Iron-catalyzed decarboxylative methylation of α,β-unsaturated acids under ligand-free conditions

Article abstract of DOI:10.1016/j.tet.2014.06.014

It is the first time to find that iron-catalyzed decarboxylative methylation of α,β-unsaturated acids could be performed in the absence of any ligands. During the reaction, the configuration of the double bond could be retained. It is noteworthy that di-t

Full text of DOI:10.1016/j.tet.2014.06.014

Accepted Manuscript
Iron-Catalyzed Decarboxylative Methylation of α,β-Unsaturated Acids under Ligand-
Free Conditions
Guangwei Rong, Defu Liu, Linhua Lu, Hong Yan, Yang Zheng, Jie Chen, Jincheng
Mao
PII:
S0040-4020(14)00860-6
10.1016/j.tet.2014.06.014
TET 25679
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 11 April 2014
Revised Date: 24 May 2014
Accepted Date: 3 June 2014
Please cite this article as: Rong G, Liu D, Lu L, Yan H, Zheng Y, Chen J, Mao J, Iron-Catalyzed
Decarboxylative Methylation of α,β-Unsaturated Acids under Ligand-Free Conditions, Tetrahedron
(2014), doi: 10.1016/j.tet.2014.06.014.
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Iron-Catalyzed Decarboxylative Methylation
of α,β-Unsaturated Acids under Ligand-Free
Conditions
Leave this area blank for abstract info.
Guangwei Rong, Defu Liu, Linhua Lu, Hong Yan, Yang Zheng, Jie Chen, and Jincheng Mao*
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and
Materials Science, Soochow University, Suzhou 215123, P. R. China
FeCl3, DTBP
R1
COOH
R1
CH3
DMSO, Ar
R2
R2
CO2

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Iron-Catalyzed Decarboxylative Methylation of α,β-Unsaturated Acids under Ligand-
Free Conditions
Guangwei Rong, Defu Liu, Linhua Lu, Hong Yan, Yang Zheng, Jie Chen, and Jincheng Mao*
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou
215123, P. R. China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
It is the first time to find that iron-catalyzed decarboxylative methylation of α,β-unsaturated
acids could be performed in the absence of any ligands. During the reaction, the configuration of
the double bond could be retained. It is noteworthy that di-tert-butyl peroxide (DTBP) was
employed not only as the oxidant, but also as the methyl source.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
decarboxylative reactions
methylation
cinnamic acids
ligand-free
iron catalyst
1. Introduction
cinnamic acids with simple alcohols, esters etc. with good yields
(Scheme 1-3).8 Maiti and co-workers found an effective synthesis
of (E)-nitroolefins via decarboxylative nitration of cinnamic aicd
In the past several years, the development of decarboxylative
coupling of carboxylic acids has gained great attention since such
transformations employed the readily available carboxylic acids
as starting materials.1 As a consequence, many efficient catalytic
systems have been developed for a series of decarboxylative C-C
bond formation reactions in recent years.2 Among these
carboxylic acids, cinnamic acids could be considered as the
useful and direct alkenylation reagent during the
decarboxylation.3 Considering that alkenylarene molecules
usually display important pharmacological and physical
properties,4 we have the special interest on such decarboxylative
reaction of cinnamic acids.
t
using BuONO (t-butylnitrite) and TEMPO (2,2,6,6-tetramethyl-
1-piperidinyloxy).9 Recently, Liu disclosed an example of
copper- and iron-catalyzed decarboxylative tri- and
difluoromethylation of cinnamic acids with CF3SO2Na and
(CF2HSO2)2Zn (Scheme1-5).10 Thus, decarboxylation of
cinnamic acids gains great attention in the past several years.11
Quite differently, in this paper, we just reported the first example
of decarboxylative methylation of α,β-unsaturated acids
including cinnamic acids in the presence of readily available
FeCl3. It is noteworthy that during the reaction, DTBP was used
not only as the oxidant but also as the methyl source.
