Coupling reactions of chlorofluoro and perfluoroalkyl iodides

Article abstract of DOI:10.1135/cccc20081719

Coupling reactions of chlorofluoro- and perfluoroalkyl iodides R _f-I with R_f = ClCF₂CFCl-(CF₂) ₃CF₂-, ClCF₂CFClO(CF₂) ₃CF₂-, ClCF₂CFCl-, (CF₃) ₂CF- , (CF₃)₂CFCF₂CF₂- in the presence of a zinc/solvent system give dimers in good yields. Both homodimerizations (one iodide) and heterodimerizations (two different iodides) have been studied. The effect of temperature and solvent is shown. The zinc mediated dechlorination of vicinal chlorine atoms in the dimers afforded terminal alkenes and dienes.

Full text of DOI:10.1135/cccc20081719

Coupling Reactions
1719
COUPLING REACTIONS OF CHLOROFLUORO AND
PERFLUOROALKYL IODIDES
1,
2
Ivan WLASSICS * and Vito TORTELLI
Solvay Solexis, Viale Lombardia, 20; 20021 Bollate (MI), Italy;
1
2
e-mail: ivan.wlassics@solvay.com, vito.tortelli@solvay.com
Received April 30, 2008
Accepted August 25, 2008
Publish ed on lin e Decem ber 15, 2008
Dedicated to Professor Oldřich Paleta on the occasion of his 70th birthday.
Couplin g reaction s of ch lorofluoro- an d perfluoroalkyl iodides Rf–I with Rf = ClCF2CFCl-
(CF2)3CF2-, ClCF2CFClO(CF2)3CF2-, ClCF2CFCl-, (CF3)2CF- , (CF3)2CFCF2CF2- in th e presen ce
of a zin c/solven t system give dim ers in good yields. Both h om odim erization s (on e iodide)
an d h eterodim erization s (two differen t iodides) h ave been studied. Th e effect of tem perature
an d solven t is sh own . Th e zin c m ediated dech lorin ation of vicin al ch lorin e atom s in th e
dim ers afforded term in al alken es an d dien es.
Keyw ord s: Dim erization ; Ch lorofluoroalkyl iodides; Perfluoroalkyl iodides; Deh alogen ation ;
Perfluorodien e.
Due to th e relatively low dissociation en ergies of alkyl h alides an d in partic-
ular perfluoroalkyl iodides1 th eir radical h om o- an d h eterocouplin g reac-
tion s2–5 are an attractive an d easy syn th etic m eth od for obtain in g dim ers
bearin g th e sam e or differen t en d groups. Th ese dim ers are valuable syn -
th etic in term ediates for perfluorin ated term in al alken es an d dien es wh ich
can be used as m odifiers of fluorin ated m aterials6.
In th is work, th e couplin g reaction s of som e ch lorofluoro- an d perfluoro-
alkyl iodides in th e presen ce of zin c an d a solven t will be presen ted an d dis-
cussed. Th e experim en tal con dition s are critical: th e reaction tem perature
an d solven t effects are particularly im portan t an d can ch an ge sign ifican tly
th e ch em oselectivity.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728
© 2008 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20081719

1720
Wlassics, Tortelli:
RESULTS AND DISCUSSION
Dimerization Reactions
Both h om odim erization s (sym m etrical) an d h eterodim erization s (asym -
m etrical, cross) of fluorin ated alkyl iodides are reaction s prom oted by a
m ixture of a m etal an d acetic an h ydride (Ac2O) un der m ild con dition s4,5
.
Th e literature reports several oth er m eth ods used in couplin g iodides: ph o-
toch em ical7, electroch em ical8 an d in th e presen ce of copper2,3,9. Th e ph oto-
ch em ical m eth od h as th e m ain disadvan tage of bein g very slow, wh ile th e
Cu-m ediated dim erization requires particularly h igh reaction tem peratures
(120–200 °C); th e electroch em ical m eth od requires a soph isticated appara-
tus an d is n ot particularly suited for laboratory application s. Th e Zn -
m ediated dim erization of fluorin ated alkyl iodides was th erefore th e
m eth od of ch oice in th is work due to its feasibility on th e laboratory scale.
Hom odim erization s in volve th e couplin g of two iden tical fluoroalkyl io-
dides. Th ey proceed sm ooth ly with h igh yield an d selectivity.
