Highly efficient sulfimidation of 1,3-dithianes by Cu(I) complexes

Article abstract of DOI:10.1080/00397910701798200

A series of four Cu(I) complexes were tested for sulfimidation of 1,3-dithianes in the presence of [N-(p-tolysulfonyl)imino]phenyliodinane (PhI=NTs) as the nitrene-transfer agent. Cu(TMPhen)(PPh3)Br is an efficient catalyst with more than 90% yield of the

Full text of DOI:10.1080/00397910701798200

This article was downloaded by: [University of Guelph]
On: 21 June 2012, At: 06:58
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
Highly Efficient Sulfimidation of 1,3‐Dithianes
by Cu(I) Complexes
L. Giribabu a , Surya P. Singh a , Nandkumar M. Patil b , M. Lakshmi Kantam a
, Sunil P. Gupte b & Raghunath V. Chaudhari b
a Inorganic and Physical Chemistry Division, Indian Institute of Chemical
Technology, Hyderabad, India
b Homogeneous Catalysis Division, National Chemical Laboratory, Pune, India
Available online: 27 Feb 2008
To cite this article: L. Giribabu, Surya P. Singh, Nandkumar M. Patil, M. Lakshmi Kantam, Sunil P. Gupte &
Raghunath V. Chaudhari (2008): Highly Efficient Sulfimidation of 1,3‐Dithianes by Cu(I) Complexes, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 38:4,
619-625
To link to this article: http://dx.doi.org/10.1080/00397910701798200
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the
contents will be complete or accurate or up to date. The accuracy of any instructions, formulae,
and drug doses should be independently verified with primary sources. The publisher shall not
be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or
howsoever caused arising directly or indirectly in connection with or arising out of the use of this
material.

Synthetic Communicationsw, 38: 619–625, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701798200
Highly Efficient Sulfimidation
of 1,3-Dithianes by Cu(I) Complexes
L. Giribabu,1 Surya P. Singh,1 Nandkumar M. Patil,2
M. Lakshmi Kantam,1 Sunil P. Gupte,2 and Raghunath
V. Chaudhari2
1Inorganic and Physical Chemistry Division, Indian Institute of Chemical
Technology, Hyderabad, India
2Homogeneous Catalysis Division, National Chemical Laboratory, Pune,
India
Abstract: A series of four Cu(I) complexes were tested for sulfimidation of 1,3-
dithianes in the presence of [N-(p-tolysulfonyl)imino]phenyliodinane (PhI ¼ NTs) as
the nitrene-transfer agent. Cu(TMPhen)(PPh3)Br is an efficient catalyst with more
than 90% yield of the corresponding product with less reaction time as compared to
the literature copper(I) complexes.
Keywords: Cu(I) complexes, 1,3-dithianes, PhI ¼ NTs, sulfimidation
INTRODUCTION
Sulfoxides have emerged as versatile building blocks in the synthesis of
pharmaceutical products.[1] Sulfimides are the nitrogen equivalents of sulfox-
ides. Unlike sulfoxides, sulfimide use in organic synthesis is rather limited
because of the lack of convenient synthetic methods. Sulfimidation is a
nitrene-transfer reaction, and various reagents have been employed to
achieve this transformation. Clasically, sulfimidation of sulfides has been
achieved in protic solvents using chloramine-T (the sodium salt of
Received August 22, 2007
Address correspondence to Sunil P. Gupte, Homogeneous Catalysis Division,
National Chemical Laboratory, Pune 411008, India. E-mail: sp.gupte@ncl.res.in or
L. Giribabu, Inorganic and Physical Chemistry Division, Indian Institute of
Chemical Technology, Hyderabad 500007, India. E-mail: giribabu@iict.res.in
619

