Heck Reactions Catalyzed by Ultrasmall and Uniform Pd Nanoparticles Supported on Polyaniline

Article abstract of DOI:10.1021/acs.joc.5b01358

Using air as the oxidant instead of the traditionally employed persulfates, the smaller and more uniform Pd nanoparticles (around 2 nm) supported on polyaniline (Pd@PANI) can be easily fabricated by the oxidation-polymerization of aniline with PdCl₂. This material is an efficient and environmentally friendly catalyst for Heck reactions due to its recyclability, low loading, and ligand-free and mild reaction conditions. It was even tolerant to sulfur-containing substrates. This work reports the Pd@PANI-catalyzed Heck reactions with very wide substrate scopes, and discloses the catalytic mechanisms based on experimental findings and results of catalyst analysis and characterization.

Full text of DOI:10.1021/acs.joc.5b01358

Article
pubs.acs.org/joc
Heck Reactions Catalyzed by Ultrasmall and Uniform Pd
Nanoparticles Supported on Polyaniline
Lei Yu,* Yaping Huang, Zheng Wei, Yuanhua Ding, Chenliang Su,* and Qing Xu*
,†,‡
†,‡
†,§
†
,§
,†,‡
†Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, School of
Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu 225002, China
‡
Zhejiang Key Laboratory of Carbon Materials, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou,
Zhejiang 325035, China
§
SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices
and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University,
Shenzhen 518060, China
*
S Supporting Information
ABSTRACT: Using air as the oxidant instead of the
traditionally employed persulfates, the smaller and more
uniform Pd nanoparticles (around 2 nm) supported on
polyaniline (Pd@PANI) can be easily fabricated by the
oxidation−polymerization of aniline with PdCl . This material
2
is an efficient and environmentally friendly catalyst for Heck
reactions due to its recyclability, low loading, and ligand-free
and mild reaction conditions. It was even tolerant to sulfur-
containing substrates. This work reports the Pd@PANI-catalyzed Heck reactions with very wide substrate scopes, and discloses
the catalytic mechanisms based on experimental findings and results of catalyst analysis and characterization.
1
. INTRODUCTION
applications in organic reactions. Currently, M@PANIs have
been applied in limited simple organic reactions with narrow
application scopes, including Suzuki cross-couplings, the
1
,2
The Heck reaction has been one of the most important
synthetic tools to modify olefins with high selectivity and
efficiency. During the past 40 years, scientists have utilized this
tool to synthesize a wide range of the complex molecules
3
5
hydroxylation of aryl halides, and some redox reactions.
Investigations of the applications of M@PANI in other organic
reactions are warranted. Thus, as a part of our continuing
1
involving drugs and natural products. Tuning the activity of
8
investigation into green synthetic methodologies, we wish to
the transition metal by various ligands, Heck reaction could be
performed under quite mild conditions to achieve a series of
challenging objectives in organic synthesis, such as the
2b,c
make a further development on the applications of this practical
nanocatalyst in organic synthesis to develop reliable and eco-
friendly synthetic methodologies.
2
a,b
3
asymmetric synthesis,
reactions with sp organic halides,
The Pd@PANI-catalyzed classic Heck reaction is our first
research goal because of its significance in organic chemistry.
Although a few studies have been reported on this topic, there
are still enough spaces to improve the currently reported works,
which suffered the high catalyst loadings (0.9−5 mol %) and
narrow application scopes of olefins limited to only acrylic acid
and even the highly stereoselective tandem reaction proc-
2
b
esses. In line with calls for greater environmental protection
nowadays, people are interested in this synthetic methodology
using environmentally friendly novel heterogeneous catalysts
that are accessible, robust, and recyclable and can be employed
free of ligands, and developing such catalyst systems is of both
academic and industrial value.
The development of polyaniline (PANI) as an environ-
mentally benign supporter to anchor noble nanocatalysts is
an attractive area owing to the easily accessible monomer, low
cost, and the low-toxicity carrier. PANI-supported metal
catalysts (M@PANIs) should be reliable catalysts with
potentially comprehensive applications. However, the inves-
tigations on M@PANIs basically belong to the field of material
science at present, attracting less attention from organic
chemists. In the material science field, people focused a lot on
the design of the new-style M@PANI catalysts, such as the
magnetic catalysts, carbon nanotube-supported catalysts, and
the catalysts with fancy morphology, but ignored their
6
4
−6
and its esters and simple styrene. Herein, we report a
systematic study on highly efficient Pd@PANI-catalyzed Heck
reactions. This Pd@PANI catalyst was prepared using air as the
oxidant instead of traditionally employed ammonium persul-
fate. The very slow in situ polymerization of aniline monomer
and formation of Pd nanoparticles (NPs) was the key factor to
control the size of Pd and morphology of PANI, which
provided an ultrasmall and uniform Pd@PANI catalyst to
catalyze the Heck reaction with higher catalytic activity (TON
5
,6
7
5
,6
3
up to 1.7 × 10 ) and wider substrate scopes than previous
Received: June 15, 2015
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.5b01358
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
6
reports. In addition, the simple preparation procedure of the
achieve better results, a series of inorganic and organic bases
were further screened (entries 11−18). Generally, the reactions
afforded 3a in rather low yields using inorganic bases (entry
reusable catalyst also allowed exploration of large-scale Heck
reactions.
1
1), DBU (entry 12), primary or secondary amines/amides
(
entry 13), and pyridines (entry 14). It was interesting that the
2
. RESULTS AND DISCUSSION
addition of tertiary amines could improve the yield remarkably,
and EtN(i-Pr) was found to be best, affording 3a in 88% yield
We initially prepared the Pd@PANI catalyst as described in the
Experimental Section (vide infra). After heating in oven at 100
2
(
entries 18 vs 8, 15−17). The best reaction temperature and
time were found to be 80 °C and 24 h, respectively (entries
8−25). It should be noted that although in the previous
°
C for 0.5 h, it was directly used in the Heck reaction of
iodobenzene 1a with styrene 2a. The reaction was initially
performed in water, but desired product 3a was not observed
1
5
,6
works the PANI-supported catalyst could be directly used, for
Heck reaction, baking treatment is needed to activate the
catalyst (entries 26−27). The product yield did not decrease
upon 25-fold increase in the reaction scale (entry 28), showing
good practicability of this catalyst for organic synthesis.
