Highly regioselective hydroaminomethylation of terminal olefins to linear amines using rh complexes with a tetrabi phosphorus ligand

Article abstract of DOI:10.1002/chem.201103073

A highly regioselective hydroaminomethylation of terminal olefins catalyzed by Rh complexes with 2, 2′, 6, 6′-tetrakis ((diphenylphosphino) methyl)-1, 1′-biphenyl (Tetrabi) ligand has been developed. Up to 99% amine selectivity, 168 linear/branched amine product ratio (n/i), and 97.4% linear amine yield has been obtained at a substrate/rhodium precursor ratio (S/Rh) of 1000 with this methodology. The turnover number was achieved 6930 at 10000 S/Rh ratio, and the n/i can reach up to >525. Several different olefins and secondary amines have been applied successfully with high chemoselectivity (99%), yield (>98%), and regioselectivity (>120).

Full text of DOI:10.1002/chem.201103073

FULL PAPER
DOI: 10.1002/chem.201103073
Highly Regioselective Hydroaminomethylation of Terminal Olefins to Linear
Amines Using Rh Complexes with a Tetrabi Phosphorus Ligand**
Guodu Liu,[a, b] Kexuan Huang,[b] Chaoxian Cai,[b] Bonan Cao,[b] Mingxin Chang,[b]
Wenjun Wu,*[a] and Xumu Zhang*[b]
Abstract: A highly regioselective hy-
droaminomethylation of terminal ole-
fins catalyzed by Rh complexes with 2,
2’, 6, 6’-tetrakis ((diphenylphosphino)-
methyl)-1, 1’-biphenyl (Tetrabi) ligand
has been developed. Up to 99% amine
selectivity, 168 linear/branched amine
product ratio (n/i), and 97.4% linear
amine yield has been obtained at a sub-
strate/rhodium precursor ratio (S/Rh)
of 1000 with this methodology. The
turnover number was achieved 6930 at
10000 S/Rh ratio, and the n/i can reach
up to >525. Several different olefins
and secondary amines have been ap-
plied successfully with high chemose-
lectivity (99%), yield (>98%), and re-
gioselectivity (>120).
Keywords: hydroaminomethyla-
tion · linear amines · olefins · regio-
selectivity · rhodium · Tetrabi li-
gand
Introduction
Xantphos
derivatives
as
the
controlling
ligands
(Scheme 1).[6]
Linear aliphatic amines are of significant importance in the
chemical and pharmaceutical industries. Million-ton scale of
linear amines is produced per year. They are used as sol-
vents, fine chemicals, agrochemicals, pharmaceutical inter-
mediates, and vulcanization accelerators.[1] Hydroaminome-
thylation,[2] an environmentally benign, one-pot, atom-effi-
cient synthesis of amines from inexpensive ubiquitous ole-
fins, consists of an initial regioselective hydroformylation
followed by a reductive amination. Since the discovery of
this reaction at BASF AG by Reppe,[3] notable advances
have been especially reported by Eilbracht and co-workers
in the 2000 s.[4] During this time, Beller and co-workers have
made a great contribution to regioselective hydroaminome-
thylation.[5] One of their successes is the first general effi-
cient regioselective (linear to branched amine product ratio
(n/i)>98:2) hydroaminomethylation of terminal olefins by
using a practical rhodium catalyst and modified Naphos and
Scheme 1. Structures of applied ligands.
Recently, we have developed two systems of tetraphos-
phorous ligands,[7] which are based on a biphenyl backbone
and can be successfully applied in the highly regioselective
hydroformylation of terminal olefins and internal olefins.