620
L. Giribabu et al.
N-chloro-p-toluenesulfonamide) as the nitrene source, which is cheap and
readily available. The first formed chlorosulfonium salt can be prone to
hydrolysis, and the corresponding sulfoxide is often a by-product.[2] To cir-
cumvent this problem, metal catalysts and [N-(p-tolysulfonyl)imino]phenylio-
dinane (PhI ¼ NTs) as nitrene source were used in sulfimidation.[3] Evans
et al. have reported PhI ¼ NTs to be an effective asymmetric nitrene-
transfer reagent to alkenes in the presence of a catalytic amount of Cu(I)
salt together with a chiral 4,40-disubstituted bis(oxazoline) ligand.[4] Takada
and coworkers reported enatioselective synthesis of chiral sulfimides using
chiral copper(I)–bis(oxazoline) complex as a catalyst.[5] Nishikori and
Katsuki have used chiral Mn(III) and Ru(II) salen complexes for enantioselec-
tive sulfimidation of 1,3-dithianes to get up to 99% enantiomeric pure
compounds.[6] However, with these salen catalysts, the reaction time is
longer, and the synthesis of catalyst is also tedious.
On the other hand, utilization of either Cu(I) or Cu(II) salts in the sulfimi-
dation of 1,3-dithianes has well documented in the literature.[7] The most
common Cu(I) salts used in sulfimidation are Cu(OTf), Cu(PF6), CuCl,
[Cu(NCMe)4]BF4, or Cu(CH3CN)4PF6 and Cu(II) salts are Cu(OTf)2 or
Cu(acac)2. Recently, we reported sulfimidation of 1,3-dithianes by micro-
encapsulated copper(II) acetylacetonate and Cu(acac)2 immobilized in ionic
liquids using PhI ¼ NTs.[8] All these methods involve either lower yields or
high reaction times. We are interested in using Cu(I) complexes for sulfimida-
tion of 1,3-dithianes to further improve the reaction yields as well as to reduce
the reaction time. Most copper(I) salts are insoluble in organic solvents, and
hence, the reactions are often heterogeneous and require high reaction temp-
eratures. For this reason, we have chosen four Cu(I) complexes for sulfimida-
tion. They are Cu(PPh3)3Br (1), Cu(Phen)(PPh3)Br (2), Cu(neocup)(PPh3)Br
(3), and Cu(TMPhen)(PPh3)Br (4). All four Cu(I) complexes are applied for
the sulfimidation reaction, and results are presented herein. Earlier, we used
Cu(PPh3)3Br, Cu(Phen)(PPh3)Br, and Cu(neocup)(PPh3)Br complexes for triar-
ylamines synthesis.[9] Complexes 1, 2, and 3 were synthesized according to the
reported procedure.[10]
EXPERIMENTAL
1
IR spectra were recorded on a Nicolet-740 FT IR spectrometer. H NMR
spectra were recorded on a Bruker Avence 300 spectrometer at 300 MHz
and Varian Gemini 200 spectrometer at 200 MHz. Chemical shifts are given
in parts per million (ppm) with respect to internal TMS for all recorded
NMR spectra, and J values are quoted in hertz (Hz). Mass spectra were
recorded on VG Micromass-7070 H spectrometer at 70 eV. Reactions were
monitored on 0.25-mm E. Merck precoated silica-gel plates (60 F254).
Starting materials were used from commercial samples without purification.

Sulfimidation of 1,3-Dithianes
621
The complexes Cu(PPh3)3Br (1), Cu(Phen)(PPh3)Br (2), and Cu(neocup)
(PPh3)Br (3) were synthesized according to procedures reported in the
literature.[10]
Synthesis of Cu(TMPhen)(PPh3)Br (4)
Copper(I) bromide (1.98 g, 2.13 mmol) was dissolved in 150 ml of chloro-
form. To this, 0.51 g (2.13 mmol) of 3,4,7,8-tetramethyl-1,10-phenanthroline
were added. The colorless solution immediately changed to red. The reaction
mixture was stirred at room temperature for 30 min. The solvent was removed
under reduced pressure to get a yellow solid. The solid material was recrystal-
lized from chloroform and diethyl mixture to get desired compound (1.23 g,
1
80% yield). H NMR (CDCl3, 200 MHz): d 1.83 (s, 6H, CH3), 2.17 (s, 6H,
CH3), 7.24–7.70 (m, 19H, Ar-H). 13C NMR (CDCl3): d 30.67, 128.18,
129.25, 130.49, 131.86, 133.55. 31P NMR (CDCl3): d 22.77, 230.17. IR
(KBr): n 3045, 1585, 1517, 1479, 1434, 1383, 1093, 820, 748, 696, 524,
and 527 cm21. Anal. calc. for C34H31BrN2CuP: C, 63.60; H, 4.87; N, 4.36;
Br, 12.45; P, 4.92. Found: C, 62.34; H, 5.27; N, 4.95; Br, 10.95; P, 2.31.
Typical Experimental Procedure
Cu(TMPhen)(PPh3)Br (0.018 g, 0.028 mmol), methyl phenyl sulfide (0.062 g,
0.5 mmol), and PhI ¼ NTs (0.186 g, 0.5 mmol) were added to acetonitrile
(5 ml), and the reaction mixture was stirred at room temperature for the
time shown in Table 1. The reaction was monitored by the disappearance of
PhI ¼ NTs from the reaction mixture. After completion of the reaction, the
solvent was removed under reduced pressure to get the solid material
(Scheme 1). The obtained solid material was subjected to silica-gel column
chromatography and eluted with hexane/ethyl acetate (80/20, v/v) to
afford the pure product as a white solid. Yield 0.132 g (90%). Mp 1318C
Table 1. Sulfimidation of sulfides with PhI ¼ NTs using various Cu(I) catalytsa
Reaction
time (h)
Entry
Catalyst
Cu(PPh3)3Br
Cu(Phen)(PPh3)Br
Yield (%)b
1
2
3
4
2
80
78
82
90
2.5
4
Cu(neocup)(PPh3)Br
Cu(TMPhen)(PPh3)Br
1.5
aSulfide (0.5 mmol), PhI ¼ NTs (0.5 mmol), catalyst (5 mol%) in 5 ml of aceto-
nitrile at rt.
bIsolated yields.

