Co-catalysis of a bi-functional ligand containing phosphine and Lewis acidic phosphonium for hydroformylation-acetalization of olefins

Article abstract of DOI:10.1039/c5gc02127h

A novel ionic bi-functional ligand of L2 containing a phosphine and a Lewis acidic phosphonium with I^- as the counter-anion was prepared and fully characterized. The molecular structure indicated that the bi-functionalities in L2 were well retained without the incompatibility problem for quenching of the acidity of the phosphonium cation by the Lewis basic phosphine fragment or the anionic I^- when the incorporated phosphine fragment and the Lewis acidic phosphonium were strictly located in the confined cis-positions. The co-catalysis over L2-Rh(acac)(CO)₂ in the ways of synergetic catalysis and sequential catalysis was successfully fulfilled for one-pot hydroformylation-acetalization, which proved not to be the result of the simple mixture of the mono-phosphine (L4) and the phosphonium salt (L4′). In L2, the phosphonium not only acted as a Lewis acid organocatalyst to drive the sequential acetalization of aldehydes, but also contributed to the synergetic catalysis for the preceding hydroformylation through stabilizing the Rh-acyl intermediate with the phosphine cooperatively. The L2-Rh(acac)(CO)₂ system is also generally applied to hydroformylation-acetalization of a wide range of olefins in different alcohols. Advantageously, as an ionic phosphonium-based ligand, L2 could be recycled for 7 runs with Rh(acac)(CO)₂ together in RTIL of [Bmim]BF₄ without obvious activity loss or metal leaching.

Full text of DOI:10.1039/c5gc02127h

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Co-catalysis of a bi-functional ligand containing phosphine and
Lewis acidic phosphonium for hydroformylation-acetalization of
olefins
Received 00th January 20xx,
Accepted 00th January 20xx
Yong-Qi Lia, Peng Wanga, Huan Liua, Yong Lua, Xiao-Li Zhaoa and Ye Liua†
DOI: 10.1039/x0xx00000x
A novel ionic bi-functional ligand of L2 containing the phosphine and the Lewis acidic phosphonium with I- as the counter-
anion was prepared and fully characterized. The molecular structure indicated that the bi-functionalities in L2 were well
retained without incompatibility problem for the quenching of the acidity of phosphonium cation by the Lewis basic
phosphine fragment or the anionic I- when the incorporated phosphine fragment and the Lewis acidic phosphonium were
strictly located in the confined cis-positions. The co-catalysis over L2-Rh(acac)(CO)2 in the ways of synergetic catalysis and
sequential catalysis was successfully fulfilled for one-pot hydroformylation-acetalization, which proved not to be the result
of the simple mixture of the mono-phosphine (L4) and the phosphonium salt (L4’). In L2, the phosphonium not only acted
as a Lewis acid organocatalyst to drive the sequential acetalization of aldehydes, but also contributed to the synergetic
catalysis for the preceding hydroformylation through stabilizing the Rh-acyl intermediate with the phosphine
cooperatively. L2-Rh(acac)(CO)2 system was also generally applied to hydroformylation-acetalization of a wide range of
olefins in the different alcohols. Advantageously, as an ionic phosphonium-based ligand, L2 could be recycled for 7 runs
with Rh(acac)(CO)2 together in RTIL of [Bmim]BF4 without obvious activity loss or metal leaching.
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the latter as the intermediates are sequentially activated by
Lewis acid or Brønsted acid catalysts to produce acetals2,3,6-9
.
Introduction
Co-catalysis in combination of transition metal catalysis with
organocatalysis in the different ways of synergetic catalysis,
cooperative catalysis, and sequential catalysis has been
Rh-catalyzed hydroformylation is one of the most important
methods for the production of aldehydes from olefins. In
practice, aldehydes are needed to be further transformed into
alcohols, acetals, esters, amines, and many more1. Based on the
principles of atom economy and low energy consumption in
green chemistry, hydroformylation of olefins are required to be
combined with other organic reactions (such as hydrogenation,
Aldol reaction, acetalization, Mannich reaction etc.) to form
tandem reaction sequences that can be achieved under
hydroformylation conditions2,3. Hydroformylation followed by
acetalization in the presence of alcohols is an important one-
pot process for the formation of acetals, which can be used to
protect sensitive aldehyde group against side reactions or as
ingredients in fragrances, domestics, and detergents3,4. The
formation of acetals under hydroformylation conditions can be
promoted by the presence of the auxiliaries such as zeolites
support that can provide the acidic sites2a,5. The tandem
emerged as
transformations that cannot be achieved by each individual one
independently10d
Various organocatalysts such as
a powerful strategy to promote organic
.
Lewis/Brønsted acid catalysts, amine/enamine catalysts, phase
transfer catalysts and N-heterocyclic carbene catalysts have
been exploited in physical combination with transition metal
catalysts2,10. In this field, bi-functional ligands in compatible
combination of phosphines with organocatalysts by
intramolecular stable chemical bonds have unique advantages
because of the inherent coordination ability of phosphines to
transition metals (which corresponds to transition metal
catalysis) and the synergetic effect coming from the
intramolecular organocatalysts11-14
.
In practice, many examples have proved that phosphonium
[P(V)+] cations are typical Lewis acid organocatalysts15 which
can catalyze many reactions such as isomerization of olefins,
cationic polymerization, and hydrosilation of olefins and
acetylene without involvement of any metal16, as well to exhibit
activities towards C=O bond activation, such as in
cyanosilylation of ketones17, Baylis-Hillman reaction18, and Aldol
and Micheal reactions of carbonyl compounds19.
hydroformylation-acetalization is usually regarded as
a
sequential catalysis, which means that phosphine-ligated Rh-
catalyst activate the substrates of olefins producing aldehydes,
a.Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of
Chemistry and Molecular Engineering, East China Normal University, 3663 North
Zhongshan Road, Shanghai 200062, P.R. China.
