2,3-Sigmatropic rearrangement of sulfonium ylides generated by addition of samarium carbenoids

Article abstract of DOI:10.1055/s-1998-1979

Allylic sulfides are transformed into homoallylic sulfides with complete allylic inversion by treatment with SmI₂ and CH₂I₂ in THF. The reaction will involve allylic sulfonium ylides as an intermediate, which undergoes 2,3-rearrangement.

Full text of DOI:10.1055/s-1998-1979

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SYNLETT
2,3-Sigmatropic Rearrangement of Sulfonium Ylides Generated by Addition of Samarium
Carbenoids
Munetaka Kunishima,* Daisuke Nakata, Chikako Goto, Kazuhito Hioki, Shohei Tani*
Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Nishi-ku, Kobe 651-2180, Japan
Fax +81-78-974-5689; E-mail: kunisima@pharm.kobegakuin.ac.jp; tani@pharm.kobegakuin.ac.jp
Received 26 August 1998
Abstract: Allylic sulfides are transformed into homoallylic sulfides
with complete allylic inversion by treatment with SmI and CH I in
After several attempts using phenyl prenyl sulfide (1) as a substrate, we
found that reaction of 1 with 3 equiv of CH I and 6 equiv of SmI in
2
2 2
2 2
2
THF. The reaction will involve allylic sulfonium ylides as an
intermediate, which undergoes 2,3-rearrangement.
THF at room temperature gave 2,2-dimethyl-3-butenyl phenyl sulfide
(5) in 97% yield. Results are summarized in Table 1. The reaction took
9
place in good yield by using dibromomethane instead of the iodide
while dichloromethane gave a moderate yield of 2a by heating at 40 C
for 4 days (runs 2, 3). Ethylidene bromides was also found to be
effective for the reaction, giving 6. Similarly, transformation of the
allylic sulfides (2–4) to the homoallylic sulfides (7–9) was achieved in
good to excellent yield.
2,3-Sigmatropic rearrangement of allylic compounds is a useful method
for the synthesis of functionalized alkenes. Recently, we demonstrated
1
that samarium iodide (SmI ) is highly useful to effect 2,3-Wittig
2
rearrangement. Metalated ethers undergoing 2,3-rearrangement were
regioselectively generated by either an intramolecular 1,5-hydrogen
The reaction involves addition of a samarium carbenoid, arising from
transfer of a vinyl radical, generated by a single electron transfer from
2a
CH I and SmI , to a divalent sulfur leading to the formation of a
SmI to γ-halogenoallyl ethers, or a net two-electron reduction of
2 2
2
2
sulfonium ylide, which rearranged to a homoallylic sulfide (Scheme 1).
diallyl acetals with the liberation of an allyloxy samarium by SmI in
2
3
2b
As an alkene is less reactive than a sulfide towards a carbene, no
acetonitrile. In connection with this research, our attention has been
cyclopropanation of alkenes was observed in any case. Imamoto and his
coworker reported that Stevens rearrangement occurred by the reaction
of phenylthioacetic acid methyl ester with a samarium carbenoid
generated from samarium metal and diiodomethane. However, no
evidence for compounds formed by 1,2-rearrangement was obtained in
our case.
focused on development of SmI -mediated 2,3-rearrangement of allylic
sulfonium ylides.
2
Among the methods for generation of allylic sulfonium ylides,
carbenoids addition to allylic sulfides has been shown to be a useful
7
3
method. In contrast to reactions utilizing carbenoids possessing α-
3,4
carbonyl groups generated by decomposition of diazocompounds,
there is only one report for utilizing a Simmons-Smith type reagent, a
5
simple methylene carbenoid, for generation of allylic sulfonium ylides.
Recently, SmI has been shown to be useful for generation of several
2
types of carbenoids from organo-gem-dihalogen compounds under mild
6, 7, 8
conditions.
However, application of samarium carbenoids to 2,3-
rearrangement of sulfonium ylides has not been reported.
Scheme 1