Now we have a great interest to test our ligands for hydroa-
minomethylation reactions. Under the optimized reaction
conditions we obtained 99% amine selectivity, 168 n/i ratio
and 97.4% linear amine yield with full conversion, by using
[a] G. Liu, Prof. W. Wu
College of Science, Northwest A & F University
Yangling, Shaanxi 712100 (P.R. China)
Fax : (+86) 29 87093987
E-mail: wuwenjun_1@163.com
wuwenjun_1@163.com
Tetrabi[7b,d] and [Rh
ACTHNUTRGNEG(NU acac)(CO)2] at 1000 S/Rh (S/R=sub-
[b] G. Liu, K. Huang, C. Cai, B. Cao, M. Chang, Prof. X. Zhang
Department of Chemistry and Chemical Biology
and Department of Medicinal Chemistry, Rutgers
The State University of New Jersey, Piscataway
New Jersey 08854 (USA)
strate to rhodium precursor ratio). The turnover number,
which refers to the number of moles of substrate that one
mole of catalyst can convert before becoming inactivated, of
Tetrabi was 6930 with excellent amine selectivity at 10000 S/
Rh ratio, and the n/i ratio of amine can reach to >525 at
5000 to 10000 S/Rh ratio. Several different olefins and sec-
ondary amines have been applied successfully with high che-
moselectivity (99%) and regioselectivity (>120) for the
compatibility of this method.
Fax : (+1)732-445-6312
E-mail: xumu@rci.rutgers.edu
[**] Tetrabi=2, 2’, 6, 6’-tetrakis ((diphenylphosphino)methyl)-1, 1’-bi-
phenyl.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201103073.
Chem. Eur. J. 2011, 17, 14559 – 14563
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
14559

Table 1. Hydroaminomethylation of 1-hexene with piperidine by using different Rh
precursors and ligands.[a]
Results and Discussion
Two of our tetraphosphorous ligands: Tetrabi and
TPPB,[7c] have been tested for their potential in
this reaction, and three different Rh precursors
have been applied at the same time for the hydroa-
minomethylation of 1-hexene and piperidine. 4, 5-
Bis (diphenylphosphino)-9, 9-dimethylxanthene
(Xantphos)[8] and 2, 2’-bis [diphenylphosphino]-
methyl)-1, 1’-biphenyl (Bisbi)[9] have been used as
the “standard ligand” because Xantphos is the
most well-known ligand in hydroaminomethylation
for its high regioselectivity, whereas Bisbi has also
been studied for a long time for its hydroaminome-
thylation activities (Scheme 1).
Entry Ligand
[1 mmol]
Rh precursor
[4 mmol]
Conv. yield Amine
[%]
N-formyl-
piperidine
[%][d]
n/i
G
G
[%][b] selectivity
[%][c]
1
2
3
4
5
6
Tetrabi
Tetrabi
Tetrabi
BTPP
BTPP
BTPP
[Rh
[Rh
[Rh
[Rh
[Rh
[Rh
G
90.8
90.8
81.4
77.6
78.2
81.0
88.8
95.3
90.3
78.6
87.7
76.8
92.2
92.4
84.1
81.7
84.7
91.1
90.6
97.2
95.8
79.9
90.1
82.8
7.8
7.6
7.1
–
–
–
4.3
2.8
2.2
6.9
6.4
5.3
198
126
45
19
12
8
99
100
20
146
60
99
99
99
99
7
8
9
Xantphos [Rh
Xantphos [Rh
Xantphos [RhCAHTUNGTRENNNUG
A
R
99
99
10
11
12
Bisbi
Bisbi
Bisbi
[Rh
[Rh
[Rh
G
As shown in Table 1, all the entries have 99%
conversion, but the amine selectivities and n/i
ratios are very different. Tetrabi can afford a n/i
99
99
15
[a] Reaction condition: S/Rh=1000, L/Rh=4:1, [Rh] (1 mmol), 1-hexene (1 mmol), pi-
peridine (1 mmol), in methanol/toluene (3 mL 1:1) at CO:H2 =7/35 bar, 1258C for 4 h.
