Reactions of (chlorodifluoromethyl)benzene and (chlorodifluoromethoxy) benzene with nucleophilic reagents

Article abstract of DOI:10.1016/j.jfluchem.2004.10.001

Condensation reactions of (chlorodifluoromethyl)benzene and (chlorodifluoromethoxy)benzene with phenoxide and thiophenoxide ions have been performed in DMF or NMP with heating. In these conditions, the reaction between phenylselenide ion and (chlorodifluo

Full text of DOI:10.1016/j.jfluchem.2004.10.001

Journal of Fluorine Chemistry 126 (2005) 445–449
www.elsevier.com/locate/fluor
Reactions of (chlorodifluoromethyl)benzene and
chlorodifluoromethoxy)benzene with nucleophilic reagents
(
a
J e´ r oˆ me Guidotti , Vincent Schanen , Marc Tordeux , Claude Wakselman
b
a
a,*
a
SIRCOB-UMR CNRS 8086, B aˆ timent Lavoisier, Universit e´ de Versailles, 45 avenue des Etats-Unis, 78035 Versailles, France
b
Rhodia, Centre de Recherche de Lyon, 85 avenue des Fr e` res Perret, 69192 Saint-Fons Cedex, France
Received 15 July 2004; received in revised form 1 October 2004; accepted 1 October 2004
Available online 2 December 2004
Dedicated to Professor Richard D. (Dick) Chambers on the occasion of his 70th birthday.
Abstract
Condensation reactions of (chlorodifluoromethyl)benzene and (chlorodifluoromethoxy)benzene with phenoxide and thiophenoxide ions
have been performed in DMF or NMP with heating. In these conditions, the reaction between phenylselenide ion and (chlorodifluor-
omethyl)benzene did not occur. This latter reaction requires an additional visible light irradiation to proceed, as reported by Yoshida et al.
#
2004 Elsevier B.V. All rights reserved.
Keywords: Fluoroalkyl halides; Substitution reaction; Nucleophilic reagents
1
. Introduction
2. Results and discussion
Few studies have been devoted to the condensation of
nucleophilic reagents with (chlorodifluoromethyl)benzene
. Substitution of the chlorine atom by a phenylthio group
2.1. Reactions with sodium thiophenoxide
1
We confirmed the results of the initial report of
Yagupolskii and Korinko [1]: the condensation of chloride
1 with sodium thiophenoxide in refluxing DMF, or NMP, for
3 h led to [(difluorophenylmethyl)sulfanyl]benzene 3 in
yields lower or equal to 15%. For these first experiments,
sodium thiophenoxide was prepared from thiophenol and
sodium hydroxide. Better results were obtained when dry
sodium methoxide was used as a base. Moreover, the
mixture was initially protected by an inert atmosphere in
order to limit the possible oxidation of the thiophenate salt
into diphenyl disulfide. In these conditions, the yield of 3
increased to 71%. A similar result was obtained with
potassium thiophenoxide (Eq. (1)).
occured in the reaction of halide 1 with sodium thiophen-
oxide in N-methylpyrrolidone at reflux in a yield limited to
1
5% [1]. A similar substitution reaction with sodium
phenylselenide was performed in DMF at 100 8C under
visible light irradiation in 89% yield [2]. Owing to the
importance of gem-difluoro compounds [3], we proposed to
revisit these condensation reactions ourselves. We extended
our study to phenoxide ions and to another chloride,
(
chlorodifluoromethoxy)benzene 2. To our knowledge, no
reaction of this latter with nucleophiles has been reported
until now.
PhCF Cl PhOCF Cl
2
2
1
2
NMP
þ NasPh or KSPh À! PhCF SPh
1
(1)
2
3
reflux; 3 h
In order to compare the behaviour of thiophenoxide ion
with that of its selenide analogue, condensation of the
*
Corresponding author. Tel.: +33 1 39 25 44 11; fax: +33 1 39 25 44 52.
E-mail address: claude.wakselman@chimie.uvsq.fr (C. Wakselman).
thiolate with chloride 1 was attempted in DMF at 100 8C
0022-1139/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2004.10.001

446
J. Guidotti et al. / Journal of Fluorine Chemistry 126 (2005) 445–449
under visible light irradiation, as described by Yoshida et al.
2] for the selenide ion. However, no reaction occurred under
these conditions.