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SYNLETT
1367
When an allylic sulfide with a hydrogen at the γ-vinylic position was
used, the yield of the rearranged product dropped to about 50%, most
likely due to intramolecular elimination of the sulfonium ylide resulting
from addition of the carbenoid to the rearranged homoallyl sulfide
In summary, we have developed a samarium carbenoids-induced 2,3-
rearrangement of allylic sulfonium ylides. The reaction proceeds
quickly at room temperature, and no treatment with acetaldehyde to
liberate the product is required. In addition, high yield of the
homoallylic sulfides was obtained when the starting sulfides with γ-γ-
dialkyl groups were used.
10
(Table 2, runs 1, 5, 7). Since an excess carbenoid would cause the
elimination, attempts were again made either by decreasing the amount
of generating carbenoid or at a lower temperature (0 C). However, the
yields of the rearranged product decreased (runs 2, 3). Shortening the
reaction time to 1 min at room temperature resulted in a decrease of the
elimination, and homoallylic sulfides (13–15) were obtained in
somewhat higher yield (runs 4, 6, 8).
References and Notes
(1) Br ckner, R. Comprehensive Organic Synthesis; Trost, B. M.,
Ed.; Pergamon Press: Oxford, 1991; Vol. 4, pp 873–908.
(2) (a) Kunishima, M.; Hioki, K.; Kono, K.; Kato, A.; Tani, S. J. Org.
Chem. 1997, 62, 7542. (b) Hioki, K.; Kono, K.; Tani, S.;
Kunishima, M. Tetrahedron Lett. 1998, 39, 5229.
In spite of generation of a large excess of carbenoids, there is no
evidence for the formation of sulfonium salts derived from either the
starting or produced sulfide via protonation of sulfonium ylides. Cohen
and his co-worker exhibited that poor yields of rearranged products
(homoallylic sulfides) were much improved by addition of
acetaldehyde, which allows the homoallylic sulfides to regenerate from
the corresponding sulfonium ylides. However, acetaldehyde was found
(3) Trost, B. M.; Melvin, L. S., Jr. “Sulfur Ylides”; Academic Press:
New York, 1975.
(4) Ando, W.; Yamada, M.; Matsuzaki, E. Migita, T. J. Org.
Chem.1972, 37, 3791. Evans, D. A.; Sims, C. L.; Andrews, G. C.
J. Am. Chem. Soc. 1977, 99, 5453. Doyle, M. P.; Griffin, J. H.;
Chinn, M. S.; Leusen, D. J. Org. Chem. 1984, 49, 1917. Takano,
S.; Tomita, S.; Takahashi, M.; Ogasawara, K. Chem. Lett. 1987,
1569. Shi, G.; Xu, Y.; Xu, M. Tetrahedron 1991, 47, 1629.
11
to be ineffective in our reaction. Attempts to isolate sulfonium salts
derived from either the starting or produced sulfides were
12
unsuccessful. These results would indicate that the formation step of
sulfonium ylides (C) is reversible and the equilibrium would only favor
sulfides (A) and carbenoids (B) rather than C, and that the carbenoids
can decompose by itself during the reaction (Scheme 2). Almost
quantitative yield of 5 from 1 in the reaction of Table 1, run 1 may be
compatible with the assumption, and may indicate the absence of the
ylides at the end of reaction.
(5) Kosarych, Z.; Cohen, T. Tetrahedron Lett. 1982, 23, 3019.
(6) Imamoto, T.; Takiyama, N. Tetrahedron Lett. 1987, 28, 1307.
Molander, G. A.; Etter, J. B. J. Org. Chem. 1987, 52, 3942.
Molander, G. A.; Harring, L. S. J. Org. Chem. 1989, 54, 3525.
Yamazaki, T.; Lin, J. T.; Takeda, M.; Kitazume, T. Tetrahedron:
Asymmetry 1990, 1, 351. Lautens, M.; Delanghe, P. H. J. Org.
Chem. 1992, 57, 798. Lautens, M.; Ren, Y. J. Org. Chem. 1996,
61, 2210.
(7) Imamoto, T.; Hatajima, T.; Takiyama, N.; Takeyama, T.; Kamiya,
Y.; Yoshizawa, T. J. Chem. Soc., Perkin Trans. 1 1991, 3127.
(8) Fukuzawa, S.; Fujinami, T.; Sasaki, S. J. Chem. Soc., Chem.
Commun. 1987, 919. Kunishima, M.; Hioki K.; Ohara, T.; Tani S.
J. Chem. Soc., Chem. Commun. 1992, 219. Kunishima, M.; Hioki,
K.; Tani, S.; Kato, A. Tetrahedron Lett. 1994, 35, 7253.
(9) For a typical procedure: To a stirred solution of SmI (0.044 M in
2
THF , 23 mL, 1.01 mmol) containing 1 (30 mg, 0.17 mmol) was
Scheme 2

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SYNLETT
added CH I (135.2 mg, 0.50 mmol) at rt under nitrogen. The
(10) Though 1,3-dienes could not be isolated due to their low boiling
point, the formation of methyl aryl sulfides, another product
formed by elimination, could be detected.
2 2
greenish-blue color of SmI disappeared within 15 min. After
2
stirring for 1.5 hr., the mixture was poured into water and
extracted with ether. The residue was purified by preparative TLC
(hexane) to give 5 as a colorless oil. 5: IR (neat) 3083, 2964, 1637,
(11) In order to examine the effect of acetaldehyde on our reaction,
acetaldehyde was added before quenching the reaction performed
-1
1
1583, 1481, 914, 739 cm ; H NMR (400 MHz CDCl ) δ 1.15 (s,
3
under the conditions of 1 (1 eq), CH I (2 eq), and SmI (4 eq) at
2 2 2
6H), 2.96 (s 2H), 5.00 (dd, J = 1.2, 10.7 Hz, 1H), 5.03 (dd, J = 1.2,
17.4 Hz, 1H), 5.87 (dd, J = 10.7, 17.4 Hz, 1H), 7.11-7.16 (m, 1H),
7.22-7.28 (m, 2H), 7.31-7.36 (m, 2H); C NMR (100 MHz
rt where 79% of
acetaldehyde. The yield of 5 was found to be 82%.
(12) The reaction of 1 with CH I and SmI in the presence of water
5 was obtained without treatment of
13
2 2
2
CDCl ) δ 26.4, 38.0, 47.1, 111.8, 125.6, 128.8, 129.1, 138.2,
3
resulted in recovery of 1 (87%) with no detectable amount of the
sulfonium salt (5). A further attempt using diphenyl sulfide, which
was employed to avoid rearrangement of sulfonium ylides, under
the same conditions was unsuccessful.
146.4; HRMS for C
H S calcd 192.0973, found 192.0956.
12 16