A facile method for the synthesis of novel imidoyl iminosulfuranes from imidoyl azides

Article abstract of DOI:10.1016/j.tetlet.2014.09.062

A novel and environmentally friendly method for the one-pot preparation of new imidoyl iminosulfuranes in high yield under microwave (MW) and solvent-free conditions from the corresponding imidoyl azides is presented. This efficient synthetic approach benefits from non-toxic and non-explosive precursors for the synthesis of imidoyl iminosulfuranes.

Full text of DOI:10.1016/j.tetlet.2014.09.062

Tetrahedron Letters 55 (2014) 5892–5894
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
A facile method for the synthesis of novel imidoyl iminosulfuranes
from imidoyl azides
⇑
Fahimeh Movahedifar, Ali Reza Modarresi-Alam , Behzad Hosseinzadeh
Department of Chemistry, University of Sistan & Baluchestan, Zahedan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A
novel and environmentally friendly method for the one-pot preparation of new imidoyl
Received 14 January 2014
Revised 28 August 2014
Accepted 11 September 2014
Available online 21 September 2014
iminosulfuranes in high yield under microwave (MW) and solvent-free conditions from the
corresponding imidoyl azides is presented. This efficient synthetic approach benefits from non-toxic
and non-explosive precursors for the synthesis of imidoyl iminosulfuranes.
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Imidoyl azides
Imidoyl iminosulfuranes
Microwave (MW)
Solvent-free reaction
Sulfur–nitrogen ylides (also called sulfilimines, sulfilimides,
iminosulfuranes) have proved to be important reagents in organic
synthesis, particularly in reactions involving intermolecular attack
on substrates bearing an electrophilic carbon atom. A wide range of
applications have been reported based on their inherent biological
activities.1,2 In the process of sulfilimine synthesis, sulfoxides are
undesirable by-products, which affect the sulfilimine yield. Most
described procedures for sulfide to sulfonyl sulfilimine transforma-
tion use a broad range of sulfonyl nitrenoid sources known as chlo-
ramine salts (R3SO2NClNa),2 and iron-catalyzed or NBS-mediated
nitrogen transfer reactions.3
Moreover, the thermal or photochemical transfer of nitrenes
from an azide to the sulfur atom in a sulfide or sulfoxide results
in sulfilimines and sulfoximides, respectively.4 Because of the dif-
ficulties involved in liberating nitrenes, however, the yields of
these processes are low. Iron(II) chloride was reported to facilitate
the synthetic efficiency of this process by reducing the reaction
temperature from 90 °C to 0 °C.5
to low yields.8–10 Imidoyl azides, by contrast, show none of these
problems.7 Furthermore, there is no need to use transition metals
such as iron salts. The imidoyl group (ArAOAC@NAY) has been
used in order to control the stability of the azide and to increase
the selectivity of the reactive nitrene.7
In connection with the synthetic value of sulfilimines, we report
herein a simple and efficient synthesis of new aryloxyimidoyl
sulfilimines. Although Lwowski and Rao prepared dimethyl
sulfoximines by imination of DMSO with imidoyl nitrenes,11 to
the best of our knowledge however, there has been no report on
the use of imidoyl azides for the synthesis of sulfilimines.
The imidoyl sulfilimines 3 were readily prepared in high yields
by the reaction between imidoyl azides 2 and methyl phenyl
sulfide under microwave irradiation and solvent-free conditions,
Scheme 1 and Table 1. Imidoyl azides 2 were prepared from the
corresponding tetrazoles 1, and these were prepared from phenols
by a previously described general method.7
The products were characterized from their spectroscopic data
(IR, 1H NMR, and 13C NMR spectra), elemental analysis (CHNS),
and melting points.
Morita
and
coworkers
introduced
dibenzothiophene
sulfilimines as useful sources for the generation of nitrenes by
photolysis of N-substituted iminodibenzothiophene.6 Recently,
imidoyl azides have been used as convenient precursors for the
generation of nitrenes.7
However, harsh conditions are involved in the generation of
nitrenes since most azides suffer from problems such as handling
difficulties, risks of explosion, and low selectivity which also leads
In the IR spectra of compounds 3, no bands were observed in the
region corresponding to the azide group. Asymmetric and
symmetric SO2 stretches appeared at 1200–1365 cmꢀ1 and
1040–1180 cmꢀ1, respectively. Stretching vibrations of the S@N
bond typically appeared at 920–980 cmꢀ1 with various substitu-
ents on the nitrogen and sulfur atoms.1,12 However, a decrease in
the frequencies of the stretching vibrations of the S@N bond with
increasing electron-withdrawing acceptor ability of the substitu-
ents on the nitrogen atom led to a red shift from the above
⇑
Corresponding author. Tel.: +98 9153414338.
E-mail address: modaresi@chem.usb.ac.ir (A.R. Modarresi-Alam).
http://dx.doi.org/10.1016/j.tetlet.2014.09.062
0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.

