Catalytic thia-Sommelet-Hauser rearrangement: Application to the synthesis of oxindoles

Article abstract of DOI:10.1021/ol200091k

A series of 3-arylthio-1,3-disubstituted-oxindoles were prepared in good yields by the reaction of α-diazocarbonyl compounds and sulfenamides. The reaction involves a Rh-catalyzed thia-Sommelet-Hauser-type rearrangement.(Figure Presented)

Full text of DOI:10.1021/ol200091k

ORGANIC
LETTERS
2011
Vol. 13, No. 5
1210–1213
Catalytic Thia-Sommelet-Hauser
Rearrangement: Application to the
Synthesis of Oxindoles
Yuye Li,†,‡ Yi Shi,† Zhongxing Huang,† Xinhu Wu,†,‡ Pengfei Xu,‡ Jianbo Wang,*,† and
Yan Zhang*,†,‡
Beijing National Laboratory of Molecular Sciences (BNLMS) and Key Laboratory of
Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of
Chemistry, Peking University, Beijing 100871, China, and State Key Laboratory of
Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
wangjb@pku.edu.cn; yan_zhang@pku.edu.cn
Received January 12, 2011
ABSTRACT
A series of 3-arylthio-1,3-disubstituted-oxindoles were prepared in good yields by the reaction of R-diazocarbonyl compounds and sulfenamides.
The reaction involves a Rh-catalyzed thia-Sommelet-Hauser-type rearrangement.
Oxindole and its derivatives are frequently occurring
structure units in medicinally active compounds of both
natural and synthetic origin.1 Recently, a plethora of new
methods for the synthesis of oxindoles bearing quaternary
carbon centers in the 3-position have been developed
through transition-metal-catalyzed coupling reactions2 or
various cyclization methods.3 In particular, the derivatives
with a thio group at the 3-position have been widely
investigated.4,5 Among various approaches toward this
(3) (a) Marti, C.; Carreira, E. M. Eur. J. Org. Chem. 2003, 2209. (b)
Trost, B. M.; Brennan, M. K. Synthesis 2009, 3003. (c) Wei, Q.; Gong, L.
Org. Lett. 2010, 12, 1008. (d) Cheng, L.; Liu, L.; Wang, D.; Chen, Y.
Org. Lett. 2009, 11, 3874. (e) Song, R. -J.; Liu, Y.; Li, R. -J.; Li, J, -H.
Tetrahedron Lett. 2009, 50, 3912. (f) Peng, P.; Tang, B. -X.; Pi, S. -F.;
Liang, Y.; Li, J. -H. J. Org. Chem. 2009, 74, 3569. (g) Klein, J. E. M. N.;
Perry, A.; Pugh, D. S.; Taylor, R. J. K. Org. Lett. 2010, 12, 3446. (h)
Liang, J.; Chen, J.; Du, F.; Zeng, X.; Li, L.; Zhang, H. Org. Lett. 2009,
† Peking University.
‡ Lanzhou University.
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r
10.1021/ol200091k
Published on Web 02/09/2011
2011 American Chemical Society

the corresponding sulfonium salts with stoichiomeric
amount of base.8-10
Scheme 1. Indolin-2-one Synthesis via Thia-Sommelet-Hauser
Rearrangement
On the other hand, the reaction of sulfide with the in situ
generated metal carbene, which can be easily achieved by
transition-metal-catalyzed reaction of diazo compounds,
is another reliable way to form sulfonium ylide.12 This
method has been proved to be highly efficient and oper-
ationally simple and can avoid the introduction of stoi-
chiometric base. Various [2,3]-sigmatropic and 1,2-shift
rearrangements of sulfonium ylides based on this method
have been previously reported.13,14 However, application
of this approach to catalytic thia-Sommelet-Hauser re-
arrangement has been so far rather limited. Aggarwal and
co-workers reported the first catalytic thia-Sommelet-
Hauser rearrangement that was observed as side
reaction.11a Wehaverecentlydevelopeda Rh(II)-catalyzed
thia-Sommelet-Hauser rearrangement that can be used as
an efficient way to introduce a substituent to the ortho
position of arylacetates efficiently.11b As an extension of
this work, we further conceived that the sulfonium ylide
intermediate A in Gassman’s oxindole synthesis should be
accessed through a catalytic carbene transformation by
invoking a sulfenamide as substrate to react with metal
carbene (Scheme 1). If this is indeed the case, then a
catalytic version of Gassmen’s oxindole synthesis will be
achieved. Herein, we report the results of the study along
this line.
