Direct and convenient synthesis of [bis(trifluoroacetoxy)iodo]arenes from iodoarenes

Article abstract of DOI:10.1246/bcsj.79.142

An easy, safe, and effective method for preparing [bis-(trifluoroacetoxy) iodo]arenes, ArI(OCOCF₃)₂, in high yields from some iodoarenes are reported, using a K₂S₂O₈/CF ₃COOH/CH₂Cl₂ system. This procedure avoids the use of high temperature and severe reaction conditions.

Full text of DOI:10.1246/bcsj.79.142

142 Short Articles
Bull. Chem. Soc. Jpn. Vol. 79, No. 1, 142–144 (2006)
concd HNO3 and (CF3CO)2O appears only for deactivated
substrates.4 However, this procedure is accompanied with a
vigorous evolution of toxic nitrogen oxides. In the sodium per-
carbonate method,6 it is not suitable for the preparation of
NO2C6H4I(OCOCF3)2 isomers, and m-CF3C6H4I(OCOCF3)2
is obtained in only 40% yield. The oxidation of iodoarenes
with trifluoroperoxyacetic acid seems to be the most suitable
method,7 but preparation of trifluoroperoxyacetic acid requires
80% H2O2, which is not available commercially. Here, we
wish to report an alternative, direct method for the preparation
of [bis(trifluoroacetoxy)iodo]arenes from iodoarenes.
Recently, we have devised a simple, easy, and efficient
method for the direct preparation of ArI(OCOCF3)2 from the
respective iodoarenes in CF3CO2H, using commercial potassi-
um peroxodisulfate, K2S2O8, as the oxidant. For example, the
reaction of iodobenzene in a mixed solvent of CF3CO2H and
CH2Cl2 in the presence of K2S2O8 at 36–38 ꢁC for 20 h gave
[bis(trifluoroacetoxy)iodo]benzene in 76% yield. The results
are given in Table 1. K2S2O8 is used as a strong oxidizing
agent in many applications. It has the particular advantages
of being almost non-hygroscopic, having a particular good
storage stability, and being easy and safe to handle. The oxida-
tion of iodoarenes to [bis(trifluoroacetoxy)iodo]arenes can be
easily scaled up to give the advantages of K2S2O8 outlined
above, together with the complete absence of effluent or by-
product problems. The essence of our novel method is describ-
ed in Scheme 1.
Direct and Convenient Synthesis of
[Bis(trifluoroacetoxy)iodo]arenes
from Iodoarenes
ꢀ
Md. Delwar Hossain and Tsugio Kitamura
Department of Chemistry and Applied Chemistry,
Faculty of Science and Engineering, Saga University,
Honjo-machi, Saga 840-8502
Received August 19, 2005; E-mail: kitamura@cc.saga-u.ac.jp
An easy, safe, and effective method for preparing [bis-
(trifluoroacetoxy)iodo]arenes, ArI(OCOCF3)2, in high yields
from some iodoarenes are reported, using a K2S2O8/
CF3COOH/CH2Cl2 system. This procedure avoids the use
of high temperature and severe reaction conditions.
