498
Chemistry Letters Vol.35, No.5 (2006)
The Employment of Indium Nanoparticles in Barbier-type Reaction
of Allylic Chloride in Water
Jiaming Li, Zhenggen Zha, Lilin Sun, Yan Zhang, and Zhiyong WangÃ
Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemistry,
University of Science and Technology of China, Hefei 230026, P. R. China
(Received January 30, 2006; CL-060130; E-mail: zwang3@ustc.edu.cn)
Indium nanoparticles have been employed in the reactions
Table 1. The allylation of carbonyl compounds mediated by
indium nanoparticles and 200 mesh In in water
of various carbonyl compounds with allyl (crotyl) chloride in
water, affording the corresponding alcohols with high yields.
The crotylation gave exclusive ꢀ-adducts with a dominant syn-
isomer.
O
OH
nano-In
H2O
R2
R1
Cl
+
R1
R2
1
2
3
Yielda/%/Time/h
Nano-In 200 mesh In
85/10
Organic reactions in aqueous media have been attracting
much attention with the time going, and have become one of
the important branches in green chemistry.1,2 Of them, the allyl-
ations in aqueous media are investigated widely because the al-
lylations are one of the most important methods to form carbon–
carbon bond and to give the corresponding homoallylic alco-
hols.3 However, the scope of allylic substrates has usually been
limited in the active allyl bromide or iodide.4 On the other hand,
metal nanoparticles have been attracting more and more atten-
tion in material chemistry because of the remarkable electronic,
magnetic, optical, biological, mechanical, and catalytic proper-
ties over the last decade.5 The smaller the cluster of atoms, the
higher the percentages of atoms are on the surface, particularly
rendering nanoparticles specially active in catalysis and media-
tor.6 Our previous work revealed that nano-sized metal particles,
such as nano-Sn and nano-Bi, exhibited promoting activity in
allylation reaction of active allyl bromide with carbonyl com-
pounds.7 However, nano-Sn or nano-Bi did not work well to
mediate the allylation of allyl chloride or crotyl chloride with
benzaldehyde in water. The indium-mediated allylation is also
sluggish with the chloride, and acyclic ketones are usually
not sufficiently reactive and thus require longer reaction time.8
We report herein the successful allylations of various carbonyl
compounds with allyl/crotyl chloride promoted by indium nano-
particles in water.
Initially, the allylation of benzaldehyde with allyl chloride
was carried out in the mediation of granular indium, affording
the corresponding adduct in the yield of 22%. It was assumed
that this low yield resulted from the small surface area of the
granular indium. Therefore, 200 mesh of indium powder was
employed to mediate this reaction. As expected, the reaction
yield was improved to 47%. This encouraged us to investigate
this reaction further. About 100 nm of indium nanoparticle9
was employed in this allylation. As a result, the allylation prod-
uct was obtained with 85% yield while the reaction time was de-
creased to 10 h. To extend the scope of the reaction substrates,
different aldehydes were tested in this allylation. It was found
that not only aromatic aldehydes (Table 1, entries 1–9) but also
aliphatic ones (Table 1, entries 10 and 11) were allylated
smoothly under this condition, giving the corresponding adducts
in good to excellent yields. In comparison with 200 mesh of in-
dium, indium nanoparticles are more effective in mediation of
the allylations regardless of the difference of the aldehydes. Sub-
Entry
R1
R2
1
C6H5
H
H
H
H
H
H
H
H
H
H
H
47/24
71/20
55/20
56/20
47/20
38/20
53/20
72/20
75/20
49/24
56/24
2
2-ClC6H5
4-ClC6H5
2-HOC6H5
4-CH3OC6H5
2-CH3OC6H5
4-CH3C6H5
2-furanyl
95/10
78/10
99/10
96/10
75/10
95/10
99/9
3
4
5
6
7
8
9
Piperonyl
C6H5CH2
n-C6H13
97/10
80/12
79/10
10
11
aDetermined by HPLC and H NMR.
1
sequently, crotylation was investigated under the same condition
in order to extend the scope of the allylic chloride. The corre-
sponding results are summarized in Table 2. From Table 2, it
was found that crotylations of both aldehyde and ketone were
carried out smoothly in the mediation of indium nanoparticles,
affording the corresponding alcohols with high yields while
the reaction mediated by 200 mesh of indium gave the corre-
sponding product with moderate or poor yields (Table 2, entries
1–18). Also, the corresponding reaction rate was increased re-
markably. More importantly, the crotylation of the ketones
was improved largely in comparison with that mediated by
200 mesh of indium (Table 2, entries 13–18), which indicated
that indium nanoparticles is more effective to ketones than to al-
dehydes in the mediation of this crotlytion. Also, it was noted
that hydroxy group, which contained active proton, need not to
be protected and survived during the crotylation (Table 2, entries
4, 12, and 16).
In addition, the diastereoselectivity of the crotylation with
crotyl chloride is different from crotyl bromide. The crotylation
of crotyl chloride mediated by indium nanoparticles exclusively
gave ꢀ-adduct with dominant syn-isomer except entry 3 (Table 2,
entries 1–18). The anti-isomer was dominant product in the
crotylation of crotyl bromide.3b Compared to the 200 mesh of
indium, indium nanoparticles can enhance both the yield and
the stereoselectivity of the crotylations.
Based on the experimental facts, we proposed a possible re-
action mechanism (illustration in Supporting Information). At
first, both allylic chloride 2 and carbonyl compound 1 were ab-
Copyright Ó 2006 The Chemical Society of Japan
Li, Jiaming
