Hydrogenolysis-free hydrogenation by Pd black powder catalyst

Article abstract of DOI:10.1055/s-2001-17485

A new general method of hydrogenolysis-free hydrogenation using a commercially available Pd black powder catalyst has developed.

Full text of DOI:10.1055/s-2001-17485

1
590
LETTER
Hydrogenolysis-free Hydrogenation by Pd Black Powder Catalyst
H
S
ydrogenolys
h
is-fre
e
Hydro
o
genationby
j
Pd
B
la
i
c
k
Pow
r
de
r
Cata
o
lyst Maki,* Makiko Okawa, Ryo Matsui, Takashi Hirano, Haruki Niwa
Department of Applied Physics and Chemistry, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
Fax +81(424)861966; E-mail: maki@pc.uec.ac.jp
Received 17 July 2001
Table 1 Solvent Effect of Pd Black for Benzyl Ether 1
Abstract: A new general method of hydrogenolysis-free hydroge-
nation using a commercially available Pd black powder catalyst has
developed.
Key words: Pd black, selectivity, hydrogenation, hydrogenolysis,
catalytic reaction
Solvent
Time
2 (%)
3 (%)
1 (%)
1
Hydrogenation of olefinic linkages over various metal
Benzene
4 h
24 h
100
100
0
0
0
0
catalysts is one of the most important synthetic proce-
dures. Although benzyl group is one of important protect-
ing groups for hydroxyl ones, hydrogenation of alkenes
containing hydrogenolysis-susceptible O-benzyl (Bn)
group over a certain catalyst such as Pd/C often encoun-
Acetone
4 h
4 h
4 h
4 h
4 h
0
14
15
32
100
86
0
0
Petroleum ether
1,4-Dioxane
Isopropyl ether
Toluene
2
trace
trace
85
68
tered concomitant hydrogenolysis of the O-Bn linkage.
This disadvantage was overcome by developing chemose-
lective hydrogenation catalysts based on rather expensive
Rh metal. However, cheaper chemoselective catalysts
than the Rh metal-based ones are desirable for large scale
and industrial syntheses. Herein we wish to describe the
hydrogenolysis-free hydrogenation of olefins containing
benzyloxy groups by using commercially available Pd
black catalyst.
62
100
100
0
0
0
38
0
0
8
h
2
4 h
4 h
4 h
1 h
3
Ethyl acetate
Dichloromethane
Methanol
85
0
15
100
100
0
0
0
4
5
0
First of all, we chased olefin 1 containing phenolic ben-
zyl ether highly susceptible to hydrogenolysis. The hydro-
genation of 1 over Pd black was performed in various
solvents at room temperature. The results are summa-
rized in Table 1.
6
1
2
the 24 hours reaction, not only was no compound 6 pro-
duced during the hydrogenolysis, but also no by-product
1
3
was observed. However, compound 7 that was produced
by the reaction dominated by the hydrogenolysis was ob-
tained only when acetone was used as the reaction solvent,
and the formation of 5 remarkably decreased. When 1,4
dioxane was used as the reaction solvent, there was a trace
The hydrogenolysis-free hydrogenation proceeded satis-
factory when benzene or toluene was used as the solvent,
7
and only the hydrogenation product 2 was quantitatively
obtained. Though the reaction was completed in about 4
hours in benzene and in about 8 hours in toluene, the reac-
tion was further continued in order to confirm that a clear
distinction between the hydrogenation and the hydro-
genolysis could be done in these solvents. Even when the
reaction ran for 24 hours, for both reaction solvents, not
6
of 6 formed though in the most cases, reaction selectivity
was indicated.
In order to confirm the generality of this reaction for the
functional group, 7 kinds of alkenes14 were synthesized
besides compounds 1 and 4. The selectivity was examined
using benzene as the reaction solvent (Table 3). In any
case, the hydrogenolysis-free hydrogenation proceeded
satisfactorily. Though enough reaction time was allowed
after the reaction was concluded, no corresponding hydro-
genolysis product was observed. Furthermore, it was con-
firmed that neither the hydrogenolysis of the benzyl group
nor the hydrogenolysis of the allyloxy group proceeded
based on the Entry 3 result. Moreover, in order to investi-
gate the practical reaction, the reaction in toluene was
closely examined. Almost the same results for all sub-
8
only was no compound 3 produced by the hydrogenoly-
9
sis, but also no by-product was observed at all (Table 1).
