Highly effective tandem hydroformylation-acetalization of olefins using a long-life Bronsted acid-Rh bifunctional catalyst in ionic liquid-alcohol systems

Article abstract of DOI:10.1039/c3gc41231h

A robust and highly effective tandem hydroformylation-acetalization of olefins using a Bronsted acid-Rh bifunctional catalyst (ARBC) in ionic liquid-alcohol systems is reported. The key feature of the ARBC is its use of a zwitterionic phosphine ligand bearing an amino acid tag. This novel ARBC shows an excellent catalytic efficiency and a long service life without a significant drop in both the hydroformylation efficiency and the acetalization efficiency or Rh loss for more than seventeen cycles. We believe that the long-term high activity and acetal selectivity mainly benefit from the synergy between the acidic active site and the Rh active site on the ARBC and the highly effective immobilization and recycling of ARBC in ionic liquid-alcohol systems due to the strong affinity of ARBC for the ionic liquid.

Full text of DOI:10.1039/c3gc41231h

View Article Online
View Journal
Green Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Jin, K. Zhao, F. Cui, F. Kong and Q.
Liu, Green Chem., 2013, DOI: 10.1039/C3GC41231H.
This is an Accepted Manuscript, which has been through the RSC Publishing peer
review process and has been accepted for publication.
Accepted Manuscripts are published online shortly after acceptance, which is prior
Cutting-edge research for a greener sustainable future
www.rsc.org/greenchem
Volume 12 | Number 9 | September 2010 | Pages 1481–1676
to technical editing, formatting and proof reading. This free service from RSC
Publishing allows authors to make their results available to the community, in
citable form, before publication of the edited article. This Accepted Manuscript will
be replaced by the edited and formatted Advance Article as soon as this is available.
To cite this manuscript please use its permanent Digital Object Identifier (DOI®),
which is identical for all formats of publication.
More information about Accepted Manuscripts can be found in the
Information for Authors.
Please note that technical editing may introduce minor changes to the text and/or
graphics contained in the manuscript submitted by the author(s) which may alter
content, and that the standard Terms & Conditions and the ethical guidelines
that apply to the journal are still applicable. In no event shall the RSC be held
responsible for any errors or omissions in these Accepted Manuscript manuscripts or
any consequences arising from the use of any information contained in them.
ISSN 1463-9262
COMMUNICATION
CRITICAL REVIEW
Luque, Varma and Baruwati
Dumesic et al.
Magnetically seperable organocatalyst Catalytic conversion of biomass
for homocoupling of arylboronic acids to biofuels
1463-9262(2010)12:9;1-U
www.rsc.org/greenchem
Registered Charity Number 207890

Page 1 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C3GC41231H
Highly effective tandem hydroformylation-acetalization of olefins using a long-life Brønsted acid-Rh
bifunctional catalyst in ionic liquid/alcohol systems

Green Chemistry
Page 2 of 7
Dynamic Article Links ►
Green Chemistry
View Article Online
DOI: 10.1039/C3GC41231H
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/greenchem
PAPER
Highly effective tandem hydroformylation-acetalization of olefins using
a long-life Brønsted acid-Rh bifunctional catalyst in ionic liquid/alcohol
systems
Xin Jin,* a, b Kun Zhao, a Feifei Cui, a Fangfang Kong a and Qiangqiang Liu a
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
A robust and highly effective tandem hydroformylation-acetalization of olefins using a Brønsted acid-Rh
bifunctional catalyst (ARBC) in ionic liquid/alcohol systems is reported. The key feature of the ARBC is
its use of a zwitterionic phosphine ligand bearing an amino acid tag. This novel ARBC shows excellent
10 catalytic efficiency and long service life without significant drop in both the hydroformylation efficiency
and the acetalization efficiency or Rh loss for more than seventeen cycles. We believe that the long-term
high activity and acetal selectivity mainly benefit from the synergy between the acidic active site and the
Rh active site on the ARBC and the highly effective immobilization and recycling of ARBC in ionic
liquid/alcohol systems due to the strong affinity of ARBC with the ionic liquid.
15 Introduction
rarely investigated. To date, no reported catalytic system can
realize the combination of high activity, high acetal selectivity
and longer service life of catalyst in tandem hydroformylation-
50 acetalization of olefins, mainly due to difficulties in the efficient
immobilization and recycling of the Rh-catalyst.
The isolation and recycling of noble metal catalysts in
homogeneous catalytic reactions have remained a challenge in
green chemistry for the past 20 years.1 The highly effective one-
pot catalytic synthesis of chemicals and fine chemicals has also
20 been an research focus in green chemistry, since it improves atom
economy and reduces emission, E factor (kgwaste/kgproduct), and
consumption of energy and raw materials.2 Rh-catalyzed
hydroformylation is an important method for the
functionalization of alkenes to produce aldehydes in industrial
25 applications. Due to their versatile chemical properties,3
aldehydes can be further transformed into other important
chemicals. Based on the principles of atom economy and low
energy consumption in green chemistry, the hydroformylation of
alkenes can be combined with numerous other organic reactions
30 to form tandem reaction sequences that can be achieved directly
under the hydroformylation condition.4 Examples include tandem
In recent years, biphasic hydroformylation using ionic liquid
(IL) as reusable supports of Rh-catalyst has received extensive
attention.6 The key issue in IL biphasic hydroformylation is the
55 effective immobilization of Rh-catalyst in IL to avoid Rh loss.