† Correspondence author. Email: yliu@chem.ecnu.edu.cn
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Highlighted by the significant role of phosphines [P(III)] to
odulate the efficiency of Rh-catalyzed hydroformylation, as
m
well as the character of phosphoniums [P(V)+] as the Lewis
acidic organocatalysts to activate C=O bond, it was believed
that co-catalysis over bi-functional ligands in combination of
phosphines with Lewis acidic phosphoniums would be a
promising method for CO-participated hydroformylation and
the tandem acetalization if the elegant strategy is applied to
avoid incompatibility problem for the quenching of the Lewis
acidity of the phosphoniums by the Lewis bases of phosphines.
Hence, an ionic bi-functional ligand of L2 was synthesized
herein for the first time, in which the incorporated phosphine
fragment and phosphonium cation were linked by the stable
chemical bonds without interference. For comparison, the
phosphonium-free phosphines of L1, L3 and L4 were prepared
in parallel according to our previously reported method20,21
.
The present protocol provides a novel methodology for co-
catalysis of hydrformylation-acetalization in the ways of
synergetic catalysis and sequential catalysis, which means that,
in bi-functional ligand L2, the incorporated Lewis acidic
phosphonium contributes to the synergetic catalysis for
hydroformylation through stabilizing the Rh-acyl intermediate
with the phosphine cooperatively, as well as to sequential
catalysis for acetalization of aldehydes.
Me
PPh2
N
Ph2+P
I-
N
N
N
=
P
P+
MeI
Ph2
P
N
PPh2
N
P(V)+ Lewis acid
L2
N
N
PPh2
MeOTf
Me
N+
Me
N+
L1
2OTf-
N
N
Fig. 1 The single crystal structures of L1-L3 (The hydrogen atoms are omitted for
clarity)
PPh2
L3
OR'
OR'
acetals
R'O
R'
OR'
CHO
CO/H2
Rh(acac)(CO)2 / L2
R'OH
CHO
+
The molecular structures of L121 L2 and L321 determined by
,
R
+
R
R
R'
aldehydes
the single crystals X-ray diffraction are depicted in Fig. 1. The
environment of the P(III)-atoms is close to tetrahedral
structures and shows no anomalies. In L2, the phosphine-
fragment and phosphonium-fragment are properly located in
cis-position relative to 1,3-diimidazolylphenyl backbone,
whereas in L2 the two phosphine-fragments are located in
Scheme 1 A bi-functional ligand of L2 in combination of phosphine with
phosphonium for co-catalysis of hydroformylation-acetalization
Results and discussion
distortioned cis-position with
θ
of 4.3 o between phenyl-planar
It was found that the quaternization of L1 by MeI could
selectively afford L2 due to the compatibility of the soft
electrophile of MeI to the soft nucleophile of phosphine
fragment22, whereas the quaternization of L1 by hard
electrophile of MeOTf could selectively afford L321. And L4 was
prepared in parallel according to the procedures reported by us
before21.
and imidazolyl-planar, and in L3 the two phosphine-fragments
are reversely located in trans-position due to the repulsive
interaction of the two positive-charged imidazolium rings.
Although the P(III)-atom in L2 is projecting inward towards the
P(V)+-atom, their distance [P(2)-P(1): 6.4584(26) Å] is
significantly longer than the sum of the van der Waals radii of P-
atoms (3.80~4.44 Å), indicating the negligible intramolecular
acid-base pair interaction between the Lewis basic phosphine-
fragment and the Lewis acidic phosphonium due to their
separation from each other by a bulky and rigid 1,3-
diimidazolylphenyl backbone. On the other hand, the counter-
anion of I- with relatively large atom radii is located far away
from phosphonium site, further indicating the negligible acid-
2 | J. Name., 2012, 00, 1-3
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base pair interaction between P(V)+ and I-. This structural catalytic system, while Pacetals (percentage of acetals in the total
information demonstrates that our strategy to develop the bi- oxo-products) was defined to evaluate the acetalization
functional ligand of L2 in combination of phosphine with Lewis efficiency of the acidic phosphonium site in L2
.
Lewis acidic phosphonium is successful without incompatibility
problem for the quenching of the acidity of the phosphonium
by the Lewis basic phosphine fragment or the anionic I-. It was
37.34
33.73
JSe-P = 729 Hz
Selenide of PPh
3
e
noted that in L2 the bond distances in P(V)+-C linkages
N
N
Ph
Se
(1.770~1.789
Å) are universally shorter than those of P(III)-C
P
17.30
Ph
21.03
23.58
22.02
JSe-P = 753 Hz
JSe-P = 782 Hz
ones, indicating the improved stability of L2 tailed with
phosphonium cation. Consistently, the 31P NMR spectra of L2
show two types of resonances at 11.7 (singlet) and -28.5
(singlet) ppm, which are attributed to the phosphonium (-
P+Ph2Me) and phosphine-fragment (-PPh2) respectively.
d
c
Selenide of L4
2OTf-
N+
Me
Me
N+
N
N
Ph
Se
Ph
Se
P
P
Ph
Ph
19.71
Selenide of L3
I-
N
N
N
N
Ph
Ph
Se
P+
Me
P
Ph
Ph
18.31
JSe-P = 749 Hz
b
a
Selenide of L2
N
θ
, and 31P NMR signals for L1-
N
Table 1 The selected bond distances, bond angles,
L3
N
N
Ph
Se
Ph
Se
P
P
20.96
Ph
Ph
17.24
JSe-P = 751 Hz
Selenide of L1
Bond distance/Ǻ
Ligand
31P NMR /ppm
−22.4
Cimi-P
CPh-P
40
30
20
10
0
-10
-20
-30
-40
L121
L2
1.826(3)
1.837(2)
1.834(3), 1.830(3)
1.835(3), 1.838(3)
Chemical shift (ppm)
Fig. 2 31P NMR spectra (202 MHz) of the selenides of L1-L4: a) reacting elemental
selenium with L1 in CDCl3 at 70 oC for 10 h; b) reacting elemental selenium with L2
in CDCl3 at 70 oC for 10 h; c) reacting elemental selenium with L3 in DMSO-d6 at 70
oC for 10 h; d) reacting elemental selenium with L4 in CDCl3 at 70 oC for 10 h; e)
reacting elemental selenium with PPh3 in CDCl3 at 70 oC for 10 h.
