The novel selective reduction of the carbon-carbon triple bond using Pd(PPh3)4 as a catalyst

Article abstract of DOI:10.1081/SCC-100104414

A novel selective reduction system is reported in which compounds with terminal carbon-carbon triple bond and internal carbon-carbon triple bond were treated with NaBH₄-Pd(PPh₃)₄ in basic conditions and only the terminal C-C triple bond was reduced.

Full text of DOI:10.1081/SCC-100104414

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THE NOVEL SELECTIVE REDUCTION OF THE CARBON-
CARBON TRIPLE BOND USING Pd(PPh ) AS A
3
4
CATALYST
a
a
a
b
WenXin Gu , XiaoChuan Chen , XinFu Pan & AnXin Wu
a
Department of Chemistry, National Laboratory of Applied Organic Chemistry , Lanzhou
University , Lanzhou, 730000, P.R. China
b
Department of Chemistry, National Laboratory of Applied Organic Chemistry , Lanzhou
University , Lanzhou, 730000, P.R. China
Published online: 09 Nov 2006.
To cite this article: WenXin Gu , XiaoChuan Chen , XinFu Pan & AnXin Wu (2001) THE NOVEL SELECTIVE REDUCTION OF
THE CARBON-CARBON TRIPLE BOND USING Pd(PPh ) AS A CATALYST, Synthetic Communications: An International Journal
3
4
for Rapid Communication of Synthetic Organic Chemistry, 31:13, 1983-1986, DOI: 10.1081/SCC-100104414
To link to this article: http://dx.doi.org/10.1081/SCC-100104414
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SYNTHETIC COMMUNICATIONS, 31(13), 1983–1986 (2001)
THE NOVEL SELECTIVE REDUCTION OF
THE CARBON-CARBON TRIPLE BOND
USING Pd(PPh ) AS A CATALYST
3
4
WenXin Gu, XiaoChuan Chen, XinFu Pan,
and AnXin Wu*
Department of Chemistry, National Laboratory of Applied
Organic Chemistry, Lanzhou University,
Lanzhou 730000, P.R. China
ABSTRACT
A novel selective reduction system is reported in which com-
pounds with terminal carbon-carbon triple bond and internal
carbon-carbon triple bond were treated with NaBH4-
Pd(PPh3)4 in basic conditions and only the terminal C-C
triple bond was reduced.
The reduction of carbon-carbon triple bonds is a particularly valuable
1
reaction and is frequently used in organic synthetic chemistry. The reduction
of an alkyne can usually be stopped at the semihydrogenation stage because
the alkene is more strongly bound than the alkyne, and competes effectively
for the catalytic sites, blocking re-adsorption of the alkene, or displacing it.
Although various reduction reactions of alkynes have been reported in
2
3
4
which the reagents such as NaBH , DIBAL-H , LiAlH etc. are used widely,
4
4
selective reduction has not been achieved. Suzuki et al. has reported the
catalytic hydrogenation of alkynes using NaBH -PdCl in the presence of
4
2
*
Corresponding author.
1
983
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

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REPRINTS
1
984
GU ET AL.
polyethylene glycol (PEG), in which reduction system both internal carbon-
carbon triple bonds and terminal carbon-carbon triple bonds in the substrates
5
were reduced unselectively. Herein, we wish to report the preliminary results
of a study focused on a new reduction system (NaBH -Pd(PPh ) ) in which the
4
3 4
compounds with both internal carbon-carbon triple bonds and terminal
carbon-carbon triple bonds are selectively reduced at the terminal carbon-
carbon triple bond (Scheme). This reduction system has the advantages of
faster rates and high regioselectivity, together with the easy handling.
Scheme.
The typical procedure for the selective reduction of the compounds
with both internal carbon-carbon triple bonds and terminal carbon-carbon
triple bonds is described below. To a solution of 0.1 mol NaOH in 5 mL
H O/MeOH (v:v ¼ 1:1) was added successively NaBH (75 mg, 2 mmol) and
2
4
Pd (PPh ) (11.55 mg, 0.01 mmol), and the mixture stirred for 10 min at
3
4
room temperature under nitrogen. The substrate (1 mmol) was added and
the reaction mixture stirred for another 30 min. The resulting mixture was
extracted with diethylether (3 ꢀ 25 mL). The combined extracts were dried
(
Na SO ), the solvent was distilled off, and the residue was isolated by a
2 4
column chromatography to afford olefins in 85–92% yield (Table 1).
Table 1. Results of the Reactions and the Spectral Data of Products
Yield
Product (%)
Spectral Data of Products
(%)
Substrate
R
1
a
C
H
3 6
2a
90
d
2
1
H
: (CDCl , 300 MHz), 1.74 (m, 2H), 2.23 (m, 2H),
.50 (t, 7.1 Hz, 2H), 4.28 (s, 2H), 5.05 (dd, 1.6 Hz,
0.2 Hz, 1H), 5.11 (dd, 1.7 Hz, 17.1 Hz, 1H), 5.86
3
(
(
7
1
2
m, 1H), 6.73(s, 1H), 7.29 ꢁ 7.87 (m, 5H); d :
3
C
CDCl , 75 MHz), 19.9, 28.4, 33.5, 68.2, 77.3,
7.7, 78.1, 99.2, 116.2, 122.6, 128.7, 128.8, 129.1,
+
33.3, 136.8, 138.4; EI-MS (m/z): 226 (M , 12),
09 (base), 181 (21), 167 (32), 129 (18), 91 (7);
(
Found: C, 84.3; H, 8.1. C16H18O requires C,
8
4.9; H, 8.0%).
(continued )