Since the tandem hydroformylation-acetalization normally uses
alcohol as the reaction medium,5a-l if the Rh-catalyst can be
effectively immobilized in IL/alcohol systems, it would then be
possible to enable the efficient separation and recycling of Rh-
60 catalyst in the tandem hydroformylation-acetalization of olefins.
To the best of our knowledge, catalyst recycling in IL/alcohol
systems for the hydroformylation-acetalization of olefins has not
been described yet.
+
+
NH3
CO2H
NH3
hydroformylation-reduction,
hydroformylation-nucleophilic
n-Bu
X-
COO-
addition, hydroformylation-aldol condensation, etc. Among them,
an important application is the tandem hydroformylation-
35 acetalization, in which the formation of acetal may be used to
protect the sensitive aldehyde group or to further synthesize fine
chemicals such as perfume, pharmaceuticals and agricultural
chemicals. Such one-pot synthesis procedure enables multiple
catalytic reactions in series, which avoids the formation of side
40 products and circumvents the complex steps for the separation
and purification of aldehyde intermediates.2
X-
N
N
Ph2P
Ph2P
[1·H]X
X- = [BF4]-, [PF6]-, [Tf2N]-
[bmim]X
X- = [BF4]-, [PF6]-, [Tf2N]-
1
65
Scheme 1 The zwitterionic phosphine ligand with a glycine tag (1), its
ammonium salts ([1·H]X) and the imidazole-based ILs.
To achieve long-term recycling of Rh-catalyst while
Although many efforts have been devoted to the research of Rh-
catalyzed one-pot hydroformylation and acetalization process,5
most of the related works are focused on catalysts, kinetics and
45 scope of the reaction, and the separation and recycling of the
expensive Rh-catalyst in this homogeneous catalysis reaction are
70 maintaining high catalytic efficiency in the tandem
hydroformylation-acetalization of alkenes, we report the catalytic
systems consisting of Brønsted acid-Rh bifunctional catalysts,
imidazole-based ionic liquids (Scheme 1) and alcohols using a
This journal is © The Royal Society of Chemistry 2013
Green Chem., 2013, [vol], 00–00 | 1

Page 3 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C3GC41231H
Table 1 One-pot hydroformylation-acetalization of 1-octene using the ARBCs (Rh-[1⋅H]X) in MeOH or [bmim]X/MeOH systems (X− = [PF6]−, [BF4]− and
[Tf2N]−).a
Rh-[1·H]X/ CO/H2
OMe
OMe
OMe
OMe
+
5
5
MeOH or [bmim]X/MeOH
X- = [PF6]-, [BF4]-, [Tf2N]-
5
Entry
Ligand
Reaction medium
Conversion b (%) Soxo c (%)
Eace d (%)
Siso e (%)
l : b f
Rh loss g (%)
1
2
[1·H][BF4]
MeOH
98
99
99
99
99
99
94
99
99
99
99
95
94
97
98
99
97
99
98
97
97
95
94
96
94
3
2
1
1
1
1
1
1
1
1
3
78:22
70:30
76:24
78:22
84:16
75:25
77:23
77:23
82:18
86:14
84:16
—
—
—
—
—
[1·H][PF6]
MeOH
3
[1·H][Tf2N]
MeOH
4
1
MeOH
0.5
5
PPh3
MeOH
1
95
95
92
51
5
6
[1·H][BF4]
[bmim][BF4]/MeOH
[bmim][PF6]/MeOH
[bmim][Tf2N]/MeOH
[bmim][BF4]/MeOH
[bmim][PF6]/MeOH
[bmim][Tf2N]/MeOH
0.03
7
[1·H][PF6]
0.6
0.7
8
[1·H][Tf2N]
9
1
1
1
37
10
11
52
39
4
a p (H2/CO = 1/1) = 5 MPa, T = 80 °C, t = 2 h, Rh(acac)(CO)2 1.0 mg, ligand/Rh = 10, 1-octene/Rh = 1000, cyclohexane as internal standard, 1 g IL, 3 mL MeOH.
The ammonium salts [1·H]X (X− = [BF4]−, [PF6]−, [Tf2N]−) can be easily prepared in methanol through an acid-base neutralization reaction of 1 with equimolar HX
b
(HX/1/Rh = 10/10/1), and the ammonium salts can be either first isolated or used directly, which does not alter the result. Percent of converted 1-alkene,
c
determined by GC. Selectivity of total oxo products based on 1-alkene consumed, determined by GC. Total oxo products mainly consist of linear aldehyde,
d
branched aldehyde, linear acetal and branched acetal. Acetalization efficiency: Eace = (linear acetal + branched acetal)/(linear aldehyde + branched aldehyde +
e
f
linear acetal + branched acetal). Selectivity of isomerized alkenes that are mainly 2-alkene and 3-alkene, determined by GC. Ratio of linear acetal to branched
acetal. g Percentage of leached Rh in the total Rh charged, determined by ICP-AES.