1.827(6)
1.820(6), 1.838(6)
-28.5 (-PPh2),
1.770(6) (P+) 1.774 (6) (P+), 1.784(6) (P+),
1.789(6) (P+)
11.7 (-P+Ph2Me)
L321
1.829(3)
1.836(3)
1.821(4), 1.829(3)
1.824(3), 1.824(3)
−20.6
Table 2 The homogeneous hydroformylation-acetalization of 1-octene with
Rh(acac)(CO)2 as the catalyst precursor in the presence of different ligands a
a θ is the interplanar dihedral angle.
CHO
CHO
CHO
CO/H2, MeOH
CHO
+
+
+
Rh(acac(CO)2 / Ligand
aldehydes
Acetalization
Side reaction
(Isomerization)
It is believed that the involved positive-charge with strong
electron-withdrawing effect would dramatically influence the
coordination ability of the peripheral phosphine fragments.
iso-octenes
H3CO
OCH3
+
H3CO
OCH3
H3CO
OCH3
OCH3
+
+
OCH3
acetals
Me
Ph2
P
Me
Ph2+P
Ph2+P
PPh2
PPh2
PPh2
Hence, the
π-acceptor ability of L1-L4 was evaluated by
Me
I-
N+
N
N
Me
PPh2
N
N
2OTf-
N+
N
measuring the magnitude of 1JP-Se in the 77Se isotopomer of the
corresponding phosphine-selenide in 31P NMR spectra (202
MHz) according to the method reported by Taylor et al.,
N
N
N
I-
N
N
N
N
N
N
PPh2
L1
L2
L3
L4
L4'
1
e
because an increase of JP-Se indicates an increase in the
character of π-acceptor ability (i.e., less σ
-donor ability)23. In
Entry
Additive
Conv.
(%)b
41
Soxo
(%)b,c
83
Pacetals
Siso-octenes
(%)b,c
17
L/Bd
TONoxo
(%)b,c
1
order to measure JP-Se, the selenide of the phosphine was
prepared by reacting the elemental selenium (with 7.63% 77Se)
with the corresponding phosphine in deuterated solvent under
the appointed conditions, which was then analyzed by a Bruker
1
2
3
4
5
6
7f
--
--
2.0
2.1
1.9
2.4
1.9
1.7
2.1
1.9
680
L1
64
88
2
12
1130
1710
1550
1400
780
L2
91
94
62
28
2
6
L3
86
90
10
Avance 500 spectrometer. As shown in Fig. 2, L3 is the
1
-acceptor with JP-Se of 782 Hz due to the most
L4
78
89
11
strongest
π
PPh3
L4/L4’
L2/TBAF
44
89
1
11
intensive electron-withdrawing effect of the positive-charged
imidazoliums on the neighbored P(III)-atoms, whereas L1 L2
-donor ability with JP-Se of
53
86
3
14
910
,
8g
88
90
2
10
1570
1
and L4 possess less and similar
π
~750 Hz which are much higher than that of PPh3 (1JP-Se =729
Rh(acac)(CO)2 0.0025 mmol, 1-octene 5.0 mmol (S/C=2000, Rh 0.05 mol%),
a
P/Rh=6:1 molar ratio (L1 or L3 0.0075 mmol; L2 or L4 0.015 mmol), CO/H2 (1:1)
b
c
4.0 MPa, MeOH 3 mL, 80 oC, reaction time 6 h; Determined by GC;
Soxo=(aldehydes+acetals)/(aldehydes+acetals+iso-octenes), Pacetals
=acetals/(aldehydes+acetals), percentage of acetals in the total oxo-products; Siso-
Hz).
The one-pot hydroformylation-acetalization of 1-octene in
MeOH was selected as a model reaction to investigate the co-
catalysis over L2 in comparison to those over the phosphine
d
octenes=iso-octenes/(aldehydes+acetals+iso-octenes);
L/B, the ratio of linear
e
nonanals and acetals to branched nonanals and acetals; TONoxo (turnover
number)=mol of oxo products⋅
(mol of Rh)-l; f 0.015 mmol of L4 and 0.015 of mmol
L4’ were mixed mechanically; g 0.015 mmol of TBAF was added additionally.
ligands of L1, L3, and L4 (Table 2). In Table 2, Conv. (conversion
of 1-octene) and Soxo [selectivity to the total oxo-products
including nonanals and dimethoxynonanes (acetals)] were
defined to evaluate the hydroformylation efficiency of the Rh-L
Under the mild reaction conditions (P/Rh=6, syngas 4.0 MPa,
6 h, 80 oC), the catalyst precursor of Rh(acac)(CO)2 itself
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exhibited the poor activity to hydroformylation with 41 % acidic phosphonium were retained intact to fulfil the synergetic
conversion of 1-octene and 83% selectivity to the oxo-products catalysis and sequential catalysis for hydroformylation-
without formation of any acetals (Entry 1). Comparatively, Rh- acetalization. On the other hand, the remote location of I-
L2 system exhibited the best activity towards hydroformylation counter-anion to the phosphonium cation in L2 indeed had no
with TON of 1710 for oxo-products, along with the good influence on the acidity of phosphonium and then the
acetalization efficiency (62%, Entry 3). In comparison, under the performance of L2
.
In addition, the use of TABI
L3, or L4 also confirmed
same conditions, Rh-L1, Rh-L3, Rh-L4 and Rh-PPh3 not only (tetrabutylammonium iodide) with L1
,
resulted in the poor catalytic activities for the acetalization due that the involved I- had no negative effect on the reactions (See
to the lack of the Lewis acidic phosphonium site, but also the data in S. Table 1 provided in ESI) Anyway, F- could badly
unexpectedly corresponded to the relatively lower quench the acidity of phosphonium due to the unique nature of
hydroformylation efficiency (Entries 2, 4-6). Although the
π
-
fluorophilicity for phosphoniums29-31. Hence, when L2 was
acceptor ligands involved Rh-catalysts have been reported to encountered with F- in TABF, the efficiency for acetalization as
be highly active for hydroformylation of olefins even like well as for hydroformylation was both decreased (Pacetasl=2%),
internal or branched ones24-28, it was noted herein that L3 (1JP- (Entry 8, TONoxo=1570).