Zn
2 Rf–I
Rf–Rf + Zn I2
In stead, h eterodim erization s in volve th e dim erization of two differen t
fluorin ated alkyl iodides. Th is will in evitably lead to th e form ation of a sta-
tistical distribution of th e dim ers, provided th at th e reactivities of th e io-
dides are th e sam e.
Zn
R1 –I + R2 –I
R1 –R2 + Zn I2
f f
f
f
As will be explain ed in m ore detail in th e Experim en tal, th e strategy
adopted in th e syn th esis of n ovel fluorin ated alkyl dim ers is th e couplin g of
ch lorofluoroalkyl iodides in th e presen ce of Zn an d acetic an h ydride at
40 °C. Subsequen t deh alogen ation of th e couplin g products in th e presen ce
of Zn in an aprotic polar solven t h as been perform ed as well to obtain in ter-
estin g term in al perfluoro alken es an d dien es10. In th e course of dim erizat-
ion of ClCF2CFCl(CF2)3CF2I, sh own in Sch em e 1, eith er th e deh alogen ation
Ac2O; CH2Cl2
ClCF2CFCl(CF2)4I + Zn
ClCF2CFCl(CF2)8CFClCF2Cl + Zn I2
SCHEME 1
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

Coupling Reactions
1721
of th e ClCF2CFCl- en d groups or th e reduction of th e term in al fluorin ated
iodide, -CF2I to -CF2H, could com pete with th e desired dim erization .
Th e results sh own in Table I dem on strate th at th e solven t system an d th e
tem perature are essen tial for selective dim erization in com petition with
dech lorin ation an d reduction .
At 40 °C n o deh alogen ation of th e 1,2-dich lorin ated ω-iodide is observed
wh ile th e reduction of th e term in al -CF2I to -CF2H occurs with very low
con version (<5 m ole %). A possible reason for th e low con version of th e re-
duction is th e low acidity of th e h ydrogen s presen t in th e reaction m edium :
on ce th e in term ediate organ om etal -CF2Zn I h as been form ed th e solven ts
CH2Cl2 or Ac2O do n ot tran sfer h ydrogen s. Th e m ain role of acetic an h y-
dride is both th e activation of th e zin c surface to allow its reaction with th e
alkyl iodide an d to provide en ough solven t polarity for sufficien t reactivity.
Om ittin g Ac2O from th e reaction , n o con version of th e fluorin ated alkyl
iodide to th e correspon din g dim er is observed. If CH2Cl2 is replaced by
DMF, still in th e presen ce of acetic an h ydride, just a 5% yield of th e deh alo-
gen ated product is obtain ed, wh ile th e m ain product is th e reduced com -
poun d, Rf–CF2H. Th is beh avior suggests th at DMF stabilizes th e organ ozin c
in term ediate so well th at it can abstract a proton from th e solven t; on th e
oth er h an d, th e oth er com petin g reaction , deh alogen ation , does n ot occur
because th e reaction tem perature is too low. In fact, in order to ach ieve
4
dim erization , th e tem perature is gen erally kept between 40 an d 50 °C
wh ile for 1,2-dech lorin ation s it lies between 70 an d 80 °C 10 wh en coordi-
n atin g solven ts such as dim eth ylform am ide or isopropyl alcoh ol are em -
ployed.
TABLE I
Yields (in %) of Zn h om odim erization of ClCF2CFCl(CF2)4I as a fun ction of solven t an d re-
action tem perature
CH2Cl2
40 °C
CH2Cl2 + Ac2O DMF + Ac2O
DMF + Ac2O
80 °C
Products
40 °C
40 °C
ClCF2CFCl(CF2)8CFClCF2Cl
ClCF2CFCl(CF2)4I
0
95
0
95
0
25
5
8
5
CF2=CF(CF2)3CF2H
ClCF2CFCl(CF2)4H
0
5
47
40
5
5
65
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

1722
Wlassics, Tortelli:
Th e th eoretical product distribution of th e couplin g reaction of two flu-
oroalkyl iodides of a very sim ilar structure, such as ClCF2CFCl(CF2)3CF2I (a)
an d ClCF2CFClO(CF2)3CF2I (b), in th e absen ce of side reaction s an d of
particular coordin atin g solven t effects, sh ould give th e statistical 1:2:1 ratio
of sym m etric (aa):asym m etric (ab):sym m etric (bb) dim ers. Th e results in
Table II sh ow th at th is is n ot th e case: on ly wh en th e m olar ratio acetic
an h ydride/total fluorin ated iodides is kept con stan t durin g th e reaction at a
sligh t m olar excess (20–25 m ole %) of Ac2O th e h eterodim erization yield
reach es th e statistical value (50%) or even m ore. With a twofold Ac2O ex-
cess, th e cross-dim er yield becom es n egligible. Hen ce, for a successful cross-
dim erization th e rate of acetic an h ydride addition (see Experim en tal) h as to
be adjusted to th e rate of iodide addition an d con version . Eviden ce th at
th is m eth odology sign ifican tly im proves th e selectivities of th e cross-dim er
is seen by com parin g th e results obtain ed in Table III with previous litera-
ture values11 for th e sam e cross-dim erization . Previous literature work in
fact reports cross-dim er selectivities <30%.
