Selective Reduction of α-Chloroketone to α-Chloroalcohol Using Hydrogen Transfer from Alcohol over Metal Oxide Catalysts

Article abstract of DOI:10.1246/cl.2003.1132

The carbonyl group of 1,3-dichloro-2-propanone was reduced selectively through hydrogen transfer from 2-butanol over MgO, SiO2*Al2O3, Al2O3, and ZrO2. It is suggested that the reaction is promoted by either base or acid site of the catalysts.

Full text of DOI:10.1246/cl.2003.1132

1
132
Chemistry Letters Vol.32, No.12 (2003)
Selective Reduction of ꢀ-Chloroketone to ꢀ-Chloroalcohol Using Hydrogen Transfer
from Alcohol over Metal Oxide Catalysts
y
ꢀ
Kunihiro Gotoh, Jun Kubo, Wataru Ueda, Tohru Mori, and Yutaka Morikawa
Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503
y
Catalysis Research Center, Hokkaido University, N-11, W-10, Kita-ku, Sapporo 060-0811
(Received August 18, 2003; CL-030756)
The carbonyl group of 1,3-dichloro-2-propanone was re-
All the catalysts were deactivated in the initial stage of reac-
tion and showed stable activities after 6 h of time on stream. The
stable activities are summarized in the following tables. The re-
sults of the reaction over MgO are shown in Table 1. In every
run, the products that originated from 2-butanol were 2-butanone
and a small amount of butenes. When the reaction was conduct-
duced selectively through hydrogen transfer from 2-butanol over
MgO, SiO2ꢁAl2O3, Al2O3, and ZrO2. It is suggested that the re-
action is promoted by either base or acid site of the catalysts.
ꢂ
ꢀ
-Chloroalcohols are useful compounds as intermediates in
ed at 150 C with 1 g catalyst (Run 1), 1,3-Clone was reduced to
fine chemical synthesis. One of the methods to obtain ꢀ-chlo-
roalcohols is the reduction of ꢀ-chloroketones or ꢀ-chloroalde-
hydes. However, the selective reduction of carbonyl group is not
so easy because the hydrodechlorination takes place simultane-
ously. 1,3-Dichloro-2-propanol (1,3-Clol) is a potential inter-
mediate to produce epichlorohydrin that is a raw material for ep-
oxy resin, synthetic rubber, etc. The reduction of 1,3-dichloro-2-
propanone (1,3-Clone) to 1,3-Clol has been claimed in two pat-
1,3-Clol at ca. 90% selectivity. The hydrodechlorination prod-
uct, 1-chloro-2-propanone (1-Clone), and Cl rearrangement
product, 1,1-dichloro-2-propanone (1,1-Clone) were also formed
at ca. 8 and 2% selectivities, respectively. Besides the products
shown in the table, trace amounts of 1-chloro-2-propanol and
acetone were detected. Increasing to twice the catalyst amount
(Run 2), the conversion increased from 24 to 80%, while the se-
lectivity of 1,3-Clol decreased to 68% and that of 1-Clone in-
creased to 23%. The facts suggest that 1-Clone was formed by
successive HCl elimination from 1,3-Clol. The selectivity of
1,1-Clone did not change appreciably with the catalyst amount
(Runs 1–3), but increased remarkably when the reaction temper-
1,2
ents, so far. One is the hydrogen reduction using ruthenium
complex catalyst, and the other is the reduction by hydrogen
1
transfer from 2-propanol using aluminum triisopropoxide as a
catalyst. They still have problems for practical application.
2
ꢂ
The ruthenium complex is expensive and is synthesized by com-
plicated procedures. Aluminum triisopropoxide is readily de-
composed by a trace amount of water present in the reactant
as an impurity. Recently, we have found that the Guerbet reac-
tion, a condensation reaction between alcohols to form longer
chain alcohols, proceeds in the gas phase over solid base cata-
ature was raised to 250 C (Runs 3–5). It is likely that the carbon-
yl reduction and the Cl rearrangement proceed concurrently and
the latter activation energy is higher than the others. The reaction
path to form the observed products can be written as follows:
CH
2
Cl-CH-CH
OH
2
Cl
CH
2
Cl-C-CH
2
Cl
3 2
CH -C-CH Cl
3
,4
5
lysts including MgO and alkali salt supported on zeolite,
O
O
and the fast hydrogen transfer from alcohol to unsaturated car-
bonyl intermediate is responsible for the formation of saturated
alcohol. The finding led us to try the reduction of 1,3-Clone into
(
1,3-Clone)
(1,3-Clol)
(1-Clone)
4
CH
3
-C-CHCl
2
1
,3-Clol by using hydrogen transfer from alcohol over metal ox-
ide catalysts.
