Premium
The Role of Ate Complexes in the Copper‐Mediated Trifluoromethylation of Alkynes
Author(s) -
Weske Sebastian,
Schoop Ramona,
Koszinowski Konrad
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.201601261
Subject(s) - trifluoromethylation , chemistry , homoleptic , trifluoromethyl , oxidizing agent , reagent , acetonitrile , medicinal chemistry , dichloromethane , alkyne , copper , alkoxide , organic chemistry , catalysis , solvent , metal , alkyl
Trifluoromethylation reactions have recently received increased attention because of the beneficial effect of the trifluoromethyl group on the pharmacological properties of numerous substances. A common method to introduce the trifluoromethyl group employs the Ruppert–Prakash reagent, that is, Si(CH 3 ) 3 CF 3 , together with a copper(I) halide. We have applied this method to the trifluoromethylation of aromatic alkynes and used electrospray‐ionization mass spectrometry to investigate the mechanism of these reactions in tetrahydrofuran, dichloromethane, and acetonitrile as well as with and without added 1,10‐phenanthroline. In the absence of the alkyne component, the homoleptic ate complexes [Cu(CF 3 ) 2 ] − and [Cu(CF 3 ) 4 ] − were observed. In the presence of the alkynes RH, the heteroleptic complexes [Cu(CF 3 ) 3 R] − were detected as well. Upon gas‐phase fragmentation, these key intermediates released the cross‐coupling products R−CF 3 with perfect selectivity. Apparently, the [Cu(CF 3 ) 3 R] − complexes did not originate from homoleptic cuprate anions, but from unobservable neutral precursors. The present results moreover point to the involvement of oxygen as the oxidizing agent.