Th e Zn con cen tration does n ot seem to affect th e selectivity of th e
h eterodim er with respect to th e h om odim er: as for th e h om odim erization ,
a 20% m olar excess of zin c relative to iodides added was em ployed.
Th e effect of tem perature on th e h eterodim erization is clear: as it in -
creases, th e reduction to -CF2H in creases at th e expen se of th e h etero-
dim erization yield.
TABLE II
Yields (in %) of h eterodim erization s as a fun ction of tem perature an d Ac2O con cen tration
TR
°C
Total
RfI:Ac2O
1
2
3
4
5
40
50
60
40
50
60
1:1.2
1:1.2
1:1.2
1:2
60
17
15
31
47
45
35
18
20
31
47
45
35
3
5
2
5
55
4
17
3
17
3
traces
traces
traces
1:2
5
5
1:2
15
15
R1–CF2I + R2–CF2I → R1–CF2CF2R2 (1), R1–CF2CF2R1 (2), R2–CF2CF2R2 (3), R1–CF2H (4) an d
R2–CF2H (5), wh ere R1 = ClCF2CFClO-, R2 = ClCF2CFCl-.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

Coupling Reactions
1723
Th e cross-dim erization of fluoroalkyl iodides h avin g differen t structures
such as (CF3)2CF(CF2)mI (m = 0, 2) an d CF2ClCFClI is less efficien t com pared
with th e reaction between sim ilar iodides. Neverth eless, a h igh er yield
h as been obtain ed followin g th e experim en tal con dition s described earlier:
a con stan t 20% m olar excess of Ac2O relative to th e total am oun t of fluori-
n ated iodides durin g th e reaction an d a low tem perature (40 °C). Th e oth er
co-solven t was ch an ged for solubility reason s: 1,1,1-trich loroeth an e was
used in stead of dich lorom eth an e (see Experim en tal).
Zn
(CF3)2CF(CF2)mI + CF2ClCFClI
(CF3)2CF(CF2)mCFClCF2Cl + Zn I2
On e of th e syn th eses of perfluorostyren e, a particularly stable arom atic
perfluorovin yl com poun d12–15 is based on a copper m ediated cross couplin g
reaction . Th e syn th etic path way is sh own in Sch em e 2.
DMA
C6F5I + BrCF=CF2 + Cu
C6F5CF=CF2 + CuBrI
SCHEME 2
Operatin g with a twofold excess of BrCF=CF2 relative to C6F5I, th e re-
action gave a 60–65 m ole % yield of th e desired styren e as is sh own in
Table IV. Th e oth er products were th e respective h om odim ers: perfluoro-
biph en yl (30–35 m ole %) an d perfluoro-1,3-butadien e (0–10 m ole %). Th e
TABLE III
Yields (in %) of h eterodim erization as a fun ction of tem perature an d Ac2O con cen tration
TR
°C
R3–R4
R3–R3
R4–R4
R3–H + CTFE
RfI:Ac2O
40
50
60
40
50
60
1:1.2
1:1.2
1:1.2
1:2
40
27
31
37
47
45
35
28
32
38
47
45
40
5
7
30
traces
traces
traces
traces
25
6
1:2
10
25
1:2
R3 = (CF3)2CF-, R4 = ClCF2CFCl-, CTFE = ClCF=CF2.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

1724
Wlassics, Tortelli:
key feature of th e reaction is a differen t reactivity of th e startin g m aterials
toward copper powder: C6F5I > CF2=CFBr. Th erefore, th e organ ocopper
C6F5CuI is form ed first an d subsequen tly quen ch ed by brom otrifluoro-
eth en e to obtain perfluorostyren e as th e m ajor product. If th e reaction is
perform ed with a twofold m olar excess of th e m ore reactive ICF=CF2, th e
yield of perfluorobutadien e in creases to 37 m ole % with a parallel decrease
in th e yield of perfluorostyren e. Usin g a stoich iom etric am oun t of trifluoro-
iodoeth en e th e reaction proceeds givin g rough ly th e statistical 1:2:1 distri-
bution of th e dim ers an d suggestin g th at th e reactivities of C6F5–I an d
CF2=CF–I are very sim ilar.