[b] Yield of n-amine. [c] Selectivity and yield was determined by GC analysis using 2-
methoxyethyl ether (0.1 mL) as an internal standard, the average value of three re-
peated runs and two injections per run. [d] Other by-products were the corresponding
aldol product and N-methylpiperidine.
ratio of up to 198 by using [RhACHTNUGRTNE(NUG acac)(CO)2] as the
precursor (Table 1, entry 1), whereas 2, 2’, 6, 6’-tet-
raki (dipyrrolylphosphoramidite)-1, 1’-biphenyl
(TPPB) unfortunately does not achieve good selec-
tivity; only an n/i ratio of 19 was achieved with
[Rh
ieved a n/i ratio of 100 and a linear amine yield of
95.3% with [Rh(cod)2]BF4 (cod=1,5-cyclooctadiene;
ACHTUNGTRENNUNG(acac)(CO)2] (Table 1, entry 4). Xantphos ach-
AHCTUNGTRENNUNG
Table 1, entry 8), which shows an excellent activity of regio-
selective hydroaminomethylation and is consistent with the
published result.[6] With regards to linear amine selectivity
and yield, Bisbi does not perform well compared with Tetra-
bi; the best result is 146 n/i ratio with only 78.6% linear
amine yield (Table 1, entry 10). Depending on the applied li-
gands and rhodium precursors, TPPB, which is an excellent
ligand for the regioselective hydroformylation of 2-hexene,
does not work for the regioselective hydroaminomethylation
of 1-hexene. It is implied that the hydroaminomethylation
reaction conditions may have a negative influence on the re-
gioselectivity of the hydroformylation step, and there is no
inevitable connection between these two reactions, especial-
ly under different reaction conditions. The reason for the
significant differences between Bisbi and Tetrabi is that Tet-
rabi has a higher concentration of the selective catalytic spe-
cies due to the presence of multiple chelating modes: a rho-
dium metal center can form four possible equivalent biden-
tate complexes[10] (Scheme 2). Compared with Xantphos, the
best and highly reproducible result of the n/i ratio was ob-
Scheme 2. Enhanced chelating ability of Tetrabi ligand.
(Table 2, entry 7). The best n/i ratio was 150, which was ob-
tained in 2-propanol with 85% conversion and 0.5% of N-
formylpiperidine, however the hydrogenation activity of en-
amine is not good enough (Table 2, entry 3). It is suggested
to use a combination of ethanol and toluene or 2-propanol
for the full conversion, excellent amine selectivity, n/i ratio,
and the suppression of N-formylpiperidine. As shown in
Table 2 (entries 9–15), ethanol mixed with toluene or etha-
nol mixed with 2-propanol have been tested in different
ratios. A regioselectivity of 215 with 92.7% linear amine
yield was achieved in 2:1 mixture of ethanol and toluene
(Table 2, entry 10), and 96.8% linear amine yield was ob-
tained applying a 2:1 mixture of 2-propanol and ethanol
with the ratio of 134 (Table 2, entry 14). We chose a 2:1 mix-
ture of 2-propanol and ethanol as the standard solvent for
further optimization. As the time increased, the conversion
extends to more than 99% at 6 h with 168 n/i ratio (Table 2,
tained by using Tetrabi and [RhACHTNUGTRENUNG(acac)(CO)2], whereas the
formation of N-formylpiperidine was little higher because of
its high formylation activity. Hence, a combination of Tetra-
bi and [RhACHTUNGTRENNUNG(acac)(CO)2] was chosen as the catalyst system
for further studies.
