Irreversible catalytic ester hydrolysis of allyl esters to give acids and aldehydes by homogeneous ruthenium and ruthenium/palladium dual catalyst systems

Article abstract of DOI:10.1002/adsc.201000369

An irreversible hydrolysis reaction of allyl esters (1) into carboxylic acids (2) and propanal (3) was achieved with a ruthenium/palladium (Ru/Pd) dual catalyst system. The optimized catalysts consists of a 1:1:1 mixture of (cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[RuCp(MeCN)₃] PF₆}, bis(acetonitrile)palladium dichloride [PdCl₂(MeCN)₂] and 1,6-bis(diphenylphosphanyl)hexane (DPPHex). The reaction proceeds via isomerization of allyl esters to 1-propenyl esters and hydrolysis of them to give 2 and 3. The first isomerization step was virtually catalyzed by the Ru components and the second hydrolysis step was mainly catalyzed by the Pd components. The optimized bidentate phosphine (DPPHex) which has long alkylene chain effectively generates two vacant sites on the Ru centers by bridging coordination. When a chelating bidentate phosphine such as DPPE was employed, only one vacant site remained on the Ru center and resulted in a low activity. This chelating Ru complex of DPPE formed even in the presence of 2 equivalents of Ru or additional 1 equivalent of Pd. These differences in coordination behaviour between DPPHex and 1,2- bis(diphenylphosphanyl)ethane (DPPE) cause the differences of the catalytic activity in the first step. The phosphine coordination to Pd center slightly decreases the activity of second hydrolysis step but which was compensated by the increasing of the stability of Pd. On the whole, the optimized Ru/Pd dual catalyst system exhibited good performances on the irreversible hydrolysis of allyl esters.

Full text of DOI:10.1002/adsc.201000369

FULL PAPERS
DOI: 10.1002/adsc.201000369
Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give
Acids and Aldehydes by Homogeneous Ruthenium and
Ruthenium/Palladium Dual Catalyst Systems
Asami Nakamura,a,c Akiyuki Hamasaki,a,c Sachihiko Goto,a,c
Masaru Utsunomiya,b and Makoto Tokunagaa,c,*
a
Department of Chemsitry, Kyushu University, Fukuoka 812-8581, Japan
Fax : (+81)-92-642-7528; phone: (+81)-92-642-7528; e-mail: mtok@chem.kyushu-univ.jp
Mitsubishi Chemical Corporation, Yokkaichi, Mie 510-8530, Japan
JST (Japan Science and Technology Corporation), CREST, Japan
b
c
Received: May 11, 2010; Revised: February 10, 2011; Published online: April 13, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000369.
Abstract: An irreversible hydrolysis reaction of allyl employed, only one vacant site remained on the Ru
esters (1) into carboxylic acids (2) and propanal (3) center and resulted in a low activity. This chelating
was achieved with a ruthenium/palladium (Ru/Pd) Ru complex of DPPE formed even in the presence
dual catalyst system. The optimized catalysts consists of 2 equivalents of Ru or additional 1 equivalent of
of a 1:1:1 mixture of (cyclopentadienyl)tris(acetoni- Pd. These differences in coordination behaviour be-
trile)ruthenium
(MeCN)3] PF6}, bis(acetonitrile)palladium dichloride ethane (DPPE) cause the differences of the catalytic
[PdCl2A(MeCN)2] and 1,6-bis(diphenylphosphanyl)- activity in the first step. The phosphine coordination
hexafluorophosphate
{[RuCp- tween DPPHex and 1,2-bis(diphenylphosphanyl)-
ACHTUNGTRENNUNG
CHTUNGTRENNUNG
hexane (DPPHex). The reaction proceeds via iso- to Pd center slightly decreases the activity of second
merization of allyl esters to 1-propenyl esters and hy- hydrolysis step but which was compensated by the
drolysis of them to give 2 and 3. The first isomeriza- increasing of the stability of Pd. On the whole, the
tion step was virtually catalyzed by the Ru compo- optimized Ru/Pd dual catalyst system exhibited good
nents and the second hydrolysis step was mainly cat- performances on the irreversible hydrolysis of allyl
alyzed by the Pd components. The optimized esters.
bidentate phosphine (DPPHex) which has long alky-
lene chain effectively generates two vacant sites on
the Ru centers by bridging coordination. When a Keywords: aldehydes; allyl esters; carboxylic acids;
chelating bidentate phosphine such as DPPE was hydrolysis; irreversible ester hyrolysis
Introduction
backward reaction, i.e., esterification can avoid the
limitation by reactive[4a] and azeotropic distillation,[4b]
Overcoming equilibrium limitations in large-scale use of a dehydrating reagent,[4c] or micelle forma-
chemical processes is an important issue to achieve tion.[4d] The basic hydrolysis of esters is an alternative
high efficiency of synthesis.[1] Catalytic ester hydroly- method which occurs in an irreversible manner but
sis[2] is a typical reaction suffers from the equilibrium requires a stoichiometric amount of the reagent and
limitation (K~0.3)[2a] as well as the Haber–Bosch re- thus is useful only in laboratory to medium scale reac-
action and methanol synthesis from CO or CO2.[3] tions. Therefore an annoying problem that becomes
Based on Le Chatelierꢀs principle, various physical more obvious in large-scale productions are the high
methods have been developed such as removal or ad- energy costs in distillative removal of excess water
dition of one component, phase separation, mem- from water miscible products[5] due to the high vapor-
brane catalysis, temperature and pressure control, ization heat of water (40.7 kJmolÀ1), thus increasing
etc.[1] However, in catalytic ester hydrolysis, introduc- the importance of hydrolysis technology in chemical
ing excess water (typically 5–10 equiv.)[2b,c] is the only and petroleum processes[3c,d] and in biomass utiliza-
method to achieve sufficient conversion, while the tion.[6] Thus, in chemical engineering, reducing the
Adv. Synth. Catal. 2011, 353, 973 – 984
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Asami Nakamura et al.