TABLE IV
Yields (in %) of perfluorostyren e by Cu-m ediated h eterodim erization
X–CF=CF2
(m ol. ratio)
C6F5CF=CF2
C6F5–C6F5
CF2=CFCF=CF2
X
2
2
1
Br
I
60
30
50
30
33
25
10
37
25
I
CONCLUSIONS
We h ave dem on strated th at th e Zn /Ac2O m ediated dim erization reaction
of fluoroalkyl iodides can be directed to h om o- or h eterodim erization
products by con trollin g th e con cen tration of acetic an h ydride an d reaction
tem perature. By ch oosin g th e appropriate fluorin ated alkyl iodides, th e pre-
cursors of term in al perfluorin ated alken es an d sym m etrical or un sym m etri-
cal dien es can be obtain ed.
EXPERIMENTAL
Gen eral
All 19F NMR spectra (δ, ppm ; J, Hz) were recorded on a Varian Mercury 300 MHz spectrom e-
ter usin g CCl3F as th e in tern al stan dard. FT-IR spectra were recorded on a Nicolet Avatar 360
FT-IR ESP in terfaced with OMNIC software. Gas ch rom atograph ic an alyses were perform ed
on a Carlo Erba GC 8000 Top gas ch rom atograph er usin g a wide-bore 25 m colum n with a
0.54 µm silicon layer.
Zn powder was activated prior to use by first wash in g several tim es with aceton e an d th en
dryin g in a vacuum oven at 150 °C for 4 h .
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

Coupling Reactions
1725
Th e iodides ClCF2CFCl–I, ClCF2CFCl–(CF2)4–I, ClCF2CFClO–(CF2)4–I, (CF3)2CF(CF2)2–I,
CF2=CFI were prepared followin g literature procedures16–19. Th e iodides (CF3)2CFI an d C6F5I
were purch ased from Aldrich Ch em ical Co., brom otrifluoroeth en e was purch ased from
Math eson Ltd. Th ey were used with out furth er purification .
Upon request, GC-MS spectra can be furn ish ed for th e com poun ds syn th esized an d dis-
cussed in th e text.
Th e followin g gen eral dim erization procedures are m odified version s of radical dim er-
ization s already described in th e literature4,5
.
Fluoroalkyl Iodide Hom odim erization . Gen eral Procedure
Th e reaction is carried out in a glass roun d-bottom vessel in an in ert atm osph ere. Fluori-
n ated alkyl iodide Rf–I (10 m m ol) is dissolved in 5 m l of dry CH2Cl2 an d placed in an addi-
tion fun n el; acetic an h ydride (20 m m ol) is dissolved in 20 m l of CH2Cl2 an d th e m ixture is
added to 12 m m ol of Zn powder. Th e Zn suspen sion is h eated to 40 °C with vigorous stir-
rin g followed by rapid addition of th e iodide. A wh ite precipitate (Zn I2) is form ed after
iodide addition . Th e reaction is m on itored both by GC an d 19F NMR (disappearen ce of -CF2I
with a con com itan t appearan ce of a n ew -CF2- peak) an d it is com plete at 40 °C after 3 h .
Vacuum distillation of th e crude reaction m ixture an d two extraction s of th e organ ic distil-
late with a 10% NaOH aqueous solution followed by dryin g th e organ ic solution over an h y-
drous MgSO4 gave th e sym m etric dim er.