Hypervalent iodine reagents have been widely used as green
oxidants in organic synthesis due to their low toxicity, ready
availability, easy handling, high efficiency, stability to air and
moisture, and them being a safe alternative to heavy metal re-
agents such as lead(IV), thallium(III), and mercury(II). Recent-
ly, extensive studies on hypervalent iodine compounds such as
(diacetoxyiodo)arenes, [bis(trifluoroacetoxy)iodo]arenes, and
[hydroxy(tosyloxy)iodo]arenes have been carried out and their
use for organic synthesis has been reported.1 Among them,
[bis(trifluoroacetoxy)iodo]arenes, ArI(OCOCF3)2, are funda-
mental reagents, potent and often chemoselective oxidants,
and widely used in modern organic synthesis. They are also
used for facile transformations of alkynes, ketones, and sulfur
compounds, phenolic oxidation, oxidation of nitrogen com-
pounds, oxidative biaryl coupling, etc.2 Several methods are
available for the preparation of ArI(OCOCF3)2. The methods
used so far are generally as follows:
The oxidative reactions shown in Scheme 1 were carried out
at 36–38 ꢁC in CF3CO2H. CH2Cl2 was added to dissolve iodo-
arenes completely. The presence of K2S2O8 (in stoichiometric
Table 1. Preparation of [Bis(trifluoroacetoxy)iodo]arenes
from Iodoarenesa)
Entry
Iodoarene
Yield/%
1
2
3
4
5
6
7
8
9
10
C6H5I
4-ClC6H4I
3-CF3C6H4I
3-NO2C6H4Ib)
4-NO2C6H4Ib)
4-FC6H4I
76
87
82
72
71
71
75
36
81
79
(a) Reaction of arenes with tris(trifluoroacetoxy)iodine.3
(b) Oxidation of iodoarenes with HNO3/(CF3CO)2O,4 xenon
bis(trifluoroacetate),5 sodium percarbonate/(CF3CO)2O/CH2-
Cl2,6 and trifluoroperoxyacetic acid.7
4-BrC6H4I
3,5-(CF3)2C6H3I
4-ClC6H4Ic)
4-ClC6H4Ic),d)
(c) Reaction of iodosylarenes with Me3Si(OCOCF3).8
(d) Ligand exchange of (diacetoxyiodo)arenes by dissolving
with heating in CF3CO2H.9
a) The reaction of an iodoarene (1 mmol) was carried out at
20 h at 36–38 ꢁC in the presence of K2S2O8 (4 mmol) in
CF3CO2H (9 mL) and CH2Cl2 (2 mL). b) CH2Cl2 (5 mL) was
added. c) 1-Chloro-4-iodobenzene (5 mmol), K2S2O8 (20
mmol), CF3CO2H (45 mL), and CH2Cl2 (10 mL) were added.
d) CF3CO2H (30 mL) was used.
(e) Reaction of (dichloroiodo)arenes with AgOCOCF3.10
The most general synthetic method of ArI(OCOCF3)2 for
laboratory use is to dissolve (diacetoxyiodo)arenes in CF3-
CO2H with heating.9 However, there is yet room for improve-
ment in this method because contamination with (diacetoxy-
iodo)arenes decreases the yields. In the reaction of I(OCOCF3)3
with arenes,3 the reactivity of the arenes decreases in the order:
p-Me2C6H4 > MePh > PhH > PhCl > PhCF3. However, this
reaction does not work in the case of nitrobenzene due to its
lack of reactivity.
K2S2O8, CH2Cl2
ArI + CF3CO2H
ArI(OCOCF3)2
36−38 °C, 20 h
36−87%
Ar = C6H5, 4-ClC6H4, 3-CF3C6H4, 3-NO2C6H4,
4-NO2C6H4, 4-FC6H4, 4-BrC6H4, 3,5-(CF3)2C6H3
Direct oxidation of iodoarenes to ArI(OCOCF3)2 is consid-
ered as a convenient method. The oxidation of iodoarenes by
Scheme 1.
Published on the web January 13, 2006; DOI 10.1246/bcsj.79.142

Bull. Chem. Soc. Jpn. Vol. 79, No. 1 (2006)
Ó 2006 The Chemical Society of Japan
143
1-[Bis(trifluoroacetoxy)iodo]-3-(trifluoromethyl)benzene:
1
quantities) in the reaction mixture was indispensable, because
without its addition the oxidation reactions did not proceed.
Iodoarenes bearing strong electron-withdrawing groups at the
meta and para positions gave ArI(OCOCF3)2 in good yields,
but the reaction of 1,3-bis(trifluoromethyl)-5-iodobenzene re-
sulted in a low yield (36%) due to its lower reactivity. This
method was not applicable for iodoarenes with strong electron-
donating groups. For example, 4-iodotoluene and iodoanisoles
were quickly oxidized in the reaction mixtures, but the reac-
tion resulted in the decomposition to tarry products.