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energy requirement in the distillative removal of
water is a major topic that is addressed by developing
complex distillation sequences.[7] Here, we disclose an
example of irreversible catalytic ester hydrolysis,
which in principle can resolve this problem. Chemi-
cally, overcoming equilibrium limitations has been
performed by successive one-pot reactions to remove
Scheme 3. Pd-catalyzed hydrolysis of vinyl esters.
the product (Scheme 1), which often requires dual was irreversible and 100% conversion was attained
catalysts for each reaction step. For example, CO con- with 1.4 equivalents of water. We expect a similar ir-
version is extensively improved by successive transfor- reversible reaction giving aldehydes to occur with
mation of CH3OH to CH3OCH3 with Cu and Al2O3 allyl esters via isomerization of double bond.
dual catalysts.[3a,b]
As related reactions, the alcoholysis of allyl ethers
In petroleum processes, allyl esters are common in- and esters has been studied with Ru complexes and
termediates manufactured by acetoxylation of ole- other catalysts by Kitamura and others.[9] The reac-
fins.[3c,d] Acid-catalyzed hydrolysis of them or reduced tions are very useful for fine chemical synthesis as
esters has been performed and the spent excess deallylation and allylation methods. However, in the
amount of water is typically 5–10 equivalents (Sche- case of petroleum processes, recycle use of acetic acid
me 2).[3c,d] The water-miscible products and the excess is necessary in order to keep the low E factor value.
water are separated by fractional distillation in indus- Therefore successive hydrolysis of product esters is
try which consumes huge amounts of energy. Suppos- required when an alcoholysis reaction is performed
ing that a hundred thousand ton/year scale plant is for deallylation. In the end, a usual acid hydrolysis
distilling 400,000 ton/year water, the energy consump- with excess water is not avoidable. In addition, most
tion becomes 9.0ꢂ1011 kJ/year (2.5ꢂ108 kWh/year) of the alcoholysis reactions are reversible thus an
for the removal of water alone. Consequently, if an ir- excess amount of alcohols is required. Consequently,
reversible hydrolysis is realized to reduce the amount direct ester hydrolysis in an irreversible manner is
of water ideally to 1.0 equivalent, an energy-saving more ideal for bulk chemical productions.
process will be accomplished.
On another front, deallylation reactions through 1-
Recently, we have reported a Pd-catalyzed hydroly- propenyl intermediates have been reported in the hy-
sis of vinyl esters to give acids and acetaldehyde as drolysis and alcoholysis of N-allylamides by us and
products (Scheme 3),[8a] and related reactions.[8] Since others.[8c,10] Particularly, propanal was detected with
the aldehyde does not form esters again, the reaction the Pd-catalyzed reaction and 18O is incorporated into
propanal when H218O was used.[8c] In contrast, in the
case of allyl esters, no report has been made on the
hydrolysis giving aldehydes, probably due to facile
formation of p-allyl complexes which afford allyl alco-
hols as a product of nucleophilic addition of water. In
addition, the water addition to p-allyl complexes
Scheme 1. Overcoming equilibrium limitations by successive
reactions.
seems to be difficult since no examples are known for
Scheme 2. Conventional catalytic hydrolysis and irreversible hydrolysis in typical petroleum processes.
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Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give Acids and Aldehydes
the addition of water to p-allyl complexes except for out under an N2 atmosphere at 808C. Several tested
butadiene telomerization,[11] to the best of our knowl- Ru(II) and Ru(0) complexes did not show the activity
edge.
for the reaction (entries 2–5), but Ru(II) complexes
In this paper, we describe the first example of over- bearing a cyclopentadienyl ligand exhibited a certain
coming the equilibrium limitation in catalytic ester activity and gave propanal (3) in moderate yields (en-
hydrolysis of allyl esters. An irreversible hydrolysis of tries 6–17).
allyl esters to give carboxylic acids and aldehydes is [RuCl(Cp)(PPh3)2] gave a small amount (6%) of
catalyzed by homogeneous Ru and Pd catalysts and propanal and the yield was slightly improved (17%)
A
coordinatively saturated complex
AHCTUNGTRENNUNG
their combination.
by the addition of AgPF6, which suggests that the cat-
ionic complex has higher activity (entries 6 and 7). A
cationic complex without phosphine gave only 3%
yield of 3 (entry 8). In these three cases, the forma-
tion of 5–12% allyl alcohol was also observed. In con-
Results and Discussion
Allyl benzoate (1a) was chosen as a substrate for the trast, when 1 equivalent of PPh3 to [RuCl(Cp)-
hydrolysis reaction. Initially, we examined palladium (MeCN)3] was added, the reaction afforded 46% of 3.
catalysts for the reaction but only unsuccessful results In addition, the normal hydrolysis giving allyl alcohol
were obtained. For example, [PdCl2A(CH3CN)2] and did not occur to an appreciable extent (entry 9).
