Study On Ultraviolet-light Mediated Trifluoromethylation Of Alkenes

The compounds containing trifluoromethyl were widely applied to pharmaceuticals, agrochemicals and materials on account of its special physical and chemical properties. Therefore, the study of the introduction the trifluoromethyl group has been the current issue in organic synthesis chemistry. Over several decades, chemists have developed varieties of insert strategies. However, some of strategies were relatively limited, for example, harsh reaction condition, not easy to get the raw materials or poor selectivity and so on. Recently, driven by organic photochemistry, the trifluromethyl reaction have made a great breakthrough.Difunctionlization of alkenes that can introduce two functional groups into organic molecules via a double bond, which has broadened the organic reaction with unlimited potential. Trifluoromethylation of alkene is one of the most important strategies of difunctionlization. Not only formation of the C-CF3 bond, but also will the reaction build the bond of C-X, C-C, C-H, C-O, C-N, or C-S. Herein, we aim to realize difunctionlization of alkenes through triluoromethylation via photocatalysis and form the intramolecular bond of C-C.Through screening some of necessary reaction conditions, such as the trifluoromethylation reagent, solvent, photosensitizers and light source, the optimal conditions were confirmed that around N2 atmosphere, under a 500 W medium mercury lamp, BP as sensitizer, dried MeCN as solvent, α,β-unsaturated aromatic ketones selected as model substrates and CF3SO2 Na as trifluoromethylation reagent,which can obtain a series of trifluromethyl phenanthrenol with moderate yields. Then, with the optimized condition, we expanded the 25 substrates and probed into the effect of the different functional groups.Furthermore, we carried out the control experiment of radical capture agent-TEMPO and detected the existence of TEMPOCF3 by GC–MS analysis to explore the proposed mechanism. Such a result suggested that the reaction involves a radical pathway. The CF3 radical, generated from CF3SO2 Na was added to C-C double bond of α,β-unsaturated aromatic ketone to form the C-centered radical. Subsequently, the radical attacked the ortho-position of benzene to produce an intramolecular cyclization ring. Finally, the benzyl radical become the desired products through enolization of ketone and abstraction of hydrogen radical.