Pioneering work from Fletcher, Heinz and Schiavelli
established the viability of acid-catalyzed decarboxylation of
cinnamic acids in various solvents.5 In recent years, Wu has
reported Palladium-catalyzed decaroxylative coupling between
cinnamic acids and aryl iodides and Miura independently found
that α, ω-diarylbutadienes and -hexatrienes could be prepared by
decarboxylative coupling of cinnamic acids with vinyl bromides
in the presence of palladium catalyst (Scheme 1-1).6 The work
from our own laboratory has demonstrated highly effective
copper- or iron-catalyzed decarboxylative C(sp2)–C(sp3) coupling
reactions via radical mechanism (Scheme 1-2).7 At the same time,
Liu also reported copper-catalyzed decarboxylative coupling of
———
*
Corresponding author. Tel (Fax): +86 512 65880403. E-mail address: jcmao@suda.edu.cn (J. Mao
)

2
Tetrahedron
of condition optimizing, no byproducts were detected, and
ACCEPTED MANUSCRIPT
conversion of cinnamic acid for entry 13 is only 60%.
Table 1. Iron-catalyzed decarboxylative methylation of various α,β-
unsaturated acids in the absence of ligand.a
CH3
COOH
cat., oxidant
DMSO, Ar
O2N
O2N
1a
2a
Yield (%)b
Entry
1
Cat.
Oxidant
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
TBHP
DCP
CuO
CuI
42
30
2
3
CuBr
27
4
Copper quinolate
Fe(acac)3
38
5
44
6
Fe powder
38
.
7
FeCl2 4H2O
40
8
FeF3
Fe2(SO4)3
Fe2O3
48
9
33
10
11
12
13
14
15
16
18
Fe3O4
31
Scheme 1. Decarboxylative couplings of cinnamic acids using various
catalysts.
Fe(NO3)3
FeCl3
30
52 (46)c
.
FeSO4 7H2O
41
FeCl3
FeCl3
41
Generally, oxidant is indispensable when it comes to
decarboxylative reaction of cinnamic acids. Oxidants such as
K2S2O8, Ag2O, tert-butyl hydroperoxide (TBHP), di-tert-butyl
peroxide (DTBP), dicumyl peroxide (DCP), have been widely
used. Different from inogranic oxidants, these organic peroxides
such as TBHP or DTBP, just act not only as the oxidants, but
also as the radical initiators since many decarboxylative reactions
go through radical process.12 In 2007, Li and co-workers reported
palladium-catalyzed methylation of aryl C–H bond by using
peroxides. In their work, DTBP acts as methylation reagent
besides as oxidant.13 Just recently, we have reported effective
synthesis of methyl esters from benzylic acohols, aldehydes or
acids via copper-catalyzed C-C cleavage from TBHP.14 Inspired
by such research, we imagine whether we could develop a
reaction system through decarboxylation and methylation process
by using organic peroxide as the methylation reagent.
36
a
Reaction conditions: p-nitro cinnamic acid (0.3 mmol), cat. (20 mol%),
o
b
oxidant (2 equiv), DMSO (2 mL), 12 h, 130 C, Ar. LC yields, biphenyl as
internal standard. c Isolated yield based on p-nitro cinnamic acid parentheses.
With the optimized conditions in hand, the scope of different
substituted cinnamic acids was investigated. As shown in table 2,
cinnamic acids with electron-withdrawing group at the para
position of the benzene ring gave moderate yields (Table 2,
entries 1–3). Meta-substituted cinnamic acids also can offer
desired products and got certain yields (Table 2, entries 4–6). It is
important to note that when methoxy-substituted cinnamic acids
were used as the substrates, lower yields of the desired products
were obtained (Table 2, entries 7–10). However, it was pleased to
find that β-substituted substrates could also be tolerated by our
reaction system (Table 2, entries 11–12). For example, β-phenyl
cinnamic acid afforded the product in the yield of 42% (Table 2,
entry 12).
2. Results and discussion
Table 2. Iron-catalyzed decarboxylative methylation of various α,β-
unsaturated acids in the absence of ligand.a
To begin our study, we chose p-nitro cinnamic acid as model
substrate using CuO as catalyst and DTBP as oxidant. Various
solvents were tested, and the desired product was detected only
when DMSO was used as solvent and gave a yield of 42% of 2a.