AHCTUNGTRENNUNG
CTHUNGTRENNUNG
PdACHTUNGTRENNUNG(OCOCF3)2 +DPPP, which are the most effective Changing PPh3 to P(p-CF3C6H4)3 or PCAHTUNTGREN(NNGU c-C6H11)3 did
catalysts for the hydrolysis of vinyl esters[8a] and N-al- not improve the yield (entries 10 and 11). Interesting-
lylamides,[8c] showed no activity and resulted in the re- ly, bidentate ligands afforded quite different results
covery of unreacted 1a.
depending on their type (entries 12–17). Loosely bind-
Then we tried the reaction with ruthenium, com- ing ligands were superior to tightly binding ligands.
plex catalysts (Table 1). The hydrolysis was carried For example, 1,6-bis(diphenylphosphanyl)hexane
Table 1. Hydrolysis of allyl benzoate (1a) with Ru catalysts.[a]
Entry
Catalyst
none
Time [h]
Conversion [%][b]
Yield of 2a [%][b]
Yield of 3 [%][b]
1
2
3
4
1
1
3
3
3
3
1
1
1
1
1
2
2
4
3
1
0.5
0
0
0
0
0
0
0
0
0
0
0
0
0
6
17
3
46
22
13
0
18
17
49
60
0
A
R
A
U
G
5
A
U
E
0
0
6[c]
R
G
E
E
27
67
14
82
32
23
11
51
51
93
99
0
27
44
14
68
32
23
7
18
34
76
61
0
7[d,e]
8[f]
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
[Ru(Cp)
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
E
ACHTUNGTRENNUNG
T
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
9[g]
10[h]
11[h]
12[h.i]
13[j,i]
14[g,i]
15[g,i]
16[j,i]
17[h,i]
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
[a]
The reactions were carried out on a 1-mmol scale.
GC analysis.
12% of allyl alcohol was observed.
5% of allyl alcohol was observed.
1 mol% AgPF6 was added.
6% of allyl alcohol was observed.
2 mol% of Ru catalyst and ligand were used.
1 mol% ligand was used.
[b]
[c]
[d]
[e]
[f]
[g]
[h]
[i]
At 858C.
[j]
2 mol% of Ru catalyst and 1 mol% ligand were used.
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(DPPHex) achieved the highest yield (49%) among which brought a 3–40% difference between substrate
the tested ligands. In contrast, DPPE and BINAP conversion and the yield of 2, especially substantial in
completely deactivated the catalyst. This result sug- the case of aliphatic carboxylic acid esters. Presuma-
gests that two vacant sites on the CpRu species are ef- bly these 1-propenyl esters are an intermediate of the
ficient for this reaction. Actually, when the amount of reaction and the hydrolysis of them into 2 and 3 is
DPPHex was reduced to half (0.5 equiv.) referred to slow in aliphatic carboxylates due to the lower elimi-
[Ru(Cp)ACHTUNGTRENNUNG(MeCN)3]PF6, the reaction became faster and nation ability because of higher pKa values of the
a higher yield (60%) was obtained (entry 16). In con- original carboxylic acids. When the pKa value of the
trast, 0.5 equivalents of DPPE resulted in a poor yield original carboxylic acid is low, the reaction becomes
(18%, entry 13).
The hydrolysis of various allyl esters (1a–n) was ex- entry 4,) but the aldehyde 3 is gradually decomposed
amined with [RuCp(PPh3)(MeCN)2]PF6 as catalyst in the presence of the formed carboxylic acid, thus
faster (e.g., 1d gave 96% of 2d and 77% of 3 at 0.5 h,
A
ACHTUNGTRENNUNG
(Table 2). Generally, higher yields were observed with longer reaction time resulted in a decrease of the
aromatic carboxylic acids esters (entries 1–7) com- yield of 3 (58% after 24 h, under the same conditions
pared to aliphatic carboxylic acids esters (entries 8– as for entry 4). Therefore further improvement of the
14). Among the tested aryl carboxylic acids esters, 1d reaction, particularly in aliphatic carboxylic acid allyl
having an electron-withdrawing group (p-NO2C6H4) esters requires an enhancement of the hydrolysis step
gave the highest yield of 3 (77%, entry 4). An elec- of 1-propenyl esters. In order to achieve this purpose,
tron-donating (p-MeOC6H4: 1b) and a hindered we tried the reaction with soft Lewis acids as a
(2,4,6-Me3C6H2: 1e) substituent decreased the yield second component catalyst such as Pd, Pt, and Au
(51% and 19%, entries 2 and 5). The highest reactivi- complexes which are effective for vinyl ester hydroly-
ty was observed with an a-keto ester (1g) (entry 7), sis.[8]
which underwent the reaction even at 408C. In con-
trast, aliphatic carboxylate esters displayed lower re- 1 mol% [RuCp
activities thus afforded lower yields both in acids (2) nent metal complexes and 0.5–2.0 mol% ligands
and propanal (3) (entries 8–13). Allyl tetrahydrofur- (Table 3). A Pd complex [PdCl2A(MeCN)2], which ex-
The hydrolysis reaction of 1a was tried with
AHCTUNGTRENNUNG
CTHUNGTRENNUNG
an-2-ylcarboxylate (1n) is an exceptional example hibited the best performance for vinyl ester hydroly-
which gave high yield (81%) perhaps due to a chelate sis,[8a] was examined as a second component catalyst
effect.
