Rh(II)-catalyzed Sommelet-Hauser rearrangement

Article abstract of DOI:10.1021/ol703058p

Catalytic Sommelet-Hauser rearrangement is reported. The Rh(II)-catalyzed reaction of aryldiazoacetates with ethyl benzylthioacetate affords Sommelet-Hauser rearrangement products in good to excellent yields. This reaction provides a reliable and efficient way to introduce a substituent to the ortho position of arylacetates.

Full text of DOI:10.1021/ol703058p

ORGANIC
LETTERS
2008
Vol. 10, No. 5
693-696
Rh(II)-Catalyzed Sommelet
Rearrangement
−Hauser
Mingyi Liao, Lingling Peng, and Jianbo Wang*
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
wangjb@pku.edu.cn
Received October 18, 2007
ABSTRACT
Catalytic Sommelet−Hauser rearrangement is reported. The Rh(II)-catalyzed reaction of aryldiazoacetates with ethyl benzylthioacetate affords
Sommelet Hauser rearrangement products in good to excellent yields. This reaction provides a reliable and efficient way to introduce a
−
substituent to the ortho position of arylacetates.
[2,3] sigmatropic rearrangement is one of the most remark-
able bond reorganization processes in organic chemistry.1
Among various types of [2,3] sigmatropic rearrangements,
the Sommelet-Hauser reaction of ammonium or sulfonium
ylide is an attractive and unique reaction, in which an
aromatic unsaturated double bond is involved.2-6 The [2,3]
sigmatropic dearomatization followed by the [1,3] shift
rearomatization process is facile with low activation energy.
It affords a unique method for the preparation of ortho-
substituted aromatic compounds.5 It also serves as a powerful
approach for constructing cyclic quaternary carbon centers
from aromatic rings.6
The common method for ammonium or sulfonium ylide
generation in Sommelet-Hauser rearrangement involves the
removal of a proton from the ammonium or sulfonium salt
with strong base. An improvement is the application of
fluoride ion-induced desilylation of [1-(trimethylsilyl)alkyl]-
ammonium or -sulfonium salts, in which the ylide is
quantitatively formed at room temperature.7,8 Besides, the
reaction of N-[(trialkylstannyl)methyl]benzylammonium salts
with organolithium compounds to generate benzylammonium
ylides was also reported.9 However, each of these methods
requires prior preparation of the corresponding salts and then
use of at least 1 equiv of reagent to generate the ylides.
(1) For reviews, see: (a) Trost, B. M.; Melvin, L. S., Jr. Sulfur Ylides;
Academic Press: New York, 1975; Chapter 7. (b) Vedejs, E. Acc. Chem.
Res. 1984, 17, 358.
(2) For seminal publications, see: (a) Sommelet, M. Compt. Rend. 1937,
205, 56. (b) Kantor, S. W.; Hauser, C. R. J. Am. Chem. Soc. 1951, 73,
4122. (c) Hauser, C. R.; Kantor, S. W.; Brasen, W. R. J. Am. Chem. Soc.
1953, 75, 2660.
(3) For recent reviews, see: (a) Marko, I. E. In CompresiVe Organic
Synthesis; Trost, B. M., Freming, I., Eds.; Pergamon Press: Oxford, UK,
1991; Vol. 6, p 913. (b) Beall, L. S.; Padwa, A. AdV. Nitrogen Heterocycl.
1998, 3, 117-158. (c) Clark, J. S. Nitrogen, Oxygen, Sulfur Ylide Chem.
2002, 1-113.
(4) For most recent examples, see: (a) Hanessian, S.; Talbot, C.;
Saravanan, P. Synthesis 2006, 723. (b) Tayama, E.; Kimura, H. Angew.
Chem., Int. Ed. 2007, 46, 8869.
(5) (a) Robert, A.; Thomas, M. T.; Foucaud, A. J. Chem. Soc., Chem.
Commun. 1979, 1048. (b) Jon´czyk, A.; Lipiak, D. J. Org. Chem. 1991, 56,
6933. (c) Ishibashi, H.; Tabata, T.; Kobayashi, T.; Takamuro, I.; Ikeda, M.