[
Attempts to apply strict thermal conditions (Eq. (1)) for
the reaction of chloride 2 with potassium thiophenoxide
showed that the reactivity of 2 is lower than that of 1.
Substitution of the chlorine atom was not complete and
Scheme 1. Reaction of substituted phenoxide ions with halides 1 and 2.
[
(difluorophenoxymethyl)sulfanyl]benzene 4 was obtained
as a mixture with diphenyl disulfide. The latter was formed
notwithstanding the precautions taken to avoid oxidation.
Compound 4 was isolated by chromatography on a silica gel
column in 14% yield (Eq. (2)).
(chlorodifluoromethyl)benzene 1, showing again the lower
reactivity of the halide 2 (Eq. (5)).
NMP
2 þ NaOPh À! PhOCF2OPh
(5)
ꢀ
1
50 C; 3 h
7
NMP
þ KSPh À! PhOCF SPh þ PhSSPh
2
(2)
2
Similarly, other phenoxides have been condensed with
halides 1 and 2 (see Scheme 1 and Table 1). In spite of the
limited yields obtained, these condensations show that even
the poorly reactive halide 2 is able to react with weak
nucleophilic reagents.
reflux; 3 h
4
2
.2. Reactions with sodium phenylselenide
The selenide ion was prepared by action of sodium
borohydride on diphenyl diselenide in ethanol [2] or by
treatment of the diselenide with sodium metal in THF under
ultrasonic irradiation [4]. Condensation of the selenide ion
with chloride 1 was performed in DMF at 100 8C under
visible light irradiation [2]. In our hands, [(difluorophe-
nylmethyl)selanyl]benzene 5 was isolated by chromatogra-
phy on silica gel in a 45% yield (Eq. (3)). Curiously enough,
the reaction did not proceed without light as reported by
Yoshida et al., though this selenide ion is considered an
excellent nucleophilic reagent [4,5].
2
.4. Comparison of substrates and nucleophilic reagents
As pointed out by Yoshida et al., the carbon-chlorine
bond in (chlorodifluoromethyl)benzene 1 is little polarized
and therefore poorly reactive towards nucleophilic attack
[2]. Owing to the inductive electron-withdrawing effect of
the oxygen atom in (chlorodifluoromethoxy)benzene 2, its
reactivity is even lower than that of 1 [8–10].
At first glance, comparison of the results obtained by
condensation of (chlorodifluoromethyl)benzene 1 with
different nucleophilic reagents appears rather puzzling
(all the results are presented in Table 2).
DMF; hv
þ NasePh À! PhCF SePh
1
(3)
2
5
ꢀ
00 C; 4 h
1
Under strict thermal conditions, the selenide ion seems
unable to perform the substitution of the chlorine atom,
which occurs with the thiophenoxide analogue and even
with the poorly nucleophilic phenoxide ion! Additional
activation by visible light irradiation is necessary in the
selenium series.
Simple thermal condensations were also attempted in
NMP at reflux, as for the thiophenoxide ion reaction (Eq.
1)), but without success.
(
2
.3. Reactions with sodium phenoxides
Concerning the simple thermal condensation of nucleo-
philic reagents with halides 1 and 2, a S 2 mechanism can be
Reaction of sodium phenoxide with chloride 1 was
N
performed in DMF at 100 8C for 24 h. (Difluorophenox-
ymethyl)benzene 6 was isolated by chromatography on
silica gel in 75% yield (Eq. (4)).
considered as proposed by Haas et al. [6] for the reaction of
PhCF Br. Alternatively, a SRN1 process could occur. In order
2
to trap a possible radical intermediate, various unsaturated
products (dec-1-ene, butyl vinyl ether, anisole) were
introduced into the reaction medium (Eq. (4)) but no adduct
DMF
þ NaOPh À! PhCF OPh
1
(4)
2
6
ꢀ
00 C; 24 h
1
was detected. A S 1 mechanism seems unlikely owing to the
N
Compound 6 has already been prepared from sodium
phenoxide and the analogous bromide PhCF Br by heating
low polarizability of the carbon-chlorine bond in halides 1
and 2. The failure of the chlorine substitution by a
phenylselanyl group is not easily explained by all these
mechanisms.
2
the DMF solution at 80 8C for 24 h [6]. The higher yield
(85%) obtained in milder conditions appears logical for a
more reactive bromide.
