Preparation and application of air-stable P,N-bidentate ligands for the selective synthesis of δ-lactone via the palladium-catalyzed telomerization of 1,3-butadiene with carbon dioxide

Article abstract of DOI:10.1016/j.jorganchem.2011.10.011

Air-stable P,N-bidentate ligands L1-L7 with cyclic secondary amine moieties linked to the benzene rings of triphenylphosphine were designed and prepared. The chelating coordination mode of the P,N-bidentate ligands to the Pd(II) center was confirmed by determining the X-ray structures of the Pd(II) complexes C1 and C2 derived from ligands L1 and L2, respectively. The ligands were used for the selective synthesis of δ-lactone through the palladium (Pd)-catalyzed telomerization of 1,3-butadiene with carbon dioxide. The highest yield (60% with 79% selectivity) was observed using the Pd₂(dba) ₃/4-(2-(diphenylphosphino)phenyl)morpholine (L2) catalyst system.

Full text of DOI:10.1016/j.jorganchem.2011.10.011

Journal of Organometallic Chemistry 696 (2012) 4309e4314
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Preparation and application of air-stable P,N-bidentate ligands for the selective
synthesis of d-lactone via the palladium-catalyzed telomerization of 1,3-butadiene
with carbon dioxide
*
**
Yao Dai, Xiujuan Feng , Bin Wang, Ren He, Ming Bao
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Air-stable P,N-bidentate ligands L1eL7 with cyclic secondary amine moieties linked to the benzene rings
of triphenylphosphine were designed and prepared. The chelating coordination mode of the P,N-
bidentate ligands to the Pd(II) center was confirmed by determining the X-ray structures of the Pd(II)
complexes C1 and C2 derived from ligands L1 and L2, respectively. The ligands were used for the
Received 22 July 2011
Received in revised form
17 September 2011
Accepted 6 October 2011
selective synthesis of d-lactone through the palladium (Pd)-catalyzed telomerization of 1,3-butadiene
with carbon dioxide. The highest yield (60% with 79% selectivity) was observed using the Pd2(dba)3/4-
(2-(diphenylphosphino)phenyl)morpholine (L2) catalyst system.
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Carbon dioxide
1,3-Butadiene
Palladium catalyst
P,N-Bidentate ligand
d
-Lactone
1. Introduction
P,N-bidentate ligands based on the air-stable triphenylphosphine
(PPh3) for the selective synthesis of d-lactone (Scheme 2, L1eL7).
The selective synthesis of
catalyzed telomerization of 1,3-butadiene with carbon dioxide
(CO2) has attracted considerable attention (Scheme 1). Since its
d
-lactone through the palladium (Pd)-
The ortho-substituted cyclic secondary amino group on a benzene
ring in triphenylphosphine is expected to increase the electron
density of the phosphorus atom and the steric hindrance of the
entire molecule. It is also expected that the newly formed sterically
bulky P,N-bidentate ligands will hinder the formation of undesired
product octadienyl ester 3 (Scheme 1) [8]. These ligands should
initial synthesis in 1978 by Musco’s group [1], d-lactone has gained
interest because it could be transformed to various useful fine
chemicals [2e7]. The Pd-catalyzed telomerization of 1,3-butadiene
with CO2 is the first successful example of the catalytic formation of
a new CeC bond between CO2 and an organic compound. Hence,
this telomerization process has become an interesting and prom-
ising means of using CO2 as a C1-builing block in synthetic organic
chemistry. Electron-rich, sterically bulky phosphine ligands such as
tricyclohexylphosphine (PCy3), triisopropylphosphine (PiPr3), and
accelerate the reductive elimination of intermediate 1 to produce d-
lactone 2 by their peculiar coordination properties [17,18]. The X-
ray structures of the Pd(II) complexes C1 and C2 derived from
ligands L1 and L2, respectively, are also presented.
2. Results and discussion
i
the P,N-bidentate ligand Pr2PeCH2CH2CH2CH2CH2CH2eCN favor
the production of d-lactone [8e12]. However, these bulky ligands
are air-sensitive and too difficult to handle for use in laboratory
2.1. Preparation and characterization of ligands L1eL7
research and industry production. Air-stable phosphine ligands are
more desirable for large-scale d-lactone synthesis.
Our group has continuously researched CO2 chemistry [13e16].
In the present study, we designed and synthesized new types of
The ligands L1eL7 were prepared according to the synthetic
routes schematically described in Scheme 3 and 4. The reaction of
a Grignard reagent generated from 1-(2-bromophenyl)piperidine
(BPPP) with diphenylphosphinous chloride (Ph2PCl) proceeded
smoothly to give ligand L1 in satisfactory yield (66%), even although
the Grignard reagent bore a relatively bulky substituent on ortho
position (Scheme 3). When the Grignard reagent generated from 4-
(2-bromophenyl)morpholine (BPMP) was treated with Ph2PCl,
dichlorophenylphosphine (PhPCl2), and phosphorus tribromide
* Corresponding author. Tel.: þ86 411 84986184; fax: þ86 411 84986181.
** Corresponding author. Tel.: þ86 411 84986180; fax: þ86 411 84896181.
E-mail addresses: fengxiujuan@dlut.edu.cn (X. Feng), mingbao@dlut.edu.cn
(M. Bao).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.10.011

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Y. Dai et al. / Journal of Organometallic Chemistry 696 (2012) 4309e4314
Scheme 1. Palladium-catalyzed telomerization of 1,3-butadiene with carbon dioxide.