Different single solvents were introduced for the suppres-
sion of N-formylpiperidine (Table 2, entries 1–7). The study
showed that full conversion of 1-hexene can be obtained in
ethanol with a 61 n/i ratio and 4% of N-formylpiperidine
(Table 2, entry 2), and the formation of N-formylpiperidine
can be suppressed to 0.5% with 65% conversion in toluene
14560
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 14559 – 14563

Regioselective Hydroaminomethylation of Terminal Olefins to Linear Amines
FULL PAPER
Table 2. Optimization of the reaction conditions for the hydroaminomethylation of 1-hexene with piperidine using [Rh
gand.[a]
ACHTUNGRTENN(UNG acac)(CO)2] and the Tetrabi li-
Selectivity [%][b]
P (CO/H2)
[bar]
T
t
Conversion n-Amine
Entry Solvent
L/Rh
Amine Enamine N-formyl- Aldol product n/i
G
[8C] [h]
[%]
yield [%]
piperidine
1
2
3
4
5
6
7
8
MeOH
EtOH
2-PrOH
EtOAc
dioxane
THF
toluene
MeOH/toluene=1:1 7/35
EtOH/toluene=1:1
EtOH/toluene=2:1
EtOH/toluene=5:1
2-PrOH/EtOH=11:1 7/35
2-PrOH/EtOH=5:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=1:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 5/25
2-PrOH/EtOH=2:1 10/50
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
2-PrOH/EtOH=2:1 7/35
7/35
7/35
7/35
7/35
7/35
7/35
7/35
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
125
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
4
6
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
2
1
4
4
4
4
4
4
>99
>99
85
65
75
86.5
91.2
77.5
4.6
3.5
7.4
89.3
93.6
91.8
7.1
4.7
10.5
5.1
–
–
9.4
4
1.3
2.4
4.9
35.5
13.9
14.9
34.2[c]
1.4
3.3
2.4
1.4
4.8
2.6
0.7
46
61
150
–
–
2.8
56.2
80.5
73.3
60.2
–
53.2
1.5
–
1.4
1.1
–
–
–
–
–
–
–
–
–
–
–
0.5
1.2
0.9
1.3
0.5
6.4
0.9
2.0
2.6
0.5
0.5
0.8
1.0
0.8
0.5
1.5
0.9
0.8
0.8
3.2
0.7
1.6
2.1
2.7
70
65
–
–
3.3
>99
>99
>99
>99
>99
>99
>99
>99
90
>99
>99
95
90
95
90.8
42.1
92.7
94.2
91.8
94.2
96.8
96.2
73.5
97.4
95.1
92.8
88.0
90.5
94.1
76.9
86.3
94.7
94.0
92.2
42.6
94.1
96.0
93.3
95.8
98.5
98.2
81.7
99.0
97.3
98.4
98.8
95.9
96.4
97.2
96.6
96.4
96.1
198
355
215
110
152
140
134
60
192
168
78
135
94
145
71
93
143
121
85
9
7/35
7/35
7/35
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
0.8
17.5[c]
0.5
125 12
1.2
0.7
0.5
3.3
0.4
2.1
1.8
1.5
125
125
125
125
115
120
130
135
6
6
6
6
6
6
6
6
>99
80
90
>99
>99
–
–
1.2
[a] Reaction conditions: [RhACTHNUTRGNE(NUG acac)(CO)2] (1 mmol), ligand=Tetrabi, 1-hexene (1 mmol), piperidine (1 mmol), solvent (3 mL). [b] Selectivity and yield
was determined by GC analysis using 2-methoxyethyl ether (0.1 mL) as an internal standard, the average value of three repeated runs and two injections
per run. [c] Major other by-products were aldehydes.
entry 17), and the n/i ratio drops from 192 to 78 (Table 2,
entries 14 and 16–18). The ratio of ligand to rhodium pre-
cursor (L/Rh) varies from 4 to 1, and the best result was
achieved using a L/Rh ratio of 4 (Table 2, entry 17). With a
1:5 ratio of CO/H2, variation of the pressure showed that 7/
35 bar is optimum; 5/25 bar leads to lower conversion and
10/50 bar results in a lower n/i ratio (Table 2, entries 21 and
22). A temperature of 1258C is favorable because a lower
temperature slows down the reaction speed and a higher
temperature decreases the n/i ratio (Table 2, entries 23–26).
Hence, under the optimized reaction conditions (1-hexene/
At a ratio of 2500, 0.2% of branched enamine was pro-
duced, and the n/i ratio of amine was 525 with full conver-
sion of 1-hexene (Table 3, entry 2). At the ratio of 5000,
8000, and 10000, the linear amine is actually quantitative
(100% of amine product as enamine was the only by-prod-
uct), whereas the conversion of 1-hexene drops from 99 to
70% (Table 3, entries 3–5). The reason for the existence of
the branched enamine should be the lower hydrogenation
activity of Tetrabi catalyst system for the branched enamine
at such a low concentration. Thus, the n/i ratio of amine
must be >525 at 5000 to 10000 S/Rh ratio with less than
1% branched enamine (for details, see the Supporting Infor-
mation). To the best of our knowledge, such a clean linear
amine has never been achieved before.