The detailed optimization is summarized in table 1. Very clearly,
other copper catalysts such as CuI are less effective than CuO
(Table 1, entries 1–4). As far as we know, iron catalyst also has a
good effect on some decarboxylative reactions. For example, Li’s
group reported a novel iron-catalyzed decarboxylative Csp3-Csp2
coupling of proline derivatives and naphthol.15 Thus, we tried to
employ a series of iron catalysts. To our delight, it was found that
iron catalysts were more effective than copper ones (Table 1,
entries 5–14). After screening various iron catalysts, we found
that FeCl3 worked best and gave 52% LC yield (46% isolated
yield). Then, other peroxides were also tested, including TBHP
and DCP. However, both of them were less effective. Other
conditions, such as temperature and reaction time were also
screened and we could not get better results. During the process
FeCl3 (20 mol%)
DTBP (2 equiv)
R1
R1
COOH
CH3
R2
R2
DMSO, Ar
1
2
Yield
(%)b
Entry
1
substrate
Product
COOH
CH3
CH3
46
53
34
O2N
O2N
NC
1a
1b
1c
2a
2b
2c
COOH
COOH
2
3
NC
CH3
MeOOC
MeOOC

3
COOH
CH3
O
O
H
D
ACCEPTED MANUSCRIPT
H
H
D
D
COOH
FeCl3
DMSO-d6, 130 oC, Ar
+
4
5
6
43
40
34
O2N
O2N
O2N
NO2
NO2
2m
1d
2d
53% major
less
CH3
COOH
COOH
COOH
COOH
CH3
FeCl3, DTBP
PhS(O)Me, 130 oC, Ar
O2IN
O2N
OCOMe
OCOMe
50% yield
1e
Ph
Ph
2e
O
O
(3)
O
CH3
CH3
FeCl3
DMSO-d6, 130 oC, Ar
+
CH3
O2N
O2N
OH
OH
40% yield
1f
2f
COOH
CH3
Scheme 2. Iron-catalyzed decarboxylative methylation of p-nitro cinnamic
acid in DMSO-D6 or MPSO using DTBP or DCP as oxidants.
MeOCO
MeOCO
7
20
42
35
OMe
OMe
2g
1g
COOH
COOH
CH3
A series of experiments was conducted in order to explore the
possible reaction mechanism. When TEMPO or BQ (benzoquinone)
was added, the reaction was almost inhibited and no product was
detected. These are indirect proofs that our reaction may go through
a radical process.
8[c]
MeO
MeO
MeO
MeO
2h
1h
CH3
CH3
9[c]
COOH
OMe
OMe
CH3
FeCl3, DTBP
2i
1i
DMSO, 130 oC, Ar
MeO
MeO
COOH
MeO
MeO
NC
NC
10[c]
36
41
53% yield
With TEMPO <1%
With BQ <1%
OMe
OMe
1j
2j
Cl
Cl
Scheme 3. Iron-catalyzed decarboxylative methylation of p-cyano cinnamic
acid.
11
COOH
CH3
Ar1
COOH
Cl
Cl
1k
1l
Ar2
2k
2l
Fe(III)
Ar1
COOFe(III)
COOH
CH3
12
42
tBuOH
Ar2
B
O
O
O
Ar1
COOH
a Reaction conditions: α,β-Unsaturated acids (0.3 mmol), DTBP (2 equiv),
Ar2
FeCl3 (20 mol%), DMSO (2 mL), 12 h, 130 C, Ar. b Isolated yield based on
o
CH3
A
α,β-unsaturated acids. c Fe(acac)3 instead of FeCl3.
O
Ar1
CH3
Ar2 COOFe(III)
Ar1
CH3
Fe(II)
In order to make sure that the methyl group was generated
from the oxidant, the decarboxylative reaction of p-nitro
cinnamic acid was performed in DMSO-d6 as shown in Scheme 2.
The NMR suggested that less [D]-product was acquired. When
DMSO was replaced by methyl phenyl sulfoxide (MPSO), the
reaction can also be carried out smoothly. When 1-(2-(2-
phenylpropan-2-ylperoxy)propan-2-yl)benzene (3) was employed,
the desired product was obtained in 40% yield as expected. In
addition, a big amount of acetophenone was acquired. This
suggests that the methyl group in the product was introduced
from this C-C bond cleavage of the oxidant (3). We guess that
the coordination of sulfoxide to iron ion plays an important role
in the reaction process.16
+
CO2
C
Ar2
Figure 1. Proposed reaction pathways for the iron-catalyzed decarboxylative
methylation.
Base on previous reports,13, 14, 17 a proposed mechanism for the
decarboxylative methylation reaction is shown in Figure 1. The
catalytic cycle starts with the generation of methyl radical
released from t-BuO.. Then, the addition of methyl radical to the
α-position of the double bond of ferric cinnamate B, which is
generated by the reaction of cinnamic acid with ferric chloride,
would give intermediate C. C then proceeds via an elimination of
carbon dioxide and Fe(II) to generate the product. Fe(II) will be
oxidized by t-BuO. and regenerates B in the presence of cinnamic
acid to complete the reaction cycle.