Chem. Pharm. Bull. 1991, 39, 2878.
(6) (a) Hauser, C. R.; Van Eenam, D. N. J. Am. Chem. Soc. 1957, 79,
5512. (b) Van Eenam, D. N.; Hauser, C. R. J. Am. Chem. Soc. 1957, 79,
5520. (c) Hauser, C. R.; Van Eenam, D. N.; Bayless, P. L. J. Org. Chem.
1958, 23, 354. (d) Shirai, N.; Sumiyama, F.; Sato, Y.; Hori, M. J. Org.
Chem. 1989, 54, 836. (e) Berger, R.; Ziller, J. W.; Van Vranken, D. L. J.
Am. Chem. Soc. 1998, 120, 841. (f) McComas, C. C.; Van Vranken, D. L.
Tetrahedron Lett. 2003, 44, 8203.
(7) Vedejs, E.; West, F. G. Chem. ReV. 1986, 86, 941.
(8) (a) Nakano, M.; Sato, Y. J. Org. Chem. 1987, 52, 1844. (b) Shirai,
N.; Sato, Y. J. Org. Chem. 1988, 53, 194. (c) Shirai, N.; Watanabe, Y.;
Sato, Y. J. Org. Chem. 1990, 55, 2767. (d) Sato, Y.; Shirai, N.; Machida,
Y.; Ito, E.; Yasui, T.; Kurono, Y.; Hatano, K. J. Org. Chem. 1992, 57,
6711. (e) Maeda, Y.; Shirai, N.; Sato, Y.; Tatewaki, H. J. Org. Chem. 1994,
59, 7897. (f) Tanzawa, T.; Ichioka, M.; Shirai, N.; Sato, Y. J. Chem. Soc.,
Perkin Trans. 1 1995, 431. (g) Tanzawa, T.; Shirai, N.; Sato, Y.; Hatano,
K.; Kurono, Y. J. Chem. Soc., Perkin Trans. 1 1995, 2845.
(9) Maeda, Y.; Sato, Y. J. Org. Chem. 1996, 61, 5188.
10.1021/ol703058p CCC: $40.75
© 2008 American Chemical Society
Published on Web 02/01/2008

On the other hand, transition metal-catalyzed reactions of
diazo compounds in the presence of sulfides or amines have
been developed into an efficient way to generate sulfonium
or ammonium ylides.10 This approach has been extensively
investigated by several groups in sulfur ylide [1,2] shift and
[2,3] sigmatropic rearrangement.11,12 It has also been applied
by Aggarwal and co-workers in epoxidation and cyclopro-
panation reactions.13 However, this catalytic process so far
has not been utilized for Sommelet-Hauser rearrangement,
except in one case in which Rh2(OAc)4-catalyzed thia-
Sommelet-Hauser rearrangement has been reported as a side
reaction.14 Here we report a catalytic thia-Sommelet-Hauser
rearrangement of sulfonium ylides. The ylide is derived from
sulfide and Rh(II) carbene, which is generated from the Rh-
(II)-catalyzed reaction of R-diazocarbonyl compounds (Scheme
1). The initially formed sulfur ylide A subsequently under-
At the outset of this investigation, we examined the
reaction of methyl phenyldiazoacetate 1a and ethyl ben-
zylthioacetate 2a with transition metal catalysts (Scheme 2).
Scheme 2. Rh2(OAc)4-Catalyzed Reaction of 1a and 2a
Scheme 1. Thia-Sommelet-Hauser Rearrangement under
When 1a and 2a were catalyzed with Rh2(OAc)4 in CH2Cl2
at room temperature, thia-Sommelet-Hauser rearrangement
product 3a was isolated in 50% yield. The reaction also
occurred in H2O with 65% isolated yield. It was worth noting
that no product 4, which might be formed from competing
[1,2] shift of the benzyl group (Stevens rearrangement),15
could be detected in this reaction. This indicates proton
transfer and the subsequent [2,3] sigmatropic rearrangements
are faster than the [1,2] shift, which has been suggested as
a radical process.16
Transition Metal-Catalyzed Conditions
Table 1. The Reaction of 1a and Sulfides 2b-f under Various
Conditionsa
goes tautomerization to generate ylide B, which is required
for Sommelet-Hauser rearrangement.