(PBr3), respectively, the desired ligands L2, L6, and L7 were ob-
tained in moderate yields (68%, 56%, and 51%, respectively; Scheme
3). Then the desired ligands L3eL5 were synthesized through Pd-
catalyzed CeN bond cross-coupling reaction (BuchwaldeHartwig
cross-coupling reaction). The reaction of (2-bromophenyl)diphe-
nylphosphine (BDPP) with piperazine was performed in the pres-
ence of catalytic amount of tris(dibenzylideneacetone)dipalladium
[Pd2(dba)3] using L7 as a ligand, which was prepared as described
above. The ligand L3 was obtained in 72% yield along with
a debrominated product (PPh3, 25%) (Scheme 4). However, the
ligand L4, an analog of L3, was isolated in excellent yield (94%) from
the reaction of BDPP with 1-methylpiperazine under the same
reaction conditions (Scheme 4). The ligand L5 was obtained in only
5% yield when the reaction of BDPP with 3,4-dihydro-2H-1,4-
benzoxazine was carried out under the same reaction conditions
as employed in the synthesis of ligands L3 and L4. The yield of L5
was increased to 44% by using (ꢀ)-2,20-bis(diphenylphosphino)-
1,10-binaphthyl [(ꢀ)-BINAP] as a ligand (Scheme 4). All the new
ligands L1eL7 were identified through their NMR and HRMS data
as well as IR spectra. Furthermore, the X-ray structure of ligand L2
was determined as shown in Fig. 1 [19].
Scheme 3. Synthesis of the ligands L1, L2, L6, and L7.
yield and 43% selectivity of
d-lactone 2 were achieved (entry 1). All
these data were higher than those obtained using the parent ligand
PPh3 (entry 9). Using L2, increased yield and selectivity of 2 (43%
and 66%, respectively) as well as slightly decreased conversion of
1,3-butadiene (65%) were achieved. With the exception of selec-
tivity, these results were better than those obtained using PCy3
(entry 10). Using L3 and L4 instead of L2, almost the same result for
the conversion of 1,3-butadiene as L2 was achieved (entries 3 and 4,
67%). However, the yield and selectivity of 2 decreased (L3: 34%
yield with 51% selectivity; L4: 33% yield with 49% selectivity). Using
L5 led to poor results (22% yield of 2 with 37% selectivity, 60%
conversion of 1,3-butadiene; entry 5). Using the more sterically
bulky ligands L6 and L7 yielded only trace amounts of 2 (entries 6
and 7). In order to evaluate the effectiveness of cyclic amino groups
in the PeN ligands, the ligand 2-(diphenylphosphino)-N,N-dime-
thylaniline [(2-Me2NC6H4)PPh2, L8] was synthesized [21] and used
for the Pd-catalyzed telomerization of 1,3-butadiene with CO2. The
2.2. X-ray structures of Pd(II) complexes C1 and C2
To confirm the chelating coordination manner of ligands L1eL7,
the Pd complexes C1 and C2 were prepared by reacting of
PdCl2(MeCN)2 with L1 or L2. The X-ray structures of C1 and C2 are
shown in Fig. 1 [20]. Clearly, the soft P and hard N atoms in L1 or L2
coordinated with the Pd(II) center to form a chelate complex. These
results indicated that these ligands can be used as hemilabile
desired product d-lactone 2 was obtained in only 11% yield with low
selectivity, and the conversion of 1,3-butadiene was also not
satisfactory (24% selectivity, 46% conversion; entry 8). These data
were quite a bit lower than those obtained using L1eL5 (entry 8
versus entries 1e5). Overall, L2 was the most effective in promoting
ligands to promote the selective synthesis of d-lactone 2.
the selective synthesis of
subsequent studies.
d-lactone 2. Therefore, L2 was used in
2.3. Pd-catalyzed telomerization of 1,3-butadiene with carbon
dioxide
2.3.1. Ligand screening
The effects of the newly formed P,N-bidentate ligands L1eL7 on
the selective synthesis of d-lactone 2 were firstly examined. The
selective synthesis involved the Pd-catalyzed telomerization of 1,3-
butadiene with carbon dioxide using Pd(acac)2 as the Pd source and
acetonitrile (MeCN) as a solvent [8]. The results are shown in
Table 1. Using L1, 72% conversion of 1,3-butadiene as well as 31%
Scheme 2. The structures of newly formed P,N-bidentate ligands.
Scheme 4. Synthesis of the ligands L3eL5.

Y. Dai et al. / Journal of Organometallic Chemistry 696 (2012) 4309e4314
4311
Fig. 1. Structures of ligand L2 (a), complexes C1 (c) and C2 (d) at 30% probability level. Hydrogen atoms are omitted for clarity.