Initially, we observed that when a 3:1 mixture of
diazoacetate 2a15 and sulfenamide 1a16 in toluene was
catalyzed by 0.5 mol % of Rh2(OAc)4, 1,3-dimethyl-
3-(phenylthio)oxindole 3a was isolated in 42% yield
(Table 1, entry 1). A series of Rh(II) catalysts were then
examined in order to optimize the reaction conditions.
Rh2(O2CCF3)4 only gave trace amount of product (entry
2);Rh2(O2CC3F7)4 and Rh2(acam)4 alsoled toloweryields
(entries 3 and 4). Chiral dirhodium catalysts Rh2(S-DOSP)4
and Rh2(S-TBSP)4 afforded oxindole 3a with relatively
high yields (entries 5 and 6). It was noted that the reaction
type of oxindoles,4-9 we noticed that Gassman and co-
workers developed a useful method to synthesize (3-
methylthio)oxindoles by the reaction of R-carboalkoxy
sulfides and aniline derivatives through a thia-Somme-
let-Hauser rearrangement (Scheme 1).8 The synthesis
needs several steps, which include (a) formation of mono-
N-chloroaniline; (b) generatation of azasulfonium salt; (c)
the formation of sulfonium ylide A by treatment of the salt
with base; (d) thia-Sommelet-Hauser-type rearrangement
leading to imine B; and (e) acid-promoted intramolecular
attack of the amino group on the carbonyl group. Later,
Wierenga further optimized this procedure.9a
In Gassman’s synthesis, thia-Sommelet-Hauser rear-
rangement is the key step, which is a unique process
involving a [2,3]-sigmatropic dearomatization with subse-
quent [1,3]-shift rearomatization. This unique rearrange-
ment is a useful way for constructing a cyclic quaternary
carbon center from aromatic rings8,9 or making ortho-
substitutedaromatic compounds.10,11 It is noteworthy that
in classic thia-Sommelet-Hauser rearrangement, the for-
mation of sulfonium ylides is achieved by the treatment of
(12) For reviews, see: (a) Hodgson, D. M.; Pierard, T. M.; Stupple,
P. A. Chem. Soc. Rev. 2001, 30, 50. (b) Mehta, G.; Muthusamy, S.
Tetrahedron 2002, 58, 9477. (c) Reggelin, M. Top. Curr. Chem. 2007, 275,
1. (d) Braverman, S.; Cherkinsky, M. Top. Curr. Chem. 2007, 275, 67. (e)
Zhang, Y.; Wang, J. Coord. Chem. Rev. 2010, 254, 941.
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Angew. Chem., Int. Ed. 2005, 44, 452. (b) Miller, M.; Vogel, J. C.; Tsang,
W.; Merrit, A.; Procter, D. J. Org. Biomol. Chem. 2009, 7, 589. (c) Miller,
M.; Tsang, W.; Merritt, A.; Procter, D. J. Chem. Commun. 2007, 498.
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Heterocycles 2001, 55, 1029.
(8) (a) Gassman, P. G.; van Bergen, T. J. J. Am. Chem. Soc. 1973, 95,
2718. (b) Gassman, P. G.; van Bergen, T. J. J. Am. Chem. Soc. 1974, 96,
5508. (c) Gassman, P. G.; Gruetzmacher, G.; van Bergen, T. J. J. Am.
Chem. Soc. 1974, 96, 5512.
