Regioselective Synthesis of 2-Vinylanilines Using O-aroyloxycarba-mates by Sequential Decarboxylation/Amination/Heck Reaction

Article abstract of DOI:10.1021/acs.joc.7b01020

A new sequential approach for 2-vinylanilines utilizing aryl carboxylic acids as stable, inexpensive and widely available arylating reagents is described. Employing a Pd-POVs catalyst system, this protocol is not only overcoming the restriction barrier of decarboxylative coupling to ortho-substituted substrates, but also provides site-special to create new C(sp²)-N and C(sp²)-C(sp²) bonds. Mechanistic experiments suggest the cleavage of C(sp²)-COOH gives priority to C(sp²)-X bond in this reaction.

Full text of DOI:10.1021/acs.joc.7b01020

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Note
Regioselective Synthesis of 2-Vinylanilines Using O-aroyloxycarbamates
by Sequential Decarboxylation/Amination/Heck Reaction
Peihe Li, Nuannuan Ma, Jikun Li, Zheng Wang, Qipu Dai, and ChangWen Hu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b01020 • Publication Date (Web): 30 Jun 2017
Downloaded from http://pubs.acs.org on June 30, 2017
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The Journal of Organic Chemistry
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Regioselective Synthesis of 2-Vinylanilines Using O-aroyloxycarba-
mates by Sequential Decarboxylation/Amination/Heck Reaction
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Peihe Li, Nuannuan Ma, Jikun Li, Zheng Wang, Qipu Dai*and Changwen Hu*
Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic,
School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People’s Republic of
China
Supporting Information Placeholder
ABSTRACT: A new sequential approach for 2-vinylanilines uti-
lizing aryl carboxylic acids as stable, inexpensive and widely
available arylating reagents is described. Employing a Pd-POVs
catalyst system, this protocol is not only overcoming the re-
striction barrier of decarboxylative coupling to ortho-substituted
substrates, but also provides site-special to create new C(sp2)-N
and C(sp2)-C(sp2) bonds. Mechanistic experiments suggest the
cleavage of C(sp2)-COOH give priority to C(sp2)-X bond in this
reaction.
Sequential reactions are a powerful method for the formation of
two or more bonds under identical reaction conditions without
isolated the intermediates or adding reagents.1 The well-known
Heck coupling reactions are one of the most direct methods to
form carbon-carbon bond in organic synthesis.2 A diverse array
of sequential reactions employing the Heck coupling have been
established such as Heck-C-H activation,3 Heck-cyanation,4
Heck-carbohalogenation5 and Heck-aza-Michael6 et al. This im-
portant and classic transition-metal catalyzed Heck-type reac-
tions has been reported variously. However, to the best of our
knowledge, no report has appeared using intramolecular decar-
boxylative amination and Heck coupling for the synthesis of 2-
vinylanilines.
reaction between alkyl hydroxycarbamates and carboxylic acid
or carboxylates with styrene, unfortunately, these reactions did
not deliver the desired products (Scheme 1, a).
Scheme 1. Synthesis of 2-vinylanilines
2-vinylaniline derivatives are widely used intermediates in
organic chemistry for the synthesis of biologically related het-
erocyclic compounds.7 Due to 2-vinylaniline usefulness, many
elegant methods have been developed for the synthesis of 2-vi-
nylanilines including Suzuki,8 Stille,9 Mizoroki-Heck cou-
plings,10 C-H activation7c and reduction11. Despite this progress,
multiple and harsh reaction conditions of these methods are
challenging, the high cost and the low stability of 2-substituted
anilines are still deficient.12 Consequently, a more general strat-
egy from easily available starting materials is still demanded.
