One-pot synthesis of pentafluorophenyl or chlorotetrafluorophenyl halogenoallenes

Article abstract of DOI:10.1016/S0022-1139(98)00344-3

The consecutive reaction of phosphonium salt (1) with n-butyllithium, hexafluorobenzene or chloropentafluorobezene, halogen acyl halide and triethylamine gives pentafluorophenyl or chlorotetrafluorophenyl halogenoallenes in 63-93% yields.

Full text of DOI:10.1016/S0022-1139(98)00344-3

Journal of Fluorine Chemistry 94 (1999) 69±71
One-pot synthesis of penta¯uorophenyl or chlorotetra¯uorophenyl
halogenoallenes
Yanchang Shen*, Zenghong Zhang
Shanghai Institute of Organic Chemistry, Academia Sinica, 354 Fenglin Lu, Shanghai 200032, China
Received 29 September 1998; accepted 18 November 1998
Abstract
The consecutive reaction of phosphonium salt (1) with n-butyllithium, hexa¯uorobenzene or chloropenta¯uorobezene, halogen acyl
halide and triethylamine gives penta¯uorophenyl or chlorotetra¯uorophenyl halogenoallenes in 63±93% yields. # 1999 Elsevier Science
S.A. All rights reserved.
Keywords: One-pot synthesis; Penta¯uorophenyl halogenoallenes; Chlorotetra¯uorophenyl halogenoallenes
1. Introduction
salts in organic synthesis [25,26], herein we report the
consecutive reaction of phosphonium salts being applicable
to the synthesis of penta¯uorophenyl or chlorotetra¯uoro-
phenyl halogenoallenes. The reaction sequence is shown in
Scheme 1.
Phosphoranes 2 generated from the corresponding phos-
phonium salts 1 and butyllithium in tetrahydrofuran (THF),
were reacted with hexa¯uorobenzene or chloropenta¯uor-
obenzene to give phosphoranes 3, which, in the reaction
medium were acylated by halogen acyl halide to give the
phosphonium salts 4. Treatment of 4 with a base (triethyl-
amine) afforded 5 with mesomeric form 6. Elimination of
triphenylphosphine oxide gave the product 7. The results are
summarized in Table 1. All compounds are new and have
Allenes occupy an important position in synthetic organic
chemistry since the allene functionality possesses intriguing
properties of structure and reactivity [1]. They are useful
intermediates in a variety of synthetic transformations and as
components of various natural products [2±11]. It has been
shown that the introduction of a penta¯uorophenyl group
into biologically active compounds often gives rise to unique
physiological activities [12], and organo¯uorine compounds
are increasingly being applied in pharmaceuticals, agro-
chemicals and other ®elds [13±15]. Moreover, penta¯uor-
ophenyl alkenes are also useful intermediates for the
synthesis of ¯uorine-containing organic compounds
[16,17]. A variety of methods for allene synthesis have been
reported [2,3,18±23]. However, to the best of our knowl-
edge, the synthesis of ¯uorinated halogenoallenes has not
been reported previously except in our preliminary commu-
nication [24]. Therefore it would be valuable to develop a
convenient method for the preparation of the title com-
pounds since they would be expected to be useful inter-
mediates for the synthesis of ¯uorine-containing
biologically active compounds.
2. Results and discussion
In our continuing investigation on the synthetic applica-
tion of the consecutive reaction of phosphonium or arsonium
Scheme 1.
*Corresponding author. Fax: +86-21-64166128.
0022-1139/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
P I I : S 0 0 2 2 - 1 1 3 9 ( 9 8 ) 0 0 3 4 4 - 3