(
Table 1, entry 1). Further screening of the reaction conditions
showed that addition of triethylamine as the base was necessary
entry 2) and DMF was a better solvent (entry 3). Contrary to
(
9
many known reports, this reaction did not require excess
amounts of base, and the maximum yield of 3a was achieved by
using only 1 equiv of Et N (entries 8 vs 3−7, 9−10). To
ICP analysis showed that the Pd@PANI catalyst contained
60.2 μg of Pd for each reaction, giving around 1555 TON at the
maximum and a Pd loading for each reaction of 0.06 mol %
based on the starting material 1a. TEM was performed to study
the morphology, composition, and crystal structure of Pd@
PANI (Figure 1). Since the Pd NPs nucleated and grew during
the in situ polymerization of PANI without additional chemical
reagents, the distribution of Pd nanoparticles on PANI
microwires was extremely uniform, and the size was ultrasmall
(around 2 nm), which could be clearly seen in Figure 1b,c.
Thus, it is not surprising to observe ultrahigh catalytic activity
of Pd@PANI for a Heck reaction as it has been recognized that
the ultrasmall particle size often results in superior performance
3
a
Table 1. Optimization of the Reaction Conditions
b
c
entry solvent
base (equiv)
T/°C t/h
3a/%
d
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
H O
2
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
40
60
100
80
80
80
80
80
80
80
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
12
18
30
36
24
24
24
NR
e
H O
2
Et N (3.5)
3
trace
49
52
54
59
67
76
46
5
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
Et N (3.5)
3
Et N (3.0)
3
Et N (2.0)
3
10
for many catalytic applications. Figure 1d showed Pd(111)
Et N (1.5)
3
lattice planes with spacing d(111) = 0.224 nm, consistent with
the reported literature value for nanocrystalline Pd. Scanning
TEM with EDX analysis also attested to the successful loading
of Pd nanoparticles on PANI microwires (Figure 1e,f).
As currently reported Heck reactions using nano-Pd@PANI
Et N (1.2)
3
Et N (1.0)
3
Et N (0.5)
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
f
inorg bases (1.0)
DBU (1.0)
0−27
6
d
catalysts have very narrow reaction scope, the substrate scope
NR
g
of this catalyst system was our next concern. The steric
hindrance effects on aryl rings were first examined: Although 4-
or 3-methyl substituted iodobenzene could react with styrene
2
2
iodobenzene shows much lower reactivity under the same
conditions (entry 3). Higher temperature was therefore applied
to address this issue, and we were very glad to find that the
yield can be remarkably improved from 47% to 96% at 120 °C
1° or 2° amines/amides (1.0)
pyridines (1.0)
0−22
h
d
NR
n-Bu N (1.0)
71
69
72
88
6
3
a smoothly to give the product 3b or 3c in good yields (Table
, entries 1−2), the reaction using 2-methyl substituted
(n-C H ) N (1.0)
8
17 3
BuNMe (1.0)
2
EtN(i-Pr) (1.0)
2
EtN(i-Pr) (1.0)
2
EtN(i-Pr) (1.0)
73
81
67
74
76
63
21
33
81
2
EtN(i-Pr) (1.0)
2
(
entry 3). Higher temperature was also needed when
EtN(i-Pr) (1.0)
2
employing electron-rich substrate 4-methoxyiodobenzene,
EtN(i-Pr) (1.0)
2
affording the product 3e in 99% yield within 12 h (entry 4).
4
EtN(i-Pr) (1.0)
2
-Iodophenol, bearing an acidic proton that might react with
EtN(i-Pr) (1.0)
2
i
base, was found to be a suitable substrate for this catalyst
system, giving product 3f in 82% yield (entry 5). Reactions of
styrene 2a with electron-poor iodobenzene was also performed,
affording the corresponding products 3g−k in moderate to
good yields (entries 6−10). The bulky 1-iodonaphthalene
could also react with styrene to afford 3l in 77% yield (entry
EtN(i-Pr) (1.0)
2
j
EtN(i-Pr) (1.0)
2
k
EtN(i-Pr) (1.0)
2
a
1
mmol of 1a, 1 mmol of 2a, and 1.5 mL of solvent were employed.
For detailed conditional optimization table, please see Table S1 in
Supporting Information. Based on the amount of 1a. Average
b
c
1
1
1). Heteroaryl iodides were also applicable substrates (entries
2−13), and it was notable that this Pd@PANI was tolerant to
d
isolated yields of three repeated reactions. No reaction detected.
e
f
Yield <3%. Na CO , NaOH, NaOAc, K CO , Ca(OH) , CaCO ,
2
3
2
3
2
3
sulfur-containing compounds, which were catalyst poisons in
many Pd-catalyzed reactions (entry 13). The application
g
MgCO , Cs CO , MgO, or Mg(OH) were tested. 1-Methylpiper-
azine, 4-methylpiperidine, PhCONH , Et NH, Bu NH, and DMEDA
were tested. Pyridine, 3-acetylpyridine, and DMAP were tested. The
catalyst Pd@PANI was directly used without drying or baking after
preparation. The catalyst was dried by air at room temperature for 10
h but without baking after preparation before use. Reaction scale
enlarged to 25 mmol.
11
3
2
3
2
2
2
2
h
i
scope for olefins was further tested. Generally, reactions of
iodobenzene 1a with electron-deficient olefins were more
favorable than those of electron-rich ones (entries 18−19 vs
14−17). It was interesting that, although generating the same
products, the reaction of iodobenzene 1a with (E)-1,2-
j
k
B
DOI: 10.1021/acs.joc.5b01358
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The Journal of Organic Chemistry
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Figure 1. TEM images and EDX spectra of Pd@PANI: (a) TEM image Pd@PANI (scale bar, 200 nm), (b) magnified view of Pd@PANI (scale bar,
0 nm; Pd, small black dots), (c) magnified view of Pd@PANI (scale bar, 5 nm; Pd, small black dots), (d) HRTEM image of Pd@PANI (scale bar, 2
nm), (e) scanning TEM image Pd@PANI (scale bar, 1 μm), and (f) EDX spectrum of Pd@PANI.