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Pd (PPh ) AS CATALYST
3
1985
4
Table 1. Continued
Yield
Product (%)
Spectral Data of Products
(%)
Substrate
R
1
b
C H
4
2b
92 d : (CDCl , 300 MHz), 1.63(m, 2H), 2.13(m, 2H),
H 3
8
2
1
.49 (t, 6.7 Hz, 2H), 4.28 (s, 2H), 5.03(dd, 1.1 Hz,
1.1 Hz, 1H), 5.09 (dd, 1.8 Hz, 18.0 Hz, 1H), 5.84
(
(
7
1
m, 1H), 6.74 (s, 1H), 7.29 ꢁ 7.88 (m, 5H); d :
3
C
CDCl
, 75 MHz), 20.4, 28.6, 28.8, 33.9, 68.1,
7.3, 77.7, 79.1, 99.3, 115.4, 122.6, 128.6, 128.8,
29.1, 133.2, 136.8, 139.1; EI-MS (m/z): 241
+
(
(
M , 11), 223(base), 181 (14), 141 (1 3) , 129 (10);
Found: C, 84.7; H, 8.2. C17 20O requires C, 85.0;
H, 8.4%).
H
1
c
C H
5
2c
88 d : (CDCl , 300 MHz), 1.48 (m, 2H), 1.65 (m,
10
H
3
2
2
1
7
2
1
1
2
H), 2.09 (m, 2H), 2.48 (t, 6.9 Hz, 2H), 4.28 (s,
H), 4.99 (dd, 1.5 Hz, 10.3Hz, 1H), 5.06 (dd,
.6 Hz, 16.4 Hz, 1H), 5.83(m, 1H), 6.72 (s, 1H),
.28 ꢁ 7.88 (m, 5H); d : (CDCl , 75 MHz), 20.3,
C
3
0.5, 29.0, 29.1, 34.3, 68.3, 77.9, 78.1, 79.0, 99.6,
15.1, 122.6, 128.7, 128.8, 129.1, 133.3, 136.8,
+
39.5; EI-MS (m/z): 255 (M , 22), 237 (base),
23 (16), 195 (13), 155 (31), 141 (26), 129 (18);
(
Found: C, 85.2; H, 8.6. C18H22O requires C,
8
5.0; H, 8.7%).
1
d
C H
6
2d
85 d : (CDCl , 300 MHz), 1.45 (m, 6H), 1.65 (m,
H 3
12
2
2
1
7
2
9
1
H), 2.10 (m, 2H), 2.48 (t, 6.9 Hz, 2H), 4.28 (s,
H), 5.00 (dd, 1.1 Hz, 10.0 Hz, 1H), 5.07 (dd,
.6 Hz, 17.2 Hz, 1H), 5.85 (m, 1H), 6.73(s, 1H),
.29 ꢁ 7.89 (m, 5H); d : (CDCl , 75 MHz), 20.5,
C
3
9.1, 29.3, 29.4, 29.5, 34.4, 68.2, 77.3, 77.7, 78.2,
9.6, 115.0, 122.6, 128.6, 128.8, 129.1, 133.1,
+
36.8, 139.6; EI-MS (m/z): 268 (M , 36), 251
(
(
8
base), 237 (16), 209 (13), 195 (14), 155 (20), 141
15); (Found: C, 84.6; H, 8.8. C19 24O requires C,
5.0; H, 9.0%).
H
In a comparison experiment, three substrates which possess only one
carbon-carbon triple bond (1e, 1f, 1g) were treated under the same con-
ditions. Compounds with a terminal carbon-carbon triple bond (1e, 1f)
were reduced in good yield and the compound with an internal carbon-
carbon triple bond (1g) was not be reduced (Table 2).

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GU ET AL.
Table 2. Results of the Reactions
Mechanistic studies and application of the present reduction method
are now in progress.
ACKNOWLEDGMENT
We are grateful to the National Science Foundation of China for
financial support.
REFERENCES
1. Rylander, P.N. Hydrogenation Methods, Academic Press: London,
1985.
2. Kijima, M.; Nambu, Y. and Endu, T. Chem. Lett. 1985, 1851.
3. Ziegler, F.E. and Mikami, K. Tetrahedron Letters 1984, 25, 131.
4. a. Corey, E.J.; Katzenellenbogen, J.A. and Posner, G.H. J. Am. Chem.
Soc. 1967, 89, 4245. b. Hoji, M.; Masuda, R. and Takagi, S. Synthesis
1978, 284.
5. Suzuki, N.; Tsukanaka, T.; Nomoto, T.; Ayaguchi, Y. and Izawa, Y.
J. Chem. Soc. Chem. Comm. 1983, 515.N.
Received in the UK May 16, 2000

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