Facile iodination of aromatic compounds having electron-withdrawing substituents. Generation of triiodine cation in the system tetra-N- iodoglycoluril-iodine-sulfuric acid

Full text of DOI:10.1134/S1070428008060286

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 6, pp. 935–936. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.K. Chaikovskii, A.A. Funk, V.D. Filimonov, T.V. Petrenko, T.S. Kets, 2008, published in Zhurnal Organicheskoi Khimii, 2008,
Vol. 44, No. 6, pp. 941–942.
SHORT
COMMUNICATIONS
Facile Iodination of Aromatic Compounds
Having Electron-Withdrawing Substituents. Generation
of Triiodine Cation in the System Tetra-N-iodoglycoluril–
Iodine–Sulfuric Acid
a
a
a
b
c
V. K. Chaikovskii , A. A. Funk , V. D. Filimonov , T. V. Petrenko , and T. S. Kets
a
Tomsk Polytechnical University, pr. Lenina 30, Tomsk, 634050 Russia
e-mail: clg@mail.ru
b
Institute of Petroleum Chemistry, Siberian Division, Russian Academy of Sciences, Tomsk, Russia
c
Tomsk State Pedagogical University, Tomsk, Russia
Received July 23, 2007
DOI: 10.1134/S1070428008060286
In the middle of the past century several methods
readily formed by gradually adding compound I to
+
for the generation of I ion by reaction of iodine with
a suspension of finely ground iodine in sulfuric acid
3
3
oxidants in oleum or sulfuric acid were proposed and
studied [1, 2]. It was shown that triodine cation in
solution exhibits enhanced electrophilicity and that
they are capable of iodinating benzene derivatives
having electron-withdrawing substituents [3, 4].
(d = 1.815–1.834 g/cm ) under stirring at 0–3°C
(Scheme 1).
We believe that the reaction of compound I with I2
in sulfuric acid leads to quantitative formation of
+
–
highly reactive iodinating intermediate I ·HSO . The
3
4
+
On the basis of spectral data and quantum-chemical
calculations we previously presumed [5–9] that dis-
process ensures fast generation of I in a high con-
3
centration. The obtained solution is stable, it has a dark
solution of N-iodo imides in sulfuric acid could give
brown color and absorbs at λ 453 and 291 nm, which is
+
3
+
rise to triodine cation I together with iodine(I) hydro-
consistent with the electronic absorption spectrum of I3
gen sulfate (IOSO H). With a view to get additional
given in [1]. The reagent readily reacts with nitroben-
zene (IIa) at 0–3°C in 40 min to give 3-iodonitro-
benzene (IIb) in 82% yield. Under analogous tem-
perature conditions, one or two iodine atoms can be
introduced in 45–60 min into molecules of 4- and
2-nitrotoluenes IIIa and IVa, benzaldehyde (Va), ben-
zoic acid (VIa), 4-fluorobenzoic acid (VIIa), benzo-
phenone (VIIIa), benzil (IXa), and fluorenone (Xa);
the corresponding products, 2-iodo-4-nitrotoluene
3
support to the above assumption we made an attempt
+
3
to obtain a solution of I by reaction of tetra-N-iodo-
glycoluril (I, 1,3,4,6-tetraiodoperhydroimidazo[4,5-d]-
imidazole-2,5-dione) with iodine in sulfuric acid. As
a result, we have developed an effective alternative
+
3
+
3
way for the generation of I . A solution containing I is
Scheme 1.
I
I
I
(
IIIb), 2,6-diiodo-4-nitrotoluene (IIIc), 4-iodo-2-nitro-
N
N
N
N
toluene (IVb), 3-iodobenzaldehyde (Vb), 3-iodoben-
zoic acid (VIb), 4-fluoro-3-iodobenzoic acid (VIIb),
O
O + 4I2 + 4H SO
2 4
3
,3′-diiodobenzophenone (VIIIb), 3,3′-diiodobenzil
I
(
IXb), and 2,7-diiodofluorenone (Xb), were isolated in
I
4
2–70% yield.
H
H
N
N
The reactions with aromatic substrates are accom-
O
O + 4I · HSO
3 4
panied by appreciable decoloration of the reaction
mixture. During the process, the complex I ·HSO
N
H
N
H
+
3
–
4
9
35