2.3.2. Pd catalyst precursor screening for telomerization
Using L2, Pd catalyst precursors were screened for the selective
synthesis of d-lactone 2. As shown in Table 2, Pd catalyst precursors
significantly influenced the selective formation of 2. Using Pd(a-
cac)2, which was also employed in section 2.3.1, yielded 43% of
product 2 with 66% selectivity (entry 1). Pd(OAc)2 showed inferior
efficiency and yielded 30% of product 2 with 50% selectivity (entry
2). Using Pd2(dba)3 yielded 44% of product 2 with 68% selectivity
(entry 3). These results were slightly higher than those observed
using Pd(acac)2. Pd2(dba)3 is a stable commercially available Pd0
source, which could coordinate with L2 to directly generate an
active Pd species in situ.
2.3.3. Effects of reaction temperature on telomerization
The catalyst system Pd2(dba)3/L2 was chosen for reaction
temperature optimization. Table 2 shows that the conversion of 1,3-
butadiene increases with rising temperature (entries 3e8;
temperature: from 50 ꢁC to 100 ꢁC; conversion: from 44% to 70%).
This observation was consistent with the previous report [22]. The
yield and selectivity of 2 were also increased with rising temper-
ature within the range of 50e70 ꢁC (entries 4e6; yield: from 29% to
50%; conversion: from 44% to 61%). When the reaction of CO2 with
1,3-butadiene was performed at 80 ꢁC, almost the same results
were obtained as those obtained at 70 ꢁC (entry 7). But the yield
and selectivity of 2 decreased when the reaction temperature was
Table 1
Ligands screening for the selective synthesis of 2.a
Entry
Ligand
Conversion (%)
Yield (%)b
Selectivity (%)
1
2
3
4
5
6
7
8
9
10
L1
L2
L3
L4
L5
L6
L7
L8
72
65
67
67
60
50
10
46
64
45
31
43
34
33
43
66
51
49
higher than 80 ꢁC (entries 3 and 8). The decreasing
d-lactone-
formation was considered that due to its high temperature insta-
bility [22].
22
37
trace
trace
11
14
37
trace
trace
24
23
82
2.3.4. Effects of reaction time on telomerization
The next optimization step involved varying the reaction time,
as detailed in Table 2. The conversion of 1,3-butadiene and the yield
of 2 both increased with prolonging reaction time within the range
of 10e25 h (entries 6, 9e11; yield: from 44% to 60%; conversion:
from 56% to 76%). The selectivity is almost constant within the time
range as mentioned above. With the exception of conversion,
PPh3
PCy3
a
Reaction conditions: 0.066 mol% Pd(acac)2 (10.0 mg), 0.198 mol% ligand
(0.099 mmol), 2.70 g 1,3-butadiene (50 mmol), 2.45 g carbon dioxide (56 mmol),
5 mL MeCN, 90 ꢁC, 15 h; all reactions were carried out in 25 mL autoclave.
b
Isolated yield based on 1,3-butadiene.

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Y. Dai et al. / Journal of Organometallic Chemistry 696 (2012) 4309e4314
Table 2
grafting of L2 onto an SBA-15 mesoporous membrane for
a continuous process.
Optimization of reaction conditions for the selective synthesis of 2.a
4. Experimental section
4.1. Reagents and materials
Acetonitrile (MeCN) was dried by refluxing with CaH2 and was
distilled under nitrogen (N2) before use. 1-(2-Bromophenyl)piper-
idine (BPPP), 4-(2-bromophenyl)morpholine (BPMP), (2-
bromophenyl)diphenylphosphine (BDPP), PdCl2(MeCN)2, Pd(a-
cac)2, and 3,4-dihydro-2H-1,4-benzoxazine were prepared
according to previous reports [23e27]. Tris(dibenzylideneacetone)
dipalladium (Pd2(dba)3; 98.5%) was purchased from the Shanghai
Zealandchem Co., Ltd., China. Pd diacetate (Pd(OAc)2; trimer, 99.5%)
was purchased from the Tianjin Jinbolan Fine Chemical Co., Ltd.,
China. Tricyclohexylphosphine (PCy3; 96%) was purchased from the
Alfa Aesar China Co., Ltd. (Tianjin). Triphenylphosphine (PPh3;
99.7%) was purchased from the Tianjin Kermel Chemical Reagent
Co., Ltd., China. (ꢀ)-2,20-Bis(diphenylphosphino)-1,10-binaphthyl
[(ꢀ)-BINAP; 98%] was purchased form J&K Chemical Ltd., China
(Beijing). Phosphorus tribromide (PBr3; 98.5%) was purchased from
the Sinopharm Chemical Reagent Co., Ltd. (SCRC), China. Dichlor-
ophenylphosphine (PhPCl2; 98%) and diphenylphosphinous chlo-
ride (Ph2PCl; 97%) were purchased from Aladdin Reagent Database
Inc., China (Shanghai). Piperazine (99.5%), and 1-methylpiperazine
(99.8%) were all purchased from the SCRC. Sodium tert-butoxide
(NaOtBu; 99%) was purchased from the Zibo Fuxi’er Chemical Co.,
Ltd., China. Silica gel (200e300 mesh) was purchased from the
Qingdao Makall Group Co., Ltd., China. 1,3-Butadiene (99%) and CO2
(99.99%) were purchased from the Dalian Date Gas Co. Ltd., China.
N2 (99.999%) was purchased from the Dalian Guangming Special
Gas Products Co., Ltd., China. All other reagents were analytical
grade and were used without further purification.