yield
entry sulfide (2, E)
catalyst
Rh2(OAc)4
Rh2(OAc)4
Rh2(OAc)4
Rh2(OAc)4
solvent
time
(%)b
1
2
3
4
5
2b, CO2Et
2b, CO2Et
2b, CO2Et
2b, CO2Et
2b, CO2Et
CH2Cl2
toluene
n-hexane 24 h
H2O
2.5 h
2 h
51
67
(10) For reviews, see: (a) Ye, T.; McKervey, M. A. Chem. ReV. 1994,
94, 1091. (b) Doyle, M. P.; McKervey, M. A.; Ye, T. Modern Catalytic
Methods for Organic Synthesis with Diazo Compounds; Wiley-Inter-
science: New York, 1998. (c) Li, A.-H.; Dai, L.-X.; Aggarwal, V. K. Chem.
ReV. 1997, 97, 2341. (d) Doyle, M. P.; Forbes, D. C. Chem. ReV. 1998, 98,
911. (e) Hodgson, O. M.; Pierard, F. Y. T. M.; Stupple, P. A. Chem. Soc.
ReV. 2001, 30, 50.
(11) For recent reports on transition metal-catalyzed sulfur ylide [1,2]
shift, see: (a) Nair, V.; Nair, S. M.; Mathai, S.; Liebscher, J.; Ziemer, B.;
Narsimulu, K. Tetrahedron Lett. 2004, 45, 5759. (b) Ellis-Holder, K. K.;
Peppers, B. P.; Kovalevsky, A. Y.; Diver, S. T. Org. Lett. 2006, 8, 2511.
(c) Stepakov, A. V.; Molchanov, A. P.; Magull, J.; Vidovic, D.; Starova,
G. L.; Kopfc, J.; Kostikov, R. R. Tetrahedron 2006, 62, 3610.
(12) 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.
65
1 h
54
c
Cu(CH3CN)4PF6 CH2Cl2
Rh2(acam)4
16 h
1.5 h
0.5 h
trace
64
6d 2b, CO2Et
toluene
toluene
7
8
2b, CO2Et
2b, CO2Et
2b, CO2Et
2b, CO2Et
2b, CO2Et
2c, CN
Rh2(O2CCF3)4
Rh2(O2CCF3)4
Rh2(O2CC3F7)4
Rh2(O2CC7H15
Rh2(S-DOSP)4
Rh2(O2CCF3)4
Rh2(O2CCF3)4
87
n-hexane 40 min 70
9
toluene
toluene
toluene
toluene
toluene
toluene
toluene
0.5 h
2 h
4.5 h
3.5 h
24 h
0.5 h
22 h
76
78
74f
56
g
h
i
10
11
12
13
14
15
)
4
e
2d, NO2
2e, p-NO2C6H4 Rh2(O2CCF3)4
2f, n-Pr
Rh2(OAc)4
a Unless otherwise noted, reaction conditions are as follows: 1a (0.2
mmol), 2b-f (0.3 mmol), 0.5 mol % catalyst, 5 mL of solvent. b Isolated
yields after column chromatography. c 10% mol catalyst was used. d The
reaction was carried out at 80 °C. e Rh2(S-DOSP)4: tetrakis {1-[(4-
alkyl(C11-C13)phenyl)sulfonyl]-(2S)-pyrrolidinecarboxylate}dirhodium.
f The reaction gave a racemic product. g The reaction was carried out at
80 °C and no reaction occurred. h The reaction gave [1,2]-shift product in
54% isolated yield. i No reaction occurred.
(13) For reviews, see: (a) Aggarwal, V. K.; Winn, C. L. Acc. Chem.
Res. 2004, 37, 611. (b) Fulton, J. R.; Aggarwal, V. K.; Vicente, J. D. Eur.