In conclusion, we have developed a new (or considerably
improved) preparative procedure, which is easy and cheap.
The new method gives [bis(trifluoroacetoxy)iodo]arenes in
high yields by the reaction of iodoarenes with K2S2O8 in CF3-
CO2H and CH2Cl2 at 36–38 ꢁC. Because of its simplicity and
convenience, we are sure that the present method will continue
to attract significant research activity in the future.
0.416 g (82%); mp 96–97 ꢁC (lit.,3 mp 99–100 ꢁC). H NMR (300
MHz, CDCl3) ꢀ 7.80 (t, J ¼ 8 Hz, 1H, ArH), 8.0 (d, J ¼ 8 Hz, 1H,
ArH), 8.39 (d, J ¼ 8 Hz, 1H, ArH), 8.44 (s, 1H, ArH). 13C NMR
(75 MHz, CDCl3) ꢀ 161.23 (q, JCF ¼ 41 Hz, COCF3), 138.12,
134.22 (q, JCF ¼ 34 Hz, CCF3), 132.51, 131.82 (q, JCF ¼ 4 Hz,
CCCF3), 130.42 (q, JCF ¼ 4 Hz, CCCF3), 122.30 (q, JCF ¼ 271
Hz, CCF3), 121.79, 112.84 (q, JCF ¼ 286 Hz, COCF3).
1-[Bis(trifluoroacetoxy)iodo]-3-nitrobenzene: 0.347 g (72%);
mp 143–144 ꢁC (lit.,4 mp 143 ꢁC). 1H NMR (300 MHz, CDCl3)
ꢀ 7.87 (t, J ¼ 8 Hz, 1H, ArH), 8.51 (d, J ¼ 8 Hz, 1H, ArH), 8.55
(d, J ¼ 8 Hz, 1H, ArH), 9.04 (s, 1H, ArH). 13C NMR (75 MHz,
CDCl3) ꢀ 162.17 (q, JCF ¼ 43 Hz, COCF3), 149.29, 141.02,
133.27, 130.77, 128.79, 121.42, 114.54 (q, JCF ¼ 282 Hz, COCF3).
1-[Bis(trifluoroacetoxy)iodo]-4-nitrobenzene: 0.341 g (71%);
mp 158–159 ꢁC (lit.,4 mp 161 ꢁC). 1H NMR (300 MHz, CDCl3)
ꢀ 8.41–8.49 (m, 4H, ArH). 13C NMR (75 MHz, CDCl3) ꢀ 161.03
(q, JCF ¼ 44 Hz, COCF3), 150.39, 136.31, 126.95, 126.83, 114.22
(q, JCF ¼ 284 Hz, COCF3).
Experimental
1-[Bis(trifluoroacetoxy)iodo]-4-fluorobenzene: 0.319 g (71%);
1
General. Melting points were determined with a Yanaco
1
mp 94–96 ꢁC (lit.,6 mp 103–105 ꢁC). H NMR (300 MHz, CDCl3)
micro-melting point apparatus and are uncorrected. H NMR and
ꢀ 7.29 (dd, J ¼ 8, 9 Hz, 2H, ArH), 8.24 (dd, J ¼ 5, 9 Hz, 2H, ArH).
13C NMR (75 MHz, CDCl3) ꢀ 165.31 (d, JCF ¼ 259 Hz, CF),
161.17 (q, JCF ¼ 41 Hz, COCF3), 138.25 (q, JCF ¼ 9 Hz, CCCF),
119.76 (q, JCF ¼ 23 Hz, CCF), 116.38, 112.83 (q, JCF ¼ 286 Hz,
COCF3).
13C NMR spectra were recorded on a JEOL JNM-AL300 spec-
trometer and the chemical shifts were expressed in parts per
million downfield from tetramethylsilane. Elemental analysis
was conducted by the Service Center of the Elemental Analysis of
Organic Compounds, Faculty of Science, Kyushu University.