Se=782 Hz) possessing the stronger
(1JP-Se=751 Hz) contrarily led to the lower hydroformylation
efficiency (Entry 3 vs 4). As for L1 which possessed the similar
π-acceptor ability than L2
Me
π
-
OR'
OR'
Sequential catalysis for
acetalization over P(V)+
PPh2 Ph2+P
N
I-
R
acceptor ability to L2 for the incorporated phosphine fragments
(1JP-Se~750 Hz), the tight chelation of L1 as a diphosphine ligand
to Rh-center (not facilitating the ligand dissociation to provide
the unsaturation site for the substrate insertion) and the lack of
Lewis acidic phosphonium site reasonably accounted for the
activity drop over L1 (Entry 2, TONoxo=1130). While L4, which
could be regarded as the separate phosphine fragment of L2
N
Acetals
P+
N
N
P+
P
=
Rh(acac)(CO)2
+
P
P(V)+ Lewis acid
CO/H2
L2
2R'OH
R
H
P+
P
O
R
Aldehydes
C
O
O
C
Rh
C
-CO
H
O
π ;
-acceptor ability (1JP-Se=753 Hz for L4 1JP-
Se=749 Hz for L2), was used to repeat the reaction, the
H2-heterolysis
with the similar
A
+P
P
P+
P
efficiency neither for hydroformylation nor acetalization could
Synergetic catalysis
O
C
R
C
O
O
Rh
O
C
Rh
C
for hydroformylation
over P(III)...P(V) +
H
reach the level over L2 (Entry 5). In contrast to L1-L4, the
-donor ability (1JP-Se=729
C
O
R
traditional PPh3 with the strongest
σ
B
D: Rh-acyl intermediate
Hz) led to the poorest activity in terms of hydroformylation and
acetalization (Entry 6, TONoxo= 784). In addition, when L2 was
replace by the mixture of L4 and L4’, which could be regarded
as the mechanical adduct of the independent phosphine and
phosphonium units in L2, the efficiency for hydroformylation-
acetalization over L4/L4’ was found to be decreased
dramatically only with 53% conversion of 1-octene and very
poor Pacetals of 3% (Entry 7). All these results indicated that the
combination of the phosphine fragment and phosphonium by
chemical bonds in L2 was not the result of the simple mixture of
(Stabilized transition state)
P+
P
CO
O
C
Rh
C O
CO
R
C
Scheme 2 Co-catalysis of bi-functional ligand of L2 containing phosphine and
Lewis acidic phosphonium [P(V)+] for hydroformylation-acetalization
The generality of L2-Rh(acac)(CO)2 as the catalyst for
hydroformylation-acetalization in different alcohols was
examined on different olefins (Table 3). Under the higher
the mono-phosphine of L4 and the phosphonium salt of L4’
.
The incorporated phosphonium not only contributed to the
sequential acetalization of nonanals, but also synergetically
promoted the hydroformylation through working together with
the cis-positioned phosphine fragment to cooperatively
o
reaction temperature of 120 C, the system of L2-Rh(acac)(CO)2
universally
exhibited
excellent
activities
towards
hydrofomylation of different olefins and good to excellent
performance for acetalization. The applied alcohols had the
obvious influence on the reaction rate of acetalization. Glycol
indeed gave more rise to acetalization than MeOH due to the
formation of thermodynamically stable five-member 1,3-
dioxolanyl ring (Entry 2 vs 1). However, the acetalization of
nonanals with t-BuOH was completely inhibited along with the
decreased hydroformylation efficiency due to bulky steric
hindrance and the possible solvent effect of t-BuOH (Entry 3 vs
1). The repeat of the reaction with styrene instead of 1-octene
also produced the desired oxo-products with the high yields of
95~98%, in which acetals were in percentage of 45-89%
depending on the structures of alcohols (Entries 4-7). It was
noted when styrene was used as the substrate, the
stabilize the Rh-acyl intermediate (D) by forming the bonding
interaction between P(V)+-atom and O atom (in C=O), which
facilitated the expedition of the rate controlling step of H2-
heterolysis from
D to A as proposed in Scheme 2.
It was obvious that in L2, there is no incompatibility problem
for quenching the acidity of phosphonium site by the Lewis
basic phosphine fragment when they are strictly located in the
proper cis-positions as shown in Fig. 1, whereas in the
mechanical mixture of L4 and L4’, the individual properties of
the phosphine fragment in L4 and the phosphonium site in L4’
could be quenched to some extent through the acid-base pair
interaction because of their free mobility. Consequently, the bi-
functionalities of L2 in combination of phosphine and Lewis
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regioselectivity to the branched oxo-products was more with glycol, the excellent hydroformylation was performed with
favoured due to the formation of a stable benzylic Rh-species 98% yield of oxo-products, in which only 42% was converted to
induced by the η2-electron donation from the benzene ring32,33
.
the acetalized products of 2-(tetrahydrofuran-2-yl)-1,3-
However, the more steric hindrance of propane-1,2-diol in dioxolane and 2-(tetrahydrofuran-3-yl)-1,3-dioxolane (Entry 8).
comparison to that glycol reasonably resulted in the sluggish Rationally, since the electron-richer tetrahydrofuranyl ring
reaction rate for acetalization of phenylpropanal and then the rendered the carbonyl group (C=O) less electrophilic, the
low yields of the corresponding acetals (Entry 6 vs 5). When nucleophilic attack of glycol to C-atom of C=O group was to be
glycerol was used, the higher Pacetals of 89% was obtained badly suppressed, leading to the decreased yields of acetals in
because of the predominant formation of the comparison to the acetalization of phenylpropanal with glycol
thermodynamically favoured six-member-ring dioxolane [75%; (Pacetals = 42 %, Entry 8 vs 5). As for the hydroformylation-
See ESI for the 1H NMR analysis of the mixed acetalized acetalization of cyclohexene with glycol, the sole acetalized
products of 2-phenethyl-1,3-dioxan-5-ol and (2-phenethyl-1,3- product of 2-cyclohexyl-1,3-dioxolane was obtained with the
dioxolan-4-yl)methanol] as another driving force for acetlization highest acetalization efficiency (Pacetal = 96%) but the relatively
(Entry 7). When the cycloolefin of 2,5-dihydrofuran was applied
low conversion of cyclohexene (Entry 9).