in the absence of ligand but the reaction was sluggish
In these Ru-catalyzed reactions, the formation of 1- (entry 1). However, the addition of phosphines in-
propenyl esters was observed by GC and GC-MS, creased the activity; 1 and 2 mol% PPh3 improved the
Table 2. Ru-catalyzed hydrolysis of various substrates.[a]
Entry
R
T [8C]
Conversion [%][b]
Yield of 2a–n [%][b]
Yield of 3 [%][b]
1
2
Ph (1a)
80
85
85
85
85
85
40
85
85
80
85
85
85
85
82
93
97
100
29
99
100
45
75
78
68
70
75
96
26
75
93
35
48
32
30
44
58
>99
46
51
59
77
19
63
53
35
35
16
31
33
50
81
4-MeOC6H4 (1b)
4-ClC6H4 (1c)
4-NO2C6H4 (1d)
2,4,6-Me3C6H2 (1e)
PhCH=CH (1f)
PhCO (1g)
Me (1h)
n-Pr (1i)
n-C5H11 (1j)
c-C6H11 (1k)
3
4[c]
5
6
7[d]
8
9
10
11
12
13
14
86
83
88
100
t-Bu (1l)
MeCOCH2CH2 (1m)
tetrahydrofuran-2-yl (1n)
[a]
The reactions were carried out on a 1-mmol scale.
GC analysis.
At 0.5 h.
[b]
[c]
[d]
At 22 h.
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Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give Acids and Aldehydes
Table 3. Hydrolysis of allyl benzoate (1a) with Ru catalysts.[a]
Entry
Second catalyst
[PdCl2A(MeCN)2]
Ligand, [mol%]
Time [min]
Conversion [%][b]
Yield of 2a [%][b]
Yield of 3 [%][b]
1[c]
2
3
G
E
non
PPh3, 1
PPh3, 2
DPPHex, 1
DPPHex, 2
DPPHex, 0.5
PPh3, 1
PPh3, 1
DPPHex, 1
PPh3, 2
180
60
90
20
90
7
7
4
A
U
100
100
100
23
0
>99
>99
>99
23
0
8
42
60
99
63
15
52
81
5
0
2
42
57
82
63
A
U
4
A
U
5[c]
6[d]
7
A
U
A
U
60
N
N
120
120
60
60
60
8
8
9
65
60
100
70
A
U
10[e]
11[e]
T
A
DPPHex, 1
[a]
The reactions were carried out on a 1-mmol scale.
GC analysis.
10% of allyl alcohol was observed.
Without Ru catalyst.
[b]
[c]
[d]
[e]
2 mol% Ru catalyst were used.
yield of 3 to 15 and 52%, respectively (entries 2 and ethane, although the catalyst was soluble in these sol-
3). The addition of 1 mol% DPPHex improved the re- vents.
action more clearly, 81% of 3 formed in 20 min
(entry 4). Compared to the reaction with only Ru/Pd catalysts (Table 5). Interestingly, alkylene-
[Ru(Cp)(MeCN)3]PF6 +DPPHex catalyst, much linked bidentate phosphines displayed contrasting re-
A series of bidentate ligands was examined for the
A
a
faster rate was attained (cf. 60% yield at 1 h, Table 1, sults depending on the length of alkylene chain (en-
entry 16). On the other hand, the addition of 2 mol% tries 1–6). Along with the change of the alkylene
DPPHex caused a decrease of activity and the forma- length from 1 to 6, yield of 3 increased as 2, 14, 26,
tion of allyl alcohol was observed (entry 5). As ex- 42, 85, and 89%, consequently, DPPHex exhibited the
pected, the reaction with only Pd complex gave no best performance. Other bidentate ligands such as
conversion of 1a (entry 6). Palladium acetate and tri- DPPF, DPEphos, XANTPhos, and BINAP were also
fluoroacetate with 1 mol% PPh3 proved less active less effective. Noteworthy is that facile formation of
than chloride (entries 7 and 8). A Pt complex [PtCl2 Pd black was observed during the reactions, except
ACHTUNGTRENNUNG
plexes were found to be effective too. An Au complex the optimized Ru/Pd+DPPHex catalyst (Table 6). In
[AuClPPh3] with PPh3 and DPPHex provided 82 and general, the reaction proceeded faster than with the
63% yield of 3 (entries 10 and 11). On the basis of simple Ru catalyst (Table 2) and better yields of 3
the obtained results, we performed further investiga- were accomplished. For example, in the reaction of
tions on the dual catalyst system. Here, we chose Ru/ 1a, the yield was improved from 49% to 89%
Pd catalytic system based on two reasons: (i) the reac- (entry 1, cf Table 2, entry 1). Eleven substrates out of
tions were faster than with Ru/Pt and Ru/Au systems, fourteen gave >80% yield and four substrates record-
(ii) the Ru/Au system readily formed a gold mirror ed >90% yield. When acidity of the original carbox-
derived from the deactivated Au(0), whereas the Ru/ ylic acid is low, high yields (96%) of 3 were achieved
Pd system employing DPPHex did not give palladium (1b and 1h, entries 2 and 8). However, when the acidi-
black.
ty is high, the yield decreased to <70% (entries 4 and
The effect of solvent was studied with the Ru/Pd+ 7). A sterically hindered substrate 1e resulted in poor
DPPHex catalyst (Table 4). The good performance of yield and the major product was allyl alcohol
the catalyst was obtained in ether solvents (entries 1– (entry 5). A major feature of this catalyst system is
3), especially in 1,2-dimethoxyethane (entry 2). Lower the disappearance of the 1-propenyl intermediates,
activities were observed in other solvents such as 2- GC analysis during the reaction detected only trace
propanol, acetonitrile, toluene, and 1,2-dichloro- amount of that species.