Moreover, for the reaction using benzyl ester 410 as the
substrate, the result was almost similar to that of benzyl
ether 1 (Table 2). When benzene or toluene is used as the
solvent, the hydrogenolysis-free hydrogenation proceed-
ed satisfactorily, and only the hydrogenation reaction
1
1
product 5 was afforded in quantitative yield. Even for
Synlett 2001, No. 10, 28 09 2001. Article Identifier:
1
©
437-2096,E;2001,0,10,1590,1592,ftx,en;Y15001ST.pdf.
Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

LETTER
Hydrogenolysis-free Hydrogenation by Pd Black Powder Catalyst
1591
(
3) (a) Sajiki, H.; Hirota, K. J. Org. Chem 1998, 63, 7990.
Table 2 Solvent effect of Pd black for benzyl ester 4
(
(
b) Sajiki, H.; Hirota, K. Tetrahedron 1998, 54, 13981.
c) Maki, S.; Harada, Y.; Hirano, T.; Niwa, H.; Yoshida, Y.;
Ogata, S.; Nakamatsu, S.; Inoue, H.; Iwakura, C. Syntt.
Commun. 2000, 30, 3575.
(
(
4) Woko Pure Chemical Industries, Ltd.
5) 1: IR (neat) 1510, 1610, 1640 cm ; H NMR (270 MHz,
CDCl3) 1.30 (3 H, d, J = 7.0 Hz), 3.83 (6 H, s), 3.90–4.00
-
1 1
(
(
1 H, m), 5.00–5.08 (2 H, complex), 5.04 (2 H, s), 5.96–6.09
1 H, m), 6.58 (1 H, s), 6.71 (1 H, s), 7.32–7.46 (5 H,
1
3
complex); C NMR (75 MHz, CDCl ) 19.59 (q), 35.20 (d),
3
5
(
1
6.12 (q), 56.56 (q), 71.80 (t), 99.84 (d), 111.58 (d), 112.82
t), 126.33 (s), 127.33 (d), 127.82 (d), 128.50 (d), 137.46 (s),
42.94 (d), 143.48 (s), 147.58 (s), 149.79 (s); HRMS: found
Solvent
Time
4 h
5 (%)
6 (%)
7 (%)
4 (%)
Benzene
100
100
0
0
0
0
0
0
+
m/z 298.1573 (M ), calcd for C H O 298.1569.
24 h
19 22
3
(
(
6) All reactants were simply filtered and concentrated, then the
generation rate and construction of the reaction products
Acetone
4 h
0
5
0
65
30
24
70
6
1
8
h
were confirmed by measuring H NMR without any
treatment, for example isolating or purifying, the residue.
Moreover, a further experiment was carried out for all the
reactions, and the reproducibility was confirmed.
Petroleum ether
4 h
46
54
0
0
1
,4-Dioxane
4 h
85
100
0
0
0
0
15
0
-
1 1
7) 2: IR (neat) 1505, 1610, 1630 cm ; H NMR (270 MHz,
CDCl3) 0.83 (3 H, d, J = 7.6 Hz), 1.18 (3 H, d, J = 6.9 Hz),
8
h
1
(
.51–1.63 (1 H, m), 1.56 (1 H, dquin, J = 7.6, 2.3 Hz), 3.13
1 H, dt, J = 7.2, 6.9 Hz), 3.83 (3 H, s), 3.85 (3 H, s), 5.02 (2
H, s), 6.56 (1 H, s), 6.72 (1 H, s), 7.31–7.44 (5 H, complex);
Isopropyl ether
Toluene
4 h
4 h
82
18
0
0
84
100
100
0
0
0
0
0
0
16
0
0
1
3
8
h
C NMR (75 MHz, CDCl ) 12.18 (q), 20.87 (q), 30.14 (t),
3
24 h
33.21 (d), 55.98 (q), 56.53 (q), 71.74 (t), 98.81 (d), 110.94
d), 127.18 (d), 127.65 (d), 128.30 (s), 128.38 (d), 137.55 (s),
(
Ethyl acetate
4 h
53
21
47
79
0
0
0
0
143.47 (s), 147.08 (s), 150.12 (s); HRMS: found m/z
8
h
+
300.1728 (M ), calcd for C H O 300.1725.