Table 3 Generality of Rh(acac)(CO)2-L2 for hydroformylation-acetalizationa
Entry Olefin
Alcohol
MeOH
Linear acetal
Conv. (%) b
97
Soxo (%)b,c
98
Pacetals (%)b,c
86
L/Bd
1.9
TONoxo
1900
OMe
OMe
1
1-Octene
O
2
1-Octene
Glycol
96
98
94
1.1
1880
O
3
4
1-Octene
Styrene
t-BuOH
82
99
80
99
0
2.2
0.2
1310
1960
CHO
OMe
OMe
MeOH
88
O
5
6
Styrene
Styrene
Glycol
98
98
99
99
83
45
0.3
0.1
1940
1940
O
Me
Propane-1,2-diol
O
O
7e
Styrene
Glycerol
96
99
89
0.2
1900
OH
O
O
O
O
OH
8f
9
Glycol
99
62
99
99
42
96
--
1960
1228
O
O
O
O
O
O
O
O
O
Cyclohexene Glycol
2-cyclohexyl-1,3-dioxolane
a
Rh(acac)(CO)2 0.0025 mmol, olefin 5.0 mmol (S/C=2000), L2 0.015 mmol (P/Rh=6:1), CO/H2 (1:1) 4.0 MPa, temperature 120 oC, alcohol 3 mL,
reaction time 2 h; b Determined by GC and GC-Mass; Soxo=(aldyhydes+acetals)/(aldyhydes+acetals+iso-olefins); Pacetals=acetals/(aldehydes+acetals);
L/B, the ratio of linear aldehydes and acetals to branched aldehydes and acetals; The mixed acetalized products of 2-phenethyl-1,3-dioxan-5-ol
c
d
e
and (2-phenethyl-1,3-dioxolan-4-yl)methanol were isolated for 1H NMR analysis (See SEI); The ratio of tetrahydrofuran-3-carbaldehyde and 2-
(tetrahydrofuran-3-yl)-1,3-dioxolane to tetrahydrofuran-2-carbaldehyde and 2-(tetrahydrofuran-2-yl)-1,3-dioxolane is 2.5.
f
Moreover, as the ionic ligand, L2 could be used with a room shown in Table 4, Rh(acac)(CO)2-L2 could be recycled at least 7
temperature ionic liquid (RTIL) solvent as the efficient runs along with the slightly decreased conversion of styrene
alternative to immobilize the transition metal catalysts for and the unchanged selectivity to the aldehydes (TONs
recovery and recycling19,34,35. To demonstrate that issue, the decreased from 1960 to 1700). After the seven-run recycling
recovery and recycling experiments were investigated over uses, the total loss of Rh(acac)(CO)2-L2 system in the combined
Rh(acac)(CO)2-L2 system dissolved in [Bmim]BF4 (1-butyl-3- organic phase was 0.3% for Rh and 0.1% for P (ICP-AES
methylimidazolium tetrafloruoborate) and glycol for analysis), which revealed that the catalyst could be locked in
hydroforformylation-acetalization. Due to the mass transfer [Bmim]BF4 medium with very slight leaching into the organic
limitation in the biphasic reaction system by using [Bmim]BF4 phase especially for the phosphine of L2 with the ionic
as the solvent, the reaction time was prolonged to 7 h. As compatibility. Hence, the observed decrease for the
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conversion of styrene was mainly attributed to the mechanical instrument equipped with an Agilent 5973 mass selective
loss of Rh-P catalyst during the recycling treatment. However, detector. Elemental analyses for CHN were obtained using an
the reason for the gradually increased L/B value was not clear Elementar Vario EL III instrument.
at present stage.
Synthesis of L1-L4’
Firstly the diphosphine of L1 [1,3-bis(2’-diphenylphosphino-3’-
Table
4 Recycling of Rh(acac)(CO)2-L2 system in [Bmim]BF4 for biphasic
hydroformylation-acetalization of styrene with glycola
imidazole)benzene] was prepared according to the reported
methods20,21. Then L1 was quaternized by MeI at one P-
position to selectively afford ionic L2 according to the
preparation procedures as described as follows.
O
O
O
CHO
CHO
Rh(acac)(CO)2-L2
O
Me
Me
+
CO
+
H2
+
+
+
Glycol/[Bmim]BF4
At room temperature, the solution of L1 (1.27 g, 2.2 mmol)
in 20 ml of absolute toluene (refluxed with sodium and
distilled freshly before use) was treated with iodomethane
(0.31 g, 2.2 mmol). The obtained mixture solution was stirred
vigorously for 24 h and the white precipitates were formed
gradually. The precipitates were collected after filtration and
then washed with diethyl ether to give a white solid as the
product of L2 (0.8 g, yield 50 %). 1H NMR (δ, ppm, CDCl3): 7.78-
7.34 (m, 27H, Ar), 7.13 (s, 1H, NCC
P(V)+-CH3). 31P NMR (
, ppm, CDCl3): −28.5 (s,
(Me
H
CN), 2.93-2.90 (d, 3H,
δ
PPh2), 11.7
P
+Ph2). CHN-elemental analysis (%, Found): C 61.49, H
4.58, N 7.56 (Calcd: C 61.67, H 4.31, N 7.78). ESI-MS (M+/z):
593 ([C37H31N4P2]+=593).
