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PO
LIT
EC
NIC
O D
I M
ILA
NO
M. Sansoteraa, P. Metrangoloa, W. Navarrinia, G. Resnatia, I. Wlassicsb
a Dip-CMIC “Giulio Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milan, Italyb R&D Centre, Solvay Solexis, viale Lombardia 20, 20021 Bollate (MI), Italy
15th European Symposium on Fluorine Chemistry 15-20 July 2007, Prague, Czech Republic
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New Advances in Perfluoroalkytation of Aromatics: Products and Mechanism
PERFLUOROALKYLATIONSTRATEGIES
NUCLEOPHILIC ATTACK ON PERFLUOROALKENES
R
R
F
F
NuC
R
RF
F
Nu
ER
RF
F
Nu E
R
R
F
Nu-F_
+
_
F
F
F
F
F
F
F
F
R
R
F
R
C
R
RF
R
FE
R
RF
R
F EF
+
F
F
F
F
F
F F F
F
PERFLUOROALKYLATIONSTRATEGIES
NUCLEOPHILIC ADDITION
- Organometallic Reagents, RFZn or RFLi
- Trifluoromethylation with CF3Si(CH3)3
R'
O
RMR
R'R
R
OH
R, R' = H, AlkylM = Li, Zn
F
F
R'
O
RSi(CH3)3CF3
R'R
CF3
OH
R, R' = H, Alkyl
PERFLUOROALKYLATIONSTRATEGIES
ELECTROPHILIC PERFLUOROALKYLATION
R I R I (OCOCF3)2 R I+
Ph
OH2O2, (CF3CO)2O C6H6, CF3SO2OH (TfOH)
Tf
NuRNu
R I+
Ph
O Tf
Nu = carbanions, activated aromatics, enolate derivatives.
F F F
FF
FITS
PERFLUOROALKYLATIONSTRATEGIES
- Iodoperfluorocompound in presence of peroxidic agent
- Perfluoroalkylsulfonyl chloride catalyzed by Ru
- Perflurodiacyl Peroxide
IR CO2Ar RROOR'
Ar H IR+ ++F F
SO2ClR SO2Ar RRu
2+
Ar H+ +F F
FREE RADICAL
OO
O
O
RR Solvent
OH
O
R CO2ArR+ Ar - H ++F
F FF
SYNTHESIS OFPERFLUORODIACYL PEROXIDES
H2O2 OO
O
O
RR
NaOH/H2O
Solvent2 +- NaF F
F
Preparation of PERFLUORODIACYL PEROXIDES[1]
CF2
OO
O
O
CF2
CF2
CF2
CF3
CF3
Perfluorodi-n-butyryl Peroxide
Yield 50%
CF3
OO
O
O
CF3
CF3F
CF3F
Perfluorodi-iso-butyryl Peroxide
Yield 70%
CF3
OO
O
O
CF2
CF2
CF3
Perfluorodipropionyl Peroxide
Yield 30%
[1] W. Navarrini, M. Galimberti, E. Barchiesi J.F.C. 2005, 126, 587
CHARACTERIZATIONPERFLUORODIACYL PEROXIDES
FT-IR
CF2CF3RF =
CF3
CF3 FRF =
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
%T
1858 cm-1
1830 cm-1
1500 2000
Wavenumbers (cm-1)
1856 cm-1
1827 cm-1
1500 2000 1500 2000
1860 cm-1
1831 cm-1
CF2CF2CF3RF =
19F-NMR
ppm
Solvent Peaks
CF3 CF2
Solvent Peaks
-100-500
0
1000
2000
3000
4000
3.1
2.0
ppm -80.0-75.0-70.0-65.0-60.0-55.0
0
10000
20000
30000
40000
50000
6.0
ppm-185.3-185.2-185.1
0.9
F
Solvent PeaksCF32
ppm -100-50
0
5000
10000
15000
20000
25000
3.6
2.0
2.1
CF3 CF2 CF2
CF2CF2CF3RF =
CF3
CF3 FRF =
CF2CF3RF =
kd x 105 (s–1)
DECOMPOSITION OFPERFLUORODIACYL PEROXIDESDecomposition kinetics[2] of PERFLUORODIACYL
PEROXIDES
R
O
O O
O
R R
O
O O
O
R
CO2R.2 + 2F F F F F
[2] M. Sansotera, C. Corvaja, A. Famulari, L. Franco, M. Galimberti, P. Metrangolo, W. Navarrini, G. ResnatiChemToday 2006, 24, 3, 17
3,7
2,530
30 5,3
7,8
Peroxide T (°C) t1/2 (h)
CF2
OO
O
O
CF2
CF2
CF2
CF3
CF3
CF3
OO
O
O
CF3
CF3F
CF3F
CF3
OO
O
O
CF2
CF2
CF3
60 4,4 4,4
SOURCES OFPERFLUORINATED RADICALS
EPR-characterization of PERFLUORORADICALS
C C
F
F
FF
F. C
CF
F F
C F
FF
F
.