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Table 4. Ru-catalyzed hydrolysis of various substrates.[a]
Entry
Solvent
Conversion [%][b]
Yield of 2a [%][b]
Yield of 3 [%][b]
1
2
3
4
5
6
7
THF
100
100
97
96
12
>99
>99
96
92
12
81
89
64
17
1
1,2-dimethoxyethane
1,4-dioxane
2-propanol
acetonitrile
toluene
27
12
27
12
8
12
1,2-dichloroethane
[a]
The reactions were carried out on 1 mmol scale.
GC analysis.
[b]
Table 5. Ru/Pd-catalyzed hydrolysis of 1a with various bidentate phosphines.[a]
Entry
Ligand
Conversion [%][b]
Yield of 2a–n [%][b]
Yield of 3 [%][b]
1
DPPM
DPPE
DPPP
DPPB
DPPPent
DPPHex
DPPF
DPEPhos
XANTPhos
rac-BINAP
8
8
2
2[c]
3[d]
4[e]
5
27
35
55
96
100
37
10
5
27
35
55
93
>99
37
10
5
14
26
42
85
89
29
3
6
7
8
9
0
0
10
0
0
[a]
The reactions were carried out on a 1-mmol scale.
GC analysis.
14% of allyl alcohol was observed.
6% of allyl alcohol was observed.
5% of allyl alcohol was observed.
[b]
[c]
[d]
[e]
A 10-mmol scale hydrolysis reaction of allyl acetate from all the substrates, yields were generally low
(1h) was carried out with the optimized catalyst (<30%). Development of more highly active catalysts
system, and attained >99% yield both in acetic acid for substituted allylic esters is an issue for future stud-
(2h) and propanal (3) (Scheme 4). The result suggests ies.
this reaction is potentially applicable to large-scale re-
actions.
We assume three pathways for this reaction. The
pathway (1) involves isomerization of allyl esters to
When the reaction was performed with a reduced 1-propenyl esters and subsequent hydrolysis into car-
amount of water, somewhat lower yields were ob- boxylic acids and propanal. The pathway (2) contains
served. The reaction of 1h with 1.5 equiv. of water a p-allyl intermediate and its hydrolysis into allyl al-
gave 3 in 87% and this was isolated in 80% as a cohol and subsequent isomerization to propanal, and
DME solution by distillation. The reaction with (3) is a normal hydrolysis of carboxylic esters into
1.2 equiv. of water afforded 3 in 76% at 1 h. The hy- acids and allyl alcohol.
drolysis reactions were applied for 2- or 3-methyl-sub-
In order to see which is more plausible, hydrolysis
stituted allyl esters and (Z)-1,4-diacetoxy-2-butene. reactions of 1a with H218O were performed with Ru
Although the corresponding aldehydes were formed (see Supporting Information, Scheme S-1) and Ru/Pd
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Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give Acids and Aldehydes
Table 6. Ru-catalyzed hydrolysis of various substrates.[a]
Entry
R
Catalyst
loadings (x)
Time
[min]
Conversion
[%][b]
Yield of 2a–n
Yield of 3
G
[%][b]
[%][b]
1
2
3
Ph (1a)
1
2
1
0.5
1
1
1
2
2
2
2
2
1
20
60
20
20
60
20
10
30
60
30
120
60
60
20
100
100
100
92
27
100
96
100
97
100
100
96
>99
>99
>99
91
26
>99
96
>99
97
>99
>99
92
89
96
80
64
1
84
66
96
81
90
82
90
82
84
4-MeOC6H4 (1b)
4-ClC6H4 (1c)
4-NO2C6H4 (1d)
2,4,6-Me3C6H2 (1e)
PhCH=CH (1f)
PhCO (1g)
Me (1h)
n-Pr (1i)
n-C5H11 (1j)
c-C6H11 (1k)
4
5[c]
6
7
8
9
10
11
12
13
14
t-Bu (1l)
MeCOCH2CH2 (1m)
tetrahydrofuran-2-yl (1n)
100
100
89
>99
1
[a]
The reactions were carried out on 1 mmol scale.
GC analysis.
21% of allyl alcohol was observed.
[b]
[c]
Scheme 4. Ru/Pd/DPPHex-catalyzed hydrolysis of 1h on a 10-mmol scale.
Scheme 5. Hydrolysis of 1a with 18O-labeled water.
(Scheme 5) catalysts. GC and GC-MS analyses (see 94.1). However, Pd/DPPHex did not catalyze the re-
Supporting Information, Figure S-1) indicated that action, thus 1a remained intact (Scheme 6).
18O was incorporated into 3 but not in 2a. In addition,
The hydrolysis reactions of 5 were carried out with
a saturated substrate, propyl benzoate (4) was not hy- [PdCl2A(MeCN)2] and Ru/Pd+DPPHex catalysts. The
drolyzed under these conditions. These results sug- former Pd catalyst, effective for vinyl ester hydroly-
gested that the pathway (3) is not reasonable.
sis,[8a] hydrolyzed 5 into 2a and 3 in 83% and 81%
CTHUNGTRENNUNG
Next, 1a was exposed under the reaction conditions yields in 0.5 h (Scheme 7). The Ru/Pd catalyst also
in the absence of H2O with a Ru catalyst. The isomer- catalyzed the reaction but the yields of 2a and 3 were
ization into 1-propenyl benzoate (5) proceeded 23% and 14% (see Supporting Information, Scheme
smoothly in 92% isolated yield. Here, the reaction S-2). The lower activity is maybe because of the coor-
became slow in the later part probably due to an dination of the phosphine to Pd. Interestingly, conta-
equilibrium between 1a and 5, thus the 1a/5 ratio at minated 1a as an impurity of 5 remained unreacted
24 h (6.4/93.6) did not change so much at 96 h (5.9/ when [PdCl2ACHTNUTRGNE(UNG MeCN)2] was used.