Preparation of [Bis(trifluoroacetoxy)iodo]arenes from Iodo-
arenes. A solution of an appropriate iodoarene (1 mmol) in a
mixture of CF3CO2H (9 mL) and CH2Cl2 (2 mL) was heated with
stirring to 36–38 ꢁC. Next, K2S2O8 (4 mmol) was added portion-
wise over 10 min and the stirring was continued until TLC analy-
sis indicated completion of the reaction. Reaction times needed
20 h. After completion of the reaction, water (10 mL) was added.
The precipitated product was collected by filtration under reduced
pressure, washed with CH2Cl2 (10 mL), and discarded. The crude
product was obtained by extraction of the filtrate with dichloro-
methane (3 ꢂ 10 mL), followed by drying (anhydrous Na2SO4),
filtration, and removal of the solvent by evaporation under reduced
pressure. The crude product was washed with hexane (10 mL) and
purified by recrystallization from CF3CO2H/hexane.
1-[Bis(trifluoroacetoxy)iodo]-4-bromobenzene: 0.384 g (75%);
mp 125–127 ꢁC. 1H NMR (300 MHz, CDCl3) ꢀ 7.74 (d, J ¼ 9 Hz,
2H, ArH), 8.05 (d, J ¼ 9 Hz, 2H, ArH). 13C NMR (75 MHz,
CDCl3) ꢀ 161.18 (q, JCF ¼ 41 Hz, COCF3), 136.53, 135.29,
129.23, 120.45, 112.82 (q, JCF ¼ 286 Hz, COCF3). Found: C,
23.48; H, 0.77%. Calcd for C10H4BrF6IO4: C, 23.60; H, 0.79%.
1-[Bis(trifluoroacetoxy)iodo]-3,5-bis(trifluoromethyl)benzene:
0.205 g (36%); mp 121–123 ꢁC (lit.,7 mp 83 ꢁC). 1H NMR (300
MHz, CDCl3) ꢀ 8.27 (s, 1H, ArH), 8.75 (s, 2H, ArH). 13C NMR
(75 MHz, CDCl3) ꢀ 162.76 (q, JCF ¼ 38 Hz, COCF3), 134.81 (q,
JCF ¼ 4 Hz, CCCF3), 134.49 (q, JCF ¼ 34 Hz, CCF3), 126.54 (q,
JCF ¼ 4 Hz, CCCF3) 123.57 (q, JCF ¼ 271 Hz, CCF3), 123.29,
115.55 (q, JCF ¼ 287 Hz, COCF3).
References
Large scale synthesis was conducted for 1-[bis(trifluoroacet-
oxy)iodo]-4-chlorobenzene in a similar manner. A solution of
1-chloro-4-iodobenzene (1.196 g, 5 mmol) in a mixture of CF3-
COOH (45 mL) and CH2Cl2 (10 mL) was heated with stirring to
36–38 ꢁC. Next, K2S2O8 (20 mmol) was added portionwise over
20 min and the stirring was continued for 20 h. Workup of the
reaction mixture gave the purified product (1.881 g, 81%). When
CF3CO2H was decreased from 45 to 30 mL under the above con-
ditions, the yield was slightly decreased (1.841 g, 79%).
1
Reviews on organohypervalent iodine compounds and
their applications in organic synthesis: a) A. Varvoglis, Chem.
Soc. Rev. 1981, 10, 377. b) E. B. Merkushev, Russ. Chem. Rev.
(Engl. Transl.) 1987, 56, 826. c) M. Ochiai, Rev. Heteroat. Chem.
1989, 2, 92. d) R. M. Moriarty, R. K. Vaid, G. F. Koser, Synlett
1990, 365. e) R. M. Moriarty, R. K. Vaid, Synthesis 1990, 431.
f) A. Varvoglis, The Organic Chemistry of Polycoordinated
Iodine, VCH, Weinheim, 1992. g) P. J. Stang, Angew. Chem., Int.
Ed. Engl. 1992, 31, 274. h) O. Prakash, N. Sainai, P. K. Sharma,
Synlett 1994, 221. i) P. J. Stang, V. V. Zhdankin, Chem. Rev.