Finally, several different terminal olefins and secondary
amines were introduced to demonstrate the compatibility of
our method. In all cases, the reaction proceeds with an ex-
tremely high degree of chemoselectivity (99%) and amine
yield (>98%) towards the linear amines. We were pleased
to find that not only lower but also higher aliphatic olefins
react well with piperidine to give the linear amine products
with excellent selectivity (up to 208), whereas higher 1-
octene needs a longer time to get full conversion (121 n/i
ratio) (Table 4, entries 1–3). N-methylbenzylamine and
other aliphatic secondary amines (such as morpholine or di-
Tetrabi/[Rh
G
1-hexene/piperidine
(1:1) in a mixture of 2-propanol and ethanol (2:1, 3 mL), at
CO:H2 =7/35 bar and 1258C for 6 h) the product is generat-
ed with 99% amine selectivity, 168 n/i ratio, and 97.4%
linear amine yield with full conversion.
Next, we studied the turnover number (the number of
moles of substrate that one mole of catalyst can convert
before becoming inactivated; TON) of Tetrabi to explore its
activity. The S/Rh ratio was increased from 1000 to 10000,
with a longer time required for the complete conversion of
1-hexene. The TON of the linear amine can reach 6930 ac-
cording to the reaction with [RhACHTUNRGTNEUNG(acac)(CO)2], to give 99%
amine selectivity and 100% linear amine at 10000 S/Rh
ratio, in which the only by-product is the branched enamine.
Chem. Eur. J. 2011, 17, 14559 – 14563
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
14561

X. Zhang, W. Wu et al.
Table 3. Turnover number test of Tetrabi with [Rh
thylation.[a]
ACHTUNGRTENN(UNG acac)(CO)2] for hydroaminome-
minal olefins and secondary amines have been ap-
plied successfully for the compatibility of this
method. In general, aliphatic olefins and secondary
amines give the corresponding linear amines with a
high degree of chemoselectivity (99%), regioselec-
tivity (>120), and amine yield (>98%).
Furthermore, we have already produced
amounts of Tetrabi (100 g) and a ligand system of
Tetrabi derivatives, which will probably give solid
prospective support for the further application of
other functional olefins and amines, such as inter-
nal olefins, styrene derivatives, and primary
amines. Therefore, this atom-economic and envi-
ronmentally friendly synthesis of amines with Tet-
rabi will be valuable to the chemical and pharma-
ceutical industries.
Selectivity [%][b]
Entry S/Rh
t
Conv. yield Amine Iso
enamine By-pro-
TON[e] n/i[f]
[h] [%]
[%][c]
duct[d]
–
1
2
3
4
5
1000
6
99
97.5 99.1
97.4 99.0
94.6 99.6
84.7 99.7
69.3 99.0
0.9
981
156
2500 12 99
5000 24 95
8000 30 85
10000 36 70
0.2
0.4
0.3
1.0
0.8
2450
4731
6780
6930
525
–
>525[f]
>525[f]
>525[f]
–
–
[a] Reaction conditions: Tetrabi/[RhACTHUNTRGNEU(GN acac)(CO)2]=4:1, 1-hexene (1 mmol), piperidine
(1 mmol), 1258C, CO/H2 =7/35 bar, 2-propanol/ethanol (2:1, 3 mL). [b] Selectivity and
yield was determined by GC analysis using 2-methoxyethyl ether (0.1 mL) as an inter-
nal standard, the average value of three repeated runs and two injections per run.
[c] Yield of n-amine. [d] The major by-product is N-formylpiperidine. [e] Turnover
number was determined on the basis of GC, error is estimated at <200. [f] No
branched amine observed by GC.
hexylamine) also react well with 1-hexene to give the corre-
sponding amines in high yield and selectivity; the highest n/i
Experimental Section
General methods: All reactions and manipulations were performed in a
nitrogen-filled glove box or using standard Schlenk techniques, unless
otherwise noted. Anhydrous solvents were purchased from EMD chemi-
ratio of 250 was obtained with dihexylamine (Table 4, en-
tries 4–6). We have also tested the internal olefins and other
functional olefins with different functional amines at the
same time, and have already achieved good results; these re-
sults are beyond the scope of this article and will therefore
be published in due course.
