Hydroformylation of monosubstituted alkenes catalyzed by W-Rh bimetallic complex

Article abstract of DOI:10.1246/cl.2006.540

By using a heterobimetallic catalyst, (CO)₄(PEtPh ₂)-W(μ-PPh₂)Rh(CO)(PPh₃), chemoselective hydroformylation of monosubstituted alkenes proceeds efficiently at room temperature under atmospheric pressure of CO/H<

Full text of DOI:10.1246/cl.2006.540

540
Chemistry Letters Vol.35, No.5 (2006)
Hydroformylation of Monosubstituted Alkenes Catalyzed by W–Rh Bimetallic Complex
Motoki Yamane, Noriaki Yukimura, Hiroshi Ishiai, and Koichi Narasakaꢀ
Department of Chemistry, Graduate School of Science, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033
(Received March 1, 2006; CL-060244; E-mail: narasaka@chem.s.u-tokyo.ac.jp)
By using a heterobimetallic catalyst, (CO)4(PEtPh2)-
Table 1. Hydroformylation of terminal alkene 4a catalyzed by
rhodium complexes
W(ꢀ-PPh2)Rh(CO)(PPh3), chemoselective hydroformylation
of monosubstituted alkenes proceeds efficiently at room temper-
ature under atmospheric pressure of CO/H2, without affecting
functional groups such as disubstituted alkene moieties, aryl and
alkenyl iodide moieties, and hydroxy and carboxy groups.
Catalyst
CO (0.5 atm)
H2 (0.5 atm)
CHO
+
Toluene
4a
5a
Temp.Time
6a
Yield/%
/°C /h 5a(n:iso)a 6a
Entry
1
Catalyst
(mol. amt.)
Hydroformylation of alkenes is an important process to pro-
duce aldehydes, where rhodium complexes are often used as cat-
alysts due to their high catalytic ability.1 One of the problems on
alkene hydroformylation is competitive alkene hydrogenation
and isomerization, which produce undesired products without
incorporation of CO. It is supposed that rapid formation of acyl-
rhodium intermediates via efficient CO insertion would suppress
these side reactions.
Ph2
P
(0.2) 25 20 92(2.5:1) <0.5
(0.02) 25 185 95(2.5:1) <0.5
1
(CO) (PEtPh )W Rh(PPh3)(CO)
2
3
4
4
2
RhH(CO)(PPh3)3
2
3
(0.2) 25 20 83(2.5:1)
8
[Rh(µ-PPh2)(cod)]2
(0.2) 50 18 6 (3:1) 89
aRatio of n- and iso-isomer estimated by 1H NMR analysis.
Bimetallic catalysis has now been employed in organic syn-
thesis,2,3 because it is expected that two metal centers take part in
a reaction together. We have been interested in bimetallic cata-
lysts including a rhodium nucleus. It is considered that rhodium
bimetallic system would provide ideal catalysis in hydrofor-
mylation if the counter metal part assists the rhodium center
for the incorporation of CO. Group 6 metal carbonyl complexes
are known as good CO sources in palladium-catalyzed carbonyl-
ation for preparation of amides4 and esters,5 and in some cases
CO is incorporated more efficiently rather than using atmo-
spheric CO gas. Therefore, our attention was directed to use a
rhodium–tungsten bimetallic complex, (CO)4(PEtPh2)W(ꢀ-
PPh2)Rh(CO)(PPh3) (1),6 for hydroformylation of alkenes in
an expectation of rapid formation of the acylrhodium intermedi-
ate with an intramolecular assistance of the tungsten carbonyl
part. In this article is described rhodium–tungsten bimetallic
complex-catalyzed hydroformylation of alkenes and its chemo-
selectivity is discussed as compared to the reaction with
RhH(CO)(PPh3)3 (2), which is recognized as one of the efficient
catalysts for hydroformylation.7
plex 3,10 without tungsten part, was ineffective in hydroformyla-
tion (Entry 4).
The hydroformylation of alkene 4a with 1 also proceeded
efficiently even under lower partial pressure (1/8 or 1/16 atm)
of CO (Entries 1 and 2 in Table 2). On the contrary, reactions
catalyzed by RhH(CO)(PPh3)3 gave a significant amount of un-
desired isomerization and hydrogenation products (Entries 3 and
4). These results suggest that the tungsten carbonyl part assists
incorporation of CO in the hydroformylation.
The bimetallic complex-catalyzed hydroformylation is sen-
sitive to the substitution pattern of alkenes. The reactions of di-
substituted alkenes required heating (50 ꢁC) and a longer reac-
tion time (Table 3, Entries 1 and 2). It is supposed that the steric
bulkiness of bimetallic complex 1 suppressed the interaction of
the multisubstituted alkene part to the rhodium center.
This property allowed a monosubstituted alkene-selective
hydroformylation. In the hydroformylation of diene 4e, monoal-
dehydes 5e were selectively formed without affecting the inner
alkene part (eq 1). In contrast, the reaction with RhH(CO)-
(PPh3)3 gave 5e only in 60% yield and a mixture of side products
First, the hydroformylation of 1-(but-3-en-1-yl)naphthalene
(4a) was examined by using 1 (0.2 mol. amt.) at room tempera-
ture under 0.5 atm each of H2 and CO partial pressure (Entry 1
in Table 1).8 The corresponding aldehydes 5a were obtained
as a mixture of n- and iso-isomers (n:iso = 2.5:1) in 92% total
yield with only a trace amount of isomerized alkenes 6a. The
hydroformylation was monitored by 31P NMR analysis and
the peak of ꢀ-PPh2 was observed during the reaction course.9
This observation indicates that the bimetallic structure, W(ꢀ-
PPh2)Rh, is maintained in the reaction. Aldehydes 5a were
obtained in high yield even with a reduced amount of catalyst
1 (0.02 mol. amt.) (Entry 2). In the hydroformylation with
RhH(CO)(PPh3)3 (2), a considerable amount of undesired inner
alkenes 6a (8%) were produced, even though aldehydes 5a were
obtained in 83% (Entry 3). Diphenylphosphido bisrhodium com-
Table 2. Hydroformylation of 4a under low partial pressure of
CO
Catalyst (0.2 mol. amt.)
CHO
+
CO/H2 (1 atm)
+
Toluene, rt, 20 h
4a
5a
6a
7a
Partial Pressure
Yield/%
Entry
Catalyst
CO/atm H2/atm
5a
6a
7a
0
1
2
3
4
1
1
2
2
0.875
0.937
0.875
0.937
92
92
62
51
2
4
0.125
0.063
0.125
0.063
0
14
13
12
31
Copyright Ó 2006 The Chemical Society of Japan