ClCF2CFClO(CF2)8OCFClCFCl (1)20. Th e correspon din g dim er 1 (3.46 g, 4.70 m m ol) was ob-
tain ed from ClCF2CFClO(CF2)4I (4.9 g, 10 m m ol) according to General procedure. B.p. 270 °C;
yield 95 m ole %. 19F NMR (CFCl3) of ClCF2CFClO–CF2(1CF22CF23CF2)2CF2–OCFClCF2Cl:
2
3
2
3
–68.3 dq, JFF = 165, JFF
= =
5JFF = 11 (2 F, first sign al of ClCF2-); –69.2 dq, JFF = 165, JFF
5JFF = 13 (2 F, secon d sign al of ClCF2-); –74.9 m (2 F, -CFCl-O); –81.1 m (4 F, -OCF2-);
–119.0 s (4 F, -1CF2-); –123.1 s (4 F, -2CF2-); –125.5 s (4 F, -3CF2-).
ClCF2CFCl(CF2)8CFClCF2Cl (2)21. Th e correspon din g dim er 2 (3.06 g, 4.34 m m ol) was ob-
tain ed from ClCF2CFCl(CF2)4I (4.78 g, 10 m m ol) accordin g to Gen eral procedure. B.p. 290 °C;
yield 87 m ole %. 19F NMR (CFCl3) of ClCF2CFCl(1CF22CF23CF24CF2)2CFClCF2Cl: –65.2 dq,
3
2
3
2JFF = 171, JFF
= =
4JFF = 9 (2 F, first sign al of ClCF2-); –65.9 dq, JFF = 167, JFF 4JFF = 13 (2 F,
secon d sign al of ClCF2-); –116.0 m (8 F, -1CF2-, -4CF2-); –123.1 m (8 F, -2CF2-, -3CF2-);
3
3
–133.5 dt, JFF = 10, JFF = 13 (2 F, -CFCl-).
Fluoroalkyl Iodide Heterodim erization s. Gen eral Procedure
In th e sam e reactor as above two differen t (per)fluorin ated alkyl iodides R1 –I (5 m m ol) an d
f
R2 –I (5 m m ol) are dissolved in 5 m l of dry CH2Cl2 an d placed in addition fun n el 1. Twelve
f
m m ol of acetic an h ydride are dissolved in 10 m l of CH2Cl2 an d are placed in addition fun -
n el 2. Zn (12 m m ol) suspen ded in 20 m l of CH2Cl2 is placed in th e reaction vessel. Th e Zn
suspen sion is h eated to 40 °C with vigorous stirrin g followed by slow, sim ultan eous addition
of th e iodides (addition fun n el 1) an d acetic an h ydride (addition fun n el 2). After 3 h , a
wh ite precipitate (Zn I2) starts to form . Th e reaction is m on itored both by GC an d 19F NMR
as above an d it is com plete after 10 h of stirrin g at 40 °C. Vacuum distillation of th e crude
reaction m ixture an d two extraction s of th e organ ic distillate with a 10% NaOH aqueous so-
lution followed by dryin g th e organ ic solution over an h ydrous MgSO4 gave th e cross-dim er
alon g with th e sym m etric dim ers an d th e reduced alkan e.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

1726
Wlassics, Tortelli:
ClCF2CFClCF2(CF2CF2CF2)3CF2OCFClCF2Cl (3). A m ixture (4.6 g) com posed of th e
dim ers 1–3, with th e followin g selectivities: 67% 3, 11% 1, 22% 2, was obtain ed from
ClCF2CFClO(CF2)4I (2.47 g, 5 m m ol) an d ClCF2CFCl(CF2)4I (2.39 g, 5 m m ol) accordin g to
Gen eral procedure. 19F NMR (CFCl3) of ClCF2CFClaCF2(1CF22CF23CF2)3CF2OCFClCF2Cl:
2
3
2
–64.9 dq, JFF = 165, JFF
=
4JFF = 11 (1 F, first sign al of ClCF2CFCl-CF2-); –69.2 dq, JFF = 165,
2
3
3JFF
=
4JFF = 13 (2 F, secon d sign al of ClCF22CFCl-CF2-); –71.9 dq, JFF = 171, JFF
=
4JFF = 9
=
4JFF = 12 (2 F, secon d sign al of
3
(1 F, first sign al of ClCF2CFClO-); –72.7 dq, JFF = 167, JFF
ClCF2CFClO-); –78.2 m (1 F, ClCF2CFClO-); –85.5 m (2 F,-CF2O-); –108.5 s (2 F, -aCF2-);
–116.3 s (2 F, -1CF2-); –123.8 s (2 F, -2CF2-); –126.6 s (2 F, -3CF2-); –131.8 dt, JFF = 9, JFF
=
3
3
12 (1 F, ClCF2CFCl-CF2-).