622
L. Giribabu et al.
Scheme 1.
(lit.[11]: 131–1328C). 1H NMR (CDCl3, 300 MHz): d 2.34 (S, 3H, CH3), 2.81
(s, 3H, CH3), 7.12–7.71 (m, 9H, Ar-H); IR (KBr): n 3030, 2928, 1597, 1447,
1279, 1142, 1090, 963, 756, 662, 575 cm21. Anal. calc. for C14H15NO2S2: C,
57.31; H, 5.15; N, 4.77; S, 21.84. Found: C, 57.35; H, 5.17; N, 4.75; S, 21.60.
Results and Discussion
In this article, we report a highly efficient sulfimidation of 1,3-dithianes by
using a series of four Cu(I) complexes with PhI ¼ NTs as nitrene-transfer
agent. The catalysts 1, 2, and 3 were synthesized and characterized according
to the reported procedure in the literature,[10] whereas catalyst 4 was accom-
plished by copper(I) bromide and 3,4,7,8-tetramethyl-1,10-phenanthroline in
chloroform, and the characterization of the complex was satisfactory.
Initially, the catalytic activity of all four copper(I) complexes were
examined for sulfimidation of methyl phenyl sulfide using PhI ¼ NTs as
nitrene source at room temperature in acetonitrile solvent. The results are
presented in Table 1. From Table 1, it is clear that the reaction time of sulfi-
midation of methyl phenyl sulfide follows the order 3 . 2 . 1 . 4, whereas
yield follows the order 4 . 3 . 1 . 2. Hence, we decided to use the catalyst 4
for variety of 1,3-dithianes for sulfimidation.
Under optimized conditions, a variety of 1,3-dithianes (including both
aromatic and aliphatic sulfides) underwent reaction with PhI ¼ NTs using
5 mol% of Cu(TMPhen)(PPh3)Br (4) catalyst. The results are summarized
in Table 2. Both aliphatic and aromatic sulfides gave more than 70% yields.
Aliphatic sulfides undergo sulfimidation faster than aromatic sulfides
(entries 13, 14, and 15). Aromatic sulfides bearing electron-releasing groups
(entry 5) are more reactive than those bearing electron-withdrawing groups
in the sulfimidation reaction. But, in the sulfimidation of thiophene (entry
9), the yield is very low and reaction rate is also slow, whereas in the case
of 3,4-dicyano thiophene (entry 10), sulfimidation did not occur even after
10 h under these conditions, probably due to the electron-withdrawing
nature of the cyano group. The present catalytic system for sulfimidation is
highly efficient when compared to other catalytic systems reported in the lit-
erature. The preparation of catalyst is straightforward and not air sensitive. We
have achieved sulfimidation of aliphatic 1,3-dithianes with high yields (93%,
entry 12), and the reaction time is only 0.5 h. In contrast, as sulfimidation of

Sulfimidation of 1,3-Dithianes
623
Table 2. Sulfimidation of sulfides with PhI ¼ NTs using Cu(TMPhen)(PPh3)Bra
Reaction
time (h)
Entry
1
Sulfides
Yield (%)b
71
5
2
3
5
4
81
85
4
5
1.5
2
89
92
6
7
5
4
85
70
8
9
4.5
0.5
4
73
93
81
10
11
12
3
55
—
10
13
14
15
CH3-S-CH3
Cl-CH2-CH2-S-CH3
CH3(CH2)3S(CH2)3CH
0.5
0.5
0.5
90
91
93
aSulfide (0.5 mmol), PhI ¼ NTs (0.5 mmol), catalyst 4 (5 mol%) in 5 ml of aceto-
nitrile at rt.
bIsolated yields.

