Anionic σ-complexes of 1,3,5-tris(fluorosulfonyl)benzene

Article abstract of DOI:10.1016/j.tetlet.2008.02.151

We have found that symmetrical benzene trisulfonic-acid trifluoride 1 is able to undergo nucleophilic addition at free positions on the aromatic ring. Its reactions with sodium sulfite, morpholine and carbanions of malonic and acetoacetic esters, dimedone and nitromethane lead to the formation of comparatively stable anionic σ-complexes 3-8.

Full text of DOI:10.1016/j.tetlet.2008.02.151

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Tetrahedron Letters 49 (2008) 2719–2721
Anionic r-complexes of 1,3,5-tris(fluorosulfonyl)benzene
Vladimir N. Boiko *, Oksana M. Kamoshenkova, Andrey A. Filatov
Institute of Organic Chemistry, Ukrainian National Academy of Science, 5 Murmanskaya Street, 02660 Kyiv-94, Ukraine
Received 11 January 2008; revised 14 February 2008; accepted 28 February 2008
Available online 2 March 2008
Abstract
We have found that symmetrical benzene trisulfonic-acid trifluoride 1 is able to undergo nucleophilic addition at free positions
on the aromatic ring. Its reactions with sodium sulfite, morpholine and carbanions of malonic and acetoacetic esters, dimedone and
nitromethane lead to the formation of comparatively stable anionic r-complexes 3–8.
Ó 2008 Published by Elsevier Ltd.
Keywords: 1,3,5-Tris(fluorosulfonyl)benzene; Anionic r-complexes; Aromatic sulfonic-acid fluorides; Aromatic nucleophilic addition
The reactions of benzene derivatives which contain
strong electron-withdrawing groups at the 1,3,5-positions
with different nucleophilic agents are of great interest
because of the formation of products of both nucleophilic
aromatic substitution and intermediate Meisenheimer-type
anionic r-complexes. There are numerous investigations
devoted to such complexes of sym-trinitrobenzene.1
1,3,5-Tris(trifluoromethylsulfonyl)benzene (2) is known
to form more stable r-complexes2 because the SO2CF3
group is a stronger electron-withdrawing group (rp 1.04)3
than a nitro group (rp 0.78).4 At the same time the SO2F
(rp 1.01)5 and SO2CF3 groups are very similar in their elec-
tronic nature.
onic-acid fluorides, in contrast to aryl trifluoromethyl sulf-
ones, prefer to interact with nucleophilic agents on the
sulfonyl centre. For example, in reactions with anilines,
the corresponding sulfonyl anilides are formed7 and when
ArSO2F is activated by strong electron-withdrawing
groups, hydrolysis can occur even in neutral aqueous
dioxane.8
Nevertheless, we have found that compound 1 on reac-
tion with nucleophilic agents such as sodium sulfite, mor-
pholine, the carbanions of malonic and acetoacetic esters,
dimedone and nitromethane in DMSO forms the Meisen-
heimer-type anionic r-complexes 3–8 (Scheme 1).
Equimolar mixtures of sulfonyl fluoride 1 and the previ-
ously mentioned reagents (for morpholine 2 equiv) at 10 °C
to room temperature form bright yellow, fluorescent-col-
oured solutions. Both the 19F and 1H NMR spectra exhibit
two signals (intensity 2:1) instead of the one singlet typical
for compound 1 (Table 1). Acidification of the complexes
(e.g., 7 and 8) causes discolouration of the solutions and
the disappearance of the two signals in the NMR spectra.
Instead the singlet of the starting sulfonyl fluoride 1
reappears.
SO2F
F3CO2S
SO2CF3
FO2S
SO2F
SO2CF3
2
1
Although 1,3,5-tris(fluorosulfonyl)benzene 1 is a known
compound,6 its reactions with nucleophilic agents have not
been investigated previously. The exception is heating with
potassium fluoride when the SO2F group is substituted by a
fluorine atom.6b However, it is known that aromatic sulf-
The 13C NMR spectra of adducts 3–8 also demonstrate
typical signal shifts similar to those of 1,3,5-trinitrobenz-
ene9 or 2,4,6-trinitroanisole.10 The signals of the C2, C4
and C6 atoms are shifted high field, whereas those of the
C3 and C5 atoms moved downfield (Table 2).
*
Corresponding author. Fax: +38 044 5732643.
E-mail address: boikovolodymyr@yandex.ru (V. N. Boiko).
0040-4039/$ - see front matter Ó 2008 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2008.02.151