(13) For selected recent reports on transition metal-catalyzed sulfur
ylide [1,2] shift, see: (a) Murphy, G. K.; West, F. G. Org. Lett. 2005, 7,
1801. (b) Nair, V.; Nair, S. M.; Mathai, S.; Liebscher, J.; Ziemer, B.;
Narsimulu, K. Tetrahedron Lett. 2004, 45, 5759. (c) Ellis-Holder, K. K.;
Peppers, B. P.; Kovalevsky, A. Y.; Diver, S. T. Org. Lett. 2006, 8, 2511.
(d) Stepakov, A. V.; Molchanov, A. P.; Magull, J.; Vidovic, D.; Starova,
G. L.; Kopf, J.; Kostikov, R. R. Tetrahedron 2006, 62, 3610.
(14) For selected recent reports on transition metal-catalyzed sulfur
ylide [2,3] sigmatropic rearrangement, see: (a) Novikov, A. V.; Kennedy,
A. R.; Rainier, J. D. J. Org. Chem. 2003, 68, 993. (b) Nyong, A. M.;
Rainier, J. D. J. Org. Chem. 2005, 70, 746. (c) Ma, M.; Peng, L.; Li, C.;
Zhang, X.; Wang, J. J. Am. Chem. Soc. 2005, 127, 15016. (d) Liao, M.;
Wang, J. Green Chem. 2007, 9, 184.
(15) For preparation of diazo compounds 2a-f, see: (a) Peng, C.;
Wang, Y.; Wang, J. J. Am. Chem. Soc. 2008, 130, 1566. (b) Shi, G.; Xu,
Y. J. Chem. Soc. Chem. Commun. 1989, 607. (c) Taber, D. F.; You, K.;
Song, Y. J. Org. Chem. 1995, 60, 1093. (d) Taber, D. F.; Sheth, R. B.;
Joshi, P. V. J. Org. Chem. 2005, 70, 2851.
(16) For preparation of sulfenamides, see: (a) Barrett, A. G. M.;
Dhanak, D.; Graboski, G. G.; Taylor, S. J. Org. Synth. 1993, 68, 8. (b)
Davis, F. A.; Horner, C. J.; Fretz, E. R.; Stackhouse, J. F. J. Org. Chem.
1973, 38, 695.
(9) (a) Wierenga, W.; Griffin, J.; Warpehoski, M. A. Tetrahedron
Lett. 1983, 24, 2437. (b) Karp, G. M.; Condon, M. E. J. Heterocycl.
Chem. 1994, 31, 1513.
(10) (a) Ishibashi, H.; Tabata, T.; Kobayashi, T.; Takamuro, I.;
Ikeda, M. Chem. Pharm. Bull. 1991, 39, 2878. (b) Berger, R.; Ziller,
J. W.; Van Vranken, D. L. J. Am. Chem. Soc. 1998, 120, 841. (c) Padwa,
A.; Gasdaska, J. R. J. Org. Chem. 1986, 51, 2857. (d) Mitani, M.;
Tsuchida, M.; T.; Koyama, K. J. Chem. Soc. Chem.Commun. 1974, 869.
(e) Yamamoto, M.; Kakinuma, M.; Kohmoto, S.; Yamada, K. Bull.
Chem. Soc. Jpn. 1989, 62, 958. (f) Tanzawa, T.; Ichioka, M.; Shirai, N.;
Sato, Y. J. Chem. Soc. Perkin Trans. 1 1995, 431.
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Fieldhouse, R.; Spey, S. E. J. Chem. Soc. Perkin Trans. 1 2000, 3267. (b)
Liao, M.; Peng, L.; Wang, J. Org. Lett. 2008, 10, 693.