2
diphenylethene was favored over that with 1,1-diphenylethene
entry 20 vs 16), probably due to decreased steric hindrance of
ammonium persulfate, which also strengthened the interaction
between supported Pd NPs and PANI surfaces and thus
avoided the accumulation of Pd NPs to form stable larger
(
the organometallic intermediates (Figure 2). Aryl bromides
were also employed, but only gave the products in low to
moderate yields even at high temperature (entries 21−29),
except for the reaction with 1-bromo-4-nitrobenzene, which
afforded the coupling product (E)-1-nitro-4-styrylbenzene 3u
in 91% yield under mild conditions (entry 25). The reactions of
styrene with aryl chlorides were also tested, but resulted in very
low product yields, even if the electron-enriched phosphorus
ligands were employed (entries 30−33).
Most impressively, PANI-supported ultrasmall Pd NPs can
be reused by simple centrifugation and show excellent stability
and recyclability. As can be seen in Figure 3, the recycled
catalyst retained its high catalytic activity up to the sixth cycle
tested, and its activity was slightly decreased in the seventh and
eighth runs, probably due to a small amount of Pd leaking
during reaction and separation procedures. ICP analysis
demonstrated that, in each cycle, 3.2% of Pd leached into the
solution, highlighting the stability of this heterogeneous Pd
catalyst. To confirm that the reactions were catalyzed by Pd@
PANI NPs and not by the leached homogeneous Pd species, an
experiment was designed and performed to test the catalytic
activity of the leaked Pd in solution (Scheme 1): A standard
reaction of 1a with 2a was first performed under the conditions
described in Table 1, entry 13. Then, the heterogeneous Pd@
PANI NPs were removed by centrifugation, and a batch of fresh
clusters. The role of EtN(i-Pr) was also studied. Table 1 and
2
Figure 3 suggest several important implications: First, tertiary
amines had overwhelming advantages over any other bases such
as inorganic bases, DBU, pyridines and primary or secondary
amines or amides (Table 1, entries 8, 15−18 vs 11−14).
Second, the recovered catalyst had significantly higher activity
than its first use (Figure 3). On the basis of the above results as
12
well as the reference report, we propose that trialkyl amines
were able to reduce Pd(II) to activate Pd(0) in catalyst through
the coordination followed by β-hydride transfer and reductive
12
elimination of HX. The aforementioned mechanism was
clearly supported by the fact that PdCl (1 mmol %) could
2
efficiently catalyze the Heck reaction (77.5% isolated yield)
with EtN(i-Pr) as a base. The X-ray photoelectron spectros-
2
copy (XPS) results as shown in Figure 4 further attested to the
significant role of EtN(i-Pr) in the Heck reaction: First, the
2
palladium species at the surface of Pd@PANI catalyst can be
very easily to be oxidized to Pd(II) with exposure to the air.
This can be demonstrated by the XPS spectrum of the catalyst
before and after argon ion etching the surface layers of Pd@
PANI sample. The observed binding energy value of 343.0 eV
(Pd 3d3) and 337.7 eV (Pd 3d5) on the XPS spectrum of the
catalyst before the argon ion etching indicated the existence of
palladium as Pd(II) on the surface of Pd@PANI (Figure 4a).
The XPS spectrum of the catalyst after argon ion etching
showed obvious binding energy peaks at 341.3 eV (Pd 3d3)
and 336.0 eV (Pd 3d5), which were the characteristics of
Pd(0), the real catalyst species in the Heck reaction (Figure
4b). Upon exposure to reaction conditions, the Pd(II) species
PhI and EtN(i-Pr) was added into the supernatant liquid. The
2
liquid was heated at 120 °C for 24 h under N protection, as
2
the conditions described in Table 2, entry 20, but the second
step coupling product 3p was obtained in only 9% yield. This
indicates that the leached Pd species had low activity because,
for the same reaction catalyzed by Pd@PANI NPs, the 3p yield
could reach 93%, as shown in Table 2, entry 20.
12
on the surface of Pd@PANI can be reduced to Pd(0) by
EtN(i-Pr) or/and etched away during the reaction to expose
2
6
In a comparison with previous works, the higher activity of
the Pd(0) to the reactants, supported by the fact that the
content of Pd(0) was remarkably increased as shown in Figure
4c. When another base, such as DBU, was employed, Pd(II)
was still the major species on the surface of the palladium
this Pd@PANI catalyst was probably attributed to the very slow
in situ polymerization of PANI polymer and formation of Pd
NPs using air instead of the strong chemical oxidant
C
DOI: 10.1021/acs.joc.5b01358
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The Journal of Organic Chemistry
Article
Table 2. Pd@PANI-Catalyzed Heck Cross-Couplings of Aryl
a
Halides 1 with Olefins 2
Figure 3. Recyclability of Pd@PANI in Heck reaction. Reaction scale:
1
0 mmol. For detailed reaction conditions, see Table 1, entry 13; yield
refers to isolated yield. Pd@PANI catalyst was recovered by
centrifugation.
Scheme 1. Catalytic Activity Test of the Leached Pd Species
the catalyst fabrication allowed Pd NPs to nucleate and grow
slowly with high resistance during the in situ polymerization of
PANI without additional chemical reagents, giving the
ultrasmall and uniform Pd@PANI with ultrahigh catalytic
activity. The research findings show that the Pd@PANI is an
accessible, practical, and stable catalyst and might be developed
to be a reliable alternative catalyst to the traditionally employed
palladium complexes. Thus, more attention should be paid to
extending the application scope of this catalyst in organic
synthesis. More related works are ongoing in our laboratory to
develop the practical green synthetic methodologies.
a
1
mmol of 1, 1 mmol of 2, and 1.5 mL of DMF were employed and
4. EXPERIMENTAL SECTION
b
the reactions were monitored by TLC. Isolated yields (E/Z ratio
calculated by H NMR in parentheses; E-isomers only if no E/Z was
4.1. General Methods. Chemicals and solvents were all purchased
1
and used as received. All reactions were monitored by TLC and/or
c
d
provided). Reaction not completed. 0.6 mol % catalyst employed.
GC analysis. Products 3 were all purified by column chromatogram.
e
f
g
Product yield <3%. 0.1 mmol of dppe was employed as ligand. 0.1
1
13
H and C NMR spectra were recorded using CDCl as the solvent
3
h
mmol of PCy was employed as ligand. 0.1 mmol of P(n-Bu) was
employed as ligand.