Conv. (%)b
Soxo (%)b,c
99
Pacetals (%)b,c
L/Bd
0.2
0.3
0.3
0.4
0.5
0.6
0.7
TONoxo
1960
1940
1880
1800
1740
1720
1700
The quaternization of L1 by MeOTf (methyl-
trifluoromethane sulfonate) at N-positions of two imidazolyl
rings selectively could afford the ionic L3 according to the
method reported by us prevoulsy21. And L4 was also prepared
in parallel for comparison21. On the basis of the preparation of
L4, its corresponding phosphonium salt of L4’ was prepared as
follows.
Run
1
99
99
95
91
88
87
86
97
98
98
98
98
98
98
2e
99
3
99
4
99
5
99
6
99
The solution of L4 (0.3 g, 0.9 mmol) in 10 mL of absolute
toluene (refluxed with sodium and distilled freshly before use)
was treated with iodomethane (0.14 g, 1 mmol). The obtained
solution was stirred vigorously at room temperature for 24 h.
Then the formed precipitates were collected after filtration
and washed with diethyl ether to give a white solid as the
7
99
a
Rh(acac)(CO)2 0.0025 mmol, styrene 5.0 mmol (S/C=2000), L2 0.015 mmol
3
(P/Rh=6:1), CO/H2 (1:1) 4.0 MPa, temperature 100 oC, glycol 3 mL, [Bmim]BF4
b
c
mL,
Soxo=(aldyhydes+acetals)/(aldyhydes+acetals+iso-olefins).
reaction
time
d
7
h;
Determined
by GC;
Pacetals=acetals/
(aldehydes+acetals); L/B, the ratio of linear aldehydes and acetals to branched
aldehydes and acetals; e 1.5 mL glycol was added additionally.
1
product of L4’ (0.24 g, yield 55 %). H NMR (δ, ppm, CDCl3):
7.79-7.71 (m, 6H, Ar), 7.65-7.62 (m, 5H, Ar), 7.75-7.54 (d, 1H,
H
), 7.43-7.16 (m, 5H, Ar), 2.85-2.82 (d, 3H, P(V)+-CH3).
Experimental
PhNCNC
31P NMR (
δ
, ppm, CDCl3): 11.92 (MeP
+Ph2).
Reagents and analysis
The chemical reagents were purchased from Shanghai Aladdin
Chemical Reagent Co. Ltd. and Alfa Aesar China, and used as
received. FT-IR spectra were recorded on a Nicolet NEXUS 670
X-Ray crystallography
Intensity data were collected at 173 K for L2 on a Bruker
1
spectrometer. The H and 31P NMR spectra for the analyses of
SMARTAPEX II diffractometer using graphite monochromated
Mo-K
α radiation (λ = 0.71073 Å). Data reduction included
the common compounds were recorded on a Bruker Avance
400 spectrometer. The 31P NMR spectra for the analyses of the
phosphine-selenides (as shown in Fig. 2) were recorded on a
Bruker Avance 500 spectrometer. The 31P NMR spectra were
referenced to 85% H3PO4 sealed in a capillary tube as an
internal standard. The amount of Rh in the sample was
quantified using an inductive coupled plasma atomic emission
spectrometer (ICP-AES) on an IRIS Intrepid II XSP instrument
(Thermo Electron Corporation). Gas chromatography (GC) was
performed on a SHIMADZU-2014 equipped with a DM-1
absorption corrections by the multi-scan method. The
structures were solved by direct methods and refined by full
matrix least-squares using SHELXS-97 (Sheldrick, 1990), with all
non-hydrogen atoms refined anisotropically. Hydrogen atoms
were added at their geometrically ideal positions and refined
isotropically. The crystal data and refinement details of L2 are
given in Table 5. The crystal data and refinement details of L1
and L3 could be found in Ref. 21.
General procedures for hydroformylation-acetalization of olefin in
alcohols
capillary column (30 m × 0.25 mm × 0.25 ꢀm). GC-mass
spectrometry (GC-MS) was recorded on an Agilent 6890
6 | J. Name., 2012, 00, 1-3
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In
ARTICLE
a
typical experiment, the commercial complex of chemical bonds was synthesized and fully characterized. The
Rh(acac)(CO)2 (0.0025 mmol) and the pure L2 (0.015 mmol) incorporated phosphonium showed no effect on the
were added into 1-octene (5 mmol, or the other olefin) and coordination ability of the peripheral phosphine fragment with
1
methanol (3 mL, or the other alcohol) sequentially. The the indication of the same JSe-P of 750 Hz as that of L1 and L4
.
obtained mixture in a 50 mL sealed Teflon-lined stainless steel In co-catalysis for hydroformylation-acetalization, the
autoclave was pressured by syngas to 4.0 MPa. The reaction phosphonium in L2 not only contributed to the sequential
mixture was stirred vigorously at the appointed temperature acetalization of nonanals as
a
typical Lewis acidic
for some time. Upon completion, the autoclave was cooled organocatalyst, but also synergetically promoted the
down to room temperature and depressurized carefully. The phosphine-ligated Rh-complex catalyzed hydroformylation
reaction solution was analysed by GC to determine the through activating C=O by developing the bonding interaction
conversions (n-dodecane as internal standard) and the between P(V)+ centre and O atom (in C=O) to cooperatively
selectivities (normalization method), and the products were stabilize the Rh-acyl intermediate. Moreover, the
further identified by GC-Mass.
Rh(acac)(CO)2-L2 system with the wide substrate generality
When [Bmim]BF4 was used as the solvent for the biphasic could be applied as a recoverable and recyclable catalyst in
hydroformylation-acetalization, in which styrene (5 mmol), RTIL of [Bmim]BF4 without the obvious deactivation.
glycol (3 mL), Rh(acac)(CO)2 (0.0025 mmol), L2 (0.015 mmol)
were mixed sequentially. Upon reaction, the upper organic
Acknowledgements
phase was decanted from the obtained biphasic reaction
mixture, and the left IL phase was washed with n-hexane (3 mL
This work was financially supported by the National Natural
Science Foundation of China (Nos. 21473058, 21273077, and
21076083), and 973 Program from Ministry of Science and
Technology of China (2011CB201403).
