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Decarboxylative Trifluoromethylating Reagent [Cu(O 2 CCF 3 )(phen)] and Difluorocarbene Precursor [Cu(phen) 2 ][O 2 CCF 2 Cl]
Author(s) -
Lin Xiaoxi,
Hou Chuanqi,
Li Haohong,
Weng Zhiqiang
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504306
Subject(s) - difluorocarbene , trifluoromethyl , chemistry , reagent , nucleophile , denticity , aryl , medicinal chemistry , trifluoromethylation , ligand (biochemistry) , crystallography , alkyl , organic chemistry , crystal structure , catalysis , biochemistry , receptor
This article describes the new economic decarboxylative trifluoromethylating reagent [Cu(phen)(O 2 CCF 3 )] ( 1 ; phen=1,10‐phenanthroline) and the efficient difluorocarbene precursor [Cu(phen) 2 ][O 2 CCF 2 Cl] ( 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 CH 3 CN 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 ( ρ )=+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.