5
glycine tagged zwitterionic phosphine ligand7 and its ammonium 35 acetalization, which promotes the synergy between both catalytic
salts (Scheme 1, 1 and [1·H]X). The first successful application
active sites and enables the simulatneous immobilization and
recycling of both the Rh catalyst and the acid co-catalyst. (3) The
formation of the ammonium salts [1·H]X increases the electric
charge of the ARBCs molecule, which improves the affinity of
40 the ARBCs with ILs [bmim]X as catalyst carriers and effectively
reduces catalyst loss.
of catalyst recycling via IL/alcohol systems in tandem
10 hydroformylation-acetalization of olefins here is demonstrated.
Results and discussion
The acetalization of aldehydes is normally catalyzed by Lewis
acids or Brønsted acids in alcohols or orthoesters.8 Therefore, all
In Table 1 (entries 1–3), the tandem hydroformylation-
acetalization of 1-octene in methanol is used as a model reaction
to evaluate the catalytic efficiency of ARBCs for the
45 hydroformylation and acetalization reactions. The conversion of
alkene and Soxo (selectivity for total oxo products including
aldehyde and acetal) characterize the hydroformylation efficiency
of the Rh active site, while Eace characterizes the acetalization
efficiency of the acidic active site formed on the glycine side
50 chain of Rh-[1·H]X. Gratifyingly, in MeOH the ARBCs (Rh-
[1⋅H]X) exhibit excellent hydroformylation efficiency with high
conversion of alkene (98%–99%), high selectivity for oxo
products (94%–97%) and low selectivity for isomerized alkenes
(1%–3%), as well as good acetalization efficiency (94%–96%)
55 and moderate regioselectivity for the linear acetal (70%–78%),
and the type of Brønsted acid does not affect the acetalization
currently reported Rh-catalyzed tandem hydroformylation-
5a-l
15 acetalization of olefins are carried out in alcohols
5m-q
or
orthoesters
in the presence of Lewis acids or Brønsted acids
as co-catalysts. The acidic co-catalysts usually need to be added
and are sometimes generated in situ.5g-i,
5j-q
p, 9
separately
However, because the Rh-catalyst and the acidic co-catalysts
20 exist independently, their simultaneous immobilization and
recycling become difficult. The Brønsted acid-Rh bifunctional
catalysts (ARBCs) that we report here elegantly resolve this
problem by empolying a glycine-tagged zwitterionic phosphine
ligand 1 in the form of an internal salt, which can form
25 ammonium salts with equimolar amount of Brønsted acids HX
(X− = [PF6]−, [BF4]− and [Tf2N]−). The ammonium salt [1·H]X
can then be complexed with Rh precursor under
hydroformylation condition to form the ARBCs Rh-[1·H]X. The
advantages of the ARBCs are as follows. (1) The ammonium
30 salts [1·H]X can be easily prepared and can be either isolated and
added separately or used directly. There is no need to add other
acid co-catalysts, which makes the reaction greener. (2) The
ARBCs embed both the Rh active site that catalyzes the
hydroformylation and the acidic active site that catalyzes the
efficiency. In comparison, the zwitterionic ligand
1 and
triphenylphosphine (PPh3) are exmined under identical conditions.
It can be seen that Rh-1 and Rh-PPh3 have similar catalytic
60 behavior (Table 1, entries
4 and 5), both giving high
hydroformylation efficiency but essentially no catalytic activity
for the acetalization reaction. This demonstrates that the glycine
side chain of the internal salt 1 does not possess an effective
acidic active site that can provide adequate concentration of H+ to
2
| Green Chem., 2013, [vol], 00–00
This journal is © The Royal Society of Chemistry 2013

Green Chemistry
Page 4 of 7
View Article Online
DOI: 10.1039/C3GC41231H
Table 2 One-pot hydroformylation-acetalization of different alkenes using Rh-
[1·H][BF4] in [bmim][BF4]/alcohols systems.a
[bmim]X/MeOH systems (Table 1, entries 9–11), only
a
moderate amount of acetal can be obtained with the highest
acetalization efficiency being only 51%, which is due to the
35 presence of minor amount of acidic impurities in the ILs. Besides,
ICP analysis shows that significant amount of Rh is leached from
the ILs into the extraction phase.
Conver.
(%)
Soxo
(%)
Eace
(%)
Entry Alkene
Main product
l : b
OMe
OMe
OEt
5
5
1
2
99
98
97
84
95
91
75:25
74:26
5
5
The above results demonstrate that the ligand 1 with weak
charge does not have strong electrostatic interaction with the ILs
40 and thus cannot effectively immobilize Rh in the ILs. In contrast,
the ammonium salts ([1·H]X) of 1 are strongly charged, which
results in the strong electrostatic attraction between the ARBCs
and the ILs. In particlar, the same X− anion in Rh-[1·H]X and
[bmim]X further increases the affinity between the ARBCs and
45 the ILs and significantly reduces Rh loss.