Org. Lett., Vol. 13, No. 5, 2011
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Table 1. Conditions on the Reaction of Sulfenamide 1a and
Diazoester 2aa
Table 2. Reaction of 1a with 2a-fa
entry
cat. (mol %)
solvent temp (°C) time (h) yieldb (%)
entry
2, R =
2a, CH3
3, yieldb (%)
1
2
3
4
Rh2(OAc)4 (0.5)
toluene
60
60
60
60
0
10
10
10
10
2
42
trace
24
22
51
49
7
1
2
3
4
5
6
3a, 70
3b, 55
3c, 51
3d, 44
3e, -c
3f, -c
Rh2(O2CCF3)4 (0.5) toluene
Rh2(O2CC3F7)4 (0.5) toluene
2b, CH3CH2CH2
2c, C6H5CH2
2d, CF3
Rh2(acam)4 (0.5)
toluene
5c Rh2(S-DOSP)4 (0.5) toluene
6c Rh2(S-TBSP)4 (0.5) toluene
2e, (CH3)2CH
2f, c-hexyl
0
2
7
8
9
Cu(CH3CN)4PF6 (10) DCE
60
60
0
2
a Reaction conditions: to a solution of sulfenamide 1a (0.5 mmol, 1.0
equiv) and Rh2(OAc)4 (0.01 mmol, 2 mol %) in 2 mL of DCE were added
diazo compounds 2a-f (1.5 mmol, 3.0 equiv) in 1 mL of DCE over 5 h
with a syringe pump. The solution was further stirred for 10 h at 0 °C.
b Isolated yields after column chromatography. c No expected products
could be identified.
CuI (10)
toluene
2
10
45
68
68
61
58
43
44
70
67
NRd
30
48
64
37
Rh2(OAc)4 (1)
toluene
toluene
toluene
toluene
toluene
toluene
toluene
DCE
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10 Rh2(OAc)4 (2)
11 Rh2(OAc)4 (3)
12 Rh2(OAc)4 (2)
13 Rh2(OAc)4 (2)
14 Rh2(OAc)4 (2)
15 Rh2(OAc)4 (2)
16 Rh2(OAc)4(2)
17 Rh2(OAc)4 (2)
18 Rh2(OAc)4 (2)
19 Rh2(OAc)4 (2)
20 Rh2(OAc)4 (2)
21 Rh2(OAc)4 (2)
22 Rh2(OAc)4 (2)
0
0
rt
-20
-40
-78
0
With the optimized reaction conditions in hand, we
then explored the scope of the diazo compounds15 in
the reaction (Table 2). The reaction with the diazoace-
tates bearing primary alkyl substituents worked well to
afford the corresponding oxindole products in moder-
ate yields (entries 1 and 2). Diazoacetates bearing a
benzyl or CF3 substituent also worked, although the
yields were slightly diminished (entries 3 and 4). It was
observed that the reaction of diazoacetates bearing
secondary alkyl substituents failed to afford the corre-
sponding oxindole products (entries 5 and 6). The fail-
ure in these cases might be attributed to the increase of
the steric hindrance of the diazo substrates, which poses
a negative effect on the reaction of Rh(II) carbene
intermediate with sulfenamide and also on the subse-
quent rearrangement step.
Next, the scope of sulfenamide substrates 1b-p16 was
examined (Scheme 2). First, the electronic effect of sub-
stituents on the aromatic ring of SAr group was investi-
gated. To our delight, the sulfenaminde substrates bearing
either electron-rich or electron-deficient substituents on
the aromatic ring of SAr all underwent the reaction
smoothly to afford the corresponding oxindole products
3g-j in good yields, which indicates that the electronic
effect of SAr has no significant influence on the reaction.
Subsequently, we studied the effect of the substituents
on the aromatic ring attached to nitrogen. A series of
substituents were investigated, including p-CF3, p-F, p-Cl,
p-NO2, and p-OMe. The reactions afforded the corre-
sponding oxindole products 3k-o in moderate to high
yields, which indicate that the thia-Sommelet-Hauser
rearrangement is not subjected to significant electronic
effects of the aromatic ring. When a meta substituent is
introduced to the aromatic ring attached to the nitrogen,
the thia-Sommelet-Hauser rearrangement encounters
CH2Cl2
DMF
0
rt
CH3CN
THF
rt
0
dioxane
n-hexane
15
15
a The reaction was carried out with 1.0 equiv of 1a and 3.0 equiv of
2a. b Isolated yields after column chromatography. c The reaction gave a
racemic product, as determined by HPLC with chiral OD-chromato-
graphy column. d NR: no reaction occurred.
could be carried out efficiently at 0 °C. However, the
reaction did not show any enantioselectivity. Copper(I)
catalysts were also investigated but neither of them was as
effective as Rh(II) salt for the reaction (entries 7 and 8).
