Study On Trifluoromethylation Of Aryl Boronic Acids

The CF3 group has an effect on the properties of organic molecules, such as metabolic,thermal stability and lipophilicity, due to its high electronegativity and small size with change of molecular polarity. Consequently, compounds with trifluoromethyl group have extensively application in biologically active pharmaceutical, agrochemical, as well as function materials.The key role of trifluoromethyl group in compounds has attracted much more attention by organic, material, medicinal, and agricultural chemists. Without organofluorine compounds in nature, the selective introduction of trifluoromethyl group into organic molecules has a great significance with the development of general and practical methods. In this thesis, a series of aryl boronic acids were synthesized through Grignard’s reagent. We have developed an innovative reaction system,(CF3SO2Cl/BPO), which was applied to the copper-catalyzed trifluoromethylation of aryl boric acids. A possible mechanism, copper-mediated radical trifluoromethylation, was suggested.Firstly, we have synthesized five aryl boronic acids: phenylboronic acid,2,4,6-trimethylphenylboronic acid, 4-methylphenylboronic acid, 4-chlorophenylboronic acid and 3,5-dimethylphenylboronic acid from bromobenzenes through those Grignard’s reagent.All of them have been characterized by melting point, IR and 1H-NMR.Secondly, a new method of trifluoromethylation with aryl boronic acid as substrate and CF3SO2 Cl as the trifluoromethyl reagent has been explored. The optimized reaction conditions of the copper-catalyzed trifluoromethylation for aryl boronic acids have been present, with toluene or Me CN as the solvent, BPO as a radical initiator, supplemented K2CO3,1,10-phenanthroline, room temperature and oxygen environment. A series of aromatic trifluoromethyl compounds have been achieved and characterized by melting point, IR,elemental analysis and NMR. Meanwhile, a possible reaction mechanism was also proposed in this thesis. it is noted that the CF3SO2Cl/BPO system has shown the promising future to radical trifluoromethylation of CF3SO2 Cl in the fulture, instead of expensive ruthenium catalysts in light conditions.The above catalyzed reaction system, as a cost-effective and easy-to-handle CF3 reagents,can also work to trifluoromethylation of halogenated aromatic compounds, although BPO can not make CF3CO2 Na as the·CF3 precursor at lower temperatures.