OEt
O
5
5
7
3
99
99
99
99
94
97
90
88
96
99
93
91
76:24
77:23
70:30
70:30
5
5
7
9
O
O
4
O
To explore the scope of the reaction, different alcohols were
used for the hydroformylation-acetalization of 1-octene with Rh-
[1·H][BF4] in [bmim][BF4]/alcohols (Table 2, entries 1–4), in
which the alcohols mainly serve as the reactant. In certain cases
50 (e.g., Table 2, entries 5, 6 and 8) where a large excess of alcohol
is used, the alcohol also serves as the solvent. Besides methanol,
we have especially focused on ethanol, ethylene glycol, and 1,2-
propanediol. Using ethanol results in lower acetalization
efficiency than using methanol, while using ethylene glycol and
55 1,2-propanediol results in higher acetalization efficiency of 96%
and 99%, which is in agreement with literature report.5i These
acetalization reactions have important applications in chemical
synthesis. For example, the diethyl and cyclic acetals of nonanal
are important perfumes.
OMe
5 b
OMe
OMe
6 c
9
OMe
OMe
MeO
7
100
63
99
99
99
95
8:92
8:92
MeO OMe
8 d
a
The reaction conditions are the same as in Table 1; 1/HBF4 = 1/1, 1/Rh =
10, alkenes/Rh = 1000, 1 g [bmim][BF4], 3 mL methanol, 5 mL ethanol, 0.5
b
mL glycol, 0.5 mL 1,2-propanediol. 6 mL methanol, n-octane as internal
standard. c 11 mL methanol, n-decane as internal standard. d 10 mL methanol,
60
The scope of the reaction was also evaluated by using different
1-alkenes in the [bmim][BF4]/MeOH system (Table 2, entries 5–
8). For linear 1-alkenes, the conversion is always very high, and
the selectivity for oxo products and the acetalization efficiency
decrease slightly from 1-octene to 1-dodecene, but the
n-decane as internal standard.
5
catalyze the acetalization reaction.
In our opinion, the addition of one equivalent of Brønsted acid
allows the formation of a carboxylic acid from the protonation of
the carboxylate group of the internal salt 1. This carboxylic acid
is the true acidic active site for catalyzing acetalization, since the
65 acetalization efficiency is still always higher than 90%. In
contrast, 100% conversion, 99% oxo products selectivity and
99% acetalization efficiency are obtained for styrene with
excellent regioselectivity (92%) toward the branched acetal. The
conversion of 2-vinylnaphthalene is low (63%) mainly due to its
70 low solubility in MeOH, but the oxo products selectivity,
acetalization efficiency and regioselectivity are still at high levels.
GC and GC/MS analyses show that, in all reactions, except for
the water generated from the acetalization reaction, other minor
byproducts include aldehydes (linear aldehydes and branched
75 aldehydes), alkene hydrogenation product (<1%), as well as
isomerized alkenes (2-alkenes and 3-alkenes) and their
corresponding aldehydes and acetals from hydroformylation-
acetalization.
10 carboxylic acid moeity is more acidic than the ammonium
functional group. Pneumatikakis et al.5p reported
a
hydroformylation-acetalization promoted by a Rh/thioamino acid
system, in which the thioamino acid is generated in situ under
hydroformylation condition. Nevertheless, the tandem
15 hydroformylation-acetalization of olefins using bifunctional
catalysts containing both glycine and Rh remains unprecedented.
Subsequently, we selected the most commonly used IL
[bmim]X (X− = [BF4]−, [PF6]− and [Tf2N]−) as the catalyst carrier
to evaluate the catalytic and immobilization efficiency of ARBCs
20 (Rh-[1·H]X) in the [bmim]X/MeOH systems (Table 1, entries 6–
8). It can be seen that both the hydroformylation efficiency and
the acetalization efficiency of Rh-[1·H]X in [bmim]X/MeOH are
comparably high to those in MeOH alone. To evaluate the
immobilization efficiency of ARBCs in ILs, methanol was
25 removed by vacuum evaporation and the products were extracted
with n-heptane, and the Rh loss to the n-heptane phase was
analyzed by ICP-AES. The results show that Rh-[1·H]X can be
effectively immobilized in [bmim]X and the Rh losses are all less
than 1%. In particular, [bmim][BF4] shows the best
30 immobilization effect for Rh-[1·H][BF4] with only 0.03% Rh loss.
In contrast, when using Rh-1 as the catalyst in the
To investigate the recycling and service life of the ARBCs in
80 the IL/alcohol systems, the phase behavior and miscibility of the
IL/alcohol/1-alkene systems were first characterized (see
supporting information). The investigation focused particularly
on the [bmim][BF4]/MeOH (or EtOH)/1-alkenes (1-octene, 1-
decene or 1-dodecene) and [bmim][BF4]/diols (ethylene glycol or
85 1,2-propanediol)/1-octene systems. The results show that
[bmim][BF4] and 1-alkenes are both readily soluble in MeOH or
EtOH, but [bmim][BF4] and 1-alkenes are not miscible.
Therefore, the mixture of [bmim][BF4], 1-alkenes and MeOH (or
EtOH) at an appropriate ratio and above a certain temperature can
This journal is © The Royal Society of Chemistry 2013
Green Chem., 2013, [vol], 00–00 | 3

Page 5 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C3GC41231H
become a homogeneous system. The miscibility determinations
model catalyst and the hydroformylation-acetalization of 1-
octene in [bmim][BF4]/MeOH and [bmim][BF4]/1,2-propanediol
as model reaction systems. In [bmim][BF4]/MeOH system (Fig. 1,
were carried out by cloud titration method according to literature
report.10 The system with fixed amount of IL, 1-alkene and
internal standard was maintained at a fixed temperature (T), and 40 A), by adjusting the temperature and the ratio between
5
the minimum amount of alcohol (MeOH or EtOH) to make the
system miscible is measured by dropwise addition. It was also
noted that when the system became miscible, the system would
become biphasic again when the temperature dropped below T
[bmim][BF4], 1-octene and MeOH, the hydroformylation-
acetalization can proceed in the homogeneous system. After
completing the reaction and cooling to room temperature, the
reaction system remains homogeneous. The volatile methanol
and return to homogeneous when the temperature came back to T 45 and the water generated from acetalization can be readily
10 or exceeded T. Further studies showed that the introduction of
minor amount of ligand and Rh had no influence on the phase
behavior and miscibility of the system.
