Pentakis(trifluoromethyl)phenyl, a sterically crowded and electron-withdrawing group: synthesis and acidity of pentakis(trifluoromethyl)benzene, -toluene, -phenol, and -aniline.
A general route to functionalized pentakis(trifluoromethyl)phenyl (C6(CF3)5) derivatives, promising building blocks for designing novel stable carbenes, radical species, superacids, weakly coordinating anions and other practically and theoretically useful species, is presented. This pertrifluoromethylation route proceeds via conveniently pregenerated (trifluoromethyl)copper (CF3Cu) species in DMF, stabilized by addition of 1,3-dimethyl-2-imidazolidinone (DMI). These species react with hexaiodobenzene at ambient temperature to give the potassium pentakis(trifluoromethyl)phenoxide along with hexakis(trifluoromethyl)benzene and pentakis(trifluoromethyl)benzene in a combined yield of 80%. A possible reaction pathway explaining the formation of pentakis(trifluoromethyl)phenoxide is proposed. Pentakis(trifluoromethyl)phenol gives rise to easily functionalized pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)aniline. Pertrifluoromethylation of pentaiodochlorobenzene and pentaiodotoluene allows straightforward access to pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)toluene, respectively. XRD structures of several C6(CF3)5 derivatives were determined and compared with the calculated structures. Due to the steric crowding the aromatic rings in all C6(CF3)5 derivatives are significantly distorted. The gas-phase acidities (Delta Gacid) and pKa values in different solvents (acetonitrile (AN), DMSO, water) for the title compounds and a number of related compounds have been measured. The origin of the acidifying effect of the C6(CF3)5 group has been explored using the isodesmic reactions approach.
Kütt
Agnes
A
University of Tartu, Institute of Chemistry, 2 Jakobi St., 51014 Tartu, Estonia.
Movchun
Valeria
V
Rodima
Toomas
T
Dansauer
Timo
T
Rusanov
Eduard B
EB
Leito
Ivo
I
Kaljurand
Ivari
I
Koppel
Juta
J
Pihl
Viljar
V
Koppel
Ivar
I
Ovsjannikov
Gea
G
Toom
Lauri
L
Mishima
Masaaki
M
Medebielle
Maurice
M
Lork
Enno
E
Röschenthaler
Gerd-Volker
GV
Koppel
Ilmar A
IA
Kolomeitsev
Alexander A
AA
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004583:Electrons; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
D006845:Hydrocarbons, Fluorinated