70
Y. Shen, Z. Zhang / Journal of Fluorine Chemistry 94 (1999) 69±71
Table 1
3.1.1. 1-Chloro-3-pentafluorophenylbuta-1,2-diene (7a)
Bp: 808C 2 mm Hg 1. Analysis: Calc. for C10H4ClF5
(254.59): C, 47.18; H, 1.58%. Found: C, 46.99; H,
Preparation of substituted fluorinated halogeno-1,2-dienes
Entry
R1
R
Z
X
Yield (%)a
‡
1.45%. MS m/z (rel. int): 255 (M ‡1, 14), 219 (67), 181
7a
7b
7c
7d
7e
7f
H
CH3
H
Cl
Cl
Cl
Br
Br
Br
Br
Br
Br
Br
F
84
77
83
84
90
72
85
82
93
63
1
(100). IR (®lm): 1950, 1640, 1260, 1200; 770. H NMR
H
Cl
Cl
F
(CDCl3) ꢀ: 2.15 (d, 3H, Jˆ1.8 Hz), 6.20 (q, 1H,
Jˆ2.2 Hz) ppm. 19F NMR (CDCl3) ꢀ: 63.0 (m, 2F), 77.5
(m, 1F), 84.0 (m, 2F) ppm.
H
CH3
H
H
CH3
CH3
H
H
F
CH3
H
F
7g
7h
7i
Cl
Cl
Cl
Cl
3.1.2. 1-Chloro-3-(4-chlorotetrafluorophenyl)propa-1,2-
diene (7b)
H
CH3
H
CH3
CH3
Bp: 808C 2 mm Hg 1. Analysis: Calc. for C9H2Cl2F4
(257.01): C, 42.06; H, 0.78%. Found: C, 41.58; H,
7j
CH3
aIsolated yields.
‡
‡
0.83%. MS m/z (rel. int): 258 (M ‡1, 11), 257 (M , 3),
221 (100), 186 (25). IR (®lm): 1950, 1650, 1310, 1140; 790.
1H NMR (CDCl3) ꢀ: 6.46 (d, 1H, Jˆ6.2 Hz), 6.65 (d, 1H,
Jˆ6.2 Hz) ppm. 19F NMR (CDCl3) ꢀ: 63.0 64.1 (m, 2F),
64.1 65.0 (m, 2F) ppm.
been characterized by microanalyses IR, NMR and mass
spectroscopy.
Thus, this one-pot synthesis is very convenient for the
synthesis of the title compounds with good to excellent
yields starting from commercially available substances.
3.1.3. 1-Chloro-3-(4-chlorotetrafluorophenyl)buta-1,2-
diene (7c)
Bp: 1008C 2 mm Hg 1. Analysis: Calc. for C10H4Cl2F4
(271.04): C, 44.31; H, 1.49%. Found: C, 44.40; H, 1.30%.
3. Experimental
‡
‡
MS m/z (rel. int): 272 (M ‡1, 4), 271 (M , 1), 235 (100),
200 (55). IR (®lm): 1960, 1650, 1310, 1080; 790. 1H NMR
(CDCl3) ꢀ: 2.21 (d, 3H, Jˆ2.2 Hz), 6.25 (q, 1H,
Jˆ2.2 Hz) ppm. 19F NMR (CDCl3) ꢀ: 62.0 62.9 (m, 2F),
62.9 64.0 (m, 2F) ppm.
All boiling points and melting points are uncorrected. The
IR spectra of products of solid products were obtained as
KCl disks and of liquid products as ®lms on a Digilab FTS-
1
20E spectrometer. H NMR spectra were recorded on a
Bruker AM-300 (300 MHz) spectrometer (ꢀ values in ppm
from tetramethylsilane, in CDCl3, J-values are given in Hz).
19F NMR spectra were taken on a Varian EM-360 (60 MHz)
spectrometer (ꢀ in ppm from external tri¯uoroacetic acid, in
CDCl3, positive for up®eld shifts). Mass spectra were
measured on a Finnigan GC±MS-4021 mass spectrometer.
3.1.4. 1-Bromo-3-pentafluorophenylpropa-1,2-diene (7d)
Bp: 608C 2 mm Hg 1. Analysis: Calc. for C9H2BrF5
(285.01): C, 37.93; H, 0.71%. Found: C, 37.69; H,
‡
‡
0.78%. MS m/z (rel. int): 286 (M ‡1, 4), 285 (M , 1),
‡
284 (M 1, 5), 205 (100). IR (®lm): 1950, 1640, 1380,
1
1120; 790. H NMR (CDCl3) ꢀ: 6.30 6.50 (m, 2H) ppm.
19F NMR (CDCl3) ꢀ: 64.0 (m, 2F), 77.0 (m, 1F), 85.0 (m,
2F) ppm.
3.1. General procedure for the synthesis of substituted
pentafluorophenyl or chlorotetrafluorophenyl
halogenoallenes 7
3.1.5. 1-Pentafluorophenyl-3-bromobuta-1,2-diene (7e)
Bp: 758C 2 mm Hg 1. Analysis: Calc. for C10H4BrF5
(299.04): C, 40.17; H, 1.34%. Found: C, 40.03; H, 1.25%.
Butyllithium (4 mmol in 2 ml of hexane) was added
dropwise with stirring to a suspension of triphenylphospho-
nium salt (4 mmol) in absolute THF (10 ml) at 208C under
nitrogen. The reaction mixture was stirred for 30 min from
208C to 08C and hexa¯uorobenzene or chloropenta¯uor-
obenzene (2 mmol) was slowly added. The mixture was
allowed to warm to 208C, stirred for 1 h, recooled to 08C.
Halogen acyl halide (2 mmol) and then triethylamine (0.2 g,
2 mmol) were slowly added. After these additions, the
mixture was stirred at 208C for 3 h and then water
(20 ml) was added. The reaction mixture was extracted with
ether (3Â25 ml). The combined organic layer was washed
with brine (30 ml) and dried over anhydrous Na2SO4.
Evaporation of the solvent gave a residue which was puri®ed
by ¯ash chromatography on silica gel eluting with petro-
leum ether (60±908C) to give the product 7.
‡
MS m/z (rel. int): 299 (M , 18), 235 (49), 219 (100), 208
1
(21). IR (®lm): 1950, 1650, 1310, 1160; 790. H NMR
(CDCl3) ꢀ: 2.00 (d, 3H, Jˆ3.1 Hz), 5.60 (d, 1H,
Jˆ3.2 Hz) ppm. 19F NMR (CDCl3) ꢀ: 67.0 (m, 2F), 79.5
(m, 1F), 87.0 (m, 2F) ppm.
3.1.6. 1-Bromo-1-methyl-3-pentafluorophenylbuta-1,2-
diene (7f)
Mp: 308C. Analysis: Calc. for C11H6BrF5 (313.06): C,
42.20; H, 1.93%. Found: C, 42.36; H, 2.17%. MS m/z (rel.
int): 233 (100), 218 (14), 193 (13), 181 (24). IR (KCl): 1900,
1640, 1650, 1320; 1200. 1H NMR (CDCl3) ꢀ: 2.10 (s, 3H),
2.30 (s, 3H) ppm. 19F NMR (CDCl3) ꢀ: 65.0 (m, 2F), 77.5
(m, 1F), 85.0 (m, 2F) ppm.