4
Tetrahedron
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1
3. Conclusions
(E)-1-Nitro-3-(prop-1-enyl)benzene: Yellow oil; H NMR (400
MHz, CDCl3) (δ, ppm) 8.07 (s, 1H), 7.93 (d, J = 8.0 Hz, 1H),
7.51 (d, J = 7.6 Hz, 1H), 7.35 (t, J = 8.0 Hz, 1H), 6.39 – 6.25 (m,
2H), 1.83 (d, J = 5.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) (δ,
ppm) 148.6, 139.7, 134.8, 131.7, 129.3, 129.0, 121.3, 120.4,
In conclusion, we developed
a
novel iron-catalyzed
decarboxylative methylation reaction of cinnamic acids in the
presence of DTBP as methylation resource. This reaction system
could tolerate various cinnamic acids. It provides a new strategy
to prepare α-methyl styrene. It is noteworthy that during the
reaction, the configuration of the double bond could be retained.
However, our protocol also shows the disadvantage of low yield.
Therefore, the aim of our future work is to find out a more
effective catalyst and its application in the synthesis of some
biological compounds.
18.5; MS (m/z) calcd for C9H9NO2 163.1, found 163.1 (M+H)+
.
(E)-3-(Prop-1-enyl)phenyl acetate: Colorless oil; 1H NMR (400
MHz, CDCl3) (δ, ppm) 7.28 (t, J = 8.0 Hz, 1H), 7.17 (d, J = 7.6
Hz, 1H), 7.04 (s, 1H), 6.90 (d, J = 7.6 Hz, 1H), 6.36 (d, J = 16.0
Hz, 1H), 6.29 – 6.17 (m, 1H), 2.29 (s, 3H), 1.87 (d, J = 6.4 Hz,
3H); 13C NMR (100 MHz, CDCl3) (100 MHz, CDCl3) (δ, ppm)
169.5, 150.9, 139.6, 130.1, 129.3, 126.9, 123.4, 119.7, 118.6,
21.1, 18.4; MS (m/z) calcd for C11H12O2 176.1, found 176.1
4. Experiment
4.1 General information
(M+H)+
.
General information: All reactions were carried out under an
argon atmosphere condition. Various iron catalysts, cinnamic
acids and oxidants were purchased from Aldrich, Acros or Alfa.
Column chromatography was generally performed on silica gel
(100-200 mesh) and reactions were monitored by thin layer
chromatography (TLC) using UV light (254 nm) to visualize the
1
(E)-3-(Prop-1-enyl)phenol: Colorless oil; H NMR (400 MHz,
CDCl3) (δ, ppm) 7.07 (t, J = 8.0 Hz, 1H), 6.82 (d, J = 7.6 Hz,
1H), 6.73 (s, 1H), 6.59 (d, J = 8.0 Hz, 1H), 6.25 (d, J = 15.6 Hz,
1H), 6.19 – 6.07 (m, 1H), 4.94 (s, 1H), 1.78 (d, J = 6.4 Hz, 3H);
13C NMR (100 MHz, CDCl3) (δ, ppm) 155.7, 139.7, 130.6,
129.7, 126.3, 118.7, 113.8, 112.5, 18.5; MS (m/z) calcd for
1
course of the reactions. The H (300 MHz or 400 MHz) and 13C
C9H10O 134.1, found 134.1 (M+H)+
.
NMR (75 MHz or 100 MHz) data were recorded on Varian 300
M or 400 M spectrometers using CDCl3 as solvent. The chemical
shifts (δ) are reported in ppm and coupling constants (J) in Hz.
1H NMR spectra was recorded with tetramethylsilane (δ = 0.00
ppm) as internal reference; 13C NMR spectra was recorded with
CDCl3 (δ = 77.000 ppm) or DMSO-d6 (δ = 39.500 ppm) as
internal reference. ESI-MS and HRMS were performed by the
State-authorized Analytical Center in Soochow University.