1996, 96, 1123. j) T. Umemoto, Chem. Rev. 1996, 96, 1757.
k) Y. Kita, T. Takada, H. Toma, Pure Appl. Chem. 1996, 68,
627. l) A. Varvoglis, Hypervalent Iodine in Organic Synthesis,
Academic Press, San Diego, 1997. m) T. Kitamura, Y. Fujiwara,
Org. Prep. Proced. Int. 1997, 29, 409. n) A. Varvoglis, Tetra-
hedron 1997, 53, 1179. o) T. Muraki, H. Togo, M. Yokoyama,
Rev. Heteroat. Chem. 1997, 17, 213. p) H. Togo, Y. Hoshina,
G. Nogami, M. Yokoyama, Yuki Gosei Kagaku Kyokaishi 1997,
55, 90. q) V. V. Zhdankin, Rev. Heteroat. Chem. 1997, 17, 133.
r) A. Kirschning, J. Prakt. Chem./Chem.-Ztg. 1998, 340, 184.
[Bis(trifluoroacetoxy)iodo]benzene: 0.335 g (76%); mp 119–
120 ꢁC (lit.,3 mp 120–121 ꢁC). 1H NMR (300 MHz, CDCl3) ꢀ 7.62
(t, J ¼ 8 Hz, 1H, ArH), 7.74 (t, J ¼ 8 Hz, 2H, ArH), 8.20 (d, J ¼
8 Hz, 2H, ArH). 13C NMR (75 MHz, CDCl3) ꢀ 161.07 (q, JCF
41 Hz, COCF3), 135.14, 133.67, 132.02, 122.76, 112.84 (q, JCF
286 Hz, COCF3).
¼
¼
1-[Bis(trifluoroacetoxy)iodo]-4-chlorobenzene: 0.404 g (87%);
mp 129–130 ꢁC (lit.,9b mp 131–133 ꢁC). 1H NMR (300 MHz,
CDCl3) ꢀ 7.58 (d, J ¼ 9 Hz, 2H, ArH), 8.14 (d, J ¼ 9 Hz, 2H,
ArH). 13C NMR (75 MHz, CDCl3) ꢀ 161.15 (q, JCF ¼ 41 Hz,
COCF3), 140.84, 136.56, 132.38, 119.59, 112.82 (q, JCF ¼ 286
Hz, COCF3).

144 Md. D. Hossain et al.
Bull. Chem. Soc. Jpn. Vol. 79, No. 1 (2006)
s) R. M. Moriarty, O. Prakash, Adv. Heterocycl. Chem. 1998, 69,
1. t) A. Kirschning, Eur. J. Org. Chem. 1998, 2267. u) V. V.
Zhdankin, P. J. Stang, Tetrahedron 1998, 54, 10927. v) A.
Varvoglis, S. Spyroudis, Synlett 1998, 221. w) Y. Kita, M. Egi,
T. Takada, H. Thoma, Synthesis 1999, 885. x) T. Wirth, V. H.
Hirt, Synthesis 1999, 1271. y) V. V. Grushin, Chem. Soc. Rev.
2000, 29, 315. z) M. Ochiai, Y. Kitagawa, Yuki Gosei Kagaku
Kyokaishi 2000, 58, 1048. aa) G. Pohnert, J. Prakt. Chem. 2000,
342, 731. bb) S. S. Chaudhari, Synlett 2000, 278. cc) T. Wirth,
Angew. Chem., Int. Ed. 2001, 40, 2812. dd) H. Togo, M. Katohgi,
Synlett 2001, 565. ee) V. V. Zhdankin, P. J. Stang, Chem. Rev.
2002, 102, 2523. ff) H. Togo, K. Sakuratani, Synlett 2002, 1966.
gg) Hypervalent Iodine Chemistry: Modern Developments in
Organic Synthesis, ed. by T. Wirth, Springer-Verlag, Berlin, 2003.
hh) H. Thoma, Y. Kita, Adv. Synth. Catal. 2004, 346, 111. ii) H.