Initiation of the selenide ion reaction has been interpreted
as a photo-induced electron transfer from the nucleophile to
the (chlorodifluoromethyl)benzene 1 [2]. A similar process
could be involved in the reaction of the thiophenoxide ion
[11], but it does not seem to occur. Obviously, the
mechanisms involved in these condensations need more
study [12].
Reaction of sodium phenoxide with chloride 2 was also
examined. The condensation was performed in NMP at
0
1
50 8C for 24 h. 1,1 -[Difluoromethylene(bis)oxy]-diben-
zene 7 [7] was obtained in 37% yield. The transformation of
chlorodifluoromethoxy)benzene 2 was not complete in
stronger conditions than that used for the condensation of
(

J. Guidotti et al. / Journal of Fluorine Chemistry 126 (2005) 445–449
447
Table 1
Reaction of substituted phenoxide ions with halides 1 or 2
1
1
or 2 Phenoxide
Yield (%)
d
F
(ppm)
d
C
(ppm) (J: Hz)
20.8 (C10) 121.9 (C
28.3 (C ) 129.8 130.7 (C
m/z (%)
a
67
4
+ꢁ
À65.7 (CF
2
; s)
; s)
7
) 125.6 (C
) 135.2
, t, JCF = 33 Hz) 148.3 (C
3
, t, JCF = 4 Hz)
CI methane 239 (M + 1 , 36)
+
219 (M À HF , 100)
1
8
1
2
(
C
4
6
)
b
54
3
+ꢁ
1
1
À66.3 (CF
2
115.9 (C
8
, d, JCF = 23) 123.7 (C
7
, d, JCF = 8)
, t, JCF = 4 Hz) 128.5 (C ) 130.9
) 160.3 (C10, d, JCF = 244)
CI methane 235 (M + 1 , 43)
+
215 (M À HF , 100)
4
À117.5 (CF; m) 125.5 (C
3
2
(
C
1
) 146.2 (C
6
c
31
1
+ꢁ
À66.0 (CF
2
; s)
55.9 (C12) 112.6 120.5 122.4 (C
5
, t, JCF = 263)
CI methane 231 (M + 1 , 100)
4
, t, JCF = 4 Hz)
1
1
24.5 125.8 (C
3
26.6 128.3 (C
8
) 130.7 (C
1
) 133.9
2
, t, JCF = 32 Hz) 152.6
(
C
4
d
1
, t, JCF = 255)
+
2
2
2
2
45
À56.0 (CF
2
; s)
; s)
21.2 (C10) 120.5 120.6 (C
5
143 (6 PhOCF
2
) 77 (28)
1
1
1
21.0 (C
30.3 (C
50.3 (C
3
8
4
8
3
1
4
5
7
9
4
7 1 2
) 125.4 (C ) 125.9 (C ) 129.7 (C )
) 135.2 147.7 (C
6
, t, JCF = 2)
, t, JCF = 2)
1
, t, JCF = 252)
+ꢁ
25
20
À56.4 (CF
2
116.1 (C
d, JCF = 23) 120.8 (C
5
254 (M , 100) 235 (27)
159 (50) 143 (39) 77 (92)
3
, d, JCF = 9)
À117.0 (CF; m) 121.0 (C
) 122.9 (C
) 129.5 (C
7
4
. t, JCF = 2)
1
26.0 (C
50.3 (C
2
) 146.2 (C
6
1
, t, JCF = 2) 160.4 (C10, d, JCF = 254)
4
1
, t, JCF = 254) 120.9 (C
+ꢁ
+ꢁ
À56.1 (CF
2
; s)
; s)
120.8 (C
3
, t, JCF = 1)
8
, C )
272 (M , 26) 270 (M , 85)
251 (14) 143 (41) 77 (100)
4
122.4 (C
131.4 (C
150.2 (C
, t, JCF = 1) 126.0 (C
1
) 129.6 (C
, t, JCF = 2)
, t, JCF = 2)
2
3
) 148.8 (C
6
3
e
29
+ꢁ
À55.9 (CF
2
55.7 (C12) 112.8(C10) 120.4 (C
8
) 120.85(C
, t, JCF = 254) 122.7(C ) 125.6(C
) 129.3 (C ) 139.2 (C11) 150.5
3
)
254 (M , 100) 235 (27),
1
1
21.1 (C
26.9 (C
5
7
1
)
159 (50) 143 (39) 77 (92.)
