Lewis acid mediated reactions of allyl chalcogenides with ethyl glyoxylate

Article abstract of DOI:10.1246/cl.2007.826

Allyl mesityl sulfide reacted with ethyl glyoxylate in the presence of tin(IV) chloride to give a tetrahydrofuran derivative. The presence of a bulky substituent on the sulfur atom was crucial to the present reaction. The reaction of allyl mesityl selenid

Full text of DOI:10.1246/cl.2007.826

826
Chemistry Letters Vol.36, No.7 (2007)
Lewis Acid Mediated Reactions of Allyl Chalcogenides with Ethyl Glyoxylate
Kazunori Hirabayashi, Hideki Sato, Yu Kuriyama, Jun-ichi Matsuo, Soichi Sato,
Toshio Shimizu,ꢀ and Nobumasa Kamigata
Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University,
1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397
(Received March 22, 2007; CL-070300; E-mail: shimizu-toshio@tmu.ac.jp)
Table 1. Lewis acid catalyzed [3 + 2] cycloaddition reactions
of 1 with 2a
Allyl mesityl sulfide reacted with ethyl glyoxylate in the
presence of tin(IV) chloride to give a tetrahydrofuran derivative.
The presence of a bulky substituent on the sulfur atom was
crucial to the present reaction. The reaction of allyl mesityl
selenide also gave a cycloaddition product, whereas allylation
occurred when allyl mesityl telluride was used.
Entry
2
LA
Time/h
Yield/%
cis/transb
1
2
3
4
5
2a
2a
2b
2c
2c
SnCl4
SnCl4
SnCl4
SnCl4
1
18
18 (3a)
30 (3a)
43 (3b)
78 (3c)
36 (3c)
9/1
9/1
9/1
9/1
3/7
0.5
0.5
96
.
BF3 OEt2
Episulfonium ions are synthetically useful and mechanisti-
cally interesting functional groups.1 The nucleophilic addition
to episulfonium ions occurs to form carbon–carbon or carbon–
heteroatom bonds. Episulfonium ions are often generated in situ
and used without isolation because they are relatively unstable.
Usually, episulfonium ions are prepared from sulfides that pos-
sess an sp2 or sp carbon or a leaving group at the ꢀ-position.2
It was also reported that the reaction of allylic sulfides, which
possessed an sp2 carbon at the ꢀ-position, with bromine
proceeded through the episulfonium ion as an intermediate.3
Thus, the reaction of allylic sulfides with substrates having both
electrophilic and nucleophilic functional groups would afford
cycloaddition products (eq 1).
aAll reactions were carried out with 1 (1.0 mmol), 2 (1.0 mmol),
and Lewis acid (LA) (1.0 mmol) in CH2Cl2 (2 mL) at rt. bThe ratio
1
was determined by H NMR.
the yield was slightly increased (Entry 2). When the substituents
on the sulfur atom were changed from methyl group to phenyl or
mesityl (Mes) group, the product yields were increased as well
(Entries 3 and 4). The results showed that the [3 + 2] cycload-
dition reactions required a bulky group on the sulfur atom of
allyl sulfides. Lewis acids can interact with sulfide groups or
carbonyl groups; however, such bulky groups as mesityl group
hinder the interaction with sulfide groups. Hence, Lewis acids
could activate carbonyl groups and the reaction of 2c proceeded
smoothly to give 3c in good yield. The stereochemistry of the
product was determined by X-ray analysis of a carboxylic acid
derivative obtained by hydrolysis of 3c.6 These cycloaddition
reactions gave cis adducts as major products (cis/trans =
+
SR
SR
SR
Nu
(1)
E
E
Nu
E
Nu
.
9/1). When BF3 OEt2 was used, the yield was low even though
In the reactions of carbonyl compounds with weak nucleo-
philes, Lewis acid catalysts are usually used to enhance the
electrophilicity of carbonyl compounds.4 Various Lewis acids
catalyzed reactions, such as allylation or cycloaddition, of
allylic reagents with carbonyl compounds have been reported.5
However, to the best of our knowledge, no Lewis acid catalyzed
reactions of allylic sulfides with carbonyl compounds have been
reported so far. Similarly, the reactions of allylic selenides and
tellurides with carbonyl compounds are unknown. Reported here
are the first Lewis acid catalyzed [3 + 2] cycloaddition reactions
of allyl sulfides and selenides with carbonyl compounds (eq 2)
and the allylation reactions of allyl telluride.
the reaction time was long, and the major product was a trans
adduct (cis/trans = 3/7) (Entry 5). This is because the coordina-
tion of Lewis acids to ethyl glyoxylate were different between
7
.
SnCl4 and BF3 OEt2. In contrast, no reactions occurred when
other Lewis acids (TiCl4, Ti(OiPr)4, AlCl3, or ZnCl2) were used.
The reactions of allyl selenides 4a and 4b were carried out
initially at ꢁ80 ꢂC, after which the reaction temperature was
gradually raised to room temperature. Cycloaddition products
5a and 5b were obtained in good yields (Table 2, Entries 1
and 2). However, the stereoselectivity of 5a was different from
that of 5b. These results indicated that the substituents on the se-
lenium atom affected not the yield but the stereoselectivity.
O
Table 2. Lewis acid catalyzed [3 + 2] cycloaddition reactions
of 1 with 4a
EtO2C
O
LA
ChR
2, 4
+
(2)
CH2Cl2
EtO2C
H
cis/transb
ChR
Entry
4
LA
Time/h
Yield/%
1
3, 5
1
4a
4b
4a
4a
SnCl4
SnCl4
SnCl4
2
2
84 (5a)
94 (5b)
18 (5a)
22 (5a)
3/7
5/5
7/3
3/7
2a, 3a
2b, 3b
2c, 3c
4a, 5a
: Ch = S, R = Me
: Ch = S, R = Ph
: Ch = S, R = Mes
: Ch = Se, R = Mes
: Ch = Se, R = Ph
4b, 5b
2
3c
3
17
.
The cycloaddition reactions of allyl sulfides 2 with ethyl
glyoxylate (1) were surveyed (Table 1). The reaction of allyl
methyl sulfide (2a) with 1 proceeded in the presence of SnCl4
at room temperature to give tetrahydrofuran derivative 3a in
very low yield (Entry 1). When the reaction time was extended,
4
BF3 OEt2
aUnless otherwise noted, the reactions were carried out with 1
(1.0 mmol), 4 (1.0 mmol), and LA (1.0 mmol) in CH2Cl2 (2 mL)
at ꢁ80 ꢂC to rt. bThe ratio was determined by 1H NMR. cThe reac-
tion was carried out at ꢁ80 ꢂC.
Copyright Ó 2007 The Chemical Society of Japan