Adv. Synth. Catal. 2011, 353, 973 – 984
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Asami Nakamura et al.
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the combined yield of 3 was 177% (see Supporting In-
formation, Scheme S-3). This result suggests at least
the later part of the pathway (2) is possible.
Then substrate 6 bearing a 1,1-dimethylallyl group,
which cannot be isomerized into the 1-propenyl form,
was examined (Scheme 8). Recently this group has
been used as a protective group for carboxylic
acids[13a] in place of tert-butyl esters. Facile formation
of the p-allyl intermediate is known when Pd(0) com-
plexes were used.[13b] The substrate 6 underwent hy-
drolysis slowly and the OH group is introduced only
on the tertiary carbon but not on the terminal carbon,
Scheme 6. Ru- and Pd-catalyzed isomerisation of 1a.
Based on these observations, we think the reaction which suggests the addition of OH group occurred
proceeds with the pathway (1). The first isomerization through a carbocation intermediate or normal hydrol-
step was virtually catalyzed by the Ru components ysis because generally terminal addition is predomi-
and the second hydrolysis step was mainly catalyzed nant to p-allyl complexes.[13b]
by the Pd components. There are several examples of
In this reaction, the phosphine structure affected
similar dual- or two-catalyst systems,[12] in which the the catalytic activity to a considerable extent. Typical-
each catalyst plays different roles on sequential multi- ly, DPPHex is the most suitable ligand for this reac-
step reactions, although our reaction is too simple to tion; on the other hand, DPPE deactivated the cata-
be called a tandem reaction. Fewer examples were lyst both in Ru and Ru/Pd catalyst systems. Thus, the
found for one-pot, one-step procedures[12a,f] compared difference of the metal complex species between
to one-pot, two-step procedures.[12b–e]
these two ligands was studied. First, simple Ru com-
Nonetheless, a mechanism including the formation plexes were compared. When DPPE was added to
of a p-allyl intermediate, the pathway (2), cannot be [RuCp
U
a
known chelate complex
excluded completely. When the reaction was carried [RuCp
ACHTUNGTNER(NUNG MeCN)]PF6 was formed selectively
out in the presence of allyl alcohol (1.0 equiv.), the al- (Scheme 9).[14] The 31P NMR showed a singlet peak at
cohol was isomerized into propanal (3) smoothly and 80.2 ppm (see Supporting Information, Figure S-2-1).
Scheme 7. Hydrolysis of 5 with Pd catalysts.
Scheme 8. Hydrolysis of 6 with Ru/Pd catalysts.
Scheme 9. The formation of a chelate complex with DPPE and a bridged complex with DPPHex.
980
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Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give Acids and Aldehydes
Figure 1. FAB-mass spectrum of [Ru(Cp)ACHTNUGRTNEUNG(MeCN)3]PF6 +0.5 equiv. DPPHex complex.
This complex primarily formed even when 0.5 equiv. formation, Figure S-5). This observation is consistent
of DPPE was used (see Supporting Information, with the poor activity of the Ru/Pd+DPPE catalyst.
Figure S-2-2). In contrast, when 0.5 equiv. of DPPHex On the other hand, when DPPHex was added, several
was added to [RuCpACHTNUGTRENUNG(MeCN)3]PF6, a singlet peak ap- sharp and broad peaks were observed (see Supporting
peared at 41.3 ppm, which can be assigned as a Information, Figure S-6). One of the major sharp
À À À
bridged dinuclear complex (Ru P P Ru) (Scheme 9, peaks around 42 ppm is close to the chemical shift of
Supporting Information, Figure S-3-1). The chemical the Ru P P Ru species. When the temperature was
À À À
shifts of these complexes were in good accordance decreased to À808C, this peak did not change so
with a previous study carried out with DPPE.[14] The much but two new sharp peaks appeared around 18–
1H NMR spectrum of the bridged dinuclear complex 28 ppm, those were estimated as phosphorus coordi-
of DPPHex showed a free MeCN peak at 1.95 ppm nating to Pd. A similar trend was observed in an
(6H) and a coordinated MeCN peak at 2.18 ppm FAB-MS analysis (see Supporting Information, Figure
(12H), respectively (see Supporting Information, S-7). The Pd P bonds seems to be weak compared to
Figure S-3-2). An FAB-MS analysis afforded peaks at the Ru P bonds, thus several similar peaks to the
À
À
m/z=1096, 1056, 1015, 974, and 933, which corre- [RuCp
spond to [Cp2Ru2A(dpphex)
(MeCN)3]PF6 +0.5 DPPHex mixture were ob-
C
(MeCN)n]PF6 (n=0–4) served but few peaks can be assigned as Pd com-
(Figure 1 and Supporting Information, Figure S-4).
In the simple Ru system, the highest activity was
achieved with 0.5 equiv. of DPPHex (Table 1,
plexes.
entry 16), which is attributable to the bridged dinu- Conclusions
clear complex having two vacant sites at the Ru
center. Actually, [RuCpPPh3ACHTUNTRGENUNG(MeCN)2]PF6, which has An efficient irreversible hydrolysis of allyl esters (1)
two vacant sites is known as a good catalyst for olefin into carboxylic acids (2) and propanal (3) was ach-
isomerization.[15] The low activity of the DPPE com- ieved with an Ru/Pd dual catalyst system for the first
plexes can be explained by only one vacant site be- time. The optimized catalyst consists of a 1:1:1 mix-
cause of the preference of chelate coordination. Two ture of [RuCpACHTNUGTRENNU(G MeCN)3]PF6, PdCl2ACHUTTGNREN(NUGN MeCN)2 and
coordination sites maybe required for isomerization DPPHex. A 10-mmol scale hydrolysis reaction of allyl
of allyl esters to 1-propenyl esters via oxidative addi- acetate (1h) gave acetic acid (2h) and 3 both in
À
tion of an allylic C H bond.