9
36
CHAIKOVSKII et al.
and purified by recrystallization. Compounds IIb–Vb
Scheme 2.
H SO , 0–3°C
were isolated by extraction into methylene chloride,
2
4
4
0–60 min
the extract was dried over CaCl , the solvent was dis-
2
ArH
+
I3 · HSO4
ArI + I2 + H SO4
2
tilled off, and the residue was purified by recrystal-
lization.
decomposes to give molecular iodine (Scheme 2)
which separates from the solution; it can be filtered off
and reused.
The electronic absorption spectra were measured on
a Uvikon-943 spectrophotometer using 10-mm cells.
The progress of reactions and the purity of products
were monitored by TLC on Sorbfil plates (detection
under UV light). The structure of the iodination prod-
ucts was confirmed by spectral and analytical methods
and by comparing with authentic samples.
According to the GC–MS data, the iodination of
nitrobenzene (IIa) was characterized by complete con-
version of the substrate. It should be noted that, unlike
iodination with a solution of I in sulfuric acid in the
absence of molecular iodine [5], the iodination of
+
3
arenes with I generated from compound I and I in
2
sulfuric acid requires no double excess of active iodine
in I. This is very important, taking into account high
cost of reagent I.
REFERENCES
1
2
3
4
5
6
. Arotsky, J., Mishra, H.C., and Symons, M.C.R.,
J. Chem. Soc., 1961, p. 12.
Preparation of a solution containing triiodine
cation. Tetraiodoglycoluril I was synthesized accord-
ing to the procedure described in [10]. A suspension of
. Arotsky, J., Mishra, H.C., and Symons, M.C.R.,
J. Chem. Soc., 1962, p. 2582.
. Arotsky, J., Butler, R., and Darby, A.C., J. Chem. Soc.,
1
.016 g (4 mmol) of finely ground iodine in 30 ml of
3
1970, p. 1480.
sulfuric acid (d = 1.815 g/cm ) was cooled to 0–3°C
using an ice–water bath, and 0.646 g (1 mmol) of
compound I was added in four portions under
vigorous stirring. The mixture was stirred for ~30 min
at room temperature (until the iodine dissolved com-
. Arotsky, J., Darby, A.C., and Hamilton, B.A., J. Chem.
Soc., Perkin Trans. 2, 1973, p. 595.
. Chaikovski, V.K., Filimonov, V.D., Yagovkin, A.Y., and
Kharlova, T.S., Tetrahedron Lett., 2000, vol. 41, p. 9101.
. Chaikovskii, V.K., Filimonov, V.D., Yagovkin, A.Yu.,
and Ogorodnikov, V.D., Izv. Ross. Akad. Nauk, Ser.
Khim., 2001, p. 2302.
pletely) to obtain a dark brown homogeneous solution.
+
3
A 0.01-ml portion of the solution of I was diluted with
2
ml of sulfuric acid, and its electronic absorption
7
8
9
. Filimonov, V.D., Krasnokutskaya, E.A., Pole-
shchuk, O.Kh., Lesina, Yu.A., and Chaikovskii, V.K.,
Izv. Ross. Akad. Nauk, Ser. Khim., 2006, p. 1280.
spectrum showed maxima at λ 453 and 291 nm.
Typical procedure for the iodination of aromatic
+
3
compounds IIa–Xa with I . Arene IIa–VIIa, 4 mmol,
. Chaikovskii, V.K., Filimonov, V.D., Skorokhodov, V.I.,
and Ogorodnikov, V.D., Russ. J. Org. Chem., 2007,
vol. 43, p, 1278.
was added to 30 ml of a preliminarily prepared solu-
+
3
tion of I , cooled to 0–3°C, and the mixture was stirred
for 40–60 min. In the synthesis of diiodo derivatives
IIIc and VIIIb–Xb, the amount of the substrate was
reduced by half (2 mmol). The mixture was poured
onto ice and washed with a 2% solution of Na SO .
. Chaikovskii, V.K., Filimonov, V.D., Funk, A.A., Skoro-
khodov, V.I., and Ogorodnikov, V.D., Russ. J. Org.
Chem., 2007, vol. 43, p. 1291.
2
3
10. Yagovkin, A.Yu., Bakibaev, A.A., and Bystritskii, E.L.,
Products IIIc and VIb–Xb were separated by filtration
Khim. Geterotsikl. Soedin., 1995, p. 1695.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 6 2008