Novel Palladium-on-Carbon/Diphenyl Sulfide Complex
COMMUNICATIONS
Table 2. Reuse test of Pd/C
A
H
R
U
G
stored in a regular reagent bottle at room temperature with-
out any special handling and alternation of the catalyst ac-
tivity.
2
General Procedure for the Chemoselective
Hydrogenation using Pd/C[Ph S]
A
H
R
U
G
2
A substrate (0.50 mmol), Pd/C[Ph S] (10 wt% of the sub-
A
H
R
U
G
2
strate), and MeOH (1 mL) were added to a test tube con-
taining a stir bar and sealed with a septum. After two
Run Ratio of
:2:3
Yield of
2
Yield of Recovered Pd/C-
[Ph S]
[
a]
1
ACHTREUNG
2
vacuum/H cycles to replace the air inside with hydrogen,
2
the mixture was vigorously stirred at room temperature
under ordinary hydrogen pressure (balloon) for 24 h. The
reaction mixture was filtered using a membrane filter (Milli-
pore, Millex -LH, 0.45 mm) and the filtrate was concentrat-
ed under vacuum to provide the pure product without fur-
ther purification.
1
2
3
4
5
0:100:0
0:100:0
0:100:0
0:100:0
0:100:0
100
92
97
99
99
99
98
97
100
100
ꢂ
[
a]
Isolated yield.
References
tries 18 and 21), aromatic chloride (entry 19) and
benzylester (entry 20) functionailties intact. The hy-
[
1] R. C. Larock, Comprehensive Organic Transformations,
nd edn., Wiley VCH: New York, 1999.
drogenation of the azide moiety using Pd/C[Ph S] was
A
H
R
U
G
2
2
also investigated (entries 22–25) and they were effi-
ciently hydrogenated to the corresponding amines re-
gardless of the electronic circumstances of the aro-
matic ring.
[
2] a) S. Nishimura, Handbook of Heterogeneous Catalytic
Hydrogenation for Organic Synthesis, Wiley-Inter-
science: New York, 2001; b) M. Hudlicky, Reductions
in Organic Chemistry, 2nd edn., ACS, Washington, DC,
1996; c) P. N. Rylander, Hydrogenation Methods, Aca-
demic Press, New York, 1985.
We next investigated the reusability of Pd/C
in the chemoselective hydrogenation of benzyl cinna-
mate. Pd/C[Ph S] could be reused at least until the
fifth run without significant loss of the selectivity and
A
H
R
U
G
A
C
H
T
R
E
U
N
G
[3] S. F. Dovell, H. Greenfield, J. Am. Chem. Soc. 1965, 87,
767–2768.
2
2
[22]
[4] G. Wu, M. Huang, M. Richards, M. Poirier, X. Wen,
yield (Table 2).
R. W. Draper, Synthesis 2003, 1657–1660.
5] Y. Miyazaki, H. Hagio, S. Kobayashi, Org. Biomol.
Chem. 2006, 4, 2529–2531.
6] M. Studer, S. Neto, H.-U. Blaser, Topics in Catalysis
In summary, we have developed a novel and isola-
ble diphenyl sulfide-supported Pd/C catalyst (Pd/C-
[
[
[
A
C
H
T
R
E
U
N
G
[Ph S]) possessing an excellent chemoselectivity
2
toward hydrogenation; olefin, acetylene, nitro, and
2
000, 13, 205–212.
azide functionalities were smoothly hydrogenated,
while aromatic carbonyl and halide, benzyl ester and
N-Cbz functionalities were not. Such an efficient ex-
pression of the chemoselectivity has its roots in the
catalyst properties based upon the reasonable and
7] M. Hoogenraad, J. B. van der Linden, A. A. Smith,
Org. Process Res. Dev. 2004, 8, 469–476.
[8] Benzylether cou dl survive in the semihydrogenation
conditions using nickel nanoparticles, see F. Alonso, I.
Osante, M. Yus, Tetrahedron 2007, 63, 93–102.
[
9] Y. Segura, N. Lꢃpez, J. Pꢄrez-Ramꢅrez, J. Catal. 2007,
47, 383–386.
partialinteraction with Ph S on the active sites of the
2
2
Pd surface (PdÀS bonding). These findings reinforce
[
[
10] a) H. Lindlar, Helv. Chim. Acta 1952, 35, 446–450;
b) H. Lindlar, R. Dubuis, Org. Synth. Coll. Vol. 5, 1973,
the versatility of such reducible functionalities in syn-
thetic chemistry, and the Pd/C[Ph S] catalyst has been
A
H
R
U
G
2
8
80–882; c) K. W. Rosenmund, Ber. Dtsch. Chem. Ges.
recognized as a chemoselective and convenient cata-
lyst for hydrogenation.
1
918, 51, 585–594; d) K. Rosenmund, F. Zetzsche, Ber.
Dtsch. Chim. Ges. 1921, 54B, 425–437.
11] a) H. Sajiki, Tetrahedron Lett. 1995, 36, 3465–3468;
b) H. Sajiki, H. Kuno, K. Hirota, Tetrahedron Lett.
1
997, 38, 399–402; c) H. Sajiki, H. Kuno, K. Hirota,
Experimental Section
Tetrahedron Lett. 1998, 39, 7127–7130; d) H. Sajiki, K.
Hirota, Tetrahedron 1998, 54, 13981–13996; e) H.
Sajiki, Yakugaku Zasshi 2000, 120, 1091–1103; f) H.
Sajiki, K. Hirota, Chem. Pharm. Bull. 2003, 51, 320–
324.
Preparation of Pd/C[Ph S]
A
H
R
U
G
2
A suspension of 532 mg of 10% Pd/C and Ph S (166 mL,
2
2.00 equiv. vs. Pd metalof Pd/C) in MeOH (5 mL) was
stirred for 5 days at room temperature under an argon at-
mosphere, and then the resulting solid was collected on
filter paper, washed successively with methanol (10 mLꢁ2)
and ether (10 mLꢁ2), and then dried under reduced pres-
[12] a) A. Mori, Y. Miyakawa, E. Ohashi, T. Haga, T. Mae-
gawa, H. Sajiki, Org. Lett. 2006, 8, 3279–3281; b) A.
Mori, T. Mizusaki, Y. Miyakawa, E. Ohashi, T. Haga,
T. Maegawa, Y. Monguchi, H. Sajiki, Tetrahedron 2006,
62, 11925–11932.
sure for 24 h to give Pd/C
A
H
R
U
G
A
T
E
N
2
Adv. Synth. Catal. 2008, 350, 406 – 410
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
409