(E)-Methyl 2-methoxy-4-(prop-1-enyl)benzoate: Colorless oil;
1H NMR (400 MHz, CDCl3) (δ, ppm) 6.94 – 6.73 (m, 3H), 6.29
(d, J = 16.0 Hz, 1H), 6.18 – 6.05 (m, 1H), 3.76 (s, 3H), 2.23 (s,
3H), 1.80 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) (δ,
ppm) 169.2, 151.0, 138.6, 137.1, 130.5, 126.1, 122.7, 118.4,
109.6, 55.8, 20.7, 18.4; MS (m/z) calcd for C12H14O3 206.1,
found 206.1 (M+H)+
.
General procedure for iron-catalyzed decarboxylative
methylation of cinnamic acid: A mixture of cinnamic acid (0.3
mmol), DTBP (0.6 mmol), FeCl3 (20 mol%), and DMSO (2 mL)
in a Schlenk tube was stirred under an argon atmosphere at 130
oC for 12 h. After that the mixture was poured into ethyl acetate,
then washed with water, extracted with ethyl acetate, dried by
anhydrous Na2SO4, then filtered and evaporated under vacuum,
the residue was purified by flash column chromatography
(petroleum ether or petroleum ether/ethyl acetate) to afford the
corresponding coupling products.
(E)-1-methoxy-4-(prop-1-enyl)benzene: Colorless oil; 1H NMR
(400 MHz, CDCl3) (δ, ppm) 7.25 (d, J = 8.8 Hz, 2H), 6.82 (d, J =
8.8 Hz, 2H), 6.33 (d, J = 15.6 Hz, 1H), 6.14 – 6.03 (m, 1H), 3.79
(s, 3H), 1.85 (dd, J = 6.4, 1.6 Hz, 3H); 13C NMR (100 MHz,
CDCl3) (δ, ppm) 158.5, 130.7, 130.2, 126.8, 123.5, 113.8, 55.2,
18.4; MS (m/z) calcd for C10H12O 148.1, found 148.1 (M+H)+
.
(E)-1,2-Dimethoxy-4-(prop-1-enyl)benzene: Colorless oil; 1H
NMR (400 MHz, CDCl3) (δ, ppm) 6.84 – 6.69 (m, 3H), 6.26 (d, J
= 15.6 Hz, 1H), 6.03 (m, 1H), 3.81 (s, 3H), 3.79 (s, 3H), 1.79 (dd,
J = 6.8, 1.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) (δ, ppm)
148.9, 148.1, 131.1, 130.6, 123.8, 118.6, 111.1, 108.4, 55.9, 55.7,
(E)-1-Nitro-4-(prop-1-enyl)benzene: Yellow solid, mp: 92 – 93
1
oC; H NMR (400 MHz, CDCl3) (δ, ppm) 8.06 (d, J = 8.8 Hz,
18.3; MS (m/z) calcd for C11H14O2 178.1, found 178.1 (M+H)+
2H), 7.35 (d, J = 8.8 Hz, 2H), 6.43-6.35 (m, 2H), 1.86 (d, J = 4.8
Hz, 3H); 13C NMR (100 MHz, CDCl3) (δ, ppm) 146.4, 144.4,
131.2, 129.4, 126.2, 123.9, 18.7; MS (m/z) calcd for C9H9NO2
.
163.1, found 163.1 (M+H)+
(E)-1,2,3-Trimethoxy-5-(prop-1-enyl)benzene: Colorless oil ;
1H NMR (400 MHz, CDCl3) (δ, ppm) 6.47 (s, 2H), 6.24 (d, J =
16.0 Hz, 1H), 6.13 – 6.01 (m, 1H), 3.78 (s, 6H), 3.75 (s, 3H),
1.79 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) (δ, ppm)
153.2, 137.1, 133.7, 130.8, 125.2, 102.7, 60.8, 55.9, 18.3; MS
.
1
(E)-4-(Prop-1-enyl)benzonitrile: Colorless oil; H NMR (400
MHz, CDCl3) (δ, ppm) 7.47 (d, J = 8.4 Hz, 2H), 7.30 (d, J = 8.4
Hz, 2H), 6.38 – 6.25 (m, 2H), 1.84 (d, J = 4.8 Hz, 3H); 13C NMR
(100 MHz, CDCl3) (δ, ppm) 142.4, 132.3, 130.2, 129.8, 126.3,
119.2, 109.9, 18.7; MS (m/z) calcd for C10H9N 143.1, found
(m/z) calcd for C12H16O3 208.1, found 208.1 (M+H)+
.
