Sulfamides and sulfamide polymers directly from sulfur dioxide

Article abstract of DOI:10.1039/b605063h

SO₂ gas is effectively used for the preparation of N,N′-diarylsulfamides and shape-persistent sulfamide polymers, which utilize a network of intermolecular N-H...O=S hydrogen bonds to self-assemble into soft porous materials. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b605063h

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Sulfamides and sulfamide polymers directly from sulfur dioxide{
Alexander V. Leontiev, H. V. Rasika Dias and Dmitry M. Rudkevich*
Received (in Austin, TX, USA) 8th April 2006, Accepted 14th May 2006
First published as an Advance Article on the web 31st May 2006
DOI: 10.1039/b605063h
SO2 gas is effectively used for the preparation of N,N9-
diarylsulfamides and shape-persistent sulfamide polymers,
…
which utilize a network of intermolecular N–H OLS hydrogen
bonds to self-assemble into soft porous materials.
Sulfur dioxide, or SO2, is an environmentally important gas that is
formed upon burning sulfur-containing fuels.1 SO2 interacts with
moisture and chemicals in the air to generate acid rain, sulfites,
sulfates and other toxic products. SO2 also contributes to
respiratory illnesses. The development of novel methods for the
chemical utilization of SO2 are ongoing. Organic reactions of SO2
include cycloadditions and the synthesis of sulfinic acids, sulfones,
sulfoxides and sulfolenes.2 Additionally, liquid SO2 is used as a
Scheme 1 Preparation of N,N9-diarylsulfamides 1 from anilines 3 (top)
solvent for organic synthesis.3 In this communication, we present a
convenient, one-step procedure for the preparation of diaryl
sulfamides 1 directly from SO2. We further describe how to use
SO2 to make novel materials—sulfamide polymers 2 of unique,
persistent shape. Finally, we demonstrate how sulfamides self-
assemble into porous nanostructures through self-complementary
hydrogen bonds. Taken together, this study continues to explore
the use of environmentally toxic gases in the preparation of new
materials.4
Sulfamides are known for their biological activity.5 They are
also used as chelating agents6 and in self-assembly.7 Symmetric
N,N9-sulfamides are typically prepared by reactions of amines with
sulfuryl chloride.8 However, the latter reagent is made from SO2.
Moreover, only dialkylsulfamides can be obtained in reasonable
yields from this procedure.9 Reactions with aromatic amines
mostly give complex mixtures, containing chlorination and
oxidation products. We found that an excess (y100-fold) of SO2
together with I2 and Py or Et3N in MeCN smoothly and rapidly
converted primary anilines into N,N9-diarylsulfamides (Scheme 1).
An ice-cold MeCN solution of Py or Et3N (3 equiv.) was saturated
with SO2, and then I2 (1 equiv.) and anilines 3 (1 equiv.) were
added. After 2 h at room temperature, sulfamides 1 were isolated
in 20–87% yield (see ESI{). The reaction does not work in the
absence of the amine base or I2. Furthermore, when smaller
quantities of I2 were employed, much lower yields were obtained.
It has been known for many years that SO2 and tertiary amines
form stable charge-transfer complexes.10 Olah et al. used these
complexes in a synthetic methodology.11 These complexes are
often solids and therefore easy to handle. In a single case, a
mixture of Py, I2 and liquid SO2 was employed as a dehydrating
reagent for the formation of carboxamides and sulfamides.12
and the synthesis of sulfamide polymer 2 from phenylenediamine (4)
(bottom).
Inconveniently, the liquid SO2 had to be handled in a high-
pressure vessel.
Under the conditions described here, the amine base (for
example, Py) most probably forms the known13,10 donor–acceptor
complexes Py–I+I2 and further Py–I+I3 with I2, and Py+–SO2
with SO2. These complexes further lead to iodosulfinate (SO2I2)
and the still elusive14 sulfuryl iodide (SO2I2), which then
successively react with ArNH2 in nucleophilic substitution
reactions to produce first ArNHSO2I and then sulfamides 1.
While further elucidation of this mechanism is ongoing, we
disclose some important features of this reaction:
2
2
1. Generally, the Et3N/SO2/I2 system gives better yields than
does the Py/SO2/I2 system; however, the product is more difficult
to purify. Using DMAP or quinuclidine as a base provided better
yields and higher purities.
2. Both anilines with electron-donating and electron-with-
drawing substituents give reasonable yields (see Table 1 in the
ESI{). To our knowledge, this is the only procedure for preparing
sulfamides directly from electron-rich anilines.
3. Polymer-supported amines, such as commercial 2% cross-
linked polyvinylpyridine and Amberlite IRA-67, can also be used;
however, the yields drop significantly (up to 10–20% for para-
toluidine, for example).
4. Dialkylsulfamides can also be synthesized.
The developed protocol was then applied to the synthesis of
polymeric sulfamide material 2 (Scheme 1). There are only a few
examples of sulfamide polymers, dating from the early 1960s, and
none of them are aromatic.15 These polyalkylsulfamides were
prepared by a condensation between sulfamide (NH2SO2NH2)
and aliphatic diamines or formaldehyde, affording insoluble solids.
In our protocol, the ice-cold MeCN solution of Et3N was
saturated with SO2, after which I2 and para-phenylenediamine (4)
were added. The reaction mixture was stirred for 2 h at room
Department of Chemistry & Biochemistry, The University of Texas at
Arlington, Arlington, Texas 76019-0065, USA.
E-mail: rudkevich@uta.edu; Fax: +1 817 272 3808; Tel: +1 817 272 5245
{ Electronic supplementary information (ESI) available: Synthetic proce-
dures and crystallographic details.
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Chem. Commun., 2006, 2887–2889 | 2887