(CF3)2CF(CF2CF2)mCFClCF2Cl, m = 0 (4) an d m = 1 (5). Th is an d subsequen t syn th eses are
sligh tly differen t from all of th e oth er dim erization s discussed: CH2Cl2 is substituted, for sol-
ubility reason s, with 1,1,1-trich loroeth an e.
(CF3)2CFCFClCF2Cl (4). Perfluoroisopropyl iodide (2.36 g, 8 m m ol) an d ICFClCF2Cl (3.33 g,
12 m m ol) were added to 10 m l of 1,1,1-trich loroeth an e an d th e m ixture was placed in drop-
pin g fun n el 1. Acetic an h ydride (25 m m ol) diluted with 10 m l of 1,1,1-trich loroeth an e was
placed in droppin g fun n el 2. In a roun d-bottom flask, 24 m m ol of activated powdered Zn
were suspen ded in 10 m l of 1,1,1-trich loroeth an e. Th e Zn suspen sion was h eated to 40 °C
with vigorous stirrin g an d th en th e solution of both addition fun n els was added to th e Zn
suspen sion over a period of 6 h . Care sh ould be taken to avoid an excess of ICFClCF2Cl in
th e Zn slurry to m in im ize its decom position to CTFE, as well as its dim erization . Th e cross-
coupled product, (CF3)2CFCFClCF2Cl, was purified by distillation to afford 1.03 g of pure
2
3
m aterial. B.p. 80 °C; yield 40%. 19F NMR (CFCl3): –65.7 dq, JFF = 169, JFF
=
4JFF = 13 (1 F,
2
3
first sign al of ClCF2-); –66.5 dt, JFF = 169, JFF
=
4JFF = 11 (1 F, secon d sign al of ClCF2-);
3
–74.5 d (6 F, CF3-); –133.0 dt, JFF = 9, 12 (1 F, -CFCl-); –187.7 m (1 F, -CF-).
(CF3)2CF1CF22CF2CFClCF2Cl (5). Before perform in g th e dim erization reaction , ICFClCF2Cl
(5 g, 18 m m ol) was first telom erized17 with C2F4, th en ICF2CF2CFClCF2Cl (4.53 g, 12 m m ol)
was cross-dim erized with perfluoroisopropyl iodide (2.36 g, 8 m m ol) as described above. Af-
ter distillation , (CF3)2CF(CF2)2CFClCF23Cl (2.43 g) was obtain ed. B.p. 105 °C; yield 71%.
2
19F NMR (CFCl3): –63.9 dq, JFF = 171, JFF
=
4JFF = 11 (1 F, first sign al of ClCF2-); –67.7 dq,
2JFF = 169, JFF
=
4JFF = 11 (1 F, secon d sign al of ClCF2-); –74.1 d (6 F, CF3-); –116.0 s (2 F,
-1CF2-); –122.3 s (2 F, -2CF2-); –131.0 dt, JFF = 9, JFF = 12 (1 F, -CFCl-); –189.0 m (1 F, -CF-).
3
3
3
Dech lorin ation of Dim ers. Gen eral Procedure
Activated powdered Zn (12 m m ol), suspen ded in 20 m l of isopropyl alcoh ol (IPA), was
placed in a roun d-bottom flask equipped with a m agn etic stirrer, th erm om eter, reflux con -
den ser an d an addition fun n el. Th e suspen sion was h eated to 70–75 °C wh ile stirrin g. On ce
th e reaction tem perature was reach ed, 10 m m ol of th e ch lorin ated dim er, previously diluted
in 5 m l of IPA, was added from th e addition fun n el. Th e dech lorin ation began after ca. 20%
of th e ch lorin ated dim er h ad been added an d proceeded sm ooth ly to full con version . A tem -
perature in crease of 5–10 °C of was observed. Th e con version was m on itored by NMR. On ce
com plete con version was ach ieved, th e crude m ixture was cooled an d Zn Cl2 was filtered off.
If th e alken e form ed was h igh -boilin g, th e IPA m ixture was wash ed with distilled H2O an d
th e alken e th at separated from th e H2O layer was isolated an d dried over an h ydrous MgSO4.