Entry Pd source T (ꢁC) Time (h) Conversion (%) Yield (%)b Selectivity (%)
1
2
3
4
5
6
7
8
Pd(acac)2
Pd(OAc)2
90
90
15
15
15
15
15
15
15
15
10
20
25
30
25
25
25
65
60
65
44
57
61
63
70
56
70
76
82
67
55
49
43
30
44
29
44
50
51
33
44
54
60
59
50
37
26
66
50
68
66
77
82
81
47
79
77
79
72
75
67
53
Pd2(dba)3 90
Pd2(dba)3 50
Pd2(dba)3 60
Pd2(dba)3 70
Pd2(dba)3 80
Pd2(dba)3 100
Pd2(dba)3 70
Pd2(dba)3 70
Pd2(dba)3 70
Pd2(dba)3 70
Pd2(dba)3 70
Pd2(dba)3 70
Pd2(dba)3 70
9
10
11
12
13c
14d
15e
a
Reaction conditions: 0.066 mol% Pd(acac)2 (10.0 mg), 0.066 mol% Pd(OAc)2
(7.4 mg), 0.033 mol% Pd2(dba)3 (15.1 mg), 0.198 mol% L2 (34.4 mg), 2.70 g 1,3-
butadiene (50 mmol), 2.45 g carbon dioxide (56 mmol), 5 mL MeCN; all reactions
were carried out in 25 mL autoclave unless otherwise noted.
b
Isolated yield based on 1,3-butadiene.
0.017 mol% Pd2(dba)3 (7.6 mg) and 0.099 mol% L2 (17.4 mg) were used.
A mixture of 0.008 mol% Pd2(dba)3 (11.4 mg), 0.048 mol% L2 (25.0 mg), 8.10 g
c
d
1,3-butadiene (150 mmol), 7.40 g carbon dioxide (168 mmol), and 15 mL MeCN was
treated in 75 mL autoclave.
e
A mixture of 0.004 mol% Pd2(dba)3 (14.3 mg), 0.024 mol% L2 (33.4 mg), 21.60 g
1,3-butadiene (400 mmol), 19.70 g carbon dioxide (448 mmol), and 40 mL MeCN
was treated in 200 mL autoclave.
slightly decreased yield and selectivity were observed when the
reaction of CO2 with 1,3-butadiene was carried out under the same
4.2. Characterization
reaction conditions for
a prolonged time (30 h, entry 12).
Comparatively better results were obtained when the reaction time
was 25 h (entry 11).
1H, 13C, and 31P nuclear magnetic resonance spectra were
recorded in a CDCl3 solution on a Bruker DPX-400 spectrometer
(400 MHz for 1H, 101 MHz for 13C, and 162 MHz for 31P). Chemical
2.3.5. Effects of Pd2(dba)3 loading on telomerization
shifts (d
) were given relative to residual solvent signals for 1H and
The effects of Pd2(dba)3 loading on the telomerization reaction
of CO2 with 1,3-butadiene was investigated using L2. The results are
shown in Table 2. The Pd2(dba)3/L2 catalyst system exhibited a high
13C. H3PO4 (85%) was used as the external standard for 31P. Infrared
(IR) spectra were recorded on a PerkineElmer FTIR 430 spec-
trometer. High-resolution mass spectra were recorded on a Micro-
mass GC-TOF EI-MS spectrometer. Elemental analyses were
recorded on an Elemental Vario EL-III elemental analyzer. Melting
points were determined using an X-6 micro-melting point appa-
ratus and were uncorrected.
activity for the selective synthesis of
d-lactone 2. Even when
Pd2(dba)3 loading was decreased to 0.004 mol%, relatively better
results were still obtained (entry 15; 26% yield of 2 with 53%
selectivity; 49% conversion of 1,3-butadiene; turnover number,
TON of 1560). The yield and selectivity of 2 as well as the conversion
of 1,3-butadiene all decreased with decreased Pd2(dba)3 loading
(entries 11, 13e15).
4.3. Synthesis of ligands L1, L2, L6, and L7
4.3.1. 1-(2-(Diphenylphosphino)phenyl)piperidine (L1)
3. Conclusion
A solution of Grignard reagent was prepared from BPPP (2.64 g,
11 mmol) and magnesium powder (268 mg, 11 mmol) in THF
(10 mL). A solution of Ph2PCl (2.21 g, 10 mmol) in THF (5 mL) was
then added dropwise at room temperature, and the mixture was
stirred for 1 h. After the reaction mixture was further stirred at
80 ꢁC for 2 h, excess saturated NH4Cl aqueous solution was added at
room temperature. The product was extracted with ether
(20 mL ꢂ 3) and dried over Na2SO4. The solvent was then evapo-
rated in vacuo and the remaining solid was recrystallized by
ethanol to give L1 as a white crystal (2.28 g, 66% yield).