1
9
2
3
3
(
C
4
–C
6
, t, JCF = 2) 152.0 (C
6
–C
4
, t, JCF = 2)
3
118.2 (C11 q, JCF = 4) 120.8 (C
1
, t, JCF = 255)
+ꢁ
2
28
À55.9 (CF
2
; s)
; s)
5
304 (68, M ) 285 (26)
3
q, JCF = 9) 123.5
À63.3 (CF
3
121.0 (C
3
) 122.7 (C
9
143 (38) 77 (100)
1
12 q, JCF = 263) 124.3 (C ) 126.17 (C )
(
C
7
1
2
1
1
29.6 (C
50.1 (C
2
6
) 130.20 (C ) 132.2 (C10 q, JCF = 33)
3
, t, JCF = 2) 150.5 (C
3
4
–C
6
6
–C
4
, t, JCF = 2)
a
ppm: 2.23 (3H, CH
b
, s) 7.12, 7.70 (9H, Harom, m). 7.02–7.78 (9H, Harom, m). 3.92 (3H, CH
c
d
, s) 6.92–7.78 (9H, Harom, m). 2.23 (3H, CH , s) 7.09–7.44 (9H,
d
H
3
3
3
e
H
3
arom, m). 3.75 (3H, CH , s) 6.88–7.31 (9H, Harom, m).
Table 2
Reaction of (chlorodifluoromethyl)benzene 1 with various nucleophiles
thermally stable nucleophilic reagents (phenoxides, thio-
phenoxides, arylselenides ions) occurs in dipolar aprotic
solvents, either under simple thermal conditions or under
additional visible light irradiation.
Nucleophile
Conditions
Product
Yield (%)
PhSNa
PhSeNa
PhSNa
PhSeNa
PhONa
a
NMP, reflux 3 h
NMP, reflux 3 h
hv, DMF, 100 8C, 4 h
hv, DMF, 100 8C, 4 h
DMF, 100 8C, 24 h
19
3
5
3
5
6
71
a
–
a
–
45
76
4. Experimental
Not detected by F NMR analysis of the reaction mixture.
THF (tetrahydrofuran) was distilled over sodium/benzo-
phenone. DMF and NMP were distilled over calcium
hydride. Solvents were kept under argon. Sodium phenates
and thiophenates were prepared from equimolecular
quantities of phenol (0.05 M) or thiophenol and sodium
methoxide (0.05 M) in 100 ml of anhydrous methanol; the
solvent was removed in vacuo and the salt was protected
from moisture and oxygen. NMR spectra were recorded as
CDCl3 solutions on a Bruker AC-300 spectrometer.
Reported coupling constants and chemicals shifts were
based on a first order analysis. Internal reference was the
3
. Conclusion
The starting chlorides 1 and 2 are formed as secondary
products in the chlorine to fluorine exchange reaction by
hydrogen fluoride used generally to produce trifluoromethy-
lated compounds [15]. They can also be prepared on purpose
when the halogen exchange is performed with pyridinium
poly(hydrogen fluoride) [16]. In spite of the feeble reactivity
of chlorides 1 and 2, substitution of the chlorine atom by
1
residual peak of CHCl3 (7.27 ppm) for H (300 MHz),

448
J. Guidotti et al. / Journal of Fluorine Chemistry 126 (2005) 445–449
1
central peak of CDCl (77 ppm) for C (75 MHz) spectra
3
1 (65 mg, 0.4 mmol, 1 eq.) in DMF (3 mL) was added. The
mixture was irradiated in a Pyrex tube under argon at 100 8C
with a 500 W halogen lamp (distance 15 cm) for 8 h. After
addition of water (25 mL) at room temperature, the mixture
was extracted with ether (3 mL ꢂ 20 mL). The organic layer
was dried over magnesium sulfate and concentrated in
vacuo. The product was purified by preparative thin layer
chromatography on silica gel (pentane/ether: 95/5) (white
3
1
and internal CFCl3 (0 ppm) for F (282 MHz) NMR
9
spectra. IR spectra were recorded as CCl solutions on an
4
Impact 400D Nicolet spectrophotometer. GCMS were
performed with Chrompack CP Sil 19 CB chromatography
column, length 30 m, diameter 0.25 mm, film thickness
0
1
.25 mm, initial temperature 50 8C over 2 min, gradient
0 8C/min, final temperature 250 8C on a HP 5989B
1
9
quadrupolar mass spectrometer. High resolution mass
spectra were performed with a Finnigan MAT 95S spectro-
meter. Boiling points were determined by the Siwoloboff
method on a Buchi melting point apparatus.
crystals; m.p.: 75 8C, yield: 45%). F NMR: À70.5 (CF , s).