J. Org. Chem. 2005, 1479.
(14) Aggarwal, V. K.; Smith, H. W.; Hynd, G.; Jones, R. V. H.;
Fieldhouse, R.; Spey, S. E. J. Chem. Soc., Perkin Trans. 1 2000, 3267.
694
Org. Lett., Vol. 10, No. 5, 2008

Table 2. Reaction of Diazo Compounds 1b-m with Sulfides 2b,c,ga
a Reaction conditions: diazo compound (0.2 mmol), sulfide (0.3 mmol), 0.5 mol % Rh2(O2CCF3)4, 5 mL of toluene. b Isolated yields after column
chromatography. c The reaction was carried out at 60 °C. d The data in parentheses refer to the conversion yield. PNB: p-NO2C6H4CH2-.
Further investigation by altering reaction parameters
(solvent, sulfide, and catalyst) reveals some interesting
aspects about this reaction (Table 1). First, the reaction could
be carried out in various solvents to afford the product in
similar yields, but the reaction time varied. Second, polar
solvent was found to accelerate the reaction (entries 1-4).
Third, the reaction was affected by catalysts. Cu(CH3CN)4PF6
was found not to be effective (entry 5). Among the Rh(II)
catalysts, Rh2(O2CCF3)4 afforded the optimal result (entry
essentially no asymmetric induction (entry 11). Finally, the
effect of sulfides was investigated. Compared with the
benzylthioacetate 2a, the reaction time with phenylthioacetate
2b was significantly shortened. The ester group could be
replaced with the cyano group (entry 12). Alternatively, when
the ester group of 1a was replaced by a nitro group, no
reaction occurred even at elevated temperature (entry 13).
The reaction with phenyl p-nitrobenzyl sulfide 2e, on the
other hand, gave the [1,2] shift product in 54% yield (entry
14). No reaction occurred with n-propylphenyl sulfide 2f.
This indicates the requirement of electron-withdrawing
substituents in sulfides for this reaction.
Subsequently, the optimized reaction conditions were
applied to a series of aryldiazoacetates 1b-m18 and sulfides
2b,c,g (Table 2). For ortho-substituted diazo compounds, we
expected that the reaction should occur at another ortho
position. However, the reactions of o-methyl-, o-chloro-, or
17
7). The reaction with chiral Rh(II) complex Rh2(S-DOSP)4
gave the rearrangement product in good yield, but with
(15) For a recent study about competition between [1,2] Stevens and
[2,3] Sommelet-Hauser rearrangement, see: Jon´czyk, A.; Lipiak, D.;
Sienkiewicz, K. Synlett 1991, 493.
(16) (a) Ollis, W. D.; Rey, M.; Sutherland, I. O. J. Chem. Soc., Perkin
Trans. 1 1983, 1009. (b) Eberlein, T. H.; West, F. G.; Tester, R. W. J.
Org. Chem. 1992, 57, 3479.
(17) (a) Davies, H. M. L.; Hutcheson, D. K. Tetrahedron Lett. 1993,
34, 7243. (b) Davies, H. M. L.; Bruzinski, P. R.; Lake, D. H.; Kong, N.;
Fall, M. J. J. Am. Chem. Soc. 1996, 118, 6897.
(18) Qu, Z.; Shi, W.; Wang, J. J. Org. Chem. 2001, 66, 8139.
Org. Lett., Vol. 10, No. 5, 2008
695

o,p-dichloro-substituted diazo compounds only gave a com-
plex mixture. When the ortho substituent was ethynyl, the
reaction worked, but afforded the corresponding product in
low yield (entry 1).