Y. Shen, Z. Zhang / Journal of Fluorine Chemistry 94 (1999) 69±71
71
3.1.7. 1-Bromo-3-(4-chloro-tetrafluorophenyl)propa-1,2-
diene (7g)
Acknowledgements
Bp: 808C 2 mm Hg 1. Analysis: Calc. for C9H2BrClF4
(301.47): C, 35.86; H, 0.67%. Found: C, 35.81; H, 0.62%.
The authors thank the National Natural Science Founda-
tion of China, Laboratory of Organometallic Chemistry and
Academia Sinica for ®nancial support.
‡
‡
MS m/z (rel. int): 302 (M ‡1, 7), 301 (M , 2), 300 (5),
223 (42), 221 (100). IR (®lm): 1930, 1640, 1380, 1200;
790. 1H NMR (CDCl3) ꢀ: 6.30 6.50 (m, 2H) ppm.
19F NMR (CDCl3) ꢀ: 62.0 63.5 (m, 2F), 63.5 65.0
(m, 2F) ppm.
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‡
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1
(KCl): 1950, 1650, 1380, 1140; 790. H NMR (CDCl3) ꢀ:
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‡
MS m/z (rel. int): 315 (M ‡1, 4), 237 (41), 235 (100), 200
1
(96). IR (®lm): 1960, 1640, 1390, 1070; 790. H NMR
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(CDCl3) ꢀ: 2.35 (d, 3H, Jˆ3.1 Hz), 6.20 (q, 1H,
Jˆ3.2 Hz) ppm. 19F NMR (CDCl3) ꢀ: 63.0 63.9 (m, 2F),
63.9 65.0 (m, 2F) ppm.
3.1.10. 1-Bromo-3-(4-chloro-tetrafluorophenyl)buta-1,2-
diene (7j)
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int): 249 (100), 214 (44), 197 (17), 251 (36). IR (KCl): 1950,
1650, 1380; 1210. 1H NMR (CDCl3) ꢀ: 2.15 (s, 3H), 2.30 (s,
3H) ppm. 19F NMR (CDCl3) ꢀ: 61.5 62.6 (m, 2F),
62.6 63.6 (m, 2F) ppm.
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