1
143.1 (M+H)+
4,4'-(Prop-1-ene-1,1-diyl)bis(chlorobenzene): Colorless oil; H
.
NMR (400 MHz, CDCl3) (δ, ppm) 7.26 (d, J = 8.8 Hz, 2H), 7.13
(d, J = 8.8 Hz, 2H), 7.05 – 6.95 (m, 4H), 6.07 (q, J = 7.2 Hz, 1H),
1.66 (d, J = 7.2 Hz, 3H); 13C NMR(100 MHz, CDCl3) (δ, ppm)
140.9, 140.2, 137.9, 132.9, 132.7, 131.3, 128.5, 128.4, 128.2,
125.2, 15.7; MS (m/z) calcd for C15H12Cl2 263.1, found 263.1
(M+H)+.
(E)-Methyl 4-(prop-1-enyl)benzoate: Yellow oil; 1H NMR (400
MHz, CDCl3) (δ, ppm) 7.88 (d, J = 8.4 Hz, 2H), 7.16 (d, J = 8.4
Hz, 2H), 6.40 – 6.23 (m, 2H), 3.82 (s, 3H), 1.83 (d, J = 5.6 Hz,
3H); 13C NMR (100 MHz, CDCl3) (δ, ppm) 168.0, 142.4, 130.3,
129.8, 128.8, 128.1, 125.6, 52.0, 18.6; MS (m/z) calcd for
C11H11O2 176.1, found 176.1 (M+H)+
.

5
o
1
15. Bi, H.-P.; Chen, W.-W.; Liang, Y.-M.; Li, C.-J. Org. Lett. 2009,
Prop-1-ene-1,1-diyldibenzene: White solid, mp: 49–50 C; H
NMR (400 MHz, CDCl3) (δ, ppm) 7.30 (t, J = 7.6 Hz, 2H), 7.25
– 7.04 (m, 8H), 6.10 (q, J = 7.2 Hz, 1H), 1.69 (d, J = 6.8 Hz, 3H);
13C NMR (δ, ppm) 142.9, 142.4, 140.0, 130.0, 128.1, 128.0,
127.2, 126.8, 126.7, 124.1, 15.7, MS (m/z) calcd for C15H14
ACCEPTED MANUSCRIPT
11, 3246–3249.
16. (a) Whiteoak, C. J., Martin, E.; Belmonte, M. M.; Buchholz, J. B.;
Kleij, A. W. Adv. Synth. Catal. 2012, 354, 469–476; (b) Amani,
V.; Safari, N.; Notash, B.; Khavasi, H. R. J. Coord. Chem. 2009,
62, 1939–1950.
17. Gephart, R. T.; McMullin, C. L.; Sapiezynski, N. G.; Jang, E. S.;
Aguila, M. J. B.; Cundari, T. R.; Warren, T. H. J. Am. Chem. Soc.
2012, 134, 17350–17353.
194.1, found 194.1 (M+H)+
.
(E)-1-Nitro-4-(prop-1-enyl)benzene (2m): Yellow solid, mp: 92
o
1
– 93 C; H NMR (400 MHz, CDCl3) (δ, ppm) 8.15 (d, J = 8.8
Hz, 2H), 7.44 (d, J = 8.8 Hz, 2H), 6.51 – 6.43 (m, 2H), 1.95 (d, J
= 4.4 Hz, 3H). MS (m/z) calcd for C9H9NO2 163.1, found 163.1
(M+H)+.
Acknowledgments
We are grateful to the grants from the Scientific Research
Foundation for the Returned Overseas Chinese Scholars, State
Education Ministry, the Priority Academic Program
Development of Jiangsu Higher Education Institutions, The
Project of Scientific and Technologic Infrastructure of Suzhou
(SZS201207), and the Key Laboratory of Organic Synthesis of
Jiangsu Province.
References and notes
1. (a) Goossen, L. J.; Rodríguez, N; Melzer, B; Linder, C.; Deng, G.;
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Supporting Information
Iron-Catalyzed Decarboxylative Methylation of
α,β-Unsaturated Acids under Ligand-Free Conditions
Guangwei Rong,a Defu Liu,a Linhua Lu,a Hong Yana, Yang Zhenga, Jie Chena,
and Jincheng Mao*,a
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry,
Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P.