cals Inc. [RhACHTUNGRTNEUNG(acac)(CO)2] was purchased from Strem chemicals. All re-
agents were purchased from either Aldrich or VWR and were used with-
out further purification. All olefins, amines, and catalysts were stored in
the nitrogen filled glove box before use. Tetrabi was prepared according
to the literature procedure.[7d] 1H and 13C NMR spectra were recorded on
a Varian Mercury 400 MHz FT-NMR spectrometer. All chemical shifts
are reported in ppm. A positive ion mass spectrum of sample was ac-
quired on a Thermo LTQ-FT mass spectrometer with an electrospray
ionization source. Gas chromatography (GC) was performed on a HP
7890 series system using a b-Dex 225 column from Supelco, (30 m x
0.25 mm ID). The products were isolated from the reaction mixture by
solvent evaporation and further purified by column chromatography on
200–400 mesh silica gel supplied by Sorbent technologies. All yields re-
ported refer to GC using 2-methoxyethyl ether as an internal standard.
The purity of isolated compounds was confirmed to be>98% pure by
GC, NMR. The linear to branched ratios were determined by GC analy-
sis of the crude reaction mixtures prior to flash chromatography. Com-
Conclusion
Our Tetrabi ligand was first successfully applied in the
direct synthesis of amines from terminal olefins with secon-
dary amines by hydroaminomethylation. The key to the suc-
cess is the use of a Tetrabi ligand together with [Rh-
ACHTUNGTRENNUNG(acac)(CO)2]. Remarkably, the highest regioselectivity (>
525) was achieved with 99% amine selectivity by using 1-
hexene and piperidine as the basic reactants, whereas the
TON can reach to 6930 at 10000 S/Rh ratio. A variety of ter-
1
pounds known in the literature were characterized by comparing their H
Table 4. Hydroaminomethylation of various olefins and amines.[a]
Entry
Olefin
Amine
Major
product
Conv.
[%]
Amine[b]
selectivity [%]
Amine
n/i
yield[b] [%]
1
>99
>99
>99
>99
99
99
99
99
>98
>98
>98
>98
208
183
121
167
2
3[c]
4
5[c]
6
>99
>99
99
99
>98
>98
140
250
[a] Reaction conditions: [RhACHTNUGTRENUNG(acac)(CO)2] (1 mmol), Tetrabi (4 mmol), olefin (1 mmol), amine (1 mmol), 2-propanol/ethanol (3 mL, 2:1), CO/H2 =7/35 bar
at 1258C, for 6 h. [b] Selectivity and yield was determined by GC analysis using 2-methoxyethyl ether (0.1 mL) as an internal standard, the average value
of three repeated runs and two injections per run. [c] 1258C for 12 h.
14562
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 14559 – 14563

Regioselective Hydroaminomethylation of Terminal Olefins to Linear Amines
FULL PAPER
and 13C NMR data to the previously reported data. New products were
further characterized by HRMS.
Org. Chem. 1999, 653–660; c) F. Koc, M. Wyszogrodzka, P. Eil-
bracht, R. Haag, J. Org. Chem. 2005, 70, 2021–2025.
General procedure for the hydroaminomethylation:[7, 11] All hydroamino-
methylation experiments were performed in the nitrogen-filled glove
box. Tetrabi (4 mmol, 3.8 mg) and [Rh (acac)(CO)2] (1 mmol, 0.1 mL of
10 mmol solution in toluene) was added to a 10 mL long neck vial with a
magnetic stirring bar. The mixture was stirred for 10 min; 1-hexene
(1 mmol, 0.125 mL) and piperidine (1 mmol, 0.098 mL) was then added,
followed by 2-methoxyethyl ether (0.1 mL) as internal standard, 2-propa-
nol (2 mL) and ethanol (1 mL). The reaction mixture was transferred to
an autoclave vial covered with a simple lid. The autoclave was purged
with H2 three times and subsequently charged with CO (7 bar) and H2
(35 bar). The reaction was carried out at 1258C for 6 h. After 6 h, the au-
toclave was then cooled to room temperature and depressurized carefully
in a well-ventilated hood. The reaction mixture was immediately ana-
lyzed by GC to determine the conversion and regioselectivity.