Chemistry Letters Vol.35, No.5 (2006)
541
Table 3. Hydroformylation of multisubstituted alkenes 4b–4d
catalyzed by 1 at 50 ꢁCa
of tungsten part in bimetallic complex 1 might prevent an ap-
proach of the iodo moiety to the rhodium center.
(n:iso)b
Catalyst (0.2 mol. amt.)
CO/H2 (0.5 atm each)
Entry
Alkene 4
Time/h
Yield of 5/%
I
I
CHO
(2)
Toluene, rt, 34 h
1
4b
43
82
()c
4l (E:Z = 1:>99)
5l (E:Z = 1:>99)
-PPh2)Rh(CO)(PPh3) 1: 92% (n:iso = 3:1)
RhH(CO)(PPh3)3 2: 68% (n:iso = 3:1)
Catalyst: (CO)4(PEtPh2)W(
µ
2
3
4c
4d
50
50
94
0
(n only)
()
Ph
In conclusion, the phosphido-bridged rhodium–tungsten
complex 1 is an efficient catalyst for the chemoselective hydro-
formylation of monosubstituted alkenes. This catalytic system
does not affect various functional groups under the hydrofor-
mylation conditions.
aReaction conditions: 1 (0.2 mol. amt.), CO/H2 (0.5 atm each),
toluene, 50 ꢁC. bRatio of n- and iso-isomer estimated by
1H NMR analysis. Three aldehydes 5b, 5b0, and 5b00 were ob-
tained (Ar = naphthalen-1-yl).
c
This work was supported by the Grant-in-Aid for Scientific
Research (A) from Japan Society for the Promotion of Science,
and the Grant-in-Aid for The 21st Century COE Program for
Frontiers in Fundamental Chemistry from the Ministry of Educa-
tion, Culture, Sports, Science and Technology, Japan.
CHO
Ar
Ar
Ar
CHO
CHO
Ph
5b
61%
5b' 17%
5b"
4%
including dialdehydes 6 (ca. 12%).
Catalyst (0.2 mol. amt.)
CO/H2 (0.5 atm each)
CHO
References and Notes
+
dials (1)
1
J. L. Leighton, in Modern Rhodium-Catalyzed Organic Reactions,
ed. by P. A. Evans, Wiley-VCH Verlag GmbH & Co. KGaA,
Weinheim, 2005, Chap. 5, pp. 93–110; J. K. Stille, in Comprehen-
sive Organic Synthesis, ed. by B. M. Trost, I. Fleming, Pergamon
Press, Oxford, 1991, Vol. 4, Chap. 5, pp. 913–950; B. Breit,
W. Seiche, Synthesis 2001, 1784; M. Beller, B. Cornils, C. D.
Frohning, C. W. Kohlpaintner, J. Mol. Catal. A 2002, 104, 17.
Multimetallic Catalysts in Organic Synthesis, ed. by M. Shibasaki,
Y. Yamamoto, Wiley-VCH Verlag GmbH & Co. KGaA, Wein-
Ph
Toluene, rt, 36 h
6
4e
5e (n:iso = 2.5:1)
-PPh2)Rh(CO)(PPh3) 1: 89%
RhH(CO)(PPh3)3 2:
Catalyst: (CO)4(PEtPh2)W(
µ
−
60% ca. 12%
We investigated the functional group compatibility in this
hydroformylation (Table 4 and eq 2). It is of interest that alkenes
containing a hydroxy or carboxy were efficiently transformed to
aldehydes (Entries 3 and 4). To the best of our knowledge, the
hydroformylation of alkenes having an aryl or an alkenyl iodide
moiety has not been reported. Although aryl and alkenyl iodides
are potentially sensitive to oxidative addition, the iodo moiety
was not affected in the reaction (Entry 6 and eq 2). On the other
hand, the mononuclear rhodium catalyst 2 reacted with the iodo