1
13
3
3
and Me Si as the internal standard. Chemical shifts for H and
C
4
NMR were referred to internal Me Si (0 ppm), and J-values were
4
shown in Hz. Melting points were measured using a digital instrument.
4.2. Preparation for the Catalyst Pd@PANI. A 465.9 mg (5
mmol) portion of aniline was dissolved in 50 mL of HCl (1 M, aq) to
make solution A. A 22 mg (0.125 mmol) portion of PdCl2 was
dissolved in 50 mL of aqueous HCl (1 M, aq) to make solution B.
Solution B was added to solution A and stirred for 2 min. The mixture
stood for 24 h, and then its pH was adjusted to 7.0 with NaOH (1 M,
aq). The generated precipitate was isolated by centrifugation and
washed with deionized water. Then, 6 mL of deionized water was
added to make a suspension. The suspension should be kept below 4
Figure 2. Comparison of the organometallic intermediates for reaction
of entry 16 with entry 20.
°
C in a refrigerator. A 0.6 mL portion of the above suspension was
diluted to 5 mL with deionized water. In each Heck cross-coupling
reaction, 0.5 mL of the above diluted suspension was used. The diluted
suspension was separated by centrifugation to remove water. Then, the
precipitate of Pd@PANI polymer was baked in an oven at 100 °C for
catalyst after the reaction, as shown in its XPS spectra as well
(Figure 4d).
0
.5 h to give 0.6 mg of dried catalyst and was used in the cross-
3. CONCLUSIONS
coupling reaction as catalyst.
In conclusion, we report a practical ligand-free and relatively
wider-scope Heck reaction catalyzed by the recyclable
heterogeneous Pd@PANI catalyst. Using air as the oxidant in
4
.3. General Procedure for Heck Cross-Couplings (Catalyst
Was Not Recycled, for Table 2). Under N protection, a solution of
2
halohydrocarbons 1 (1 mmol), alkene 2 (1 mmol), and EtN(i-Pr) (1
2
D
DOI: 10.1021/acs.joc.5b01358
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The Journal of Organic Chemistry
Article
Figure 4. (a, b) XPS spectra of Pd@PANI before and after argon ion etching. (c) X-ray photoelectron spectra for Pd@PANI after reaction with
EtN(i-Pr) as base. (d) X-ray photoelectron spectra for Pd@PANI after reaction with DBU as base.
2
mmol) in DMF (1.5 mL) was injected into a reaction tube containing
a magnetic bar and Pd@PANI (0.6 mg) which had been treated as
leached Pd species had very low activity because 3p was obtained in
only 9% yield, but for the same reaction catalyzed by Pd@PANI, the
3p yield could reach 93%, as shown in Table 2, entry 20 in text.
4.6. Characterization of the Products. (E)-1,2-Diphenylethene
3a. 159 mg, 88%. White solid, mp 123.0−124.6 °C. (Lit. 124−125
°C.) IR (KBr): 3077, 3057, 3022, 1597, 1495, 1452, 1072, 1028, 984,
described above. The mixture was stirred under N at 80−120 °C for
2
12−48 h. After the reaction, 2 mL of saturated NaCl solution was
added, and the mixture was extracted by EtOAc (2 mL × 3). Solvents
in the combined organic layer were evaporated under vacuum, and the
residue was purified by flash column chromatogram (eluent:
petroleum ether) to afford the corresponding products 3.
−1 1
909, 764, 692, 540, 468 cm . H NMR (600 MHz, CDCl
7.48 (d, J = 7.2 Hz, 4H), 7.32 (t, J = 7.2 Hz, 4H), 7.23 (t, J = 7.2 Hz,
2H), 7.08 (s, 2H). 13C NMR (150 MHz, CDCl
): δ137.5, 128.8(d),
127.7, 126.7. MS (EI, 70 eV): m/z (%) 180 (97) [M ], 179 (100), 178
, TMS): δ
3
4
.4. Procedure for Heck Cross-Coupling of 1a with 2a
3
+
(
Catalyst Recycled, for Figure 3). Under N protection, a solution
2
1
3a
of 1a (10 mmol), 2a (10 mmol), and EtN(i-Pr) (10 mmol) in DMF
(65), 165 (52). Known compound (103-30-0).
2
(
15 mL) was injected into a reaction tube containing a magnetic stir
(E)-1-Methyl-4-styrylbenzene 3b. 138 mg, 71%. White solid, mp
121.3−122.3 °C. (Lit. 121−122 °C.) IR (KBr): 3023, 1594, 1509,
bar and Pd@PANI (6.0 mg) which had been treated as described
above. The mixture was stirred under N at 80 °C for 24 h. After the
−1 1
1447, 967, 808, 748, 690, 531, 494 cm . H NMR (600 MHz, CDCl ,
2
3
reaction, the mixture was cooled to room temperature, and most Pd@
PANI was observed to be attached on the magnetic bar and the tube
wall. Then, the liquid was removed into a glass centrifuge tube for
centrifugation. After centrifugation, the glass centrifugal tube and the
reaction tube with magnetic bar which contained the recycled Pd@
PANI catalyst were baked for the next turn of reaction. The
supernatant liquid was added into saturated NaCl solution (20 mL)
and extracted by EtOAc (20 mL × 3). Solvents in the combined
organic layers were evaporated under vacuum, and the residue was
purified by flash column chromatography (eluent: petroleum ether).
The Pd@PANI in centrifuge tube could be washed into the reaction
tube by DMF and reused in the next cycle of reaction together with
the Pd@PANI attached on the magnetic bar and the tube wall, which
was mentioned above.
TMS): δ 7.47 (d, J = 7.8 Hz, 2H), 7.38 (d, J = 7.2 Hz, 2H), 7.30−7.33
(m, 2H), 7.21−7.22 (m, 1H), 7.13 (d, J = 7.2 Hz, 2H), 7.01−7.08 (m,
2H), 2.32 (s, 3H). 13C NMR (150 MHz, CDCl ): δ 137.6, 137.5,
3
134.6, 129.4, 128.7(d), 127.7, 127.4, 126.5, 126.4, 21.3. MS (EI, 70
+
+
eV): m/z (%) 195 (16) [M + 1], 194 (96) [M ], 179 (100), 178
1
3a
(73). Known compound (1860-17-9).
