Copper Catalyzed Trifluoromethylation Of Potassium Aryltrifluoroborates And Potassium Alkynyltrifluoroborates

The fluorine atom has relatively strong electronegativity and small volume, so incorporation of fluorine atoms to a molecule often results in the improvement of its desirable characteristics such as polarity, stability and lipophilic. The oganotri-fluoroborates compounds are used as active ingredients of pharmaceuticals, agro-chemicals, functional materials and dyes based on their excellent chemical and biological activity.Potassium organotrifluoroborates have some good properties such as stability, no toxicity, and high reactivity, but sparingly be used for the trifluoromethylation reaction. Accordingly, we were prompted to conduct experiments using Togni’s reagent to develop a method for the trifluoromethylation of potassium aryltrifluoro-borates and potassium alkynyltriuoroborates, catalyzed by copper.Firstly, we explored the conditions of trifluoromethylation of organotrifluoro-borates to trifluoromethylarenes by using different copper salts, ligands, solvents, and the amount of catalyst. The optimized reaction conditions were established as follows: Cu(TFA)2 (0.3 equiv),2,2-bipy (0.3 equiv),4 A powdered molecular sieve (200 mg/mmol), Togni’s reagent (1.2 equiv) and ArBF3K (1 equiv), room temperature,12 h, the highest of responding yields was 95%. In contract with relational trifluoromethyl-ation of aromatic componds, our catalytic reactions proceed smoothly at room temperature, in the absence of added base to afford trifluoromethylarenes in good or excellent yields and can tolerate a variety of functionalities, so it enlarged the appliction of reactants.On the base of the former conclusions, we tried to explore the conditions of copper catalyzed trifluoromethylation of potassium alkynyltrifluoroborates. We chose CuSCN as catalyst after comparing different copper salts. According to the results of experiments, we got the best reaction condition as:0.3 equiv of CuSCN,0.3 equiv of 2,2-bipy,200 mg/mmol 4 A powdered molecular sieve,1.2 equiv of Togni’s reagent and 1 equiv of ArBF3K in MeCN, then reacted at room temperature for 16h, the highest of responding yields was 88%. It was easy to find that both electron-rich or-defieient aryl alkynyltrifluoroborates are readily to give expected trifluoromethyl-ation products in good or excellent yields. This method can also catalyzed alkanes such as potassium hept-1-ynyltrifluroborate, its 19F NMR yield was 75%. In contract with former synthesis of trifluoromethylated acetylenes, the method had the advantages of easy workup, mild condition and wide scope of this transformation.