moiety to give a deiodination product 7 (Entry 7). The bulkiness
2
´
heim, 2004; P. Braunstein, J. Rose, in Comprehensive Organo-
metallic Chemistry II, ed. by E. W. Abel, F. G. A. Stone, G.
Willkinson, Elsevier Science Ltd., Oxford, 1995, Vol. 10,
Chap. 7, pp. 351–385; H. Suzuki, Y. Takaya, T. Takemori, M.
Tanaka, J. Am. Chem. Soc. 1994, 116, 10779; N. Tsukada, T.
Mitsuboshi, H. Setoguchi, Y. Inoue, J. Am. Chem. Soc. 2003,
125, 12103; N. Wheatly, P. Kalck, Chem. Rev. 1999, 99, 3379;
Y. Nishibayshi, H. Imajima, G. Onodera, M. Hidai, S. Uemura,
Organometallics 2004, 23, 26.
3
For bimetallic complex-catalyzed hydroformylation of alkene,
see: P. Kalck, J.-M. Frances, P.-M. Pfister, T. G. Southern, A.
Thorez, J. Chem. Soc., Chem. Commun. 1983, 510; M. Hidai, H.
Matsuzuka, Polyhedron 1988, 7, 2369; L. Geimini, D. W.
Stephane, Organometllics 1988, 7, 849; M. E. Broussard, B. Juma,
S. G. Train, W.-J. Peng, S. A. Laneman, G. G. Stanley, Science
1993, 260, 1784; C. Li, E. Widjaja, M. Garland, Organometallics
2004, 23, 4131; H. Itoi, N. Tsukada, Y. Inoue, 85th Annual
Meeting of the Chemical Society of Japan, Yokohama, March
26–29, 2005, Abstr., No. 4E2-07.
Table 4. Investigation on the functional group tolerance in the
hydroformylation catalyzed by 1 or 2
Catalyst (0.2 mol. amt.)
CHO
CO/H2 (0.5 atm each)
Toluene, rt
R
R
4f−4k
5f−5k
Entry
R
Catalyst
Time/h
Yield of 5/%a
n:isob
1
2
3
4
5
6
7
OCOCH3
46
57
50
42
36
34
34
93 (98)
82 (94)
88 (96)
86
1:23
1:12
1:12
1:20
1:30
1:29
1:21
1
1
1
1
1
1
2
4
5
6
N. F. K. Kaiser, A. Hallberg, M. Larhed, J. Comb. Chem. 2002, 4,
109.
J. Georgsson, A. Hallberg, M. Larhed, J. Comb. Chem. 2003, 5,
350.
NMe2
OH
CO2H
P. M. Shulman, E. D. Burkhardt, E. G. Lundquist, R. S. Pilato,
G. L. Geoffroy, A. L. Rheingold, Organometallics 1987, 6, 101.
C. K. Brown, G. Willkinson, J. Chem. Soc. A 1970, 2753.
Typical procedure is as follows. A mixture of 1-(but-3-en-1-yl)-
naphthalene (4a; 0.50 mmol) and catalyst 1 (0.10 mmol) in toluene
(7.5 mL) was stirred at room temperature for 20 h under CO/H2
(0.5 atm each). Aldehydes 5a were obtained by purification using
florisil column chromatography (hexane/ethyl acetate = 9:1).
Br
92
7
8
I
I
95 (96)
83c
aNumber in parentheses shows yield estimated by GC analysis.
bRatio of n- and iso-isomer estimated by 1H NMR analysis.
cAldehyde 7 was obtained.
The peak, ꢁ ¼ 89:3 (ddd, 2J
¼ 177:8 Hz, 1J
¼
31
103
31P
{
P
Rh
31P
{
Rh
9
ꢀ
ꢀ
89:0 Hz, 2J
lites (1J
¼ 22:6 Hz, ꢀ-PPh2), which shows 183W satel-
31P
{
31PW
ꢀ
CHO
31P
{
183W
¼ 215:8 Hz), was observed as the bridged phos-
ꢀ
phorous atom.
10 P. E. Kreter, D. W. Meek, Inorg. Chem. 1983, 22, 319.
7
8%
Published on the web (Advance View) April 22, 2006; DOI: 10.1246/cl.2006.540