624
L. Giribabu et al.
existing catalytic systems were achieved only up to 70%, and the reaction time
was around 20 h.
In conclusion, four Cu(I) complexes were used as catalysts for sulfimida-
tion of 1,3-dithianes in the presence of PhI ¼ NTs as nitrene-transfer agent.
The catalyst Cu(TMPhen)(PPh3)Br shows good performance in sulfimidation.
We have achieved the sulfimidation up to 93% with this system. Currently, the
application of these Cu(I) complexes to other reactions such as aziridination,
aza Michael reaction, and asymmetric sulfimidation is under way.
ACKNOWLEDGEMENTS
We thank the CSIR for financial support under the Task Force Project
CMM-0005.
REFERENCES
1. (a) Fernandez, I.; Khiar, N. Recent developments in the synthesis and utilization
of sulfoxides. Chem. Rev. 2003, 103, 3651–3706; (b) Hiroi, K.; Suzuki, Y.;
Abe, I.; Kawagishi, R. New chiral sulfoxide ligands possessing a phosphano or
phosphanoamino functionality in palladium-catalyzed asymmetric allylic nucleo-
philic substitution reactions. Tetrahedron 2000, 56, 4701–4710; (c) Cotton, H.;
Elebring, T.; Larsson, M.; Li, L.; Sorensen, H.; von Unge, S. Asymmetric
synthesis of esomeprazole. Tetrahedron: Asymmetry 2000, 11, 3819–3825;
(d) Tanaka, M.; Yamazaki, H.; Hakusui, N.; Nakamichi, N.; Sekino, H. Differen-
tial stereoselective pharmakokinetics of pantoprazole, a proton pump inhibitor in
extensive and poor metabolizers of pantoprazole—A preliminary study.
Chirality 1997, 9, 17–21.
2. (a) Tsujihara, K.; Furukawa, N.; Oae, K.; Oae, S.; Sulfilimine, I. Sulfilimines, 1:
synthesis and formation mechanism. Bull. Chem. Soc. Jpn. 1969, 42,
2631–2635; (b) Gilichrist, T. L.; Moody, C. J. The chemistry of sulfilimines.
Chem. Rev. 1977, 77, 409–435.
3. Otani, T.; Sugihara, Y.; Ishii, A.; Nakayama, J. 1-Imino and 1,1-diimino deriva-
tives of 3,4-di-tert-butylthiophene. Tetrahedron Lett. 1999, 40, 5549–5552.
4. Evans, D. A.; Faul, M. M.; Bilodeau, M. T.; Anderson, B. A.; Barnes, D. M.
Bis(oxazoline)-copper complexes as chiral catalysts for the enatioselective aziridi-
nation of olefins. J. Am. Chem. Soc. 1993, 115, 5328–5329.
5. (a) Takada, H.; Nishibayashi, Y.; Ohe, K.; Uemura, S. Novel asymmetric catalytic
synthesis of sulfimides. J. Chem. Soc., Chem. Commun. 1996, 931–932;
(b) Takada, H.; Nishibayash, Y.; Ohe, K.; Uemura, S.; Baird, C. P.;
Sparey, T. J.; Taylor, P. C. Catalytic asymmetric sulfimidation. J. Org. Chem.
1997, 62, 6512–6518; (c) Miyake, Y.; Takada, H.; Ohe, K.; Uemura, S.
Catalytic asymmetric sulfimidation of 1,3-dithianes. J. Chem. Soc., Perkin
Trans.1 1998, 2373–2376.
6. (a) Nishikori, H.; Katsuki, T. Catalytic and highly enantioselective aziridination of
styrene derivatives. Tetrahedron Lett. 1996, 37, 9245–9248; (b) Kokubo, C.;
Katsuki, T. Highly enatioselective catalytic oxidation of alkyl aryl sulfides using
Mn-salen catalyst. Tetrahedron 1996, 52, 13895–13900.

Sulfimidation of 1,3-Dithianes
625
7. Takada, H.; Oda, M.; Oyamada, A.; Ohe, K.; Uemura, S. Catalytic diastereoselec-
tive sulfimidation of diaryl sulfides and application of chiral sulfides to asymmetric
allylic alkylation. Chirality 2000, 299–312.
8. Kantam, M. L.; Kavita, B.; Neeraja, V.; Haritha, Y.; Chaudhuri, M. K.;
Dehury, S. K. Heterogeneous catalytic sulfimidation using immobilized
Cu(acac)2. Adv. Synth. Catal. 2005, 347, 641–645.
9. (a) Kelkar, A. A.; Patil, N. M.; Chaudhari, R. V. Copper-catalyzed amination of
aryl halides: single step synthesis of triarylamins. Tetrahedron Lett. 2002, 43,
7143–7146; (b) Patil, N. M.; Kelkar, A. A.; Chaudhari, R. V. Synthesis of
triaryl amines by copper catalyzed amination of aryl halides. J. Mol. Catal. A
2004, 223, 45–50.
10. (a) Gujadhur, R. K.; Bates, C. G.; Venkataraman, D. Formation of aryl-nitrogen,
aryl-oxygen, aryl-carbon bonds using well defined copper(I)-based catalysts.
Org. Lett. 2001, 3, 4315–4317; (b) Tamura, Y.; Matsushima, J.;
Minamikawa, J.; Ikeda, M.; Sumoto, K. Synthesis and some properties of N-unsub-
stituted sulfimines. Tetrahedron 1975, 31, 3035–3040.