the strategy of visible light catalysis, we synthesized various CF3-containing pyrazolines and Isoxazolines starting from β,γ- unsaturated hydrazones or oximes, using Umemoto’s reagent as the trifluoromethyl radical source. Those reactions all proceed through a intramolecular cyclization of the key intermediate, namely β-CF3 carbon cation, by the nucleophilic attack of nitrogen or oxygen of the hydrazones or oximes, giving the corresponding products in good to excllect yield. Finally, according to relevant literature and our group’s previous works, we proposed a possible mechanism for the reaction.