Application of tin and nanometer tin in allylation of carbonyl compounds in tap water.

Article abstract of DOI:10.1021/ol0257326

[reaction: see text] Nanometer tin-mediated allylation of aldehydes or ketones in distilled or tap water gave rise to corresponding homoallyl alcohol in high yield without any other assistance such as heat or supersonic or acidic media.

Full text of DOI:10.1021/ol0257326

ORGANIC
LETTERS
2002
Vol. 4, No. 10
1683-1685
Application of Tin and Nanometer Tin in
Allylation of Carbonyl Compounds in
Tap Water
Zhiyong Wang,* Zhenggen Zha, and Cunliu Zhou
Department of Chemistry, UniVersity of Science and Technology of China, Hefei,
Anhui 230026, China
zwang3@ustc.edu.cn
Received February 17, 2002
ABSTRACT
Nanometer tin-mediated allylation of aldehydes or ketones in distilled or tap water gave rise to corresponding homoallyl alcohol in high yield
without any other assistance such as heat or supersonic or acidic media.
With the development of industrialization, organic chemists
have been confronted with a new challenge of finding novel
methods in organic synthesis that can reduce and finally
eliminate the impact of volatile organic solvents and hazard-
ous toxic chemicals on the environment. So, using aqueous
media to perform organic reactions has attracted considerable
interest recently because water is considered to be a safe
and environmentally benign solvent.1 Allylations of alde-
hydes and ketones to give homoallylic alcohols are the most
common reactions among these.2 Such reactions can be
achieved by use of metals such as copper/manganese,3
calcium, and tetraallylgermane.4 Also, all of these reactions
occurred on unprotected carbohydrates in protic media under
mild conditions. Nevertheless, it is necessary that most of
these reactions be carried out with acidic coreagents such
as ammonium chloride, hydrobromic acid, and cosolvents
such as mixtures of THF and water. To simplify the
allylation, chemists have been searching for effective cata-
lysts and benign solvents under mild reaction conditions.
Nanometer materials, as we know, present remarkable
electronic,5 magnetic,6 optical,7 biological,8 mechanical, and
catalytic properties9 that differ from the bulk materials. Of
them, the special catalytic activities of nanomaterials in-
trigued our interest. Because of the larger specific surface
area, the metal nanoparticle has a high surface activity, which
results in a more robust catalytic activity than bulk metals.
Particularly, when the nanoparticles are less than 5 nm in
diameter, the catalytic activity presents special selectivity.
However, to the best of our knowledge, little study has been
carried out and no report about allylations catalyzed by
nanometer materials has been presented yet. The following
is the first report of our research on allylations catalyzed by
nanometer tin in water.
To initiate the experiment, a mixture of benzaldehyde, allyl
bromide, and the metal powder in 3 mL of distilled or tap
water without any coreagent or cosolvent was stirred at room
temperature. After about 24 h, the reaction was monitored
by TLC, and the reaction mixture was extracted with ether;
subsequently, the ether extract was washed with water and
dried with magnesium sulfate. After removal of the solvent,
the crude product was obtained. The yield of the allylation
(1) (a) Li, C. J.; Chan, T. H. Organic Reactions in Aqueous Media; John
Wiley & Sons, Inc.; New York, 1993. (b) Li, C. J. Chem. ReV. 1993, 93,
2023. (c) Chan, T. H.; Li, C. J.; Lee, M. C.; Wei, Z. Y. Can J. Chem.
1994, 72, 1181. (d) Lubineau, A.; Auge, J.; Queneau, Y. Synthesis 1994,
741. (e) Li, C. J. Tetrahedron 1996, 52, 5643. (f) Chan, T. H.; Issac, B. M.
Pure Appl. Chem. 1996, 68, 919.
(2) Anastas, P., Williamson, T. C., Eds.; Green Chemistry: Frontiers
in Benign Chemical Synthesis and Processing; Oxford University Press:
New York, 1988.
(5) Cai, Z. H.; Martin, C. R. J. Am. Chem. Soc. 1989, 111, 4138.
(6) Whitney, T. M.; Jiang, J. S.; Searson, P. C.; Chien, C. L. Science
1993, 261, 1316.
(7) Foss, C. A., Jr.; Hornyak, G. L.; Stockert, J. A.; Martin, C. R. J.
Phys. Chem. 1992, 96, 7497.
(3) Li, C. J.; Meng, Y.; Yi, X. H. J. Org. Chem. 1997, 62, 8632.
(4) Akiyama, T.; Iwai, J. Tetrahedron Lett. 1997, 38, 853.
(8) Schmid, G. Chem. ReV. 1992, 92, 1709
(9) Lu, L.; Sui, M. L.; Lu, K. Science 2000, 287, 1463
10.1021/ol0257326 CCC: $22.00 © 2002 American Chemical Society
Published on Web 04/23/2002