(E)-1-Methyl-3-styrylbenzene 3c. 142 mg, 73%. White solid, mp
49.1−49.9 °C. (Lit. 48−49 °C.) IR (KBr): 3023, 2921, 1949, 1581,
−1 1
1449, 1037, 967, 782, 749, 694, 559, 486 cm . H NMR (600 MHz,
CDCl , TMS): δ 7.53 (d, J = 7.2 Hz, 2H), 7.40−7.34 (m, 4H), 7.29−
3
13
7.27 (m, 2H), 7.12−7.10 (m, 3H), 2.40 (s, 3H). C NMR (150 MHz,
CDCl ): δ 138.2, 137.5, 137.3, 128.9, 128.7, 128.6, 128.5(d), 127.6,
3
+
127.2, 126.5, 123.7, 21.5. MS (EI, 70 eV): m/z 195 (13) [M + 1], 194
(77) [M ], 179 (100), 178 (84). Known compound (14064-48-3).
+
13b
4
.5. Test of the Catalytic Activity of Leached Pd. A reaction
(E)-1-Methyl-2-styrylbenzene 3d. 187 mg, 96%. Colorless oil. IR
(film): 3024, 2947, 1944, 1599, 1495, 1460, 961, 758, 712, 691, 539,
was performed according to the experiment in Table 1, entry 18. Then,
Pd@PANI was removed by centrifugation, and 1 mol of PhI and 1
−1 1
490 cm . H NMR (600 MHz, CDCl , TMS): δ 7.56 (d, J = 7.2 Hz,
3
mmol of EtN(i-Pr) were added. The mixture was treated as Table 2,
entry 20 in text, and after the reaction, 153 mg of 3a (0.85 mmol) and
1H), 7.48 (d, J = 7.8 Hz, 2H), 7.33−7.29 (m, 3H), 7.22 (t, J = 7.2 Hz,
2
1H), 7.19−7.16 (m, 1H), 7.14 (d, J = 4.2 Hz, 2H), 6.96 (d, J = 16.2
23 mg of 3p (0.09 mmol) were obtained. The result indicating that the
Hz, 1H), 2.39 (s, 3H). 13C NMR (150 MHz, CDCl ): δ 137.8, 136.5,
3
E
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35.9, 130.5, 130.1, 128.8, 127.7 (d), 126.7 (d), 126.4, 125.5, 20.1. MS
146.3, 140.8, 136.4, 128.4 (d), 128.3, 128.2, 128.1, 116.0, 26.7. MS (EI,
+
+
+
+
70 eV): m/z 223 (7) [M + 1], 222 (49) [M ], 179 (20), 178 (79).
13b
13i
Known compound (20488-42-0).
(
(E)-1-Styrylnaphthalene 3l. 173 mg, 75%. White solid, mp 70.0−
71.3 °C. (Lit. 70−71 °C.) IR (KBr): 3030, 2411, 1944, 1811, 1591,
1448, 1253, 1207, 1167, 1073, 1028, 959, 793, 775, 748, 692, 559, 492
−1
1
−1 1
cm . H NMR (600 MHz, CDCl , TMS): 8.17 (d, J = 8.4 Hz, 1H),
3
3
7.83−7.73 (m, 2H), 7.67−7.53 (m, 2H), 7.48 (d, J = 7.8 Hz, 2H),
13
7.46−7.40 (m, 3H), 7.34 (t, J = 7.5 Hz, 2H), 7.24 (t, J = 7.2 Hz, 1H),
7.08 (d, J = 16.2 Hz, 1H). 13C NMR (150 MHz, CDCl ): δ 137.9,
3
3
+
+
135.3, 134.1, 132.1, 131.8, 129.1, 129.0, 128.4, 128.1, 127.0, 126.4,
13c
+
126.1(d), 126.0, 124.1, 124.0. MS (EI, 70 eV): m/z 231 (18) [M +
+
(
1], 230 (100) [M ], 215 (22), 152 (26). Known compound (2840-87-
12
j
1).
−1 1
(E)-3-Styrylpyridine 3m. 111 mg, 61%. White solid, mp 81.2−82.3
°C. (Lit. 81−83 °C.) IR (KBr): 3024, 2925, 1564, 1492, 1448, 1412,
1221, 1177, 1123, 1099, 1073, 1022, 964, 801, 751, 706, 617, 530
3
−
1 1
cm . H NMR (600 MHz, CDCl , TMS): δ 8.73 (s, 1H), 8.48 (d, J =
3
C NMR (150 MHz, CDCl ): δ155.2, 137.6, 130.4, 128.7, 128.1,
4.2 Hz, 1H), 7.83 (d, J = 7.8 Hz, 1H), 7.53 (d, J = 7.8 Hz, 2H), 7.38 (t,
3
+
27.9, 127.3, 126.8, 126.3, 115.6. MS (EI, 70 eV): m/z 197 (12) [M +
], 196 100) [M ], 179 (11), 178 (12). Known compound (6554-98-
J = 7.2 Hz, 2H), 7.31−7.28 (m, 2H), 7.16 (d, J = 16.2 Hz, 1H), 7.07
+
13
(d, J = 16.2 Hz, 1H). C NMR (150 MHz, CDCl
): δ 148.4, 136.6,
3
13d
133.1, 132.8, 131.0, 128.8, 128.3, 126.7, 124.8, 123.6. MS (EI, 70 eV):
+
(E)-1-Fluoro-4-styrylbenzene 3g. 157 mg, 79%. White solid, mp
m/z 181 (42) [M ], 180 (100), 152 (20). Known compound (5097-
1
3k
91-6).
−1 1
(E)-2-Styrylthiophene 3n. 102 mg, 55%. Light yellow solid, mp
112.1−113.5 °C. (Lit. 111−112 °C.) IR (KBr): 3145, 3102, 3060,
3027, 1594, 1491, 1428, 1273, 1202, 961, 839, 817, 753, 707, 692, 580,
3
2.4 Hz, J = 7.2 Hz, 2H), 7.32 (t, J = 7.2 Hz, 2H), 7.23 (t, J = 7.2 Hz,
13
−1 1
546, 522 cm . H NMR (600 MHz, CDCl , TMS): δ 7.46 (d, J = 7.8
3
3
= 245.6 Hz), 137.3, 133.6 (d, J
= 3.2 Hz), 128.8, 128.6, 128.1
Hz, 2H), 7.34 (t, J = 7.5 Hz, 2H), 7.24−7.22 (m, 2H), 7.19 (d, J = 5.4
C−F
= 21.5 Hz). MS
Hz, 1H), 7.07 (d, J = 3.6 Hz, 1H), 7.00 (t, J = 4.5 Hz, 1H), 6.93 (d, J =
C−F
+
+
13
16.2 Hz, 1H). C NMR (150 MHz, CDCl ): δ 142.9, 137.0, 128.7,
3
13e
128.4, 127.6, 126.3, 126.1, 124.4, 121.8. MS (EI, 70 eV): m/z 187 (17)
+
+
(
[M + 1], 186 (100) [M ], 185 (84). Known compound (26708-50-
13j
9).