Herein we wish to report a novel sequential approach for the
synthesis of 2-vinylanilines utilizing aryl carboxylic acids as
stable, inexpensive and widely available arylating reagents. In
this new method, there are two possible pathways. Path a, the
intramolecular decarboxylative coupling (IDC) reactions which
has been reported in our research group.13 Path b, the Buchwald-
Hartwig reaction which has been reported as an elegant method
to construct C-N bond (Scheme 1, b, path b).14 Ignore the
difference of both cases, the same product 3 was obtained. Due
to the C(sp2)-COOH bond is more difficult to cleavage than
C(sp2)-X bond according to the Buchwald-Hartwig reaction.15
It is natural to expect that the new method should enable the
path b. We initially attempted a metal-catalyzed sequential
To realize the decarboxylative amination of aroyloxycarba-
mates from inert aromatic acid derivatives, the IDC reaction
was designed and the condition needs to be efficiently opti-
mized. Fortunately, we found A (Figure 1) is an excellent cata-
lyst using the sequential Decarboxylation/Amination/Heck re-
action for the synthesis of 2-vinylanilines. Based on its remark-
able activity in acidic and oxidation catalysis with wide struc-
tural diversity and O-enriched surfaces by our previously work,
we decided to use the Pd-POVs catalyst and exploit the poten-
tial application of Pd-POVs in the sequential reaction. Polyox-
ometalates (POMs) have exhibited excellent performance as a
class of nanosized metal-oxo clusters in both acidic and oxida-
tion catalysis.16 Notably various POMs-catalyzed pathways
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Page 2 of 8
have been reported with excellent catalytic activity.17 The Lind-
To further screen the decarboxylative amination/Heck coup-
qvist [V6O19]8− anion is one of the classical POM structures. The
substitution of bridging oxygen atoms in the Lindqvist
[V6O19]8− with oxygen donor-ligands is proved to be another ef-
fective method to compensate the negative charge and stabilize
the cluster.18 However, it is worth mentioning that alkoxohexa-
vanadates have fascinating electronic, magnetic, photochemical
properties and potential catalytic application.19 Untill now, very
few examples about their catalytic property have been re-
ported.20 Due to alkoxohexavanadates are extremely susceptible
by trace amount of water. Therefore, our previous work dis-
played the synthetic methods for stable and highly active cata-
lysts based on alkoxohexavanadates.21 The
ing condition of 2-halogen-aroyloxycarbamates from inert aro-
matic acid derivatives with olefin. The activity of the Pd-POVs
catalyst was tested for the sequential reaction of IDC and Heck
coupling for the synthesis of 2-vinylanilines from tert-butyl ((2-
bromobenzoyl)oxy)carbamate with styrene as the model sub-
strate. As shown in Table 1, the reaction occurred smoothly in
the presence of A, affording tert-butyl-(2-styrylphenyl)carba-
mate (3a) in 80% yield (Table 1, entry 5). According to the
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3
4
5
6
7
8
Table 2. Substrate scopea
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10
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entry
X
R1
product (time) yield (%)b
1
2
3
4
5
6
7
8
Br (1a)
Br
Br
Cl (1b)
C6H5
3a (10 h)
3b (10 h)
3c (10 h)
3a (10 h)
3a (8 h)
3b (8 h)
3c (8 h)
3d (8 h)
3e (8 h)
3f (8 h)
79
81
87
trace
78
80
86
85
74
82
76
78
55
62
80
86
4-MeC6H4
4-ClC6H4
C6H5
Figure 1. Crystal Structure of [Pd(DMAP)2(acac)]2[V6O11(O-
I (1c)
C6H5
Me)8]·H2O
(A)
[Pd(dpa)(acac)]2[V6O13(OMe)6]
(B),
I
I
I
I
I
I
I
I
I
I
I
4-MeC6H4
4-ClC6H4
4-FC6H4
2-ClC6H4
3-ClC6H4
[Pd(dpa)(acac)]2[V6O11(OMe)8] (C). (Color code: Pd, pink; V,
green; N, blue; O, red; C, gray.)
9
Pd-complex was selected as counter cation to couple with
alkoxohexavanadate cluster through electrostatic interaction.