With Rh2(OAc)4 as catalyst, we set out to further
optimize other reaction parameters. First, the yield was
improved when the loading of catalyst was increased to 2
mol % (entries 9 and 10). However, no further improve-
ment of yield was observed when the catalyst was increased
to 3 mol % (entry 11). The effect of temperature was then
studied (entries 12-15). The yields diminished, the reac-
tion was then carried out at low temperature, and it was
concluded that the reaction at 0 °C provided optimal
results in terms of reaction time and yield. Finally, the
effect of solvent was investigated, and dichloroethane
(DCE), dichloromethane (DCM), and toluene afforded
the products in approximately same yields (entries 10, 16,
and 17). DCE led to a slightly cleaner reaction system. It
was observed that polar solvent was disfavored for this
reaction (entries 18-21). The reaction also proceeded
inefficiently in solvent such as n-hexane as the sulfen-
amide 1a became poorly soluble under such conditions
(entry 22).
1212
Org. Lett., Vol. 13, No. 5, 2011

substituted sulfenamides (1k, 1l and 1m, respectively),
affording a mixture of (3p þ 3p0), (3q þ 3q0), and (3r þ
3r0), respectively.
At last, we varied another substituent on nitrogen (R0).
The reaction with N-benzyl or N-allyl substituents af-
forded similar results (for 3s and 3t). However, the yield
was significantly diminished when bulkier substituent,
such as isopropyl, was introduced (3u).
Scheme 2. Reaction of Sulfenamides 1b-p with Diazo Com-
pound 2aa
The oxindole products obtained above were character-
ized by 1H and 13C NMR spectra. For one of the products,
3a, the structure was determined by X-ray crystallography
as show in Figure 1.
Figure 1. X-ray structures of 3a.
In summary, we have achieved a catalytic version of
Gassman’s oxindole synthesis. With this Rh2(OAc)4-cata-
lyzed transformation, a series of 3-arylthio-1,3-disubsti-
tuted oxindoles can be synthesized in one-step from easily
available sulfenamides and diazoacetates. The catalytic
reaction occurs under neutral conditions and can be
carried out at low temperature, affording the products in
moderately high yields. The reaction also shows excellent
functional group tolerance. This reaction further demon-
strates the efficacy of metal carbene-based catalytic thia-
Sommelet-Hauser rearrangement in organic synthesis.
a Reaction conditions: To a solution of sulfenamides 1b-q (0.5 mmol,
1.0 equiv) and Rh2(OAc)4 (0.01 mmol, 2 mol %) in 2 mL of dichlor-
oethane was added diazo compound 2a (1.5 mmol, 3.0 equiv) in 1 mL of
DCE over 5 h with a syringe pump. The solution was stirred for 10 h at 0 °C.
Acknowledgment. The project is supported by the Nat-
ural Science Foundation of China (Grant Nos. 20832002,
20821062, 20902005, 21072009) and the National Basic
Research Program of China (973 Program No. 2009-
CB825300).
b Isolated yields after column chromatography.
regioselectivity problem. In Gassman’s synthesis of oxi-
ndole, generally low regioselectivity has been observed in
the thia-Sommelet-Hauser rearrangement.8b,9 We also
observed low regioselectivities in our catalytic reaction
system for the reaction with m-F-, m-Cl-, and m,p-Cl2-
Supporting Information Available. Experimental pro-
cedure, characterization data, 1H and 13C NMR spectra,
and X-ray data (CIF) for 3a. This material is available
free of charge via the Internet at http://pubs.acs.org.
Org. Lett., Vol. 13, No. 5, 2011
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