−1 1
450, 1266, 1205, 1147, 966, 873, 781, 753, 695, 519 cm . H NMR
(E)-1-Bromo-4-styrylbenzene 3o. 181 mg, 70%. White solid, mp
127.4−128.1 °C. (Lit. 126−128 °C.) IR (KBr): 3080, 3019, 2964,
1494, 1449, 1401, 1330, 1304, 1261, 1074, 1007, 967, 863, 814, 750,
3
−1
1
704, 690, 528 cm . H NMR (600 MHz, CDCl , TMS): δ 7.50−7.46
3
3
63.3 (d, JC−F = 243.8 Hz), 139.8 (d, JC−F = 7.7 Hz), 136.9, 130.2 (d,
(m, 4H), 7.38−7.35 (m, 4H), 7.27 (t, J = 7.2 Hz, 1H), 7.09 (d, J = 16.2
Hz, 1H), 7.03 (d, J = 16.2 Hz, 1H). 13C NMR (150 MHz, CDCl ): δ
3
22.6 (d, JC−F = 2.6 Hz), 114.5 (d, JC−F = 21.3 Hz), 112.9 (d, J
=
137.0, 136.3, 131.8, 129.5, 128.8, 128.0, 127.9, 127.4, 126.6, 121.3. MS
C−F
+
+
+
+
1.8). MS (EI, 70 eV): m/z 199 (14) [M + 1], 198 (100) [M ], 196
(EI, 70 eV): m/z 259 (6) [M + 1], 258 (33) [M ], 179 (64), 178
13f
13l
(100). Known compound (13041-70-8).
(
1,1,2-Triphenylethene 3p. 238 mg, 93%. White solid, mp 68.6−
69.3 °C. (Lit. 69−70 °C.) IR (KBr): 3080, 3019, 2964, 1494, 1449,
−1
1
−1 1
455, 1231, 1210, 1094, 968, 842, 783, 760, 690, 501 cm . H NMR
1401, 1074, 1007, 967, 863, 814, 750, 704, 690, 528 cm . H NMR
(
(
600 MHz, CDCl , TMS): δ 7.61 (dt, J = 1.2 Hz, J = 7.8 Hz, 1H), 7.54
(600 MHz, CDCl , TMS): δ7.26−7.20 (m, 8H), 7.14−7.13 (m, 2H),
3
3
1
3
d, J = 7.2 Hz, 2H), 7.37 (t, J = 7.2 Hz, 2H), 7.29−7.27 (m, 2H),
7.07−7.02 (m, 3H), 6.95 (d, J = 6.6 Hz, 2H), 6.89 (s, 1H). C NMR
7
7
1
.23−7.21 (m, 1H), 7.18 (d, J = 16.8 Hz, 1H), 7.14 (t, J = 7.2 Hz, 1H),
(150 MHz, CDCl ): δ143.4, 142.6, 140.3, 137.4, 130.4, 129.5, 128.6,
3
.07 (dt, J = 1.2 Hz, J = 9.0 Hz, 1H). 1 C NMR (150 MHz, CDCl ): δ
3
3
128.2, 128.1, 127.9, 127.6, 127.5, 127.4, 126.7. MS (EI, 70 eV): m/z
+
+
60.5 (d, JC−F = 248.0 Hz), 137.3, 131.0 (d, JC−F = 4.8 Hz), 128.8 (d,
257 (20) [M + 1], 256 (100) [M ], 178 (68). Known compound
13m
JC−F = 8.4 Hz), 128.7, 127.9, 127.1 (d, JC−F = 3.5 Hz), 126.7, 125.3 (d,
(58-72-0).
(E)-1,3-Diphenylprop-1-ene 3q. 134 mg, 69%. Colorless oil. IR
+
(film): 3060, 3026, 2898, 1600, 1495, 1451, 1075, 1029, 965, 740, 696,
−1 1
584, 494 cm . H NMR (600 MHz, CDCl , TMS): δ 7.32−7.15 (m,
3
13
10H), 6.43−6.30 (m, 2H), 3.50 (d, J = 7.2 Hz 2H). C NMR (100
MHz, CDCl ): δ 140.3, 137.6, 131.2, 129.3, 128.8, 128.6, 127.2, 126.6,
3
+
126.3, 126.2, 39.5. MS (EI, 70 eV): m/z 194 (87) [M ], 193 (64), 179
(45), 178 (46), 116 (48), 115 (100). Known compound (3412-44-
1
3n
0).
Methyl Cinnamate 3r. 156 mg, 96%. Colorless oil. IR (film): 3062,
3028, 2998, 2950, 1718, 1637, 1578, 1496, 1451, 1435, 1329, 1316,
1276, 1203, 1171, 1072, 1039, 1014, 980, 935, 863, 768, 712, 684, 575
−1 1
cm . H NMR (600 MHz, CDCl , TMS): δ 7.69 (d, J = 15.6 Hz,
3
(
E)-1-(4-Styrylphenyl)ethanone 3k. 169 mg, 76%. White solid, mp
1H), 7.52−7.51 (m, 2H), 7.38−7.37 (m, 3H), 6.44 (d, J = 16.2 Hz,
1
1
48.1−150.4 °C. (Lit. 149−151 °C.) IR (KBr): 1682, 1602, 1358,
307, 1266, 1182, 958, 907, 847, 779, 701, 594 cm . H NMR (600
MHz, CDCl , TMS): δ 7.96 (d, J = 8.4 Hz, 2H), 7.59 (d, J = 8.4 Hz,
1H), 3.80 (s, 3H). 13C NMR (150 MHz, CDCl ): δ 167.4, 144.9,
3
−1 1
134.4, 130.3, 128.9, 128.1, 117.8, 51.7. MS (EI, 70 eV): m/z 162 (46)
+
13o
[M ], 161 (28), 131 (100). Known compound (1754-62-7).
