Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 22, Issue 6, Pages 2075-2084Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201504306
Keywords
aryl difluoromethyl ethers; carbenes; copper; decarboxylation; trifluoromethylation
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Funding
- National Natural Science Foundation of China (NSFC) [21372044]
- Research Fund for the Doctoral Program of Higher Education of China [20123514110003]
- Fuzhou University [022494]
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This article describes the new economic decarboxylative trifluoromethylating reagent [Cu(phen)(O2CCF3)] (1; phen=1,10-phenanthroline) and the efficient difluorocarbene precursor [Cu(phen)(2)][O2CCF2Cl] (2). Treatment of copper tert-butoxide with phen and subsequent addition of trifluoroacetic acid or chlorodifluoroacetic acid afforded air-stable complexes 1 and 2, respectively, which were characterized by X-ray crystallography. The copper(I) ion in 1 is coordinated by a bidentate phen ligand, a monodentate trifluoroacetate group, and a molecule of CH3CN in a distorted tetrahedral coordination geometry. The molecular structure of 2 adopts an ionic form that consists of a [Cu(phen)(2)](+) cation and a chlorodifluoroacetate anion. Complex 1 reacted with a variety of aryl and heteroaryl halides to form trifluoromethyl (hetero)arenes in good yields. The corresponding Hammett plot exhibited a linear relationship and a reaction parameter ()=+0.56 +/- 0.02, which indicated that the trifluoromethylation reaction proceeded via a nucleophilic reactive species. Complex 2 reacts with phenols to produce aryl difluoromethyl ethers in modest-to-excellent yields. Mechanistic investigations revealed that the difluoromethylation reaction proceeds by initial copper-mediated formation of difluorocarbene and subsequent concerted addition of difluorocarbene to the phenol to form a three-center transition state.
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