However, if th e alken e was low-boilin g, th e IPA solution was distilled.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

Coupling Reactions
1727
CF2=CFO–(CF2)8–OCF=CF2 (6)20. Com poun d 6 (2.06 g) was obtain ed from com poun d 1
(3.5 g, 4.76 m m ol) accordin g to Gen eral procedure. B.p. 190 °C; yield 73%. FT-IR (KBr;
cm –1): 1830
s
(CF2=CFO–); 1250–1105
s
(CF). 19F NMR (CFCl3) of aCF2=bCFO–cCF2-
(1CF22CF23CF2)2–cCF2–ObCF=aCF2: –82.5 m (4 F, c); –111.3 dd, JFF = 80, JFF = 65 (2 F, cis-a);
2
3
2
3
–119.5 ddt, JFF = 84, JFF = 110 (2 F, trans-a); –120.0 s (4 F, -1CF2-); –121.2 s (4 F, -2CF2-);
–123.2 s (4 F, -3CF2-); –134.0 ddt, JFF = 65, 111, JFF = 6 (2 F, b).
3
4
CF2=CF–(CF2)8–CF=CF2 (7)21. Com poun d 7 (1.85 g) was obtain ed from com poun d 2 (4.0 g,
5.68 m m ol) accordin g to Gen eral procedure. B.p. 210 °C; yield 58%. FT-IR (KBr, cm –1): 1790 s
(CF2=CF–CF2–); 1250–1100 s (CF). 19F NMR (CFCl3) of aCF2=bCF–(1CF22CF23CF24CF2)2-
bCF=aCF2: –89.0 dd, JFF = 80, JFF = 65 (2 F, cis-a); –106.5 ddt, JFF = 84, JFF = 110 (2 F,
trans-a); –120.0 s (4 F, -1CF2-); –121.2 s (4 F, -2CF2-); –123.2 s (4 F, -3CF2-); –190.5 m (2 F, b).
CF2=CF–(CF2)8–OCF=CF2 (8). Com poun d 8 (2.2 g, 3.84 m m ol) was obtain ed from th e
crude m ixture com posed of 1–3 (4.6 g, 6.4 m m ol) accordin g to Gen eral procedure followed
by fraction al distillation , as described above. B.p. 200 °C; yield 60%. FT-IR (KBr, cm –1):
2
3
2
3
1838
s
(CF2=CFO–); 1786
s
(CF2=CF–CF2–). 19F NMR (CFCl3) of aCF2=bCFcCF2-
(1CF22CF23CF2)3–dCF2–OeCF=fCF2: –91.5 m (2 F, d); –92.0 dd, JFF = 80, JFF = 65 (1 F, cis-a);
2
3
2
3
2
3
–108.3 ddt, JFF = 84, JFF = 110 (1 F, trans-a); –113.5 dd, JFF = 80, JFF = 65 (1 F, cis-f);
2
3
–122.5 ddt, JFF = 84, JFF = 110 (1 F, trans-f); –121 s (2 F, c); –123.5 s (2 F, -1CF2-); –125.5 s
(2 F, -2CF2-); –126.3 s (2 F, -3CF2-); –136.3 ddt, JFF = 65, 111, JFF = 6 (2 F, e); –189.5 m (1 F, b).
(CF3)2CFCF=CF2 (9). Com poun d 9 (0.47 g, 1.87 m m ol) was obtain ed from com poun d 4
(1 g, 3.1 m m ol) accordin g to Gen eral procedure. B.p. 30 °C; yield 60%. FT-IR (KBr, cm –1):
1786 s (CF2=CF–CF–); 1210–1150 s (CF). 19F NMR (CFCl3): –72.3 d (6 F, CF3-); –86.2 dd,
3
4
3
2
3
2JFF = 82, JFF = 63 (1 F, cis =CF2); –106.5 ddt, JFF = 83, JFF = 112 (1 F, trans =CF2); –186.8 m
(1 F, -CF); –192.7 m (1 F, =CF-).
(CF3)2CFCF2CF2CF=CF2 (10). Com poun d 10 (1.83 g, 5.24 m m ol) was obtain ed from
com poun d 5 (2.4 g, 5.7 m m ol) accordin g to Gen eral procedure. B.p. 65 °C; yield 92%.
FT-IR (KBr, cm –1): 1786
s
(CF2=CF–CF–); 1210–1150
s
(CF). 19F NMR (CFCl3) of
(CF3)2CF1CF22CF2CF=CF2: –74.3 d (6 F, CF3-); –89.4 dd, JFF = 80, JFF = 65 (1 F, cis =CF2);
2
3
2
3
–106.5 ddt, JFF = 84, JFF = 110 (1 F, trans =CF2); –120.0 s (2 F, -1CF2-); –121.2 s (2 F, -2CF2-);
–188.5 m (1 F, -CF); –191.4 m (1 F, =CF-).