MgO catalyst was obtained by decomposing Mg(OH)2 in a
O
(1,1-Clone)
Scheme 1.
ꢂ
nitrogen stream at 450 C for 2h. The detailed procedure was
mentioned in our previous papers. CaO was prepared similar-
ly, but the decomposition of hydroxide was performed at 600 C.
3
,4
ꢂ
Table 2summarizes the activities of various catalysts for the
reduction of carbonyl group in 1,3-Clone, where the data shown
in Table 1 (Run 1) were cited for comparison. Among basic met-
Cs-exchanged X-zeolite (CsX) was prepared from NaX by an
ion-exchange method using aqueous solution of CsCl. CsX-sup-
ported Cesium carbonate (Cs2CO3/CsX) and alumina-supported
potassium carbonate (K2CO3/Al2O3) were prepared by an im-
pregnation method. The other oxide catalysts were used as pur-
chased. The reaction was performed in a gas phase continuous
flow reactor under atmospheric pressure. The reaction mixture
of 1,3-Clone, 2-butanol, and cyclohexane (internal standard)
was fed into a N2 carrier gas using a syringe pump. Feed gas
Table 1. Reaction of 1,3-dichloro-2-propanone with 2-butanol
over MgO catalyst
Amounta Temp.b Conv.c
Selectivity/%
Run
ꢂ
/g
/ C
/% 1,3-Clol 1-Clone 1,1-Clone
1
2
3
4
5
1
2
0.5
0.5
0.5
150
150
150
200
250
24.2
80.0
10.6
28.4
63.6
89.4
68.0
94.4
62.6
4.4
8.3
23.0
4.21.8
26.0
48.6
c
2.2
2.4
composition was 1,3-Clone:2-butanol:cyclohexane:N2 = 0.1:5:
ꢃ1
0
.1:50, and the total flow rate was 55 mL min . The catalyst
ꢂ
9.6
46.4
was heat-treated in a nitrogen stream at 450 or 600 C for 2h be-
fore the reaction. Products were identified and analyzed quanti-
tatively by GC–MS and GC–FID, respectively.
a
b
Amount of the catalyst. Reaction temperature. Conversion of
1
,3-dichloro-2-propanone.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.12 (2003)
1133
al oxides, MgO showed the highest activity for the reduction of
carbonyl group. CaO showed no activity, although its basicity
was thought to be similar to or higher than MgO. The values
of conversion over SnO2 and ZnO were comparable to that over
MgO. However, these catalysts did not promote the reduction of
carbonyl group appreciably and gave the hydrodechlorination
and chlorine rearrangement products, respectively. Although
CsX was reported to be active for the carbonyl reduction of cit-
vealed by the kinetic studies now under way. The reduction of
acetone did not take place in the presence of CO2, indicating
the base sites on MgO are indispensable to promote the reaction.
In the presence of pyridine, the conversion of acetone decreased
gradually from 91 to 60% in 4 h, but the reaction did not stop
completely. Pyridine seems to hinder the adsorption of acetone
and/or 2-butanol on Lewis acid sites by competitive adsorption.
Lewis acid sites might facilitate the formation of surface butoxy
6
4
ronellal to form citronellol and Cs2CO3/CsX showed higher ac-
tivity for the Guerbet reaction than MgO, both catalysts yielded
species as assumed for the Guerbet reaction over MgO catalyst.