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temperature, and product 2 was formed in 35% yield as a light-
While polymer 2 was very difficult to crystallize, we prepared
brown crystalline solid that was soluble in DMF, DMSO and
1
larger quantities of acetone, MeOH and MeCN. The H NMR
shorter oligomer 5 for structural studies. It has three aromatic
units and two sulfamide groups (for further details of this and even
longer oligomers, see the ESI{). Compound 5 crystallizes with two
molecules of acetone (Fig. 3).{ The bridging aryl amine moiety sits
on an center of inversion. The backbone adopts a Z-shaped
configuration. In addition, the packing diagram shows that 5 also
forms a 2D layer porous structure due to hydrogen bonding
between N–H groups of the bridging aryl amine moiety and SLO
groups. The terminal aryl amine fragments lie above and below the
plane, and their N–H groups show hydrogen bonding to the
acetone oxygens (Fig. 4). Similar structural features are expected
from decamer 2 and its analogs. Such nanoscale, shape-persistent
objects could be important building blocks for supramolecular
chemistry.
spectrum in DMSO-d6 revealed two singlets at 8.96 and 6.96 ppm
for the NH and aromatic protons, respectively. The FTIR
spectrum showed the characteristic absorptions at 1152, 1325
and 3277 cm21 due to the symmetric and asymmetric vibrations of
the –SO2– group and the NH stretching, respectively. A sample of
2 was then dissolved in 1 M NaOH solution and precipitated with
1 M HCl (see ESI{), after which C, H, N and Cl elemental
analyses were performed. The y4% amount of Cl found for the
end amino groups in the hydrochloride salt of 2 corresponds to the
lower weight oligomer with degree of polymerization DP = 10
(decamer), and an average molecular weight of y1700 D. It
should be possible to obtain higher polymers by performing
reactions in more polar solvents. These studies are currently in
progress and also involve other phenylenediamines.
In conclusion, a convenient, one-step procedure for the
preparation of various sulfamides and their polymers is now
available that simply utilizes SO2 gas. SO2 is activated through the
formation of donor–acceptor, non-covalent complexes with amine
bases. We are currently working on widening the scope of this
reaction. Sulfamide oligomers and polymers are particularly
interesting as their shape-persistence means they can be used
as units for nanoscaffolding in larger-scale architectures and
functional molecular devices. They utilize a network of inter-
Due to the geometry of sulfamide fragments, compounds 1 and
2 have unique structural features. The solid state structure of N,N9-
diphenylsulfamide (1, R = H) was investigated using X-ray
crystallography.{ Compound 1 crystallizes in the P-1 space group
with two chemically similar molecules in the asymmetric unit. The
sulfur atoms adopt a tetrahedral geometry and the phenyl groups
lie on the opposite sides of the N–S–N axis (Fig. 1).
…
molecular N–H OLS hydrogen bonds to self-assemble into soft
Self-complementary hydrogen bonding between the N–H and
SLO groups in 1 (R = H) leads to a secondary layer structure
(Fig. 2) featuring pseudo octagonally-shaped pores with diameters
of about 11–12 s. Such a widely developed porous network, in
principle, can be used for gas entrapment and storage.
Fig. 1 Molecular structure of 1 (R = H).
Fig. 3 Molecular structure of oligomer 5–2 acetone.
Fig. 4 The packing diagram of 5–2 acetone showing the 2D layers
formed by hydrogen bonding. Hydrogen atoms have been omitted for
clarity.
Fig. 2 The packing diagram of 1 (R = H) showing the 2D layer structure
formed by hydrogen bonding interactions.
2888 | Chem. Commun., 2006, 2887–2889
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Financial support is acknowledged from the NSF (CHE-
0350958 to D. M. R.), the Alfred P. Sloan Foundation (to D. M.
R.) and the Robert A. Welch Foundation (Y-1289 to H. V. R. D.).
We also thank the NSF for funding the purchase of the 300 MHz
NMR spectrometer (CHE-0234811).
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Notes and references
{ Crystal data for 1 (R = H): C12H12N2O2S, M = 248.30, T = 100(2) K,
triclinic, space group P-1, a = 10.0786(6), b = 11.3145(7), c = 11.3378(7) s,
a = 78.4390(10), b = 72.4410(10), c = 74.6320(10)u, V = 1178.34(12) s3, Z =
4, m = 0.265 mm21, 9448 reflections collected, 4608 unique (Rint = 0.0196),
final R values (all data): R1 = 0.0442, wR2 = 0.0988. CCDC 283533.
Crystal data for 5: C24H30N4O6S2, M = 534.64, T = 100(2) K, monoclinic,
space group P2(1)/c, a = 8.8506(6), b = 9.9988(7), c = 15.2627(11) s, b =
101.1520(10)u, V = 1325.17(16) s3, Z = 2, m = 0.246 mm21, 9052 reflections
collected, 2571 unique (Rint = 0.0211), final R values (all data): R1 = 0.0407,
wR2 = 0.0970. CCDC 603875. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/b605063h
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Chem. Commun., 2006, 2887–2889 | 2889