>99% yield. The reaction proceeds via isomerization
The situation of DPPE and DPPHex in the Ru cat- of allyl esters to 1-propenyl esters and hydrolysis of
alyst seems to be reflected in the Pd/Ru dual catalyst them to give 3. The first isomerization step was virtu-
system, although the active species could not been ally catalyzed by the Ru components and the second
clearly determined due to fluxional behaviour ob- hydrolysis step was mainly catalyzed by the Pd com-
served in 31P NMR. When DPPE was added to the ponents.
mixture of [RuCp
the signals of the chelate complexes [RuCp
(MeCN)2]PF6 (80.2 ppm) and [PdCl2A(dppe)]PF6 two vacant sites on the Ru centers. When a chelating
(65.6 ppm) were mainly observed (see Supporting In- bidentate phosphine such as DPPE was employed,
A
R
The optimized bidentate phosphine (DPPHex)
AHCTUNGTRENNUNG
A
CHTUNGTRENNUNG
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Asami Nakamura et al.
FULL PAPERS
only one vacant site remained on the Ru center and Hydrolysis of Allyl Benzoate (1a), Table 1, entries 9–
brought about low activity. The chelating Ru and Pd 17
complexes of DPPE also formed in the presence of
A
screw cap test-tube was charged with [Ru(Cp)-
2 equiv. of Ru or 1 equiv. of Pd. These differences in
coordination behaviour between DPPHex and DPPE
cause the differences of the catalytic activity in the
first step. The phosphine coordination to the Pd
center slightly decreases the activity of the second hy-
drolysis step but which was compensated by the in-
crease in the stability of Pd. On the whole, the opti-
mized Ru/Pd+DPPHex dual catalyst system exhibit-
ed good performances on the irreversible hydrolysis
reactions. Monodentate phosphines such as PPh3
showed a decent performance especially in the simple
Ru catalyst system, which may generate mono-coordi-
nated complexes. However, the perfect control of co-
ordination number in the Ru/Pd system to keep
mono-coordinated Ru and Pd species seems to be dif-
ficult with PPh3 which might bring the slightly lower
performances in this reaction.
A limitation of this method is the low reactivity for
substituted allyl esters including 1,4-diacetoxy-2-
butene which is an important industrial intermediate.
In addition, much higher catalytic activities and turn-
over numbers are desirable from a practical view-
point. These are the next issues to be resolved and ef-
forts in this direction are currently underway.
AHCTUNGRTEN(NGUN MeCN)3]PF6 (10 mmol, 4.3 mg) and phosphine (10 mmol).
To the tube was added dry CH2Cl2 (0.5 mL) and the mixture
was stirred for 30 min at room temperature. After removal
of the solvent, the solid was dried under vacuum for 1 h. A
mixture of 1a (1.0 mmol, 162 mg), THF (1 mL), water
(2.0 mmol, 36 mL) and diglyme (0.25 mmol, 35 mL, internal
standard for GC analysis) was placed into a 20-mL Schlenk
tube, and the mixture was degassed by two freeze-thaw
cycles. This mixture was transferred via stainless cannula to
the screw cap test-tube which contains the Ru catalyst and
stirring bar under nitrogen pressure. The mixture was stirred
at 80–858C for 0.5–4 h. After cooling to room temperature,
the yield of the product was determined by GC analysis.
Hydrolysis of Various Allyl Esters (1a–1n), Table 2,
entries 1–14 with 1a–1n
A
screw cap test-tube was charged with [Ru(Cp)-
AHCTUNTGERN(GNUN MeCN)3]PF6 (0.020 mmol, 8.7 mg), PPh3 (0.020 mmol,
5.2 mg) and stirring bar. To the tube was added dry CH2Cl2
(0.5 mL) and the mixture was stirred for 30 min at room
temperature under a nitrogen atmosphere. After removal of
the solvent, the solid was dried under vacuum for 1 h. A
mixture of 1a–1n (1.0 mmol), THF (1 mL), water (2.0 mmol,
36 mL) and diglyme (0.25 mmol, 35 mL, internal standard for
GC analysis) was placed into a 20-mL Schlenk tube, and the
mixture was degassed by two freeze-thaw cycles. This mix-
ture was transferred via cannula to the screw cap test-tube
which contains [Ru(Cp)ACHTUNGTRENNG(U PPh3)ACHTUNGTERN(NGUN MeCN)2]PF6. The mixture
Experimental Section
was stirred at 40–858C for 0.5–22 h. After cooling to room
temperature, the yield of the product was determined by
GC analysis.
General Remarks
1H NMR (400 MHz), 13C NMR (100 MHz) and 31P NMR
(161.8 MHz) spectra were recorded on JEOL JMN-ECA-
400 instruments. GC analysis was carried out using an Agi-
lent GC 6850 equipped with J&W HP-1 column (length
30 m, 0.32 mm I.D.), and J&W INNOWax column (length
30 m, 0.25 mm I.D.). GC-MS analysis was performed with a
Thermo Fisher Scientific Polaris Q equipped with a Trace
TR-5 column (length 7 m, 0.32 mm I.D.). FAB-MS analysis
was performed with an Ultrahigh Performance Mass Spec-
trometer JMS-HX110A in the Institute for Materials
Chemistry and Engineering (IMCE), Kyushu University,
where 3-nitrobenzyl alcohol was used as a matrix. Column
chromatography was performed on silica gel (Kanto Chemi-
cals, Silica gel 60N, spherical, neutral; particle size 40–
100 mm). All organic and inorganic materials in this study
are known compounds. Syntheses of Ru and Pd complexes
and substrates 1,[16] 5, and 6 are described in supporting in-
formation.