8a presumably results from the proton transfer and subse-
quent [2,3] sigmatropic rearrangement of the allyl group as
shown in Scheme 3. The reaction with methyl p-methox-
yphenyldiazoacetate 1j, however, afforded the direct [2,3]
sigmatropic rearrangement product 7b in 91% yield without
detectable formation of 8b. These results indicate that sulfur
[2,3] sigmatropic rearrangement is a very facile process.1,12
Finally, we conceived that the key intermediate ylide B
in Scheme 1 could also be generated directly by the transition
metal-catalyzed reaction of ethyl diazoacetate with sulfide
9 (Scheme 4). Thus, ethyl diazoacetate (EDA) and sulfide 9
For meta-substituted diazo compounds, the reaction may
give two products since there are two discriminative ortho
positions. To our delight, the reaction afforded only one
product in good yield (entries 2 and 3). The reaction occurred
at the less sterically hindered ortho position.19 This result
may indicate [2,3] sigmatropic rearrangement is sensitive to
the steric effect of the aromatic substituents.20 For para-
substituted diazo compounds, the reactions proceeded smoothly
and afforded the corresponding products in high yields when
the substituents were p-Me, p-Cl, p-Br, and p-NO2 (entries
5-8). When the substituent was p-MeO, the diazo substrate
disappeared rapidly, but the expected product was isolated
in low yield (entry 9). This might be attributed to the high
reactivity of the p-MeO-substituted diazo compound, thus
resulting in side reactions. In comparison, the reaction with
p-NO2-substituted sulfide proceeded sluggishly and required
higher temperature (60 °C) (entry 8).
Scheme 4. Rh2(OAc)4-Catalyzed Reaction of 9 with EDA
In further experiments, it was found that increasing the
bulk of the ester group of the diazo substrates resulted in
longer reaction time, but the yields were comparable to those
of other substrates (entires 10-12). Finally, reactions with
phenylthioacetonitrile 2c and benzyl phenylthioacetate 2g
were also found to proceed well (entries 13 and 14).
To further explore the scope of this catalytic process, we
examined the reactions with allylthioacetate 6 (Scheme 3).
were subjected to the reaction in the presence of Rh2(OAc)4.
In this case the sulfur ylide intermediate corresponding to B
in Scheme 1 should be formed directly and then underwent
Sommelet-Hauser rearrangement to afford 3a. As expected,
thia-Sommelet-Hauser rearrangement product 3a was ob-
tained, albeit in low yield (32%). The generally good yields
obtaind with aryldiazoacetates in this Rh(II)-catalyzed pro-
cess are a further demonstration of balanced reactivity and
selectivity of donor/acceptor-susbstituted metal carbenes
derived from these diazo compounds.21
Scheme 3. Rh(II)-Catalyzed Reaction of 1a,j and 6
In conclusion, we have reported the catalytic Sommelet-
Hauser rearrangement of sulfonium ylides derived from Rh-
(II) carbenes and sulfides. The reaction can be carried out
under essentially neutral condition at room temperature. A
variety of aryldiazoacetates and sulfides are suitable sub-
strates for this reaction and the corresponding products are
obtained in good to excellent yields, thus providing an
effective and unique method for preparing ortho-substituted
aromatic compounds.22
Acknowledgment. The project is supported by NSFC
(Grant Nos. 20572002, 20521202, and 20772003) and the
MOE of China (Cheung Kong Scholars Program).
Supporting Information Available: Experiment proce-
dure, characterization data, X-ray structure of sulfone, and
1H and 13C NMR spectra for all new compounds. This
material is available free of charge via the Internet at
http://pubs.acs.org.
In these cases, the [2,3] sigmatropic rearrangement of the
intially generated sulfur ylide would compete with the proton
transfer-Sommelet-Hauser rearrangement process. In the
reaction with methyl phenyldiazoacetate 1a, direct [2,3]
sigmatropic rearrangement product 7a was isolated in 46%
yield, together with a diastereomeric mixture of 8a (28%).
OL703058P
(19) To unambiguously establish the structure of product, 5d was
converted to the corresponding sulfone, which was analyzed by X-ray
crystallography, see the Supporting Information.
(20) Similar selectivity has been recently reported in the ammonium ylide
Sommelet-Hauser rearrangement, see ref 4b.
(21) (a) Davies, H. M. L.; Bruzinski, P. R.; Fall, M. J. Tetrahedron Lett.
1996, 37, 4133. (b) Davies, H. M. L.; Beckwith, R. E. J. Chem. ReV. 2003,
103, 2861.
(22) For a recent review, see: Smith, K.; El-Hiti, G. A. Curr. Org. Synth.
2004, 1, 253.
696
Org. Lett., Vol. 10, No. 5, 2008