Air-stable hemilabile ligands L1eL7 containing soft phosphorus
and hard nitrogen atoms were prepared and were applied in the
selective synthesis of d-lactone 2. Among these ligands, L2 exhibi-
ted the best results (60% yield of 2 with 79% selectivity; 76%
conversion of 1,3-butadiene). These results are comparable with
those obtained using PCy3 as a ligand. Our method is the first
successful selective synthesis of
telomerization of CO2 with 1,3-butadiene using
d
-lactone 2 via the Pd-catalyzed
triar-
a
ylphosphine ligand. The X-ray structures of the Pd complexes C1
and C2 clearly showed the chelating coordination mode of the P,N-
bidentate ligands to the Pd(II) center. Our group is now studying the
1H NMR (400 MHz, CDCl3)
1H), 7.00 (t, J ¼ 7.4 Hz, 1H), 6.71e6.68 (m, 1H), 2.76e2.75 (m, 4H),
1.36e1.34 (m, 6H); 13C NMR (101 MHz, CDCl3):
157.4, 157.2, 138.5,
d 7.32e7.28 (m, 11H), 7.15e7.12 (m,
d

Y. Dai et al. / Journal of Organometallic Chemistry 696 (2012) 4309e4314
4313
138.4, 136.8, 136.7, 134.1, 133.9, 133.0, 129.6, 128.33, 128.30, 128.2,
124.8, 121.6, 121.6, 54.1, 26.1, 24.2.; 31P NMR (162 MHz, CDCl3):
4.4.2. 1-(2-(Diphenylphosphino)phenyl)-4-methylpiperazine (L4)
L4 was prepared similarly as L3 using 1-methylpiperazine
(150 mg, 1.5 mmol) as a starting material (L4: 339 mg, 94% yield,
yellow crystal).
d
ꢃ11.23; IR (KBr) 3051, 2938, 2850, 2797, 1579, 1466, 1433, 1224,
922þ, 765, 740, 696 cmꢃ1; HRMS (EI) calcd. for C23H24NP: 345.1646
[M] ; found: 345.1652; m.p.: 96e98 ꢁC.
1H NMR (400 MHz, CDCl3)
d
7.33e7.28 (m, 11H), 7.20e7.17 (m,
1H), 7.03 (t, J ¼ 7.4 Hz, 1H), 6.73e6.70 (m, 1H), 2.87 (t, J ¼ 4.6 Hz,
4H), 2.46e2.01 (m, 7H).; 13C NMR (101 MHz, CDCl3):
155.8, 155.6,
4.3.2. 4-(2-(Diphenylphosphino)phenyl)morpholine (L2)
L2 was prepared similarly as L1 using BPMP (2.66 g, 11 mmol) as
a starting material (L2: 2.36 g, 68% yield, white crystal).
d
138.2, 138.1, 136.8, 136.7, 134.2, 134.0, 133.2, 129.8, 128.5, 128.43,
128.35, 125.4, 121.9, 55.2, 52.3, 46.1.; 31P NMR (162 MHz, CDCl3):
1H NMR (400 MHz, CDCl3)
d
7.33e7.30 (m, 11H), 7.17e7.14 (m,
d
ꢃ12.01; IR (KBr) 3052, 2936, 2795, 1579, 1466, 1434, 1369, 1287,
1H), 7.03 (t, J ¼ 7.5 Hz, 1H), 6.75e6.72 (m, 1H), 3.48 (t, J ¼ 4.2 Hz,
1226, 1146, 1009, 927, 909, 768, 740, 742, 697 cmꢃ1; HRMS (EI)
calcd. for C23H25N2P: 360.1755 [M]þ; found: 360.1750, m.p.:
106e107 ꢁC.
4H), 2.80 (t, J ¼ 4.5 Hz, 4H).; 13C NMR (101 MHz, CDCl3):
d 155.4,
155.3, 138.0, 137.9, 136.94, 136.86, 134.2, 134.0, 133.2, 129.8, 128.6,
128.4, 128.3, 125.5, 121.8, 121.7, 67.2, 52.8, 52.8.; 31P NMR (162 MHz,
CDCl3)
d
ꢃ3.97; IR (KBr) 3052, 2956, 2853, 2814, 1580, 1466, 1433,
4.4.3. 4-(2-(Diphenylphosphino)phenyl)-3,4-dihydro-2H-benzo[b]
[1,4]oxazine (L5)
1219, 1113, 932, 767, 742, 697 cmꢃ1
; HRMS (EI) calcd. for
C22H22NOP: 347.1439 [M]þ; found: 347.1440; m.p.: 116e118 ꢁC.
L5 was prepared similarly as L3 using 3,4-dihydro-2H-1,4-
benzoxazine (203 mg, 1.5 mmol) as a starting material and
(ꢀ)-BINAP (37 mg, 0.06 mmol) as a ligand. The crude product was
purified by chromatography (5:100 ethyl acetate/petroleum ether)
to give L5 (172 mg, 44% yield) as a white crystal, and 36% of starting
material BDPP was recovered.
4.3.3. 4,40-((Phenylphosphinediyl)bis(2,1-phenylene))dimorpholine
(L6)
L6 was prepared similarly as L2 using BPMP (5.32 g, 22 mmol) as
a starting material (L6: 2.42 g, 56% yield, white crystal).