Cinnamonitrile 3s. 112 mg, 87%. Colorless oil. IR (film): 3055,
3
2
3
H), 7.54 (d, J = 7.2 Hz, 2H), 7.39 (t, J = 7.8 Hz, 2H), 7.32−7.13 (m,
H), 2.62 (s, 3H). 13C NMR (150 MHz, CDCl ): δ197.7, 149.2,
2217, 1674, 1618, 1494, 967, 749, 689 cm . H NMR (600 MHz,
−1 1
3
F
DOI: 10.1021/acs.joc.5b01358
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The Journal of Organic Chemistry
Article
CDCl , TMS): δ 7.44−7.36 (m, 6H), 5.86 (d, J = 16.8 Hz, 1H). 13C
(4) Selected recent articles: (a) Liu, H. Y.; Zhang, L. Y.; Wang, N.;
Su, D. S. Angew. Chem., Int. Ed. 2014, 53, 12634. (b) Yamada, Y. M. A.;
Yuyama, Y.; Sato, T.; Fujikawa, S.; Uozumi, Y. Angew. Chem., Int. Ed.
2014, 53, 127. (c) Chng, L. L.; Erathodiyil, N.; Ying, J. Y. Acc. Chem.
Res. 2013, 46, 1825 and references cited therein.
3
NMR (150 MHz, CDCl ): δ 150.6, 133.6, 131.3, 129.2, 127.4, 118.2,
3
+
+
9
6.4. MS (EI, 70 eV): m/z 130 (10) [M + 1], 129 (100) [M ], 128
26). Known compound (1885-38-7).
-(3,5-Bis(trifluoromethyl)styryl)benzene 3t. 174 mg, 55%. White
9d
(
1
solid, mp 51.7−53.8 °C. IR (KBr): 3089, 3043, 2929, 1777, 1638,
(5) Selected articles: (a) Wu, R.-H.; Tsai, M.-J.; Ho, K.-S.; Wei, T.-E.;
Hsieh, T.-H.; Han, Y.-K.; Kuo, C.-W.; Tseng, P.-H.; Wang, Y.-Z.
Polymer 2014, 55, 2035. (b) Han, J.; Wang, M.-G.; Cao, S.-Y.; Fang, P.;
Lu, S.; Chen, R.; Guo, R. J. Mater. Chem. A 2013, 1, 13197.
(c) Tumma, M.; Srivastava, R. Catal. Commun. 2013, 37, 64 and
references cited therein.
(6) For Pd@PANI-catalyzed classic Heck reactions, please see:
(a) Houdayer, A.; Schneider, R.; Billaud, D.; Ghanbaja, J.; Lambert, J.
Appl. Organomet. Chem. 2005, 19, 1239. (b) Nie, G.-R.; Zhang, L.; Cui,
Y.-C. React. Kinet., Mech. Catal. 2013, 108, 193. For classic Heck
reactions using other M@PANI nanocatalysts, please see: (c) Hou-
dayer, A.; Schneider, R.; Billaud, D.; Ghanbaja, J.; Lambert, J. Synth.
Met. 2005, 151, 165. Likhar et al. also reported an example of Pd@
PANI-catalzyed oxidative Heck reaction, but this reaction required
expensive and toxic boric acid as the starting materials and was a
different type of reaction from the classic Heck reaction: (d) Likhar, P.
R.; Roy, M.; Roy, S.; Subhas, M. S.; Kantam, M. L.; Sreedhar, B. Adv.
Synth. Catal. 2008, 350, 1968.
1
1
616, 1577, 1497, 1469, 1447, 1378, 1279, 1218, 1184, 1165, 1119,
−1 1
030, 966, 939, 889, 847, 753, 695, 619 cm . H NMR (400 MHz,
CDCl , TMS): δ 7.91 (s, 2H), 7.74 (s, 1H), 7.55 (d, J = 5.2 Hz, 2H),
3
7
1
.41 (t, J = 5.0 Hz, 2H), 7.34 (d, J = 4.8 Hz, 1H), 7.24 (d, J = 16.2 Hz,
H), 7.13 (d, J = 16.2 Hz, 1H). 13C NMR (100 MHz, CDCl ): δ
3
1
39.5, 136.0, 132.6, 132.1 (q, JC−F = 33.0 Hz), 128.9, 128.8, 126.9,
1
1
26.1 (d, JC−F = 2.7 Hz), 125.5, 123.4 (d, JC−F = 271.1 Hz), 120.8−
+
20.7 (m). MS (EI, 70 eV): m/z 316 (100) [M ], 178 (83). Known
13p
compound (453537-08-1).
1
-Nitro-4-styrylbenzene 3u. 205 mg, 91%. Light yellow solid, mp
1
1
53.8−155.4 °C. (Lit. 154−155 °C.) IR (KBr): 3077, 3024, 2920,
633, 1590, 1343, 1109, 971, 849, 833, 767, 695 cm . H NMR (400
−1 1
MHz, CDCl , TMS): δ 8.21 (d, J = 8.8 Hz, 2H), 7.62 (d, J = 8.8 Hz,
3
2
H), 7.54 (d, J = 7.2 Hz, 2H), 7.40 (t, J = 7.4 Hz, 2H), 7.34 (d, J = 7.2
13
Hz, 1H), 7.27 (d, J = 16.4 Hz, 1H), 7.14 (d, J = 16.4 Hz, 1H).
C
NMR (100 MHz, CDCl ): δ 146.8, 143.8, 136.2, 133.3, 128.9, 128.8,
3
+
1
(
27.0, 126.8, 126.3, 124.1. MS (EI, 70 eV): m/z 225 (54) [M ], 179
43), 176 (100). Known compound (1694-20-8).
13q
(7) Although anilines are toxic, their polymers have very low toxicity.
For details, see: (a) Oh, W.-K.; Kim, S.; Kwon, O.; Jang, J. J. Nanosci.
Nanotechnol. 2011, 11, 4254. (b) Zhao, H.-C.; Zhu, B.; Sekine, J.; Luo,
S.-C.; Yu, H.-H. ACS Appl. Mater. Interfaces 2012, 4, 680.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.5b01358.