The biphasic hydroformylation of alkene in IL6 and the
biphasic hydroformylation-acetalization of 1-hexene in ethylene
15 glycol5b have been confirmed by literature reports. For our
[bmim][BF4]/diols (ethylene glycol or 1,2-propanediol)/1-octene
systems, because [bmim][BF4] and the diols (ethylene glycol or
1,2-propanediol) are completely miscible whereas 1-octene is not
removed under reduced pressure, and the acetal product is
extracted with n-heptane and separated from the IL phase by
decanting. The [bmim][BF4] phase in the bottom layer containing
the ARBC is separated and carried through the next cycle. In the
50 [bmim][BF4]/1,2-propanediol system (Fig. 1, B), the
hydroformylation-acetalization proceeds in the biphasic system
consisting of a [bmim][BF4]/1,2-propanediol phase dissolving the
ARBC and an 1-octene phase. After completing the reaction and
cooling to room temperature, the product acetal is extracted with
miscible with [bmim][BF4] and diols (ethylene glycol or 1,2- 55 n-heptane and water is removed in vacuo. The [bmim][BF4]/1,2-
20 propanediol) from room temperature up to the hydroformylation
reaction temperature (80–120 °C), the mixture of [bmim][BF4],
diols (ethylene glycol or 1,2-propanediol) and 1-octene can form
a biphasic reaction system. The cloud titration indicated that the
system is biphasic throughout from room temperature to reaction
25 temperature.
propanediol phase in the bottom layer is carried through the next
cycle after 1,2-propanediol is replenished.
Table 3 Recycling and reuse of the Rh-[1·H][BF4] catalyst for the tandem
hydroformylation-acetalization of 1-octene in [bmim][BF4]/alcohols a
Conver. Soxo
Eace
(%)
Rh loss
(%)
Alcohol
Run
l : b
n-Heptane
H2/CO
MeOH
(%)
(%)
methanol
1
2
99
99
99
98
97
97
98
99
98
98
98
98
97
82
72
97
97
96
94
94
95
82
97
95
94
94
92
90
83
81
95
98
96
97
97
97
94
99
98
99
99
99
99
98
98
75:25
74:26
75:25
75:25
74:26
74:26
73:27
77:23
75:25
75:25
74:26
75:25
74:26
74:26
75:25
0.03
—
One-Phase Catalysis
Seperation
OMe
4
0.05
—
80°C
H2/CO
20°C
5
6
OMe
A
8
0.06
—
n-Heptane
5
10
12
1
H2O
Rh-[1·H][BF4]
Rh-[1·H][BF4]
[bmim][BF4]
—
[bmim][BF4]/MeOH
1,2-propanediol
0.08
—
3
n-Heptane/Acetal
5
—
1-Octene/MeOH
H2/CO
H2O
7
0.07
—
9
n-Heptane
12
15
17
0.1
—
Two-Phase Catalysis
Seperation
—
a The reaction conditions are the same as in Table 1, 1/HBF4=1/1, 1/Rh = 10,
H2/CO
80°C
20°C
O
5
O
n-Heptane
1-octene/Rh=1000,
propanediol.
1 g [bmim][BF4], 3 mL methanol, 0.5 mL 1,2-
5
B
H2O
Rh-[1·H][BF4]
Rh-[1·H][BF4]
60
[bmim][BF4]
1,2-Propanediol
[bmim][BF4]
1,2-Propanediol
Table 3 shows the recycling experimental results of Rh-
[1·H][BF4] in both systems (Fig. 1, A and B). Both catalytic
systems exhibit high catalytic efficiency and long service life of
n-Heptane/Acetal
H2O
1-Octene/1,2-Propanediol
65 catalyst, with no significant deterioration in conversion, oxo
products selectivity, acetalization efficiency or Rh loss for more
than twelve and seventeen cycles, respectively. This result for the
tandem hydroformylation-acetalization is thus far unparalleled in
published literature. The high hydroformylation-acetalization
70 efficiency and long service life of ARBC can be attributed to the
structural motif of ARBC and efficient recycling strategy. The
synergy between the acidic active site and the Rh active site on
the ARBC ensures that the aldehyde formed at the Rh active site
Fig. 1 The separation and recycling diagram of ARBC in [bmim][BF4]/alcohol
30 systems for the hydroformylation-acetalization of 1-octene (A: one-phase
catalysis in [bmim][BF4]/MeOH; B: two-phase catalysis in [bmim][BF4]/1,2-
propanediol).