2720
V. N. Boiko et al. / Tetrahedron Letters 49 (2008) 2719–2721
the signals of the Ha and Hb protons are typical of those
α
H
Nu
for anionic r-complexes. The analogous situation was
observed in r-complexes of sulfone 2 with nucleophiles
such as PhSNa and C4H9SNa.2b In contrast, r-complex 8
exhibits two different signals for the two ortho-SO2F
groups. This is probably a result of the presence of the
bulky dimedone in the r-complex. This may result in the
asymmetry of the two ortho-SO2F groups in the plane of
the cyclohexadiene ring and impede their rotation.
Of interest is the fact that in contrast to the correspond-
ing r-complexes of sulfone 22 most of the investigated
adducts 3–8 demonstrate 19F NMR signals shifted down-
field compared to compound 1 (Fig. 1). At the same time
their 1H NMR spectra are typical for anionic r-complexes.
They show the corresponding signals of the Ha and Hb pro-
tons in the high field region.
SO2F
FO2S
_
FO2S
SO2F
Nu
or NuH / Et3N
o
_
β
β
DMSO, 20-25
C
H
H
SO2F
Cat +
SO2F
1
3 - 8
Nu = SO3Na (3),
CH2NO2 (7),
N
+
O (4), CH(COOEt)2 (5), CH(COCH3)COOEt (6),
O
CH3
CH3
(8)
O
+
Cat+ = Na+ (3),
(4),
O
Et3NH (5-8)
H2N
Scheme 1.
There are some unexpected features in the 19F NMR
spectra of the reported r-complexes. In adducts 5 and 6
the signals of the SO2F groups at the ortho- and para-posi-
The exceptions are the r-complexes of nitromethane 7
and dimedone 8. The fluorine signals of the ortho-SO2F
groups are shifted high field in comparison to the initial
1
tions are merged together, while in their H NMR spectra,
Table 1
19F and 1H NMR spectra, d, ppm (integral intensity) of adducts 3–8a in DMSO-d6
α
H
Nu
FO2S
SO2F
_
β
β
H
H
SO2F
Compound
Nu
19F (200 MHz, CCl3F)
o-SO2F (2) p-SO2F (1)
1H (300 MHz, JH,H, Hz)
Ha (1)
4.7
Hb (2)
7.4
Others
3
4
SO3Na
72.2
71.7
72.06
72.12
4.93
7.61
2.47 (t, J = 4.9, 4H, CH2), 3.11
(t, J = 4.9, 4H, CH2)
N
O
5
6
CH(COOEt)2
71.29
70.33
4.93 (d, J = 3.5)
4.92 (d, J = 3.0)
7.49
7.41
3.15 (t, J = 6.5, 6H, CH3), 3.47
(d, J = 3.5, 1H, CH), 4.12 (q, J = 4.1, 4H, CH2)
2.08 (s, 3H, COCH3), 3.38 (d, J = 3.0, 1H, CH)b
COCH3
CH
COOEt
7
CH2NO2
65.86
70.05
73.32
4.68 (t, J = 5.1)
5.42 (d, J = 3.0)
7.50
7.21
4.47 (d, J = 5.1, 2H, CH2)
O
CH3
8
64.86(1), 64.88(1)
3.40 (d, J = 3.0, 1H, CH), 2.16 (s, 4H, CH2),
0.95 (s, 6H, CH3)
CH3
O
a
NMR spectra of compound 1 in DMSO-d6: dF 67.1 s, dH 9.2 s.
b
The signals for the C2H5 and (C2H5)3NH+ groups are superimposed.
Table 2
13C NMR spectra of compound 1 and adducts 3 and 8 (125 MHz, DMSO-d6, d, ppm, J, Hz)
Atom
1a
3
Dd: (3–1)
8
Dd: (8–1)
C1
136.05 s
135.66 d, JC,F = 28.9
136.05 s
54.23 s
100.87 d, JC,F = 23.9
137.98 s
À81.82
À34.79
+1.93
À41.63
102.90 s
105.11 d, JC,F = 13.6
138.80 s
À33.15
À30.55
+2.75
À30.70
C2 (C6)
C3 (C5)
C4
135.66 d, JC,F = 28.9
94.03 d, JC,F = 25.15
104.96 d, JC,F = 13.6
a
The numbering of the C-atoms in compound 1 is the same as in adducts 3–8:
1
6
5
2
3
4