J = 87,7 Gauss J = 70,2 GaussJ = 86,4 Gauss
C C
F
FF
F
C
F
F
F.
-- Experimental
-- Calculated
T = 40 °C T = 60 °CT = 40 °C
SOURCES OFPERFLUORINATED RADICALS
Quantum mechanic calculations[2] for the study of the structures of PERFLUORORADICALS
[2] M. Sansotera, C. Corvaja, A. Famulari, L. Franco, M. Galimberti, P. Metrangolo, W. Navarrini, G. ResnatiChemToday 2006, 24, 3, 17
The electronic structures have been investigated at the DFT-B3LYP level by means of the GAMESS-US program with the 6-311G** basis set.
Distortion from the Planarityin perfluoroethyl radical
25°
Distortion from the Planarityin perfluoro-iso-propyl radical
5°
PERFLUOROALKYLATION OF AROMATIC SUBSTRATES
OO
O
O
RR Solvent
OH
O
R CO2ArR+ Ar - H ++F
F FF
86%95% 97%RF
CF2CF3R =F
Ar-H Product Yields
CF2CF2CF3R =FCFCF3
R =2
F
96%
(4%)a
89%
(4%)a
69%
(31%)a
CH3CH3
RF
a Yields of benzylic by-products.
64%39% 68%
Cl Cl
RF
MECHANISMFROM LITERATURE
RO O
RO
O
CO2
RC
+O O
RO
OR
C O OR
O
O
O
R
O
R
OR
O
.
+
+
+
+ .
F
F
F
F
F
F
F
F
F
Mono-electronic transfer process[3]
Formation of products
RO
O
R
R
O
O H
H
HR
+ +.. +
F
F
FF
[3] H.Sawada, Chem. Rev. 1996, 96, 1779
PERFLUOROALKYLATIONMECHANISM
R
O
O O
O
R R
O
O O
O
R
CO2.2 + 2RF F F F F
Thermolytic Initiation
RO O
RO
ORH
CO2
RO
O
RH
.
+ +
.RF
F
F
FF
F
Electron Transfer Propagation
Carbocation Aromatization
RO
O
RHR
R
O
O H+ + +
F
F
F
F
O OR
O
OR
CH3
CO2
CH2
CH2
O
O
R
R H.
.RF
F
F
F
F
MECHANISM OF SECONDARY REACTION
Hydrogen Abstraction
Benzyl Radical Induced Decomposition
CH3
R H
CH2
R .+ +
.
F F
CONCLUSIONS
• A procedure for the synthesis and characterization of perfluorodiacyl peroxides has been developed.
• EPR analyses demonstrated they are source of perfluorinated radicals.
• Quantum mechanics calculations and EPR analyses in substantial agreement corroborate the deviation from planarity as important
factor of the stabilizing effect of substituents on the radical center.
• Perfluorodiacyl peroxides have been used to perfluoroalkylate different aromatic substrates and for this reaction a mechanism for
products and by-products has been proposed.
ACKNOWLEDGMENTS
Politecnico di MilanoDr. S. BiellaDr. F. MeyerDr. F. ChauxDr. G. TerraneoDr. A. FamulariMr. M. UrsiniMr. F. Venturini Ms. M. BonacinaMr. A. Marcon
Solvay Solexis – S.p.a.Dr. M. GalimbertiDr. S. RadiceDr. E. BarchiesiMr. G. Ciocca
Università degli Studi di PadovaProf. C. Corvaja Dr. L. Franco
Politecnico di Milano
Solvay Solexis – S.p.a.
Università degli Studi di Padova