1
9
24
3
-
1 1
(
8) 3: IR (neat) 1590, 3450 cm ; H NMR (270 MHz, CDCl )
3
Dichloromethane
Methanol
4 h
1 h
0
0
100
100
0
0
0
0
0.87 (3 H, d, J = 7.5 Hz), 1.22 (3 H, d, J = 6.6 Hz), 1.60 (2
H, quin, J = 7.5 Hz), 2.84 (1 H, dt, J = 7.5, 6.6 Hz), 3.81 (3
H, s), 3.83 (3 H, s), 4.25 (1 H, br. s, -OH), 6.41 (1 H, s), 6.66
1
3
(
3
(
1 H, s); C NMR (75 MHz, CDCl3) 12.17 (q), 20.75 (q),
0.12 (t), 33.82 (d), 55.92 (q), 56.76 (q), 100.86 (d), 110.94
d), 123.89 (s), 143.29 (d), 146.73 (s), 147.52 (s); HRMS:
+
strates were obtained though some delays were observed
in the reaction time for some materials.
found m/z 210.1254 (M ), calcd for C H O 210.1256.
12 18 3
(9) Control reactions employing Pd-C were as follows. 1 was
immediately converted into the 3 within an hour in 93%
yield using MeOH. In the case of using benzene, compound
In summary, though there is some restriction with respect
to the solvents, we have developed a simple method to
clearly distinguish between the hydrogenation and the hy-
drogenolysis, which was assumed to be difficult to distin-
guish using Pd black, which can be easily obtained, as the
catalyst. It is expected that this method will be widely uti-
lized.
1
was recovered after 24 hours in more than 98% yield and
after 72 hours, 2 was produced in 77% yield with generating
complex mixture.
-
1 1
(
10) 4: IR (neat) 1505, 1595, 1615, 1700 cm ; H NMR (270
MHz, CDCl3) 3.90 (3 H, s), 3.91 (3 H, s), 5.25 (2 H, s), 6.36
(1 H, d, J = 15.8 Hz), 6.86 (1 H, d, J = 8.5 Hz), 7.04 (1 H, d,
J = 2.0 Hz), 7.10 (1 H, dd, J = 8.5, 2.0 Hz), 7.31–7.44 (5 H,
complex), 7.67 (1 H, d, J = 15.8 Hz); C NMR (75 MHz,
1
3
CDCl3) 55.83 (q), 55.93 (q), 66.22 (t), 109.54 (d), 110.98
Acknowledgement
(
d), 115.51 (d), 122.67 (d), 127.30 (s), 128.19 (d), 128.24
This work financially was supported by Grants-in-Aid for Scientific
Research No.12650848 from the Ministry of Education, Science,
Sports and Culture of Japan and Mitsubishi Chemical Corporation
Fund.
(d), 128.56 (d), 136.13 (s), 145.05 (d), 149.17 (s), 151.14 (s),
166.98 (s); HRMS: found m/z 298.120 (M ), calcd for
+
C H O 298.1205.
1
8
18
4
-
1 1
(11) 5: IR (neat) 1515, 1590, 1605, 1735 cm ; H NMR (270
MHz, CDCl3) 2.67 (2 H, t, J = 7.2 Hz), 2.92 (2 H, t, J = 7.2
Hz), 3.83 (3 H, s), 3.85 (3 H, s), 5.11 (2 H, s), 6.70–6.79 (3
References and Notes
13
H, complex), 7.28–7.39 (5 H, complex); C NMR (75 MHz,
CDCl3) 30.56 (t), 36.15 (t), 55.76 (q), 55.88 (q), 66.23 (t),
(
1) Newham, J. Chem. Rev. 1963, 63, 123.