Pd-POVs (A, B, C,) (Figure 1) were synthesized in a simple and
straightforward method. The above catalysts are stable in the air
and aqueous solution, showing unexpected catalytic activities
in the oxidation of benzyl-alkanes. To exploit the property of
this kind of catalyst, we found A is an excellent catalyst using
the sequential Decarboxylation/Amination/Heck reaction for
the synthesis of 2-vinylanilines. Moreover, no report has ap-
peared for this sequential reaction.
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4-MeOC6H4 3g (8 h)
C6H5OCH2
COOMe
n-EtO
i-BuO
n-BuO
3h (14 h)
3i (10)
3j (6 h)
3k (6 h)
3l (6 h)
aReaction conditions: 1 (0.50 mmol), 2 (0.6 mmol) A, (5 mol %),
Cs2CO3 (0.50 mmol) in chlorobenzene (MCB) (5 mL) at 100 oC.
bYield of isolated product. And there are trace of (Z)-style product
be detect by TLC (3a-3i) (E/Z > 99/1). The regioselectivity of en-
tries 14-16 was detected by crude H-NMR about 11/89. The 11 is
linear Heck product (E/Z = 51/49).
Table 1. Optimization for the reaction conditionsa
results of the catalysts screening, A is the best catalyst for this
reaction in terms of the product selectivities. In the absence of
the catalyst or base no product 3a was observed (Table 1, entries
1-3). To probe the role of Pd-complex in the IDC reaction,
PdCl2/DMAP/Hacac (1:2:1) were used as catalyst system in 43%
entry catalyst
base (equiv) T (oC) yield (%)b
1
2
3
4
5
6
7
8
-
-
A
-
100
100
100
100
100
100
100
90
0
0
0
Cs2CO3
-
o
yield at 100 C in chlorobenzene (Table 1, entry 4). Other Pd-
POVs were also investigated in the reaction including B and C
to afford the corresponding product 3a in 7% and 11%, respec-
tively (Table 1, entries 8-9). Considering the influence of tem-
perature on decarboxylative reaction, different temperature
were also investigation in this IDC reaction. From the above
results, the t-butyl carbamate (Boc) group was deprotected at
120 oC with 1.0 equivalents Cs2CO3 in chlorobenzene yield 73%
(Table 1, entry 10). We were pleased to see that the 1 equivalent
Cs2CO3 performed best to the 3a (Table 1, entries 5, 11-12).
Increasing the amount of catalyst did not improve the yield (Ta-
ble 1, entry 15). The reactions were also successfully performed
at large scales without significant loss of yield (entry 16). Thus,
the optimized reaction conditions are as follow: 5 mol% A and
1 equivalent of Cs2CO3 in 2.0 mL of MCB at 100 oC for 10 h.
With the optimized reaction conditions in hand, we examined
the scope of the sequential reaction (Table 2). The substrate
scope of alkenes were investigated by the reaction of 2-halogen-
PdCl2/DMAP/Haca Cs2CO3
43
80(79)c
7
c
A
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
B
C
A
A
A
A
A
11
71
77
73
48
26
52
66
80
80d
75
9
110
120
10
11
12
13
14
15
16
17
Cs2CO3 (0.5) 100
Cs2CO3 (1.5) 100
A (1.0 mol%)
A (2.5 mol%)
A (7.5 mol%)
A
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
100
100
100
100
100
PdCl2(PPh3)2
aReaction conditions: 1 (0.20 mmol), 2 (0.24 mmol), catalyst (5.0
mol%), base (0.20 mmol, 1.0 equiv) in chlorobenzene (MCB) (2
mL) at 100 oC for 10 h. bYields determined by GC analysis using
biphenyl as internal standard. cIsolated yield. d10-mmol scale.