F. Movahedifar et al. / Tetrahedron Letters 55 (2014) 5892–5894
5893
H
N
O
N
SO2Ar'
CH3
N
SO2Ar'
S
Ar
N
Ar'SO2Cl
Ph
CH3
O
O
Et3N, EtOAc
N
N
MW (1-5 min),
solvent-free
Ar
N3
Ar
N
S
2
1
3
Ph
a: Ar = 3-MeC6H4, Ar' = 4-MeC6H4, b: Ar = 3-MeC6H4, Ar' = 4-BrC6H4,
c
d
: Ar = 4-MeC6H4, Ar' = 4-MeC6H4, : Ar = 4-MeC6H4, Ar' = C6H5,
e: Ar = 3-MeC6H4, Ar' = C6H5
Scheme 1.
Table 1
Synthesis of iminosulfuranes 3 from aryloxy imidoyl azides 2 and methyl phenyl sulfide
Entry
Substrate
Product
Yield (%)
Melting point (°C)
O
S
O
CH3
O
N
O
CH3
N
S
S
O
O
N3
N
H3C
H3C
1
90
124–126
150–152
133–135
186–187
145–147
CH3
2a
3a
O
O
CH3
O
N
O
CH3
N
S
S
O
O
N3
N
Br
Br
2
3
4
5
87
89
91
92
S
CH3
3b
2b
O
O
O
N
O
N
S
S
O
O
N3
CH3
N
CH3
H3C
H3C
S
CH3
3c
2c
O
S
O
O
N
O
N
S
O
O
N3
CH3
N
CH3
CH3
S
2d
CH3
3d
O
S
CH3
O
S
N
O
O
N
S
O
N3
O
N
2e
CH3
3e
mentioned values to 800–900 cmꢀ1 in N-acyl sulfilimines such as
R2S@NCOAR. Since there were no peaks in this region for com-
pounds 3 and, on the other hand, because of the high conjugation
of the imidoyl group (ArOAC@NASO2Ar), which results in an
increase in the electron-withdrawing acceptor ability, we attrib-
uted the absorption in the region of 850–895 cmꢀ1 to the stretch-
ing vibration of the S@N bond in compounds 3.
ArAOA, Ar0ASO2A, and PhAS@NAY, respectively. The 13C NMR
spectra and CHNS analyses clearly proved the presence of an
imidoyl sulfilimine group.
We also applied diallyl sulfide, a structurally analogous sulfide,
to test whether 2,3-allylic rearrangement8,13 into the isomeric
N,S-diallyl benzenesulfenamide 3g from the corresponding
iminosulfurane 3f would occur (Scheme 2).
In order to synthesize the desired product, the same procedure
was carried out as mentioned above. The final product was a black
solid material that was insoluble in organic solvents and water.
Minor by-products were eliminated by preparative TLC. The rear-
rangement product was not present according to NMR spectros-
copy. We suggest that diallyl sulfide (4), under these conditions,
undergoes polymerization. In fact, the formation of soluble and
linear polymers or insoluble and cross-linked polymers from
In the 1H NMR spectra, the protons of the methyls attached to
the sulfur atom, the ArAOA aromatic ring, and the ArASO2A aro-
matic ring appeared at 2.8–2.9 ppm, 2.30 ppm, and 2.39 ppm,
respectively. The same methyls occurred at 36 ppm and 21 ppm
in the 13C NMR spectra.
The signals at 162.5 ppm, 150–153 ppm, 141–143 ppm, and
139–141 ppm are attributed to the carbon atom of the imidoyl
group (ArAOAC@NAY), and the ipso carbon atoms of

5894
F. Movahedifar et al. / Tetrahedron Letters 55 (2014) 5892–5894
N
SO2Ar'
SO2Ar'
(m) cmꢀ1 1H NMR (500 MHz, CDCl3), d ppm; 2.29 (s, 3H), 2.39 (s,
.
MW (1-5 min),
solvent-free
S
O
O
3H), 2.85 (s, 3H), 6.66 (s, 1H), 6.69 (d, J = 8.1 Hz, 1H), 6.96 (d,
J = 7.4 Hz, 1H), 7.14 (t, J = 7.8 Hz, 1H), 7.19 (d, J = 7.9 Hz, 2H), 7.51
(t, J = 7.6 Hz, 2H), 7.57–7.59 [m (d+t), 3H], 7.81 (d, J = 8.0 Hz, 2H).
Ar
Ar
N3
4
2
13C NMR (125 MHz, CDCl3),
d ppm; 162.43, 152.82, 141.35,
O
N
SO2Ar'
N
S
Ar
141.01, 139.02, 134.17, 132.74, 130.09, 128.63, 128.53, 127.40,
126.73, 126.07, 122.18, 118.72, 36.09, 21.40, 21.21. Anal. calcd.
For C22H22N2O3S2: C 61.95, H 5.20, N 6.57, S 15.03; found: C
61.56, H 5.11, N 6.43, S 14.92.
N
S
N
3g
3f
Acknowledgment
We gratefully acknowledge the financial support from the
Research Council of the University of Sistan and Baluchestan.
Scheme 2.
Supplementary data
diallyl sulfides can take place depending on the polymerization
conditions.14,15 Furthermore, it has been reported that products
of dimerization of thioacrolein obtained from pyrolysis of diallyl
disulfide 4 can be polymerized.16 In addition, ring-forming poly-
merization is also possible from 3f and 3g.14
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2014.09.
062.
In summary, we have developed a novel, efficient, and mild
protocol for the one-pot preparation of new iminosulfuranes from
precursor imidoyl azides and methyl phenyl sulfide under MW
irradiation and solvent-free conditions. The advantages of the
present method in terms of facile manipulation, high yields, simple
methodology, simple work-up procedure, no chromatographic
separation, and fast reaction rates should make this protocol a
valuable alternative to existing methods. Further studies are in
progress.
References and notes
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