2
1
H NMR: 7.20–7.67 (10H, Harom, M).
4.1.4. (Difluorophenoxymethyl)benzene 6
The reaction temperature and time were, respectively,
00 8C and 24 h (elution with pentane; colourless oil, yield:
4
.1. General procedure
1
7
1
9
1
5%) [6]. F NMR: À65.8 (CF , s). H NMR: 7.23–7.51
2
3
8H, H –H –H –H , M) 7.76–7.78 (2H, H , d, J = 8 Hz).
The chloride 1 or 2 (Rhodia) (7.5 mmol) and the
(
1
1
2
3
9
7
HH
3
1
C NMR: 121.9 (C ) 122.2 (C , t, J = 262 Hz) 125.6 (C3,
nucleophilic reagent (7.5 mmol) in NMP (3 mL) were
stirred under argon in the conditions given for each
7
5
CF
5
t, J = 2 Hz) 125.6 (C ) 128.5 (C ) 129.4130.8 (C ) 133.9
CF
9
8
1
1
9
2
3
compound described. The reaction was monitored by
NMR. After hydrolysis and extraction with diethyl ether
F
(C , t, J = 31 Hz) 150.6 (C , t, J = 2 Hz). MS (CI
4 CF 6 CF
+
NH ): m/z = 220 (8%, M ) 127 (100%, PhCF ) 77 (6%, Ph).
ꢁ
3
2
(
3 mL ꢂ 15 mL) at room temperature, the organic layers
Elemental analysis calc. for C H F O: C (70.9%) H
3 10 2
1
were combined, washed with water, dried over magnesium
sulfate, concentrated in vacuo and purified by chromato-
graphy on a silica gel column.
(4.5%); found: C (71.1%) H (4.5%).
0
4
.1.5. 1,1 -[Difluoromethylene(bis)oxy]dibenzene 7
The reaction temperature and time were, respectively,
50 8C and 24 h (elution with pentane) (colourless oil; yield:
4
.1.1. [(Difluorophenylmethyl)sulfanyl]benzene 3
The reaction temperature and time were respectively
1
3
19
1
7%) [7]. F NMR: À55.8 (CF , s). H NMR: 7.24–7.27
2
1
80 8C and 3 h [1]. White crystals (m.p. 88 8C, yield 74%)
were isolated after chromatography (elution with pentane).
13
6H, H –H , M) 7.36–7.41 (4H, H , M). C NMR: 120.9
(
1 2 3
1
(
C , t, J = 254 Hz) 121.0 (C ) 125.87 (C ) 129.5 (C )
5 CF 3 1 2
1
9
1
ꢁ
+
F NMR: À72.3 (CF , s). H NMR: 7.45–7.60 (6H, M)
2
3
1
50.4 (C ). MS (CI NH ): m/z = 236 (100%, M ) 217 (17%,
4 3
1
.70–7.85 (4H, M). C NMR: 125.5 (C , t, J = 5 Hz)
1
27.6 (C ) 127.8 (C , t, J = 279 Hz) 128.4 (C ) 129.1
3
ꢁ
+
7
3
CF
M ÀF) 143 (32%, PhOCF ) 77 (78%, Ph). Elemental
2
1
6
5
CF
8
analysis calc. for C H F O : C (66.1%) H (4.3%); found:
1
3 10 2 2
2
(
C ) 130.0 (C ) 130.7 (C ) 136.1 (C , t, J = 25 Hz) 136.4
2 9 1 4 CF
C (66.0%) H (4.3%).
ꢁ
+
+
(
C ). MS (CI NH ): m/z = 236 (6%, M ) 217 (4%, M ÀF).
7
3
1
C H F S: C (66.1%) H (4.2%); found: C (65.9%) H
27 (100%, PhCF ) 77 (7%, Ph). Elemental analysis calc. for
2
1
3 10 2
Acknowledgements
(
4.2%).
We thank Rhodia for financial support (grant to JG) and
Dr. Karen Wright for advice during the preparation of the
manuscript.
