Catalytic Trifluoromethylation of Aryl- and Vinylboronic Acids by 2-Cyclopropyl-1-(trifluoromethyl)benzo[b]thiophenium Triflate

Abstract

Catalytic trifluoromethylation of aryl- and vinylboronic acids by 2-cyclopropyl-1-(trifluoromethyl)benzo[b]thiophenium triflate is described. In the presence of a catalytic amount of CuOAc and 2,4,6-collidine in ethyl acetate, the reaction proceeded in good to high yields for various substrates under mild reaction conditions at room temperature.

Carbene-Induced Intra- vs Intermolecular Transfer-Fluoromethylation of Aryl Fluoromethylthio Compounds under Rhodium Catalysis

“…3,4 They have been developing relatively slowly, probably due to the difficulty in generating a trifluoromethyl cation ( + CF 3 ), which is affected by its high group electronegativity (3.45). 5 Several shelf-stable reagents have been reported for this purpose: diaryl-(trifluoromethyl)sulfonium salts (1984, Yagupolskii), 6 chalcogenium salts (1990, Umemoto), 7 hypervalent iodine compounds (2006, Togni), 8 (trifluoromethyl)sulfoximinium and 5-thiophenium salts . 9 They are effective for the electrophilic-type trifluoromethylation of a wide range of nucleophiles, and some of them are now commercially available.…”

Organic Transformation of Benzothiophenes by C−S Bond Cleavage Beyond Reductive Desulfurization

“…[8] 2-Cyclopropyl-1-(trifluoromethyl)benzo[b]thiophenium triflate 8 a, an electrophilic trifluoromethylating (CF 3 + ) species developed by Shibata and coworkers, has been proved to be unstable to give ring-opening product 9 a in certain solvents when equivalent 2,4,6-collidine was added. [9] Comparatively, ethyl acetate was a better choice as the reaction solvent, in which the decomposition of 8 a was inhibited as the result of poor solubility. In the absence of basic additive, Shibata reagents 8 a and analogue 8 b were also found to be unstable and slowly produced the corresponding ring-opened alkynes in DMF (Scheme 3).…”

Progress in copper-catalyzed trifluoromethylation

“…Recently, the group of Shibata [ 36 ] reported a catalytic trifluoromethylation of aryl- and vinylboronic acids using 1g as a trifluoromethyl source ( Scheme 20 ), which had not been actively investigated due to its instability in some solvents [ 37 ]. Solvent screening results indicated that ethyl acetate was the best solvent for the target transformations.…”