[5] a) A. Seayad, M. Ahmed, H. Klein, R. Jackstell, T. Gross, M. Beller,
Science 2002, 297, 1676–1678; b) M. Ahmed, A. M. Seayad, R. Jack-
stell, M. Beller, Angew. Chem. 2003, 115, 5773–5777; Angew. Chem.
Int. Ed. 2003, 42, 5615–5619; c) M. Ahmed, R. P. J. Bronger, R.
Jackstell, P. C. J. Kamer, P. W. N. M. van Leeuwen, M. Beller, Chem.
Eur. J. 2006, 12, 8979–8988.
[6] M. Ahmed, A. M. Seayad, R. Jackstell, M. Beller, J. Am. Chem. Soc.
2003, 125, 10311–10318.
[7] a) Y. Yan, X. Zhang, X. Zhang, J. Am. Chem. Soc. 2006, 128,
16058–16061; b) Y. Yan, X. Zhang, X. Zhang, Adv. Synth. Catal.
2007, 349, 1582–1586; c) S. Yu, Y. Chie, Z. Guan, X. Zhang, Org.
Lett. 2008, 10, 3469–3472; d) S. Yu, X. Zhang, Y. Yan, C. Cai, L.
Dai, X. Zhang, Chem. Eur. J. 2010, 16, 4938–4943.
[8] Xantphos: a) M. Kranenburg, Y. E. M. van der Burgt, P. C. J. Kamer,
P. W. N. M. van Leeuwen, Organometallics 1995, 14, 3081–3089;
b) L. A. Van der Veen, M. D. Boele, F. R. Bregman, P. C. Paul,
P. W. N. M. van Leeuwen, K. Goubitz, J. Fraanje, H. Schenk, C. Bo,
J. Am. Chem. Soc. 1998, 120, 11616–11626; c) J. J. Carbꢂ, F. Mase-
ras, C. Bo, P. W. N. M. van Leeuwen, J. Am. Chem. Soc. 2001, 123,
7630–7037.
[9] Bisbi: a) C. P. Casey, G. T. Whiteker, M. G. Melville, L. M. Lori,
J. A. Gavney, D. R. Powell, J. Am. Chem. Soc. 1992, 114, 5535–
5543; b) C. P. Casey, E. L. Paulsen, E. W. Beuttenmueller, B. R.
Proft, L. M. Petrovich, B. A. Matter, D. R. Powell, J. Am. Chem.
Soc. 1997, 119, 11817–11825.
Acknowledgements
This research was supported by the National Science Foundation (NSF
CHE 0956784), Dow Chemical Co., China Scholarship Council and
Northwest A & F University. We thank Doc. Furong Sun for the HRMS
analysis.
[10] a) J.-C. Hierso, M. Beauperin, P. Meunier, Eur. J. Inorg. Chem. 2007,
3767–3780; b) D. Evrard, D. Lucas, Y. Mugnier, P. Meunier, J. C.
Hierso, Organometallics 2008, 27, 2643–2653.
[11] S. Yu, Y. Chie, Z. Guan, Y. Zou, W. Li, X. Zhang, Org. Lett. 2009,
11, 241–244.
[1] a) J. March, Advanced Organic Chemistry, 4th ed., Wiley, New
York, 1992, pp. 768; b) T. E. Mꢁller, M. Beller, Chem. Rev. 1998, 98,
675–703; c) Y. Yamamoto, U. Radhakrishnan, Chem. Soc. Rev.
1999, 28, 199–207.
[2] P. Eilbracht, Chem. Rev. 1999, 99, 3329.
[3] a) W. Reppe, Experientia 1949, 5, 93; b) W. Reppe, H. Vetter, Justus
Liebigs Ann. Chem. 1953, 582, 133–163.
[4] a) P. Eilbracht, C. L. Kranemann, L. Barfacker, Eur. J. Org. Chem.
1999, 1907–1914; b) T. Rische, L. Barfacker, P. Eilbracht, Eur. J.
Received: September 30, 2011
Published online: November 21, 2011
Chem. Eur. J. 2011, 17, 14559 – 14563
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
14563