C6F5CF=CF2 (11). Th e reaction was carried out in a stain less-steel vessel equipped with
a pressure gauge. C6F5I (2.39 g, 10 m m ol) an d BrCF=CF2 (3.22 g, 20 m m ol) were dissolved
in 50 m l of an h ydrous dim eth ylacetam ide (DMA) an d siph on ed in to th e evacuated ves-
sel wh ich con tain ed 20 m m ol of Cu powder. Th e slurry was h eated to 120 °C for 5 h .
GC an alysis of th e crude reaction m ixture sh owed th e followin g product distribution :
65% C6F5CF=CF2, 33% perfluorobiph en yl an d 2% perfluorobutadien e. Th e m ixture was frac-
tion ally distilled an d th e target com poun d 11 (1.4 g, 5.7 m m ol) was obtain ed. B.p. 126 °C;
yield 57%. Th e spectroscopic data m atch th ose reported in th e literature13,22,23
.
Special thanks go to Prof. J. Kvíčala for helpful discussions regarding both the manuscript and
interpretation of 19F NMR spectra.
REFERENCES
1. Lowry T. L., Richardson K. S.: Mechanism and Theory in Organic Chemistry, p. 146. Harper
and Row, New York 1981.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728

1728
Wlassics, Tortelli:
2. Henne A. L.: J. Am. Chem. Soc. 1953, 75, 5750.
3. Chen G. J., Tamborski C.: J. Fluorine Chem. 1987, 36, 123.
4. Gorbunova T. I., Zapevalov A. Ya., Saloutin V. I.: Russ. J. Org. Chem. 1999, 35, 1557.
5. Fearn J. E.: J. Res. Nat. Bureau Stds. 1971, 75A, 41.
6. a) Babb D. in: Fluoropolymers 1: Synthesis (Hougham et al., Eds), pp. 25–50. Plenum Press,
New York 1999; b) Takayuki A., Tetsuo S., Takafumi Y., Masahiro K. (Daikin Industries
Ltd.): U.S. 5,670,593 (1997); Chem. Abstr. 1997, 124, 177249.
7. Buttafava A., Guarda P. A., Marchionni G., Ronconi R., Faucitano A.: J. Fluorine Chem.
2002, 114, 9.
8. Folest J. C., Nedelec J. Y., Perichon J.: J. Chem. Res., Synop. 1989, 394.
9. Ginah F. O., Donovan T. A., Suchan S. D., Pfennig D. R., Ebert J. W.: J. Org. Chem. 1990,
55, 584.
10. Wlassics I., Tortelli V.: J. Fluorine Chem. 2008, 129, 359.
11. Knunyants I. L., Shokina V. V.: Dokl. Akad. Nauk SSSR 1959, 129, 328.
12. Wall L. A., Brow D. W.: J. Fluorine Chem. 1972, 2, 73.
13. Soloski E. J., Ward W. E., Tamborski C.: J. Fluorine Chem. 1972, 2, 361.
14. Tamborski C., Moore G. J.: J. Fluorine Chem. 1971, 26, 153.
15. DePasquale R. J., Tamborski C.: J. Org. Chem. 1969, 34, 1736.
16. Pedersen S. D., Qiu W., Qiu Z.-M., Kotov S. V., Burton D. J.: J. Org. Chem. 1995, 61,
8024.
17. Wlassics I., Tortelli V.: J. Fluorine Chem. 2006, 127, 240.
18. Améduri B., Boutevin B., Kostov G. K., Petrova P.: J. Fluorine Chem. 1995, 74, 261.
19. Hansen S. W., Spawn T. D., Burton D. J.: J. Fluorine Chem. 1987, 35, 415.
20. Tortelli V., Millesanti S., Calini P. (Ausimont): Japan 213256 (2005).
21. Knunyants I. L., Li C.-Y., Shokina V. V.: Izv. Akad. Nauk SSSR, Ser. Khim. 1961, 1462.
22. Callander D. D., Coe P. L., Matough M. F. S., Mooney E. F., Uff A. J., Winson P. H.:
Chem. Commun. 1966, 22, 820.
23. Tamborski C., Soloski E. J., DePasquale R. J.: J. Organomet. Chem. 1968, 15, 494.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1719–1728