×
3) to completely extract the reactants and products out of
the IL phase. The combined organic phase was analyzed by GC
and ICP-AES. The left IL phase was directly used without
further treatment for next run (if required glycol was added
additionally).
Notes and references
‡ CCDC-1036473 (L1)
21, CCDC-1412745 (L2) and CCDC-1036474
21
Table 5 Crystal data and structure refinement for L2
L2⋅CH2Cl2
(
L3
paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
)
contain the supplementary crystallographic data in this
Empirical formula
[C37H31N4P2]⋅I1⋅C1H2Cl2
Formula weight
Crystal system
Space group
a (Å)
805.42
Monoclinic
P21/c
1
2
3
(a) R. Franke, D. Selent and A. Börner, Chem. Rev., 2012, 112,
5675; (b) P.W.N.M. Van Leeuwen and C. Claver, Rhodium
Catalyzed Hydroformylation, Kluwer Academic Publishers,
New York, 2000.
(a) 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; (b) Z. Du and Z.
Shao, Chem. Soc. Rev., 2013, 42, 1337.
(a) X. Jin, K. Zhao, F. F. Cui, F. F. Kong and Q. Q. Liu, Green
Chem., 2013, 15, 3236; (b) Y. Jin, J. Shi, F. Zhang, Y. Zhong
and W. Zhu, J. Mol. Catal. A: Chem., 2014, 383-384, 167; (c) J.
9.5438(7)
39.836(3)
10.6814(11)
90
b (Å)
c (Å)
α
β
γ
(o)
(o)
(o)
116.464(3)
90
V (Å3)
3635.4(5)
4
Balue and J. C. Bayon, J. Mol. Catal. A: Chem., 1999, 137
,
Z
193; (d) M. M. Diwakar, R. M. Deshpande and R. V.
Chaudhari, J. Mol. Catal. A: Chem., 2005, 232, 179; (e) G.
Parrinello and J. K. Stille, J. Am. Chem. Soc., 1987, 109, 7122;
(f) B. E. Ali, J. Tijani and M. Fettouhi, Appl. Catal. A: Chem.,
2006, 303, 213.
(a) S. R. Khan and B. M. Bhanage, Tetrahedron Lett., 2013,
54, 5998; (b) J. Norinder, C. Rodrigues and A. Börner, J. Mol.
Catal. A: Chem., 2014, 391,139; (c) M. C. de Freitas, C. G.
Vieira, E. N. dos Santos and E. V. Gusevskaya, ChemCatChem,
d
calc (g cm-3)
(Mo-Kα) (mm-1)
T (K)
(A)
1.472
1.149
ꢀ
173(2)
0.71073
42503
λ
4
5
Total reflections
Unique reflections (Rint
R1 [I>2σ(I)]
)
6421 (0.1479)
0.0564
0.1233
1624
wR2 (all data)
2013, 5, 1884.
(a) V. S. Nair, B. M. Bhanage, R. M. Deshpande and R.V.
Choudhari, Rec. Adv. Basic Appl. Aspects Industr. Catal. 1998,
113, 529; (b) A. W. S. Currie and J. A. M. Andersen, Catal.
Lett. 1997, 44, 109; (c) K. Soulantica, S. Sirol, S. Koienis, G.
F(000)
Goodness-of-fit on F2
1.049
Pneumatikakis and P.Kalck, J. Organomet. Chem., 1995, 498
10.
,
6
7
P. Manjunathan, S. P. Maradur, A.B. Halgeri and G. V.
Shanbhag, J. Mol. Catal. A: Chem., 2015, 396, 47.
A. S. Poyraz, C. H. Kuo, E. Kim, Y. T. Meng, M. S. Seraji and S.
L. Suib, Chem. Mater., 2014, 26, 2803.
Conclusions
The ionic bi-functional ligand of L2 in combination of the
phosphine with the Lewis acidic phosphonium by the stable
This journal is © The Royal Society of Chemistry 20xx
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8
9
X. Li, Z. Y. Guo, C. X. Xiao, T. W. Goh, D. Tesfagaber and W. Y. 24 X. F. Wu, X. Fang, L. Wu, R. Jackstell, H. Neumann and M.
Huang, ACS Catal., 2014,
A. Herbst, A. Khutia and C. Janiak, Inorg. Chem., 2014, 53
7319.
10 (a) Y. J. Park, J. W. Park and C. H. Jun, Acc. Chem. Res., 2008,
41, 222; (b) C. Zhong and X. Shi, Eur. J. Org. Chem., 2010, 27 S. A. Ullate, J. A. Baker, V. G. González, C. Müller, J. D. Hirst
2999; (c) J. Meeuwissen and J. N. H. Reek, Nat. Chem., 2010, and J. J. Carbó, Catal. Sci. Technol., 2014, , 979.
, 615; (d) Y. Deng, S. Kumar and H. Wang, Chem. Commun., 28 H. Tricas, O. Diebolt and P. W. N. M. van Leeuwen, J. Catal.,
4, 3490.
Beller, Acc. Chem. Res., 2014, 47, 1041.
,
25 B. Breit, J. Mol. Catal. A: Chem., 1999, 143, 143.
26 O. Diebolt, H. Tricas, Z. Freixa and P. W. N. M. van Leeuwen,
ACS Catal., 2013, 3, 128.
4
2
2014, 50, 4272; (e) Z. H. Shao and H. Zhang, Chem. Soc. Rev.,
2013, 298, 198.
2009, 38, 2745; (f) A. Gualandi, L. Mengozzi, C. M. Wilson 29 S. Jeulin, S. D. de Paule, V. R. Vidal, J. P. Genêt, N. Champion
and P. G. Cozzi, Chem. Asian J., 2014, , 984. and P. Dellis, Angew. Chem. Int. Ed., 2004, 43, 320.
11 (a) M. Rueping, R. M. Koenigs and I. Atodiresei, Chem. Eur. J., 30 C. Bolli, J. Gellhaar, C. Jenne, M. Keßler, H. Scherer, H.