■
*
S
(8) Selected articles: (a) Su, C. L.; Tandiana, R.; Balapanuru, J.;
Tang, W.; Pareek, K.; Nai, C. T.; Hayashi, T.; Loh, K. P. J. Am. Chem.
Soc. 2015, 137, 685. (b) Zhang, X.; Ye, J.-Q.; Yu, L.; Shi, X.-K.; Zhang,
M.; Xu, Q.; Lautens, M. Adv. Synth. Catal. 2015, 357, 955. (c) Xu, Q.;
Chen, J.-H.; Tian, H.-W.; Yuan, X.-Q.; Li, S.-Y.; Zhou, C.-K.; Liu, J.-P.
Angew. Chem., Int. Ed. 2014, 53, 225.
Detailed conditional optimization table and H and 13C
NMR spectra of the products (PDF)
1
(
9) (a) Tay, D. W.; Jong, H.; Lim, Y. H.; Wu, W.; Chew, X.; Robins,
AUTHOR INFORMATION
Corresponding Authors
E-mail: yulei@yzu.edu.cn.
E-mail: chmsuc@hotmail.com.
E-mail: qing-xu@wzu.edu.cn.
■
*
*
*
E. G.; Johannes, C. W. J. Org. Chem. 2015, 80, 4054. (b) Rostamnia, S.;
Rahmani, T. Appl. Organomet. Chem. 2015, 29, 471. (c) Martínez, A.
V.; Leal-Duaso, A.; García, J. I.; Mayoral, J. A. RSC Adv. 2015, 5,
5
(
9983. (d) Puthiaraj, P.; Pitchumani, K. Green Chem. 2014, 16, 4223.
10) Zhang, Q.; Ge, J. P.; Pham, T.; Goebl, J.; Hu, Y. X.; Lu, Z. D.;
Yin, Y. D. Angew. Chem., Int. Ed. 2009, 48, 3516.
11) Xu, T.-Y.; Zhang, Q.-F.; Jiang, D.-H.; Liang, Q.-X.; Lu, C.-S.;
Cen, J.; Li, X.-N. RSC Adv. 2014, 4, 33347.
12) Mariampillai, B.; Herse, C.; Lautens, M. Org. Lett. 2005, 7, 4745.
Notes
(
The authors declare no competing financial interest.
(
ACKNOWLEDGMENTS
This research was supported by NNSFC (21202141,
1173182), Priority Academic Program Development of
Jiangsu Higher Education Institutions (PAPD), and Yangzhou
Nature Science Foundation (YZ2014040). We thank Prof.
Rong Guo and his group for help in catalyst preparation. We
thank Dongliang Zhang and Miss Zhe Han for assistance with
experiments. We thank Prof. Mark Lautens for suggestions in
the mechanism study.
(13) (a) Spectral Database for Organic Compounds; SDBS. http://
sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi. (b) Peng, Z.-Y.;
Ma, F.-F.; Zhu, L.-F.; Xie, X.-M.; Zhang, Z.-G. J. Org. Chem. 2009, 74,
■
2
6
855. (c) Wang, L.; Li, H.; Li, P. Tetrahedron 2009, 65, 364. (d) Sinha,
A. K.; Kumar, V.; Sharma, A.; Sharma, A.; Kumar, R. Tetrahedron
2
2
007, 63, 11070. (e) Leng, Y.; Yang, F.; Wei, K.; Wu, Y. Tetrahedron
010, 66, 1244. (f) Mochida, S.; Hirano, K.; Satoh, T.; Miura, M. Org.
Lett. 2010, 12, 5776. (g) McNulty, J.; Das, P. Eur. J. Org. Chem. 2009,
2009, 4031. (h) Sugihara, T.; Satoh, T.; Miura, M.; Nomura, M. Adv.
Synth. Catal. 2004, 346, 1765. (i) Li, H.-J.; Wang, L. Eur. J. Org. Chem.
2
006, 2006, 5099. (j) Ren, G.; Cui, X.; Yang, E.; Yang, F.; Wu, Y.
Tetrahedron 2010, 66, 4022. (k) Alacid, E.; Najera, C. J. Org. Chem.
008, 73, 2315. (l) Sugihara, T.; Satoh, T.; Miura, M.; Nomura, M.
REFERENCES
■
2
(
1) Selected recent reviews on Heck reactions, please see: (a) Kumar,
A.; Rao, G. K.; Kumar, S.; Singh, A. K. Organometallics 2014, 33, 2921.
b) Santos, C. I. M.; Barata, J. F. B.; Faustino, M. A. F.; Lodeiro, C.;
Angew. Chem., Int. Ed. 2003, 42, 4672. (m) Corsico, E. F.; Rossi, R. A.
J. Org. Chem. 2004, 69, 6427. (n) Alacid, E. Org. Lett. 2008, 10, 5011.
(
(
(
o) Dhudshia, B.; Thadani, A. N. Chem. Commun. 2006, 668.
p) Jiang, Z.-J.; Wang, W.; Zhou, R.; Zhang, L.; Fu, H.-Y.; Zheng, X.-
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S.; Du, Y.-N.; Tao, Y.-H. Youji Huaxue 2013, 33, 2325 and references
cited therein.
2) (a) Patel, H. H.; Sigman, M. S. J. Am. Chem. Soc. 2015, 137, 3462.
b) Cong, H.; Fu, G. C. J. Am. Chem. Soc. 2014, 136, 3788. (c) Liu, X.-
L.; Li, B.; Gu, Z.-H. J. Org. Chem. 2015, 80, 7547.
3) Selected recent articles for olefin modification, please see:
a) Janson, P. G.; Ilchenko, N. O.; Diez-Varga, A.; Szabo, K. J.
L.; Chen, H.; Li, R.-X. Catal. Commun. 2014, 57, 14. (q) Zhang, Z.-H.;
Wang, Z.-Y. J. Org. Chem. 2006, 71, 7485.
(
(
(
(
Tetrahedron 2015, 71, 922. (b) Tseng, K.-N. T.; Kampf, J. W.;
Szymczak, N. K. ACS Catal. 2015, 5, 411. (c) IlChenko, N. O.; Tasch,
B. O. A.; Szabo, K. J. Angew. Chem., Int. Ed. 2014, 53, 12897.
́
G
DOI: 10.1021/acs.joc.5b01358
J. Org. Chem. XXXX, XXX, XXX−XXX