Hydrolysis of Allyl Benzoate (1a), Table 3, entries 2
and 3
A
AHCTUNGTRENNUNG
screw cap test-tube was charged with [Ru(Cp)-
(MeCN)3]PF6 (0.010 mmol, 4.3 mg), PPh3 (0.010 or
0.020 mmol, 2.6 or 5.2 mg), PdCl2A(MeCN)2 (0.010 mmol,
CTHUNGTRENNUNG
2.6 mg) and stirring bar. To the tube was added dry CH2Cl2
(0.5 mL) and the mixture was stirred for 20 min at room
temperature under nitrogen atmosphere. After removal of
the solvent, the solid was dried under vacuum for 1 h. A
mixture of 1a (1.0 mmol, 162 mg), THF (1 mL), water
(2.0 mmol, 36 mL) and diglyme (0.25 mmol, 35 mL, internal
standard for GC analysis) was placed into a 20-mL Schlenk
tube, and the mixture was degassed by two freeze-thaw
cycles. This mixture was transferred via cannula to the screw
cap test-tube which contains the Ru/Pd catalyst. The mix-
ture was stirred at 858C for 60–120 min. After cooling to
room temperature, the yield of the product was determined
by GC analysis.
Hydrolysis Reactions
All hydrolysis reactions were carried out under a nitrogen
atmosphere. Typical procedures are given below.
Hydrolysis of Allyl Benzoate (1a), Table 4, entries 1–
7
A
screw cap test-tube was charged with [Ru(Cp)-
(MeCN)3]PF6 (0.010 mmol, 4.3 mg), DPPHex (0.010 mmol,
4.5 mg), PdCl2A(MeCN)2 (0.010 mmol, 2.6 mg) and stirring
AHCTUNGTRENNUNG
CTHUNGTRENNUNG
982
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Adv. Synth. Catal. 2011, 353, 973 – 984

Irreversible Catalytic Ester Hydrolysis of Allyl Esters to Give Acids and Aldehydes
bar. To the tube was added dry CH2Cl2 (0.5 mL) and the
mixture was stirred for 20 min at room temperature under a
nitrogen atmosphere. After removal of the solvent, the solid
was dried under vacuum for 1 h. A mixture of 1a (1.0 mmol,
162 mg), solvent (1 mL), water (2.0 mmol, 36 mL) and di-
glyme (0.25 mmol, 35 mL, internal standard for GC analysis)
was placed into a 20-mL Schlenk tube, and the mixture was
degassed by two freeze-thaw cycles. This mixture was trans-
ferred via cannula to the screw cap test-tube which contains
the Ru/Pd catalyst. The mixture was stirred at 858C for
20 min. After cooling to room temperature, the yield of the
product was determined by GC analysis.
the mixture was degassed by two freeze-thaw cycles. This
mixture was transferred via cannula to the screw cap test-
tube which contains the Ru/Pd catalyst. The mixture was
stirred at 858C for 30 min. After cooling to room tempera-
ture, the yield of the product was determined by GC analy-
sis (2h > 99% yield, 3 >99% yield).
Supporting Information
Complete experimental procedures, NMR data (1b, 1c, 1d,
1e, 1f, 1g, 1k, 1l, 1m, 1n, 5 and 6), and Figure S-1–S-7 are
available as Supporting Information.
Hydrolysis of Allyl Benzoate (1a), Table 5, entries 1–
10
Acknowledgements
A
ACHTUNGTRENNUNG
screw cap test-tube was charged with [Ru(Cp)-
(MeCN)3]PF6 (0.010 mmol, 4.3 mg), bidentate phosphine
(0.010 mmol), PdCl2A(MeCN)2 (0.010 mmol, 2.6 mg) and stir-
This study was supported by Industrial Technology Research
Grant Program in 2005 from New Energy and Industrial
Technology Development Organization (NEDO) of Japan.
The present work is also supported by a Grant-in-Aid for
Global-COE program, “Science for Future Molecular Sys-
tems”, Scientific Research (A) (No. 20245014), and on Priori-
ty Areas (No. 20037052, Chemistry of Concerto Catalysis)
from the Ministry of Education, Culture, Science, Sports and
Technology of Japan.
CTHUNGTRENNUNG
ring bar. To the tube was added dry CH2Cl2 (0.5 mL) and
the mixture was stirred for 20 min at room temperature
under a nitrogen atmosphere. After removal of the solvent,
the solid was dried under vacuum for 1 h. A mixture of 1a
(1.0 mmol, 162 mg), DME (1 mL), water (2.0 mmol, 36 mL)
and diglyme (0.25 mmol, 35 mL, internal standard for GC
analysis) was placed into a 20-mL Schlenk tube, and the
mixture was degassed by two freeze-thaw cycles. This mix-
ture was transferred via cannula to the screw cap test-tube
which contains the Ru/Pd catalyst. The mixture was stirred
at 858C for 20 min. After cooling to room temperature, the
yield of the product was determined by GC analysis.
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Hydrolysis Reaction, Scheme 4 (10 mmol Scale
Reaction)
A
G
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Adv. Synth. Catal. 2011, 353, 973 – 984