9
2010, 16, 9350; (b) F. Lv, S. Liu and W. Hu, Asian J. Org.
Chem. 2013, , 824.
12 (a) Q. Zhao, S. Li, K. Huang, R. Wang and X. Zhang, Org. Lett.,
Seegera and R. Uzunb, Dalton Trans., 2014, 43, 4326.
31 C. B. Caputo, L. J. Hounjet, R. Dobrovetsky and D. W.
Stephan, Science, 2013, 341, 1374.
2
2013, 15, 4014; (b) P. Daka, Z. Xu, A. Alexa and H. Wang, 32 S. C. Yu, Y. M. Chi, Z. H. Guan, Y. P. Zou, W. Li and X. M.
Chem. Commun., 2011, 47, 224; (c) Z. Xu, L. Liu, K. Wheeler Zhang, Org. Lett., 2009, 11, 241.
and H. Wang, Angew. Chem., Int. Ed., 2011, 50, 3484; (d) T. 33 S. J. Chen, Y. Q. Li, P. Wang, Y. Lu, X. L. Zhao and Y. Liu
Smejkal, D. Gribkov, J. Geier, M. Keller and B. Breit, Chem.- Mol. Catal. A: Chem., 2015, 407, 212.
Eur. J., 2010, 16, 2470; (e) D. Fuchs, G. Rousseau, L. Diab, U. 34 C. Huo and T. H. Chan, Chem. Soc. Rev., 2010, 39, 2977.
Gellrich and B. Breit, Angew. Chem., Int. Ed., 2012, 51, 2178; 35 (a) B. Ni and A. D. Headley, Chem.-Eur. J., 2010, 16, 4426; (b)
,
J.
(f) A. D. Worthy, C. L. Joe, T. E. Lightburn and K. L. Tan, J. Am.
Chem. Soc., 2010, 132, 14757; (g) C. L. Joe and K. L. Tan, J.
Org. Chem., 2011, 76, 7590; (h) K. Ohmatsu, M. Ito, T.
R. Sebesta, I. Kmentova and S. Toma, Green Chem., 2008, 10
484; (c) W. Miao and T. H. Chan, Acc. Chem. Res., 2006, 39
897.
,
,
Kunieda and T. Ooi, Nat. Chem., 2012, 4, 473.
13 (a) B. F. M. Kimmich, C. R. Landis and D. R. Powell,
Organometallics, 1996, 15, 4141; (b) N. Tsoureas, G. R. Owen,
A. Hamilton and A. G. Orpen, Dalton Trans., 2008, 6039; (c) H.
Kameo and H. Nakazawa, Organometallics, 2012, 31, 7476;
(d) G. Bouhadir, A. Amgoune and D. Bourissou, Adv.
Organomet. Chem., 2010, 58, 1; (e) R. Malacea, N. Saffon, M.
Gómez and D. Bourissou, Chem. Commun., 2011, 47, 8163; (f)
M. W. P. Bebbington, S. Bontemps, G. Bouhadir, M. J. Hanton,
R. P. Tooze, H. van Rensburg and D. Bourissou, New J. Chem.,
2010, 34, 1556; (g) F. G. Fontaine, J. Boudreau and M. H.
Thibault, Eur. J. Inorg. Chem., 2008, 5439; (h) R. Malacea, F.
Chahdoura, M. Devillard, N. Saffon, M. Gómez and D.
Bourissou, Adv. Synth. Catal., 2013, 355, 2274.
14 C. Tan, P. Wang, H. Liu, X. L. Zhao, Y. Lu and Y. Liu, Chem.
Commun., 2015, 51, 10871.
15 (a) O. Sereda; S. Tabassum and R. Wilhelm, Top. Curr. Chem.,
2010, 291, 349; (b) T. Werner, Adv. Synth. Catal., 2009, 351
,
1469; (c) M. Selva, A. Perosa, P. Tundo and Davide Brunelli, J.
Org. Chem., 2006, 71, 5770; (d) T. W. Hudnall, Y. M. Kim, M.
W. P. Bebbington, D. Bourissou and F. P. Gabbaï, J. Am.
Chem. Soc., 2008, 130, 10890.
16 (a) C. B. Caputo, L. J. Hounjet, R. Dobrovetsky and D. W.
Stephan, Science, 2013, 341, 1374; (b) M. Pérez, L. J.
Hounjet, C. B. Caputo, R. Dobrovetsky and D. W. Stephan, J.
Am. Chem. Soc., 2013, 135, 18308.
17 X. Wang and S. K. Tian, Tetrahedron Lett., 2007, 48, 6010.
18 C. L. Johnson, R. E. Donkor, W. Nawaz and N. Karodia,
Tetrahedron Lett., 2004, 45, 7359.
19 T. Mukaiyama, S. Matsui and K. Kashiwagi, Chem. Lett., 1989,
993.
20 C. Barthes, C. Lepetit, Y. Canac, C. Duhayon, D. Zargarian and
R. Chauvin, Inorg. Chem., 2013, 52, 48.
21 Y. Q. Li, P. Wang, H. Zhang, X. L. Zhao, Y. Lu, Z. Popović and Y.
Liu, J. Mol. Catal. A: Chem., 2015, 402, 37.
22 A. A. Tolmachev, A. A. Yurchenko, A. S. Merculov, M. G.
Semenova, E. V. Zarudnitskii, V. V. Ivanov and A. M. Pinchuk,
Heteroatom Chem., 1999, 10, 585.
23 (a) D. W. Allen and B. F. Taylor, Dalton Trans., 1982, 1, 51; (b)
A. S. Rrez, M. A. M. Rojas and A. Pizzano, Organometallics,
2002, 21, 4611; (c) S. Jeulin, S. D. de Paule, V. R. Vidal, J. P.
Genêt, N. Champion and P. Dellis, Angew. Chem. Int. Ed.,
2004, 43, 320.
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A table contents entry:
L2 containing the phosphine and the Lewis acidic phosphonium exhibited synergetic catalysis and
sequential catalysis for one-pot hydroformylation-acetalization.