1H NMR (400 MHz, CDCl3)
d
7.33e7.31 (m, 7H), 7.17e7.14 (m,
1H NMR (400 MHz, CDCl3)
d 7.42e7.21 (m, 13H), 6.98e6.96 (m,
2H), 7.00 (t, J ¼ 7.4 Hz, 2H), 6.70 (d, J ¼ 7.4 Hz, 2H), 3.59e3.52 (m,
1H), 6.78e6.76 (m, 1H), 6.65e6.56 (m, 2H), 6.14e6.13 (m, 1H), 4.07
(d, J ¼ 10.7 Hz, 1H), 3.97 (t, J ¼ 9.7 Hz, 1H), 3.53e3.48 (m, 1H), 3.06
8H), 2.92e2.89 (m, 4H), 2.85e2.82 (m, 4H); 13C NMR (101 MHz,
CDCl3):
129.5, 128.4, 128.3, 128.2, 125.0, 121.1, 67.3, 53.0, 52.9; 31P NMR
(162 MHz, CDCl3):
d
155.7, 155.5, 138.8, 138.7, 137.1, 137.0, 134.6, 134.4, 133.6,
(d, J ¼ 11.1 Hz,1H).; 13C NMR (101 MHz, CDCl3):
d 150.2, 150.0, 144.3,
139.4,139.3,137.1,137.0,136.7,136.5,134.6,134.3,134.0,130.7,128.9,
128.7, 128.6, 128.5, 128.4, 128.0, 127.4, 120.9, 119.0, 116.3, 115.7, 64.5,
d
ꢃ19.69; IR (KBr) 3347, 3053, 2957, 2853, 2814,
1580, 1466, 1445, 1371, 1263, 1219, 1113, 932, 919, 847, 768, 735,
699 cmꢃ1; HRMS (EI) calcd. for C26H29N2O2P: 432.1967 [M]þ;
found: 432.1973; m.p.: 153e154 ꢁC.
49.0.; 31P NMR (162 MHz, CDCl3):
2841, 1604, 1582, 1497, 1463, 1434, 1314, 1242, 1057, 909, 795, 767,
740, 697 cmꢃ1; HRMS (EI) calcd. for C26H22NOP: 395.1439 [M]þ;
found: 395.1449; m.p.: 130e131 ꢁC.
d
ꢃ13.95; IR (KBr) 3053, 2977,
4.3.4. Tris(2-morpholinophenyl)phosphine (L7)
L7 was prepared similarly as L2 using BPMP (7.98 g, 33 mmol) as
a starting material (L7: 2.64 g, 51% yield, white crystal).
4.5. Synthesis of the Pd(II) complexes C1 and C2
1H NMR (400 MHz, CDCl3)
d
7.32e7.28 (m, 3H), 7.15e7.12 (m,
3H), 6.98e6.94 (m, 3H), 6.71e6.68 (m, 3H), 3.61 (s, 12H), 3.15 (s,
6H), 2.69 (s, 6H).; 13C NMR (101 MHz, CDCl3):
156.1, 155.9, 137.0,
136.9, 134.3, 129.4, 124.8, 120.43, 120.41, 67.4, 53.1.; 31P NMR
(162 MHz, CDCl3):
4.5.1. 1-(2-(Diphenylphosphino)phenyl)piperidine Pd(II) dichloride
(C1)
d
L1 (173 mg, 0.5 mmol), PdCl2(MeCN)2 (130 mg, 0.5 mmol), and
CHCl3 (5 mL) were mixed in a Schlenk reactor at room temperature.
The reaction mixture was stirred for 1 h, filtered, and evaporated in
vacuo. The residue obtained was washed with ethanol to give C1
(237 mg, 91% yield) as a yellow powder.
d
ꢃ19.69; IR (KBr) 3051, 2956, 2851, 2812, 1580,
1466, 1444, 1370, 1295, 1253, 1220, 1113, 932, 919, 846, 768,
735 cmꢃ1; HRMS (EI) calcd. for C30H36N3O3P: 517.2494 [M]þ; found:
517.2495; m.p.: 242e244 ꢁC.
1H NMR (400 MHz, CDCl3)
d 8.19e8.15 (m, 1H), 7.82e7.77 (m,
4.4. Synthesis of ligands L3eL5
4H), 7.65e7.56 (m, 3H), 7.49e7.35 (m, 6H), 5.52e5.45 (m, 2H), 3.34
(d, J ¼ 13.2 Hz, 2H), 2.17e2.01 (m, 4H),1.70 (d, J ¼ 13.6 Hz, 2H); 13C
4.4.1. 1-(2-(Diphenylphosphino)phenyl)piperazine (L3)
NMR (101 MHz, CDCl3): d 160.4, 160.3, 134.7, 133.9, 133.8, 133.6,
BDPP (341 mg, 1 mmol), NaOtBu (114 mg, 1.5 mmol), piperazine
(129 mg, 1.5 mmol), Pd2(dba)3 (9 mg, 0.01 mmol), L7 (31 mg,
0.06 mmol), and toluene (2.5 mL) were mixed in a Schlenk reactor.
After the reaction mixture was placed in a pre-heated oil bath at
100 ꢁC for 24 h, H2O (20 mL) was added at room temperature. The
product was extracted with ether (10 mL ꢂ 3) and was dried over
Na2SO4. The solvent was evaporated in vacuo. The remaining solid
was purified by chromatography (5:100 methanol/dichloro-
methane) to give L3 (249 mg, 72% yield) as a yellow crystal along
with a debrominated product (PPh3, 25%).