5
The reactions over ZrO2 and Al2O3, which have both base and
acid sites, were not poisoned completely by the addition of
CO2 or pyridine. Over SiO2ꢁAl2O3, 2-propanol and its succes-
sive dehydration product propene were formed at 85 and 15% se-
lectivity, respectively. The reaction was stopped substantially by
the addition of pyridine.
Although the detailed mechanism is now in investigation,
we deduce that either base or acid site promotes the reduction
of carbonyl group with alcohol by individually different mech-
anisms.
only a trace amount of 1,3-Clol. K2CO3/Al2O3, whose strong
basicity was reported by Yamaguchi et al., gave 1,3-Clol at
7
about 60% selectivity which was much lower than the selectivity
observed with MgO. SiO2 used frequently as an inert support
was inactive substantially. Over ZrO2 the value of conversion
was twice higher than that over MgO and the selectivity for car-
bonyl reduction was similar to MgO. The much higher conver-
sions, more than 90%, were obtained with Al2O3 and
SiO2ꢁAl2O3, although the amount of catalyst used was a half
of MgO. The selectivity of these catalysts for the carbonyl reduc-
tion was lower than that of MgO but seemed to be comparable to
MgO, considering the high conversion level. However, they had
a disadvantage from the standpoint of stoichiometric reduction,
because a considerable amount of reductant 2-butanol was con-
sumed by being dehydrated to butenes on their acid sites.
Table 3. Effect of CO2 or pyridine addition in the reaction of
a
acetone with 2-butanol over various catalysts
b
c
Catalyst
Additive
Conv. /%
Sel. /%
None
CO2
pyridine
91.0
0.0
60.0
100
—
100
MgO
Table 2. Reaction of 1,3-dichloro-2-propanone with 2-butanol
ꢂ
over various catalysts (150 C)
None
CO2
pyridine
29.9
12.3
12.3
100
100
100
a
Catalyst
MgO
Amount/g
Conv. /%
Sel. /%
ZrO2
Al O
1.0
0.5
1.0
1.0
1.0
0.5
1.0
0.5
1.0
0.5
0.5
24.2
ꢄ 0
36.6
12.8
16.9
ꢄ 0
17.7
1.8
49.4
90.9
96.0
b
89.4
tr.
2.7
tr.
tr.
tr.
59.0
tr.
85.2
72.6
76.7
b
CaO
SnO2
None
CO2
pyridine
24.2
12.3
5.4
100
100
100
b
2
3
ZnO
CsX
Cs2CO3/CsX
K2CO3/Al2O3
SiO2
None
CO2
pyridine
38.4
42.3
0.0
85.7
93.9
—
c
SiO2ꢁAl2O3
aReaction conditions: amount of catalyst, 0.1 g; feed gas
composition, acetone : 2-butanol:N2 = 0.15:1.5:50 (None),
ZrO2
Al2O3
SiO2ꢁAl2O3
acetone:2-butanol:N2:CO2
tone:2-butanol:N2:pyridine = 0.15:1.5:50:1.5 (pyridine); to-
=
0.15:1.5:45:5(CO2), ace-
ꢃ1
ꢂ
a
tal flow rate, 52mL min ; reaction temperature, 150 C
(MgO, Al O , and SiO ꢁAl O ), 200 C (ZrO ). Conversion
Selectivity of 1,3-dichloro-2-propanol. Pretreatment tem-
ꢂ
b
ꢂ
c
ꢂ
perature, 600 C. Reaction temperature, 250 C.
2
3
c
2
2
3
2
of acetone. Selectivity to 2-propanol.
It is of interest that MgO, ZrO2, Al2O3, and SiO2ꢁAl2O3
show the high activity and selectivity for the reaction although
they are different in their acid-base properties. In order to clarify
the role of acid and base sites, poisoning effects of CO2 and pyr-
idine were studied for the similar and simple reaction, that is, the
reduction of acetone with 2-butanol. The reaction was carried
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ꢂ
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3
4
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feed were summarized in Table 3. MgO was most active for
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for the reduction of 1,3-Clone. This suggests that the rate of car-
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strongly depends on both the acid-base properties of catalyst
and the electron density on the carbonyl group, as it will be re-
6
7
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Published on the web (Advance View) November 17, 2003; DOI 10.1246/cl.2003.1132