Based on the phase behavior and miscibility of the
35 hydroformylation-acetalization systems, the separation and
recycling of ARBC are shown in Fig. 1 using Rh-[1·H][BF4] as
4
| Green Chem., 2013, [vol], 00–00
This journal is © The Royal Society of Chemistry 2013

Green Chemistry
Page 6 of 7
View Article Online
DOI: 10.1039/C3GC41231H
can be rapidly transformed into acetal by the acidic active site on
the glycine side chain in each catalytic cycle. Because the ARBC
embed both the Rh active site and the acidic active site, catalyst
recycling is significantly improved. Most importantly, the
ammonium salt structure strongly enhances the affinity between
ARBC and IL, which ensures very low Rh loss (0.03%–0.1%)
and increases the stability and reusability of ARBC in ILs, thus
extending the service life of ARBC.
55 One-phase hydroformylation-acetalization of 1-octene using
acid-Rh bifunctional catalyst Rh-[1·H]X (X- = [BF4]-, [PF6]- or
[Tf2N]-) in MeOH
In a typical experiment, under an argon atmosphere, ligands 1
(3.87×10−2 mmol) was dissolved in 3 mL of degassed MeOH.
60 The equimolar HPF6 (60% aq.), HBF4 (40% aq.) or Tf2NH was
added. The solution was allowed to stir for 60 min at 50°C to
give the ammonium salts [1•H]X (X- = [PF6]-, [BF4]- or [Tf2N]-).
The ammonium salts can be isolated or used immediately for the
hydroformylation-acetalization. 1-octene (0.6 mL, 3.82 mmol),
65 internal standard (cyclohexane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg,
3.87×10−3 mmol) and the preceding ammonium salts ([1·H]X) of
1 in 3 mL MeOH were placed in a 60 mL stainless steel
autoclave. Then the reactor was pressurized with syngas to 5.0
MPa, and the reaction system was heated to 80°C. After 2 h the
70 autoclave was rapidly cooled with ice, and the conversion and
selectivity were analysed by GC.
5
Conclusion
10 In conclusion,
a highly effective and long-life one-pot
hydroformylation-acetalization catalytic system has been
established based on Brønsted acid-Rh bifunctional catalysts and
ILs. In the IL/alcohol systems, the ARBCs showed excellent
hydroformylation and acetalization efficiency for a wide scope of
15 olefins and alcohols. We believe that the high catalytic efficiency
mainly relies on the synergy between the acidic active site and
the Rh active site on the ARBCs. The analysis of Rh loss and
catalyst recycling experiments showed that ARBCs have strong
affinity with IL and can be effectively immobilized in IL, which
20 significantly improved the stability and reusability of ARBCs
during long-term catalytic cycles. No significant loss of catalytic
efficiency or Rh was observed for more than twelve and
seventeen cycles when reacting with MeOH and 1,2-propanediol,
respectively.
One-phase hydroformylation-acetalization of 1-octene using
acid-Rh bifunctional catalyst Rh-[1·H]X in [bmim]X/MeOH
(X- =[ BF4]-, [PF6]- or [Tf2N]-)
75 In a typical experiment, 1-octene (0.6 mL, 3.82 mmol), internal
standard (cyclohexane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg,
3.87×10−3 mmol), [bmim]X (1.0 g) and the preceding ammonium
salts ([1·H]X) of 1 in 3 mL MeOH were placed in a 60 mL
stainless steel autoclave. Then the reactor was pressurized with
80 syngas to 5.0 MPa, and the reaction system was heated to 80°C.
After 2 h the autoclave was rapidly cooled with ice, and the
conversion and selectivity were analysed by GC. Subsequently,
the MeOH and generated water were removed in vacuo and the
top product layer was separated by extracting with n-heptane (3
85 mL). New 1-octene and methanol were added into the IL for next
catalytic recycling.
25 Experimental
General
The linear 1-alkenes, styrene and 2-vinylnaphthalene were
purchased from Acros company. The rhodium catalysts precursor
Rh(acac)(CO)2 was purchased from ABCR company. 1-Butyl-3-
30 methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazol-
ium hexafluorophosphate and 1-butyl-3-methylimidazolium bis
[(trifluoromethyl)sulfonyl]imide were obtained commercially
from Shanghai Chengjie Chemical Co., and all ILs contained
<0.2 wt % water and <150 ppm halide. The alcohols, HBF4 (40%
35 aq.), HPF6 (60% aq.) and Tf2NH were obtained from commercial
sources. The 4-(diphenyl-phosphino)-DL-phenylglycine (1) was
synthesized by a published method.7 The hydroformylation-
acetalization was carried out in a 60 ml homemade stainless steel
autoclave with Teflon lining and magnetic stirring under an argon
40 atmosphere using standard Schlenk techniques. The solvents and
reagents were rigorously deoxygenated prior to use. The products
of hydroformylation-acetalization were analyzed by GC
technique (OV-101 capillary column, FID detector). The
conversion and selectivity were determined by GC using
45 cyclohexane (for 1-octene and styrene), n-octane (for 1-decene)
or n-decane (for 1-dodecene and 2-vinylnaphthalene) as internal
standards. The column temperature is maintained at 80°C for 2
min, then is raised to 200°C by a programming rate of 6°C/min
and maintained at 200°C for 20 min.The products have been
50 identified by GC-MS (Agilent 6890/5973 GC-MS apparatus with
a DB-35MS capillary column) and by comparison of their GC
retention times with those of reference samples. ICP-AES was
made with an IRIS Istrepid II XSP apparatus for determining the
loss of Rh.