Thoma, Y. Kita, Yuki Gosei Kagaku Kyokaishi 2004, 62, 116.
jj) T. Wirth, Angew. Chem., Int. Ed. 2005, 44, 3656.
Trans. 1 1999, 1251. i) Y. Kita, T. Yakura, H. Terashi, J. Haruta,
Y. Tamura, Chem. Pharm. Bull. 1989, 37, 891. j) K. Kanematsu,
S. Morita, S. Fukushima, E. Osawa, J. Am. Chem. Soc. 1981, 103,
5211. k) Y. Kita, H. Thoma, M. Inagaki, K. Hatanaka, Hetero-
cycles 1992, 33, 503. l) B. D. Gates, P. Dalidowicz, A. Tebben,
A. Wang, J. S. Swenton, J. Org. Chem. 1992, 57, 2135. m) G. M.
Loudon, A. S. Radhakrishna, M. R. Almond, J. K. Blodgett,
R. H. Boutin, J. Org. Chem. 1984, 49, 4272. n) Y. Kikugawa,
M. Kawase, Chem. Lett. 1990, 581. o) Y. Kita, T. Takada, S.
Mihara, H. Tohma, Synlett 1995, 211. p) E. B. Merkushev, N. D.
Simakhina, G. M. Koveshnikova, Synthesis 1980, 486. q) S.
Spyroudis, A. Varvoglis, J. Chem. Soc., Chem. Commun. 1979,
615. r) O. V. Sing, Org. Prep. Proced. Int. 1993, 25, 693.
3
I. I. Maletina, V. V. Orda, L. M. Yagupolskii, J. Org.
Chem. USSR (Engl. Transl.) 1974, 10, 294.
L. M. Yagupolskii, I. I. Maletina, N. V. Kondratenko,
V. V. Orda, Synthesis 1977, 574.
T. M. Kasumov, V. K. Brel, Y. K. Grishin, N. S. Zefirov,
P. J. Stang, Tetrahedron 1997, 53, 1145.
4
2
Applications of [bis(trifluoroacetoxy)iodo]arenes in organ-
5
ic synthesis: a) Y. Tamura, T. Yakura, H. Tohma, K. Kikuchi,
Y. Kita, Synthesis 1989, 126. b) Y. Kita, H. Tohma, K. Hatanaka,
T. Takada, S. Fujita, S. Mitoh, H. Sakurai, S. Oka, J. Am. Chem.
Soc. 1994, 116, 3684. c) T. Takada, M. Arisawa, M. Gyoten,
R. Hamada, H. Tohma, Y. Kita, J. Org. Chem. 1998, 63, 7698.
d) R. M. Moriarty, B. A. Berglund, R. Penmasta, Tetrahedron
Lett. 1992, 33, 6065. e) Y. Tamura, T. Yakura, Y. Shirouchi, J.
Haruta, Chem. Pharm. Bull. 1986, 34, 1061. f) G. Stork, K. Zhao,
Tetrahedron Lett. 1989, 30, 287. g) R. Benhida, P. Blanchard, J. L.
Fourrey, Tetrahedron Lett. 1998, 39, 6849. h) S. V. Ley, O.
Schucht, A. W. Thomas, P. J. Murray, J. Chem. Soc., Perkin
6
7
P. Kazmierczak, L. Skulski, Molecules 2002, 7, 810.
V. V. Zhdankin, M. C. Scheuller, P. J. Stang, Tetrahedron
Lett. 1993, 34, 6853.
8 N. S. Zefirov, S. O. Safronov, A. A. Kaznacheev, V. V.
Zhdankin, J. Org. Chem. USSR (Engl. Transl.) 1989, 25, 1807.
9
a) S. Spyroudis, A. Varvoglis, Synthesis 1975, 445. b) J. D.
White, G. Caravatti, T. B. Kline, E. Edstrom, K. C. Rice, A.
Brossi, Tetrahedron 1983, 39, 2393.
10 N. W. Alcock, T. C. Waddington, J. Chem. Soc. 1963,
4103.