V. N. Boiko et al. / Tetrahedron Letters 49 (2008) 2719–2721
2721
1
Therefore, despite compound 1 being a strong aromatic
sulfonic-acid halide in reactions with various nucleophilic
agents it can undergo aromatic addition. However, the
anionic r-complexes formed are not as stable as those of
1,3,5-tris(trifluoromethylsulfonyl)benzene 2 and undergo
further transformations.
3
5
6
References and notes
7
7
1. For selected reviews see: (a) Strauss, M. J. Chem. Rev. 1970, 70,
667–712; (b) Terrier, F. Chem. Rev. 1982, 82, 77–152; (c) Artamkina,
G. A.; Egorov, M. P.; Beletskaya, I. P. Chem. Rev. 1982, 82, 427–459;
(d) Buncel, E.; Dust, J. M.; Terrier, F. Chem. Rev. 1995, 95, 2261–
2280.
8
8
4
2. For r-complexes of 1,3,5-tris(trifluoromethylsulfonyl)benzene see: (a)
Yagupolskii, L. M.; Boiko, V. N.; Shchupak, G. M.; Kondratenko,
N. V.; Sambur, V. P. Tetrahedron Lett. 1975, 49, 4413–4414; (b)
75
70
65
(ppm)
Fig. 1. The position of the 19F NMR signals of adducts 3–8 relative to
compound 1.
`
Boiko, V. N.; Ignatev, N. V.; Shchupak, G. M.; Yagupolskii, L. M.
Zh. Org. Khim. 1979, 15, 806–816; (c) Terrier, F.; Millot, A. P.;
Chatrousse, A. P.; Yagupolskii, L. M.; Boiko, V. N.; Shchupak, G.
`
M.; Ignatev, N. V. J. Chem. Res. (S) 1979, 272–273; (d) Onys‘ko, P.
compound 1. Evidently, the location of the fluorine atom
signals in the 19F NMR spectra of r-complexes 3–8
depends upon several factors. With analogy to anionic r-
complexes of sulfone 211 it can be proposed that in adducts
3–812 the positive charge on the sulfur atoms is also
enlarged. Moreover, the position of the fluorine atom adja-
cent to the S@O double bond results in its p-donating
properties.
`
P.; Gololobov, Yu. G.; Boiko, V. N.; Ignatev, N. V.; Yagupolskii, L.
M. Zh. Obshch. Khim. 1979, 49, 748–751; (e) Ignatev, N. V.; Boiko, V.
N.; Yagupolskii, L. M. Zh. Org. Khim. 1980, 16, 1501–1508; (f)
Boiko, V. N.; Ignatev, N. V.; Yagupolskii, L. M. Zh. Org. Khim.
`
`
1981, 17, 1952–1958.
3. Yagupolskii, L. M. In Aromatic and Heterocyclic Compounds with
Fluorine-Containing Substituents; Markovskii, L. N., Ed.; Naukova
Dumka: Kiev, USSR, 1988; p 245.
4. Gordon, A. J.; Ford, R. A. In The Chemist’s Companion; Mir:
Moscow, 1976; p 168.
5. Sheppard, W. A.; Sharts, C. M. In Organic Fluorine Chemistry;
Knunyants, I. L., Ed.; Mir: Moscow, 1972; p 295.
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Der Puy, M. J. Org. Chem. 1988, 53, 4398–4401.
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Soc., Perkin Trans. 2 1988, 1919–1923.
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1828.
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Trans. 2 1982, 355–360.
10. (a) Olah, G. A.; Mayr, H. J. Org. Chem. 1976, 41, 3448–3451; (b)
Simonnin, M.-P.; Pouet, M.-J.; Terrier, F. J. Org. Chem. 1978, 43,
859–955.
11. Dolenko, G. N.; Boiko, V. N.; Shchupak, G. M.; Boldeskul, I. E.;
Yagupolskii, L. M. Izv. Akad. Nauk SSSR, Ser. Khim. 1987, 3, 585–
587.
It should be noted that anionic r-complexes 3, 7 and 8
occurred as comparatively stable structures. Unfortu-
nately, they still have not been isolated as individual com-
pounds. However, in DMSO solution they were stable for
7–8 days at room temperature after which their solutions
became discoloured and the 19F NMR spectra demon-
strated signals of rearranged products. For example, in
1
the case of adduct 8, both the 19F and H NMR spectra
indicated the formation of the sulfone 9 (1H NMR
(300 MHz): d 1.07 (s, 6H, CH3), 2.21 (s, 4H, CH2), 5.32
(s, 1H, CH), 8.72 (t, J = 1.6 Hz, 1H, Haryl), 8.76 (d,
J = 1.6 Hz, 2H, Haryl); 19F NMR (200 MHz): d 66.3 (s,
SO2F).
O
12. Typical experimental procedure: To a solution of 1,3,5-tris(fluoro-
sulfonyl)benzene 1 (50 mg, 0.15 mmol) in DMSO-d6 (2 mL) cooled
to 10–15 °C, the corresponding nucleophilic agent (0.15 mmol)
(for 4—0.30 mmol), H2O (0.4 mL; for 3 only) and Et3N (0.15 mmol;
for 5–8) were added. The reaction solutions were stirred for 30 min at
this temperature then allowed to warm to 20 °C and after 15–20 h the
19F, 1H and 13C NMR spectra were recorded.
FO2S
SO2
O
SO2F
9