Two-phase hydroformylation-acetalization of 1-octene using
acid-Rh bifunctional catalyst Rh-[1·H][BF4] in
[bmim][BF4]/1,2-propanediol
90 In a typical experiment, under an argon atmosphere, 1-octene (0.6
mL, 3.82 mmol), internal standard (cyclohexane, 0.1 mL),
Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol), [bmim][BF4] (1.0 g),
1,2-propanediol (0.5 mL), ligands 1 (3.87×10−2 mmol) and
equimolar HBF4 (40% aq.) were placed in a 60 mL stainless steel
95 autoclave. The reactor was pressurized with CO/H2 (1:1) to 5.0
MPa, and the reaction system was stirred at 80°C ([1·H][BF4]
here was generated in situ for use). After 2h the system was
rapidly cooled on ice. The top product was extracted with 3 mL
n-heptane under atmospheric condition. The water was removed
100 under reduced pressure. The new 1-octene and replenished 1,2-
propanediol (0.3 mL) were added into the [bmim][BF4] for next
recycling.
One-phase hydroformylation-acetalization of 1-decene using
acid-Rh bifunctional catalyst Rh-[1·H][BF4] in [bmim][BF4]/
105 MeOH
The 1-decene (0.72 mL, 3.80 mmol), internal standard (n-octane,
0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol), [bmim][BF4]
This journal is © The Royal Society of Chemistry 2013
Green Chem., 2013, [vol], 00–00 | 5

Page 7 of 7
Green Chemistry
View Article Online
DOI: 10.1039/C3GC41231H
(1.0 g) and ammonium salts ([1·H][BF4]) of 1 (3.87×10−2 mmol)
(3.87×10−2 mmol) and equimolar HBF4 (40% aq.) were combined
in a 60 mL stainless steel autoclave in a procedure identical to
that given for 1,2-propanediol. The conversion and selectivity
55 were analysed by GC.
in 6 mL MeOH were combined in a 60 mL stainless steel
autoclave in a procedure identical to that given for 1-octene in
[bmim]X/MeOH system with Rh-[1·H]X. The conversion and
selectivity were analysed by GC.
5
Acknowledgements
One-phase hydroformylation-acetalization of 1-dodecene
using acid-Rh bifunctional catalyst Rh-[1·H][BF4] in
[bmim][BF4]/MeOH
We gratefully thank the financial support from National Natural
Science Foundation of China (Nos. 20606019 and 20976086), the
Foundation of Key Laboratory of Oil & Gas Fine Chemicals,
60 Ministry of Education, China (No. XJDX0908-2010-01) and the
Natural Science Foundation of Qingdao, China (No. 12-1-4-3-
(6)-jch).
The 1-dodecene (0.85 mL, 3.83 mmol), internal standard (n-
10 decane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol),
[bmim][BF4] (1.0 g) and ammonium salts ([1·H][BF4]) of 1
(3.87×10−2 mmol) in 11 mL MeOH were combined in a 60 mL
stainless steel autoclave in a procedure identical to that given for
1-octene in [bmim]X/MeOH system with Rh-[1·H]X. The
15 conversion and selectivity were analysed by GC.
Notes and references
a
College of Chemical Engineering, Qingdao University of Science and
65 Technology, Qingdao 266042, China. Fax: +86-532-84022719; Tel: +86-
532-84022719; E-mail: jinx1971@163.com (X. Jin).
b Key Laboratory of Oil & Gas Fine Chemicals of Ministry of Education,
Xinjiang University, Wulumuqi 830046, China.
One-phase hydroformylation-acetalization of styrene using
acid-Rh bifunctional catalyst Rh-[1·H][BF4] in [bmim][BF4]/
MeOH
70
1
2
C. D. Frohning and C. W. Kohlpainter, in Applied Homogeneous
Catalysis with Organometallic Compounds, ed. B. Cornils and W. A.
Herrmann, Wiley-VCH, Weinheim, 1st edn, 1996, p. 29.
The styrene (0.45 mL, 3.93 mmol), internal standard
20 (cyclohexane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol),
[bmim][BF4] (1.0 g) and ammonium salts ([1·H][BF4]) of 1
(3.87×10−2 mmol) in 3 mL MeOH were combined in a 60 mL
stainless steel autoclave in a procedure identical to that given for
1-octene in [bmim]X/MeOH system with Rh-[1·H]X. The
25 conversion and selectivity were analysed by GC.
(a) M. J. Climent, A. Corma and S. Lborra, Chem.Rev., 2011, 111,
1072; (b) J. C. Wasilke, S. J. Obrey, R. T. Baker and G. C. Bazan,
Chem. Rev., 2005, 105, 1001; (c) E. N. dos Santos, D. Fogg, Coord.
Chem. Rev., 2004, 248, 2365.
75
3
4
S. Patai, The Chemistry of the Carbonyl Group, Wiley-Interscience,
New York, 1966, 1970.
P. Eilbracht, L. Bärfacker, C. Buss, C. Hollmann, B. E. Kitsos-
Rzychon, C. L. Kranemann, T. Rische, R. Roggenbuck and A.