Chemistry Letters Vol.36, No.7 (2007)
827
Sn
Sn
O
ChR
O
1
+
SnCl4
Sn
O
O
ChR
O
H
or
H
O
2, 4, or 6
H
EtO
O
OEt
O
EtO
ChR
+
Ch = S, Se
Sn
Sn
+
3 or 5
O
EtO2C
ChR
ChR
O
O
7
ChR
Kinetic product
OEt
OEt
Ch = Te
8
Scheme 1. Plausible reaction mechanism.
Scheme 2. Plausible reaction pathways for cis adduct.
Then, the stereochemistry of 5a was determined with the same
procedure as that for 3c.6 The reaction of 4a produced a trans
adduct as the major product, in contrast to a cis adduct in the case
of 2c. In order to clarify the mechanism of the reaction, the
reaction was carried out at low temperature (ꢁ80 ꢂC) to give
product 5a in 18% yield, the selectivity of which was reversed
(cis/trans = 7/3) (Entry 3). The cis/trans ratio of the product
5a changed from 7/3 to 3/7 in the presence of SnCl4 at room
temperature. In addition, product 5a was treated with an equiv-
alent amount of 4b in the presence of SnCl4 at room temperature
under similar reaction conditions to afford a mixture of 5a (47%)
and 5b (45%). Therefore, in the case of 4, equilibrium exists
In summary, it was found that Lewis acid mediated reactions
of allyl sulfides and selenides proceeded to afford cycloaddition
products. These reactions required introduction of a bulky
substituent on the chalcogen atoms. In addition, allylation
proceeded when allyl mesityl telluride was used. Therefore, allyl
chalcogenides can be used in Lewis acid mediated reactions.
References and Notes
1
Organosulfur Chemistry, Synthetic Aspects, ed. by P. Page,
Academic Press, London, 1995.
2
a) J. Eames, S. Warren, J. Chem. Soc., Perkin Trans. 1 1999,
2783. b) D. J. Fox, D. House, S. Warren, F. Kerr, J. Chem.
Soc., Chem. Commun. 2000, 1781. c) M. Sasaki, K. Tanino,
M. Miyashita, J. Org. Chem. 2001, 66, 5388. d) A. Hirai, T.
Tonooka, K. Wakatsuki, K. Tanino, M. Miyashita, Angew.
Chem., Int. Ed. 2002, 41, 819. e) J. T. Kim, A. V. Kel’in, V.
Gevorgyan, Angew. Chem., Int. Ed. 2003, 42, 98. f) M.
Sivakumar, B. Borhan, Tetrahedron Lett. 2003, 44, 5547. g)
D. J. Fox, T. J. Morley, S. Warren, Org. Biomol. Chem. 2006,
4, 3120. h) L. Peng, X. Zhang, S. Zhang, J. Wang, J. Org. Chem.
2007, 72, 1192.
.
between 4 and 5. Other Lewis acids, such as BF3 OEt2, TiCl4,
Ti(Oi-Pr)4, and AlCl3, were also examined, but the reaction
.
occurred only in the case of BF3 OEt2 (Entry 4).
On the other hand, allyl mesityl telluride (6) reacted with 1
to give allylation product 7 in 90% yield instead of the [3 + 2]
cycloaddition product (eq 3).
OH
O
SnCl4
(3)
TeMes
+
EtO2C
CH2Cl2
EtO2C
H
3
a) J. M. Bland, C. H. Stammer, J. Org. Chem. 1983, 48, 4393.
b) P. Knochel, J. F. Normant, Tetrahedron Lett. 1985, 26, 425.
c) P. Auvray, P. Knochel, J. F. Normant, Tetrahedron 1988,
44, 4495.
Lewis Acids in Organic Synthesis Vols. 1 and 2, ed. by H.
Yamamoto, Wiley-VCH, Weinheim, 2000.
For reviews of [3 + 2] cycloaddition reactions of allylsilanes:
a) C. E. Masse, J. S. Panek, Chem. Rev. 1995, 95, 1293. b) L.
Chabaud, P. James, Y. Landais, Eur. J. Org. Chem. 2004, 3173.
For hydrolysis and stereochemistry of 3c and 5a, see Supporting
Information, which is available electronically on the CSJ-Jour-
nal Web site, http://www.csj.jp/journals/chem-lett/index.html.
Similar stereoselectivities were shown in the reactions of allylic
silanes. a) G. C. Micalizio, W. R. Roush, Org. Lett. 2000, 2, 461.
b) J. M. Tinsley, W. R. Roush, J. Am. Chem. Soc. 2005, 127,
10818. c) E. Mertz, J. M. Tinsley, W. R. Roush, J. Org. Chem.
2005, 70, 8035.
-80 °C to rt
1
6
7 90%
A plausible reaction mechanism is shown in Scheme 1.
First, a Lewis acid coordinated to the two carbonyl groups of
1, increasing electrophilicity of formyl carbon. Carbon–carbon
bond formation between ꢁ-position of the allyl group and formyl
carbon was accompanied by nucleophilic addition of the lone
pair on chalcogen atom to the ꢀ-carbon. Finally, in the cases
of 2 and 4, the tin alkoxide moiety attacked the carbon of
epichalcogenonium ions to form a carbon–oxygen bond. There
are two sites on the epichalcogenonium ions that can be attacked
by the tin alkoxide moiety. Since a five-membered ring is more
easily formed than a four-membered one, products 3 and 5 were
afforded. In contrast, in the case of 6, since the epitelluronium
ion was very labile, the epitelluronium ion group of 8 decom-
posed to give homoallyl alcohol 7.8
4
5
6
7
Nucleophilic addition of the allyl group occurred via syncli-
nal or antiperiplanar transition states, as shown in Scheme 2.9
Therefore, in the reactions of 2 at room temperature, the major
products were cis adducts as kinetic products. Cis adducts were
also afforded in the reactions of 4 at ꢁ80 ꢂC, based on a similar
reason. In contrast, in the reactions of 4 at room temperature, the
nucleophilic addition of a seleno group of product 5 to the ꢂ-po-
sition of furan occurred. Hence, trans adducts as thermodynamic
products were produced for the equilibrium between 4 and 5
(eq 5).
8
a) B. Lindgren, Tetrahedron Lett. 1974, 15, 4347. b) D. L. J.
Clive, S. M. Menchen, J. Chem. Soc., Chem. Commun. 1977,
658. c) J. Bergman, L. Engman, J. Organomet. Chem. 1979,
181, 335. d) J. Backvall, L. Engman, Tetrahedron Lett. 1981,
¨
22, 1919. e) D. L. J. Clive, P. L. Beaulieu, J. Org. Chem.
1982, 47, 1124. f) R. J. Batchelor, F. W. B. Einstein, I. D.
Gay, J.-H. Gu, B. D. Johnston, B. M. Pinto, J. Am. Chem. Soc.
1989, 111, 6582.
The cycloaddition reactions of allylic silanes proceeded via
synclinal transition states. a) J. S. Panek, R. Beresis, J. Org.
Chem. 1993, 58, 809. b) T. Akiyama, K. Ishikawa, S. Ozaki,
Chem. Lett. 1994, 627. See also: c) K. Mikami, K. Kawamoto,
T.-P. Loh, T. Nakai, J. Chem. Soc., Chem. Commun. 1990, 1161.
9
1 þ 2 ! 8 ! 3
1 þ 4 ꢀ 8 ꢀ 5
ð4Þ
ð5Þ
Published on the web (Advance View) May 31, 2007; doi:10.1246/cl.2007.826