1
1
1
11.28 (d), 111.63 (d), 120.10 (d), 128.15 (d), 128.19 (d),
(2) (a) Fletcher, H. G. Methods Carbohydr. Chem. 1963, II,
28.51 (d), 133.01 (s), 135.90 (s), 147.48 (s), 148.87 (s),
1
3
66. (b) Bindra, J. S.; Grodski, A. J. Org. Chem. 1978, 43,
240. (c) House, H. O. Modern Synthetic Reactions; W. A.
+
72.73 (s); HRMS: found m/z 300.1367 (M ), calcd for
C H O 300.1362.
1
8
20
4
Benjamin Inc.: California, 1972, 23.
-
1 1
(
12) 6: mp 98–100 °C; IR (neat) 1520, 1590, 1705, 3200 cm ; H
NMR (270 MHz, CDCl3) 2.67 (2 H, t, J = 7.6 Hz), 2.91 (2
H, t, J = 7.6 Hz), 3.86 (3 H, s), 3.87 (3 H, s), 6.73–6.82 (3 H,
Synlett 2001, No. 10, 1590–1592 ISSN 0936-5214 © Thieme Stuttgart · New York

1
592
S. Maki et al.
LETTER
Table 3 Hydrogenolysis-free Hydrogenation Products
Pd black (4% w/w)
Substrate
Product
+
SM
benzene, rt
Entry
1
Substrate
Product
Time (h)
4
Yield (%)
SM (%)
MeO
OBn
OBn
OBn
OBn
OBn
OBn
MeO
OBn
OBn
100
100
0
0
2
4
MeO
MeO
2
3
4
5
6
4
4
100
100
0
0
MeO
MeO
MeO
MeO
2
4
4
100
100
0
0
MeO
MeO
MeO
MeO
OBn
OBn
OBn
OBn
2
OBn
OBn
4
8
24
55
100
100
45
0
0
MeO
MeO
MeO
MeO
COOEt
CHO
COOEt
CHO
4
8
24
87
100
100
13
0
0
MeO
MeO
MeO
MeO
4
50
70
100
100
50
30
0
MeO
MeO
MeO
MeO
2
4
28
7
2
0
7
8
4
4
100
100
0
0
MeO
MeO
MeO
MeO
OBn
OBn
2
4
4
100
100
0
0
COOBn
COOBn
MeO
MeO
2
2
MeO
MeO
MeO
MeO
9
4
4
100
100
0
0
OBn
OBn
OBn
OBn
MeO
MeO
O
O
complex); 13C NMR (75 MHz, CDCl3) 30.24 (t), 35.79 (t),
J = 15.8 Hz); 13C NMR (75 MHz, CDCl3) 55.85 (q), 55.94
(q), 109.68 (d), 110.97 (d), 114.95 (d), 123.07 (d), 127.01
(s), 146.82 (d), 149.19 (s), 151.43 (s), 172.44 (s); HRMS:
55.81 (q), 55.91 (q), 111.35 (d), 111.66 (d), 120.08 (d),
1
32.76 (s), 147.58 (s), 148.92 (s), 178.54 (s); HRMS: found
+
+
m/z 210.0896 (M ), calcd for C H O 210.0892.
found m/z 208.0730 (M ), calcd for C H O 208.0736.
1
1
14
4
11 12
4
(
13) 7: mp 178–180 °C; IR (KBr) 1515, 1600, 1620, 1680, 3450
(14) The structures of the synthesized compounds and the
reaction products were determined on the basis of various
-
1 1
cm ; H NMR (270 MHz, CDCl ) 3.93 (6 H, s), 6.33 (1 H,
3
1
13
d, J = 15.8 Hz), 6.88 (1 H, d, J = 8.2 Hz), 7.08 (1 H, d,
J = 1.7 Hz), 7.14 (1 H, dd, J = 8.2, 1.7 Hz), 7.73 (1 H, d,
spectral data (IR, Mass, H NMR, C NMR).
Synlett 2001, No. 10, 1590–1592 ISSN 0936-5214 © Thieme Stuttgart · New York