product was measured by 1H NMR. The metals used varied
from Fe to Sn, and the reaction results are listed in Table 1.
Table 2. Allylation Reaction Mediated by Tina in Water
Table 1. Allylation of Benzaldehyde Mediated by Various
Metals
entries
metals
yield (%)a/time (h)
polymerization
1
2
3
4
5
6
Fe
Mg
Al
Bi
An
Sn
35/15
20/24
93/15
1
a Determined by H NMR.
Polymerization occurred when the reaction was mediated
by iron (entry 1, Table 1). When mediated by magnesium
or aluminum, the reaction did not occur (entries 2 and 3,
respectively, Table 1). In comparison with the cases that were
mediated by iron, magnesium, aluminum, zinc, and bismuth,
tin-mediated allylation (entry 6, Table 1) went on smoothly
and obtained a high yield under the reaction conditions. This
intriguing result encouraged us to investigate this tin-
catalyzed reaction further. Subsequently, a variety of alde-
hydes and ketones were tested with this allylation method.
As expected, most of the reactions were carried out smoothly
in good yield, and side reactions such as reduction and
coupling were not found (entries 1-7, Table 2). Moreover,
the reaction conditions were sufficiently mild to not affect
the methoxyl (entry 4, Table 2), chloro (entry 5, Table 2),
and methyl (entry 6 Table 2) functionalities. However,
allylations of acetophenone and N,N-dimethyl aminobenz-
aldehyde gave the corresponding products in lower yields
of 40 and 33%, respectively, (entries 8 and 9, Table 2). Also,
the allylations of aliphatic aldehydes or ketones did not work
well under this condition (entries 11 and 12, Table 2). In
particular, for 4-nitrobenzaldehyde, only N-alkylation prod-
ucts were observed instead of the allylation product (entry
10, Table 2). To solve these problems, after a series of
investigations, nanometer tin particles were prepared10 and
applied in those allylations.
a Tin was in the nanometer scale (20-30 nm). b Determined by 1H NMR.
c Data in brackets were mediated by regular tin powder. d Allyl bromide
was replaced with 4-bromobutenate.
addition, the reaction time was reduced from 8-24 h to
1.5-8 h when compared with the those catalyzed by bulk
tin powder. The aliphatic aldehydes and ketones that were
generally difficult to allylate when catalyzed by tin powder
can be also allylated smoothly under this condition (entries
11 and 12, Table 2). It was also noted that allylation of N,N-
dimethyl aminobenzaldehyde gave the corresponding product
in more than 90% yield under this condition (entry 9, Table
To compare the difference between ordinary tin and nano-
tin in this kind of reaction, the summary of the reactions
was listed in Table 2.
As for benzaldehyde (entry 1), 2-naphthaldehyde (entry
2), piperonal (entry 3), 4-methoxybenzaldehyde (entry 4),
4-chlorobenzaldehyde (entry 5), and 4-methyl-benzaldehyde
(entry 6), the allylations can be carried out very well and
finished over a short period. Especially from entries 2 to 6
in Table 2, the allylations were almost quantitative. In
Scheme 1
(10) Preparation of Nanometer Tin. To 1 L of 2.0 M 2-propanol
aqueous solution were added 2.25 g (0.01 mol) of SnCl2 and 20 g (0.5
mol) of NaOH. The reaction mixture was stirred until the dissolution of
SnCl2 and NaOH. Then, a small amount of SLS (sodium lauryl sulfate)
was added to this mixture. Afterward, the prepared solution was bubbled
by nitrogen over about 20 min and then irradiated under a γ-ray (60Co)
source for about 12 h (2.5 × 104 Gy). The nano-tin was obtained from the
solution by centrifugation.
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Org. Lett., Vol. 4, No. 10, 2002