R. China (Fax: +86-512-65880403, e-mail: jcmao@suda.edu.cn)

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Characterization of the corresponding products:
(E)-1-Nitro-4-(prop-1-enyl)benzene (2a) [cas: 1879-55-6]
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Yellow solid, mp: 92 – 93 oC; H NMR (400 MHz, CDCl3) (δ, ppm) 8.06 (d, J = 8.8
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Hz, 2H), 7.35 (d, J = 8.8 Hz, 2H), 6.43-6.35 (m, 2H), 1.86 (d, J = 4.8 Hz, 3H); C
NMR (δ, ppm) 146.4, 144.4, 131.2, 129.4, 126.2, 123.9, 18.7; MS (m/z) calcd for
C9H9NO2 164.1, found 164.1 (M+H)+
.
(E)-4-(Prop-1-enyl)benzonitrile (2b) [cas: 74254-13-0]
Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.47 (d, J = 8.4 Hz, 2H), 7.30 (d,
13
J = 8.4 Hz, 2H), 6.38 – 6.25 (m, 2H), 1.84 (d, J = 4.8 Hz, 3H); C NMR (δ, ppm)
142.4, 132.3, 130.2, 129.8, 126.3, 119.2, 109.9, 18.7; MS (m/z) calcd for C10H9N
144.1, found 144.1 (M+H)+
.
(E)-Methyl 4-(prop-1-enyl)benzoate (2c) [cas: 158475-38-8]
Yellow oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.88 (d, J = 8.4 Hz, 2H), 7.16 (d, J
= 8.4 Hz, 2H), 6.40 – 6.23 (m, 2H), 3.821 (s, 3H), 1.83 (d, J = 5.6 Hz, 3H); 13C NMR
(δ, ppm) 168.0, 142.4, 130.3, 129.8, 128.8, 128.1, 125.6, 52.0, 18.6; MS (m/z) calcd
for C11H11O2 177.1, found 177.1 (M+H)+
.
(E)-1-Nitro-3-(prop-1-enyl)benzene (2d) [cas: 23204-79-7]
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Yellow oil; H NMR (400 MHz, CDCl3) (δ, ppm) 8.07 (s, 1H), 7.93 (d, J = 8.0 Hz,
1H), 7.51 (d, J = 7.6 Hz, 1H), 7.35 (t, J = 8.0 Hz, 1H), 6.39 – 6.25 (m, 2H), 1.83 (d, J
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= 5.2 Hz, 3H); C NMR (δ, ppm) 148.6, 139.7, 134.8, 131.7, 129.3, 129.0, 121.3,
120.4, 18.5; MS (m/z) calcd for C9H9NO2 164.1, found 164.1 (M+H)+
.
(E)-3-(Prop-1-enyl)phenyl acetate (2e)
CH3
OCOMe
Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.28 (t, J = 8.0 Hz, 1H), 7.17 (d,
J = 7.6 Hz, 1H), 7.04 (s, 1H), 6.90 (d, J = 7.6 Hz, 1H), 6.36 (d, J = 16.0 Hz, 1H), 6.29
– 6.17 (m, 1H), 2.29 (s, 3H), 1.87 (d, J = 6.4 Hz, 3H); 13C NMR (δ, ppm) 169.5, 150.9,
139.6, 130.1, 129.3, 126.9, 123.4, 119.7, 118.6, 21.1, 18.4; MS (m/z) calcd for
C11H12O2 177.1, found 177.1 (M+H)+
.
(E)-3-(Prop-1-enyl)phenol (2f) [cas: 66921-90-2]
Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.07 (t, J = 8.0 Hz, 1H), 6.82 (d,
J = 7.6 Hz, 1H), 6.73 (s, 1H), 6.59 (d, J = 8.0 Hz, 1H), 6.25 (d, J = 15.6 Hz, 1H), 6.19
– 6.07 (m, 1H), 4.94 (s, 1H), 1.78 (d, J = 6.4 Hz, 3H); 13C NMR (δ, ppm) 155.7, 139.7,
130.6, 129.7, 126.3, 118.7, 113.8, 112.5, 18.5; MS (m/z) calcd for C9H10O 135.1,
found 135.1 (M+H)+
.