4
.1.2. [(Difluorophenoxymethyl)sulfanyl]benzene 4
The reaction temperature and time were, respectively,
80 8C and 3 h. The elution was performed with pentane/
1
1
9
ethyl acetate (98/2) (colourless oil, yield 14%). F NMR:
1
2
À43.3 (CF , s). H NMR: 7.15 (2H, H , d, J = 8 Hz)
2
3
HH
References
2
7
1
.22–7.54 (6H, M) 7.66 (2H, H , J = 7 Hz). 13C NMR:
7 HH
4
21.4 (C , s) 122.7 (C ) 126.6 (C , t, J = 1.4 Hz) 128.5
7
9
6
CF
[1] L.M. Yagupolskii, V.A. Korinko, J. Gen. Chem. USSR 39 (1969) 186–
1
C , t, J = 295 Hz) 129.1 (C ) 129.4 (C ) 130.1 (C )
(
189 (English translation).
5
CF
2
8
1
4
3
[
2] M. Yoshida, A. Morishima, D. Suzuki, M. Iyoda, K. Aoki, S. Ikuta,
Bull. Chem. Soc. Jpn. 69 (1996) 2019–2023.
1
36.0 (C , t, J = 1 Hz) 150.7 (C , t, J = 2 Hz). MS (CI
3 CF 4 CF
ꢁ
+
+
NH ): m/z = 252 (67%, M ) 233 (11%, M ÀF) 159 (100%,
3
[
[
3] M.J. Tozer, T.F. Herpin, Tetrahedron 52 (1996) 8619–8683.
4] S.V. Ley, I.A. O’Neil, C.M.R. Low, Tetrahedron 42 (1986) 5363–5368.
PhSCF ) 143 (39%, PhOCF ) 109 (6%, PhS) 77 (63%, Ph).
2
2
HRMS: m/z calc. for C H F OS: 252.0450, found:
2
1
3
10
[5] M. Fieser, L.F. Fieser (Eds.), Reagents for Organic Synthesis, vol. 5,
Wiley, New York, 1975, p. 272.
2
52.0425.
[6] A. Haas, M. Spitzer, M. Lieb, Chem. Ber. 121 (1988) 1329–1340.
[7] S.J. Tavener, P.A. Heath, J.H. Clark, New J. Chem. 22 (1998) 655–657.
[8] This reactivity order has also been observed in their reaction with the
system magnesium metal/trimethylsilyl chloride in DMF [9]. How-
ever, the difference of reactivity is lower in their radical allylation by
allyltributyltin [10].
4
.1.3. [(Difluorophenylmethyl)selanyl]benzene 5
A mixture of diphenyl diselenide (125 mg, 0.4 mmol)
and sodium borohydride (45 mg, 1.2 mmol, 3 eq.) in ethanol
0.2 mL) was stirred for 30 min under argon [2]. The halide
(

J. Guidotti et al. / Journal of Fluorine Chemistry 126 (2005) 445–449
449
[
9] J. Guidotti, F. Metz, M. Tordeux, C. Wakselman, Synlett. (2004) 1759–
could be initiated. However, no proof for this process are presently
available.
1762.
[
[
[
10] J. Guidotti, M. Tordeux, J.C. Blazejewski, C. Wakselman, Lett. Org.
Chem. (2005) in press.
[13] N. Sonoda, A. Ogawa, in: L.A. Paquette (Ed.), Encyclopedia of
Reagents for Organic Synthesis, vol. 1, John Wiley, Chichester, 1995,
pp. 270–271.
11] R.A. Rossi, A.B. Pierini, A.B. Penenory, Chem. Rev. 103 (2003) 71–
167, and references cited therein.
[14] K. Tsuchii, A. Ogawa, Tetrahedron Lett. 44 (2003) 8777–8780.
[15] E.T. McBee, H.B. Hass, P.E. Weimer, G.M. Rothrock, W.E. Burt, in: C.
Slesser, S.R. Schram (Eds.), Preparation, Properties and Technology of
Fluorine and Fluoro Compounds, McGraw-Hill Book Co., New York,
1951, pp. 222–243.
12] A tentative mechanism could involve the oxidation of the
nucleophilic reagent in the phenylselenate anion case. Owing to the
very easy formation of diphenyldiselenide [13], the known
visible-light breaking of the selenium-selenium bond and the
possible abstraction of the larger halogen by the phenyselenyl
radical so formed [14], the substitution reaction of the chlorine atom
[16] L. Saint-Jalmes, PCT Int. Appl. WO 9743,231 to Rh oˆ ne-Poulenc
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