132.3, 130.1, 129.6, 129.4, 129.2, 129.1, 128.2, 127.6, 126.2, 126.1, 60.7,
22.7, 21.1.; 31P NMR (162 MHz, CDCl3):
39.82; IR (KBr) 3447, 3056,
2940, 2877, 2797, 1579, 1477, 1464, 1435, 1101, 911, 729, 690 cmꢃ1
d
;
Anal. calcd. for C23H24Cl2NPPd: C, 52.85; H, 4.63; N, 2.68. Found: C,
51.95; H, 4.68; N, 2.40; m.p.: 204 ꢁC, decomposed.
4.5.2. 4-(2-(Diphenylphosphino)phenyl)morpholine Pd(II)
dichloride (C2)
C2 was prepared similarly as C1 using L2 (174 mg, 0.5 mmol) as
a ligand instead of L1 (C2: 245 mg, 94% yield, yellow powder).
1H NMR (400 MHz, CDCl3)
1H), 7.04 (t, J ¼ 7.5 Hz, 1H), 6.72e6.69 (m, 1H), 2.82 (t, J ¼ 4.5 Hz,
4H), 2.69e2.68 (m, 4H).; 13C NMR (101 MHz, CDCl3):
156.0, 155.8,
138.1, 138.0, 136.84, 136.76, 134.1, 133.9, 133.0, 129.7, 128.5, 128.4,
128.3, 125.3, 121.8, 53.4, 45.9.; 31P NMR (162 MHz, CDCl3):
d
7.34e7.28 (m, 11H), 7.18e7.15 (m,
1H NMR (400 MHz, CDCl3)
d 8.21e8.18 (m, 1H), 7.82e7.76 (m,
4H), 7.71e7.69 (m, 1H), 7.61e7.57 (m, 2H), 7.50e7.46 (m, 4H),
7.44e7.37 (m, 2H), 5.36e5.31 (m, 2H), 4.30e4.26 (m, 2H),
4.02e3.97 (m, 2H), 3.40e3.37 (m, 2H); 13C NMR (101 MHz, CDCl3):
d
d
ꢃ11.72;
d
160.1, 156.0, 134.4, 133.8, 133.7, 132.5, 129.5, 129.4, 129.3, 129.2,
129.0, 127.8, 127.1, 126.6, 126.5, 61.9, 59.5.; 31P NMR (162 MHz,
CDCl3): 38.65; IR (KBr) 3056, 2956, 2883, 1579, 1480, 1436, 1102,
910, 727, 690 cmꢃ1; Anal. calcd. for C22H22Cl2NOPPd: C, 50.36; H,
IR (KBr) 3281, 3052, 2942, 2817, 1580, 1466, 1434, 1371, 1219, 1316,
1220, 937, 909, 767, 739, 742, 697 cmꢃ1; HRMS (EI) calcd. for
C22H23N2P: 346.1599 [M]þ; found: 346.1610; m.p.: 98e100 ꢁC.
d

4314
Y. Dai et al. / Journal of Organometallic Chemistry 696 (2012) 4309e4314
4.23; N, 2.67. Found: C, 50.47; H, 4.30; N, 2.47; m.p.: 224 ꢁC,
decomposed.
Appendix A. Supplementary material
X-ray crystal data for ligand L2 as well as complexes C1and C2,
and 1H, 13C as well as 31P NMR spectra for all new products. This
material can be found in the online version, at doi:10.1016/j.
jorganchem.
4.6. Crystal structure determination
Crystal data were collected using a Bruker Smart APEX CCD area
detector diffractometer (graphite-monochromated Mo K
a radia-
tion,
l
¼ 0.71073 Å) at 273 K. The frame data were integrated with
Appendix. Supplementary material
the program SAINT. The structure was determined by direct
methods using the program SHELXS-97 [28]. Structure refinement
by full-matrix least-squares on F2 was carried out using the
program SHELXL-97 [28]. Anisotropic displacement parameters
were assigned to all the non-hydrogen atoms of the complex.
Hydrogen atoms were inserted into idealized positions and were
refined by riding with the atoms to which they were bonded.
Supplementary material related to this article can be found
online at doi:10.1016/j.jorganchem.2011.10.011. These data include
MOL files and InChiKeys of the most important compounds
described in this article.
References
4.7. Typical procedure for synthesis of 2 using Pd-catalyzed
telomerization of 1,3-butadiene with CO2
[1] A. Musco, C. Perego, V. Tartiari, Inorg. Chim. Acta 28 (1978) L147eL148.
[2] V. Haack, E. Dinjus, S. Pitter, Angew. Makromol. Chem. 257 (1998) 19e22.
[3] A. Behr, V.A. Brehme, J. Mol. Catal. A: Chem. 187 (2002) 69e80.
[4] A. Behr, V.A. Brehme, Adv. Synth. Catal. 344 (2002) 525e532.
[5] A. Behr, M. Urschey, V.A. Brehme, Green Chem. 5 (2003) 198e204.
[6] A. Behr, G. Henze, L. Johnen, S. Reyer, J. Mol. Catal. A: Chem. 287 (2008) 95e101.
[7] A. Behr, G. Henze, Green Chem. 13 (2011) 25e39.
[8] A. Behr, K.D. Juszak, J. Organometall. Chem. 255 (1983) 263e268.
[9] A. Behr, K.D. Juszak, W. Keim, Synthesis (1983) 574.
[10] A. Behr, R. He, K.D. Juszak, C. Krüger, Y.H. Tsay, Chem. Ber. 119 (1986)
991e1015.