Schmidt, Chem. Rev., 1999, 99, 3329.
80
One-phase hydroformylation-acetalization of 2-vinylnaphth-
alene using acid-Rh bifunctional catalyst Rh-[1·H][BF4] in
[bmim][BF4]/MeOH
5
(a) A. W. S. Currie and J. A. M. Andersen, Catal. Lett., 1997, 44,
109; (b) N. S. Nair, B. M. Bhanage, R. M. Deshpande and R. V.
Choudhari, Rec. Adv. Basic Appl. Aspects Indust. Catal., 1998, 113,
529; (c) R. Roggenbuck, A. Schmidt and P Eilbracht, Org. Lett.,
2002, 4, 289; (d) F. Hung-Low, G. C. Uzcátegui, J. Alvarez, M. C.
Ortega and A. J. Pardey, React. Kinet. & Cat. Lett., 2006, 88, 143; (e)
A. J. Pardey, G. C. Uzcátegui, F. Hung-Low, A. B. Rivas, J. E.
Yánez, M. C. Ortega, C. Longo, P. Aguirre and S. A. Moya, J. Mol.
Catal. A, 2005, 239, 205; (f) C. G. Vieira, J. G. da Silva, C. A. A.
Penna, E. N. dos Santos and E. V. Gusevskaya, Appl. Catal. A, 2010,
380, 125; (g) B. El Ali, J. Tijani, M. Fettouhi, J. Mol. Catal. A, 2005,
230, 9; (h) B. El Ali, J. Tijani and M. Fettouhi, Appl. Catal. A, 2006,
303, 213; (i) O. Diebolt, C. Cruzeuil, C. Müller and D. Vogt, Adv.
Synth. Catal., 2012, 354, 670; (j) A. Cabrera, A. Mortreux and F.
Petit, J. Mol. Catal., 1988, 47, 11; (k) J. Balue and J. C. Bayon, J.
Mol. Catal. A, 1999, 137, 193; (l) M. M. Diwakar, R. M. Deshpande
and R. V. Chaudhari, J. Mol. Catal. A, 2005, 232, 179; (m) G.
Parrinello and J. K. Stille, J. Am. Chem. Soc., 1987, 109, 7122; (n) J.
K. Stille, H. Su, P. Brechot, G. Parrinello and L. S. Hegedus,
Organometallics, 1991, 10, 1183; (o) E. Fernández and S. Castillón,
Tetrahedron Lett., 1994, 35, 2361; (p) K. Soulantica, S. Sirol, S.
Koïnis, G. Pneumatikakis and Ph. Kalck, J. Organomet. Chem., 1995,
498, C10; (q) E. Fernández, A. Ruiz, C. Claver, S. Castillón and A.
Pólo, Chem. Commun., 1998, 1803;
85
The 2-vinylnaphthalene (0.6 g, 3.89 mmol), internal standard (n-
30 decane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol),
[bmim][BF4] (1.0 g) and ammonium salts ([1·H][BF4]) of 1
(3.87×10−2 mmol) in 10 mL MeOH were combined in a 60 mL
stainless steel autoclave in a procedure identical to that given for
1-octene in [bmim]X/MeOH system with Rh-[1·H]X. The
35 conversion and selectivity were analysed by GC.
90
95
One-phase hydroformylation-acetalization of 1-octene using
acid-Rh bifunctional catalyst Rh-[1·H][BF4] in [bmim][BF4]/
EtOH
The 1-octene (0.6 mL, 3.82 mmol), internal standard
40 (cyclohexane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol),
[bmim][BF4] (1.0 g) and ammonium salts ([1·H][BF4]) of 1
(3.87×10−2 mmol) in 5 mL EtOH were combined in a 60 mL
stainless steel autoclave in a procedure identical to that given for
1-octene in [bmim]X/MeOH system with Rh-[1·H]X. The
45 conversion and selectivity were analysed by GC.
100
105
110
6
7
M. Haumann and A. Riisager, Chem. Rev., 2008, 108, 1474.
D. J. Brauer, S. Schenk, S. Roßenbach, M. Tepper, O. Stelzer, T.
Hausler and W. S. Sheldrick, J. Organomet. Chem., 2000, 598, 116.
(a) T. W. Greene, P. G. M. Wuts, Protective Groups in Organic
Synthesis, John Wiley & Sons Inc., New York, 2nd edn.,1991, p. 175;
(b) F. A. J. Meskens, Synthesis, 1981, 501.
8
Two-phase hydroformylation-acetalization of 1-octene using
acid-Rh bifunctional catalyst Rh-[1·H][BF4] in [bmim][BF4]/
ethylene glycol
9
X. Jin, K.Zhao, Q. Liu, F. Cui and F. Kong, in preparation, 2013.
10 A. Behr, G. Henze, D. Obst and B. Turkowski, Green Chem., 2005,
7, 645.
The 1-octene (0.6 mL, 3.82 mmol), internal standard
50 (cyclohexane, 0.1 mL), Rh(acac)(CO)2 (1.0 mg, 3.87×10−3 mmol),
[bmim][BF4] (1.0 g), ethylene glycol (0.5 mL), ligands 1
6
| Green Chem., 2013, [vol], 00–00
This journal is © The Royal Society of Chemistry 2013