(E)-Methyl 2-methoxy-4-(prop-1-enyl)benzoate (2g) [cas: 93-29-8]
Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 6.94 – 6.73 (m, 3H), 6.29 (d, J =
16.0 Hz, 1H), 6.18 – 6.05 (m, 1H), 3.76 (s, 3H), 2.23 (s, 3H), 1.80 (d, J = 6.8 Hz, 3H);
13C NMR (δ, ppm) 169.2, 151.0, 138.6, 137.1, 130.5, 126.1, 122.7, 118.4, 109.6, 55.8,
20.7, 18.4; MS (m/z) calcd for C12H14O3 207.1, found 207.1 (M+H)+
.
(E)-1-methoxy-4-(prop-1-enyl)benzene (2h) [cas: 4180-23-8]
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Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.25 (d, J = 8.8 Hz, 2H), 6.82 (d,
J = 8.8 Hz, 2H), 6.33 (d, J = 15.6 Hz, 1H), 6.14 – 6.03 (m, 1H), 3.79 (s, 3H), 1.85 (dd,
J = 6.4, 1.6 Hz, 3H); 13C NMR (δ, ppm) 158.5, 130.7, 130.2, 126.8, 123.5, 113.8, 55.2,
18.4; MS (m/z) calcd for C10H12O 149.1, found 149.1 (M+H)+
.
(E)-1,2-Dimethoxy-4-(prop-1-enyl)benzene (2i) [cas: 6379-72-2]
Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 6.84 – 6.69 (m, 3H), 6.26 (d, J =
15.6 Hz, 1H), 6.03 (m, 1H), 3.81 (s, 3H), 3.79 (s, 3H), 1.79 (dd, J = 6.8, 1.6 Hz, 3H);
13C NMR (δ, ppm) 148.9, 148.1, 131.1, 130.6, 123.8, 118.6, 111.1, 108.4, 55.9, 55.7,
18.3; MS (m/z) calcd for C11H14O2 179.1, found 179.1 (M+H)+
.
(E)-1,2,3-Trimethoxy-5-(prop-1-enyl)benzene (2j) [cas: 5273-85-8]
Colorless oil ; 1H NMR (400 MHz, CDCl3) (δ, ppm) 6.47 (s, 2H), 6.24 (d, J = 16.0 Hz,
13
1H), 6.13 – 6.01 (m, 1H), 3.78 (s, 6H), 3.75 (s, 3H), 1.79 (d, J = 6.8 Hz, 3H); C
NMR (δ, ppm) 153.2, 137.1, 133.7, 130.8, 125.2, 102.7, 60.8, 55.9, 18.3; MS (m/z)
calcd for C12H16O3 209.1, found 209.1 (M+H)+
.
4,4'-(Prop-1-ene-1,1-diyl)bis(chlorobenzene) (2k) [cas: 3439-04-1]
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Colorless oil; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.26 (d, J = 8.8 Hz, 2H), 7.13 (d,
J = 8.8 Hz, 2H), 7.05 – 6.95 (m, 4H), 6.07 (q, J = 7.2 Hz, 1H), 1.66 (d, J = 7.2 Hz,
3H); 13C NMR (δ, ppm) 140.9, 140.2, 137.9, 132.9, 132.7, 131.3, 128.5, 128.4, 128.2,
125.2, 15.7; MS (m/z) calcd for C15H12Cl2 264.1, found 264.1 (M+H)+.
Prop-1-ene-1,1-diyldibenzene (2l) [cas: 778-66-5]
CH3
White solid, mp: 49–50 oC; 1H NMR (400 MHz, CDCl3) (δ, ppm) 7.30 (t, J = 7.6 Hz,
2H), 7.25 – 7.04 (m, 8H), 6.10 (q, J = 7.2 Hz, 1H), 1.69 (d, J = 6.8 Hz, 3H); 13C NMR
(δ, ppm) 142.9, 142.4, 140.0, 130.0, 128.1, 128.0, 127.2, 126.8, 126.7, 124.1, 15.7,
MS (m/z) calcd for C15H14 195.1, found 195.1 (M+H)+
.
(E)-1-Nitro-4-(prop-1-enyl)benzene (2m) (DMSO-d6 as reaction solvent)
o
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Yellow solid, mp: 92 – 93 C; H NMR (400MHz, CDCl3) (δ, ppm) 8.15 (d, J = 8.8,
2H), 7.44 (d, J = 8.8 Hz, 2H), 6.51 – 6.43 (m, 2H), 1.95 (d, J = 4.4 Hz, 3H). MS (m/z)
calcd for C9H9NO2 164.1, found 164.1 (M+H)+
.
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2m (DMSO-d6 as reaction solvent)
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