2), whereas the reaction did not occur at all in distilled water
when Zn, Bi, or Al was used as a mediator. As for
4-nitrobenzaldehyde, the allylation could proceed smoothly
and gave about 95% yield of the desired product (entry 10,
Table 2) rather than N-alkylation products, which did not
give the desired product with several other methods.11 It was
noted that nano-tin changed the reaction selectivity in this
situation, which was very interesting for the development
of organic synthetic methodology. Meanwhile, the diaste-
reoselectivity of the allylation catalyzed by nano-tin was
studied here. The investigation was focused on the allylation
of benzaldehde with ethyl 4-bromobut-2-enoate in water
(entry 13, Table 2). The reactions catalyzed by ordinary tin
and nano-tin both gave rise to the corresponding γ-addition
product.12 However, the ratio of syn to anti isomers was
different. Benzaldehyde reacted with ethyl 4-bromobut-2-
enoate in water to give rise to the syn isomer as the dominant
product (92%) when catalyzed by nano-tin, whereas 68%
was obtained when the reaction was catalyzed by ordinary
tin. The result demonstrated that the syn isomer was a
chelate-controlled product due to the hydrogen bond between
the proton in hydroxyl groups and the oxygen in ester group.
What is more, replacing the distilled water with tap water
had no influence on the allylations. We attempted to try nano-
zinc and nano-bismuth. However, nano-zinc was too active
to exist in water and nano-bismuth gave rise to a mixture
rather than allylation products.
This study demonstrated that the unusual phenomenon of
nanometer tin-mediated allylation was caused by properties
of nanometer tin particles. The smaller the radius of tin
nanometer particles, the greater the ratio of surface to volume,
which leads to a large increase of atoms on the surface and
an abundance of suspended and unsaturated bonds and so
on, affected by the unsaturated coordination. All these make
the surface of the tin nanometer particle more active and
enhance the reaction selectivity.
In conclusion, the result demonstrated that an efficient and
clean synthesis for allylation in distilled or tap water with
high product yields can be developed. Nano-tin particles were
applied in the allylations of aldehyde and ketone, and
satisfactory results were obtained. Our work showed us that
substantial progress could be made in organic reactions in
water, which have great potential in reducing chemical
pollution.
Acknowledgment. The authors are grateful to National
Nature Science Foundation of China (No. 50073021) and
National Nature Science Foundation of Anhui Province (No.
01046301) for their support.
(11) (a) Zhang, W. C.; Li, C. J. J. Org. Chem. 1999, 64, 3230. (b) Li, C.
J.; Meng, Y.; Yi, X. H. J. Org. Chem. 1998, 63, 7498. (c) Chan, T. H.;
Issac, M. B. Pure Appl. Chem. 1996, 68, 919. (d) We have investigated
and solved this problem in another manuscript
(12) When some phase transfer catalyst was added to the reaction mixture,
the R-addition product can be obtained. The result will be reported in another
manuscript.
Supporting Information Available: Spectral data of
allylation products and the TEM of nano-tin. This material
is available free of charge via the Internet at http://pubs.acs.org.
OL0257326
Org. Lett., Vol. 4, No. 10, 2002
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