Pd2(dba)3 (15.1 mg, 0.016 mmol, 0.033 mol%) and L2 (34.4 mg,
0.099 mmol, 0.198 mol%) were placed in a 25 mL autoclave. The
sealed autoclave was purged with N2 three times. MeCN (5 mL),1,3-
butadiene (2.70 g, 50 mmol), and CO2 (2.45 g, 56 mmol) were then
charged into the autoclave at ꢃ20 ꢁC. The autoclave was placed in
a 70 ꢁC oil bath and was maintained constant for 25 h. Upon
completion of the desired reaction time, the autoclave was half-
submerged in a mixed ice/water bath. When the autoclave was
cooled to room temperature, the remaining gas was vented into
a measuring equipment to determine the conversion of 1,3-
butadiene. The remaining liquid in the autoclave was then evapo-
rated in vacuo to give the crude product. The crude product was
purified by silica gel chromatography (20:100 ethyl acetate/petro-
leum ether) to give 2 (2.27 g, 60%) as a light yellow oil. The yields of
2 as well as the amounts of Pd precursors and phosphine ligands
were all calculated based on 1,3-butadiene.
[11] S. Pitter, E. Dinjus, J. Mol. Catal. A: Chem. 125 (1997) 39e45.
[12] K. Buchmüller, N. Dahmen, E. Dinjus, D. Neumann, B. Powietzka, S. Pitter,
J. Schön, Green Chem. 5 (2003) 218e223.
[13] X.J. Feng, X.B. Lu, R. He, Appl. Catal. A 272 (2004) 347e352.
[14] X.J. Feng, X.G. Li, R. He, H. Zhou, Chin. Chem. Lett. 16 (2005) 767e770.
[15] X.J. Feng, M. Yan, T. Zhang, Y. Liu, M. Bao, Green Chem. 12 (2010) 1758e1766.
[16] X.J. Feng, M. Yan, X. Zhang, M. Bao, Chin. Chem. Lett. 22 (2011) 643e646.
[17] C.S. Slone, D.A. Weinberger, C.A. Mirkin, Prog. Inorg. Chem. 48 (1999) 233e350.
[18] P. Braunstein, F. Naud, Angew. Chem. Int. Ed. 40 (2001) 680e699.
[19] The crystal data of L2 has been deposited at Cambridge Crystallographic Data
Center on Mar. 11, 2010 (CCDC No. 769048), which can be obtained free of
charge from the Cambridge Crystallographic Data Centre through www.ccdc.
cam.ac.uk/data_request/cif. While the present paper was in preparation, K.D.
Hesp et al. reported the same structure of ligand L2 for the palladium-
1H NMR (400 MHz, CDCl3)
d 7.18e7.13 (m, 1H), 5.99e5.72 (m,
catalyzed
a-arylation of acetone with electron-deficient 4-bromobenzoni-
trile K.D. Hesp, R.J. Lundgren, M. Stradiotto, J. Am. Chem. Soc. 133 (2011)
5194e5197.
[20] The crystal data of C1 and C2 has been deposited at Cambridge Crystallo-
graphic Data Center on Sep. 28, 2010 (CCDC No. 794754, 794753), which can
be obtained free of charge from the Cambridge Crystallographic Data Centre
through www.ccdc.cam.ac.uk/data_request/cif.
1H), 5.37 (d, J ¼ 17.2 Hz, 1H), 5.25 (d, J ¼ 10.6 Hz, 1H), 4.79 (s, 1H),
2.63e2.45 (m, 2H), 2.14e1.99 (m, 1H), 1.83e1.76 (m, 4H); 13C NMR
(101 MHz,) d 166.3, 141.3, 135.8, 125.9, 117.0, 79.0, 27.7, 22.0, 14.2; IR
(KBr) 2924, 2854, 1713, 1636, 1379, 1257, 1209, 1147, 1066, 988,
723 cmꢃ1; HRMS (EI) calcd. for C9H12O2: 152.0837 [M]þ; found:
152.0840 [9].
[21] H.P. Fritz, I.R. Gordon, K.E. Schwarzhans, L.M. Venanzi, J. Chem. Soc. (1965)
5210e5216.
[22] A. Behr, P. Bahke, B. Klinger, M. Becker, J. Mol. Catal. A: Chem. 267 (2007)
149e156.
[23] W. Verboom, D.N. Reinhoudt, R. Visser, S. Harkema, J. Org. Chem. 49 (1984)
269e276.
Acknowledgments
[24] M.T. Whited, E. Rivard, J.C. Peters, Chem. Commun. (2006) 1613e1615.
[25] C.J. Mathews, P.J. Smith, T. Welton, J. Mol. Catal. A: Chem. 206 (2003) 77e82.
[26] G. Künstle, H. Siegel, Verfahren zur Herstellung von palladium(II)acetylace-
tonat DE2402383 (1975).
[27] P. Mizar, B. Myrboh, Tetrahedron Lett. 47 (2006) 7823e7826.
[28] G.M. Sheldrick, SHELX97: Program System for Crystal Structure Determina-
tion. University of Göttingen, Germany, 1997.
We are grateful to the National Natural Science Foundation of
China (21073025) for financial support. This work was partly sup-
ported by China Postdoctoral Science Foundation (20100471433)
and the Fundamental Research Funds for the Central Universities
(DUT10LK06).