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The Journal of Organic Chemistry
aroyloxycarbamates with various substituted alkenes. Surpris- In addition to the scope of aroyloxycarbamates, we also
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7
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ingly, different substituted of phenyl ring alkenes gave the cor-
responding products 3 in good yields with slightly influence. It
is shown that electron-withdrawing is better than electron-do-
nating substituted of phenyl ring alkenes for the sequential re-
action (Table 2, entries 2, 3, 6, 7, 8, 11). The influence of ortho-,
meta-, para-substitutions of phenyl ring alkenes were also
tested and with the para-, meta-, ortho- sequence the yield grad-
ually decreases (Table 2, entries 7, 9, 10). The substituted of
alkyl olefins were also investigated in this optimized conditions.
Thus, the allyl phenyl ether 2h was reacted with 1c to furnish
3h in 78% yield (Table 2, entry 12). The methyl acrylate 2i was
reacted with 1c to obtain 3i in 55% yield (Table 2, entry 13). It
is worth noting that the alkenyl ether compound
briefly investigated the feasibility of halogen-aroyloxycarba-
mates with various valuable carbamates as additional types of
deprotectable amination sources. We were pleased to see that a
wide range of carbamates were readily employed with the pre-
sent Pd-POVs catalyst system under optimized condition (Table
3). In this approach, benzyloxycarbonl (Cbz) could be tolerated
at the optimized condition (3aa). In addition, various substi-
tuted carbamates were employed including methyl, ethyl, Iso-
propyl, Isobutyl, n-butyl, n-pentyl, and even n-hexyl groups
with satisfactory yields (3ab-3ah). The meta-, para-bromo sub-
stitutions of phenyl ring of aroyloxycarbamates were also ex-
amined. The meta-bromo substitutions could be transformed
into corresponding products in good yields (3ai-3ak). But the
reaction is complex and trace desired product 3al when para-
bromo substitutions aroyloxycarbamates reacted with styrene.
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Table 3. Substrate scopea
Scheme 2. The utility of the 2-vinylanilines
The synthetic utility of the 2-vinylanilines was exhibited by
their further transformation to 2-substituted indole (Scheme 2).
It was demonstrated that 2-vinylanilines 3a, in the presence of
N-Iodosuccinimide (NIS) under the mild condition to synthesis
the 2-phenyl Indole in moderate yields 4a.22 And 3a could trans-
late into t-butyl (Z)-(2-styrylphenyl)carbamate 5a smoothly us-
ing the high pressure mercury lamp as the light resource. It has
been reported the conversion of cis-Stilbene to trans-Stilbene
using organolithium reagent by O'Shea’s group.23
Scheme 3. Proposed sequential reaction catalytic cycle
Based on previous work7,12 and our mechanistic experiments,
a plausible catalytic cycle of this sequential approach is pro-
posed (Scheme 3). Interestingly, when the sequential reaction
was carried out, the regioselectively intermediate of 6a was
observed, suggesting that the mechanistic of this sequential re-
action is the path a (Scheme 1a), we were confirmed by recent
reports from Glorius.24 Then we proposed sequential reaction
catalytic cycle is IDC13 and Heck coupling.25 In addition, the
intramolecular decarboxylative amination is faster than the
Heck reaction from the monitored of the sequential approach.
To verify whether the catalysis is truly homogeneous or not,
the model reaction of tert-butyl ((2-bromobenzoyl)oxy)carba-
mate with styrene was carried out under the optimized condi-
tions, and the reaction was filtered by filter paper from the re-
action mixture at 40% formation of 3a. After filtration, the re-
action was added one equivalent of base and stirred for another
3 h. It is still converted to 3a in 80% yield. In addition, the fil-
tered solids washed with chlorobenzene, air-dired and then re-
used directly in a model reaction without further purification.
The results showed that no product 3a was obtained. Therefore
the catalysis is truly homogeneous. In this vein, five cycles were
carried without loss of reactivity on the model reaction (Figure
2), showing that the catalyst is easily recovered without its re-
moval from the solvent.
aReaction conditions: 1 (0.50 mmol), 2 (0.6 mmol) A, (5 mol %),
Cs2CO3 (0.50 mmol) in chlorobenzene (MCB) (5 mL) at 100 oC.
bYield of isolated product. And there are trace of (Z)-style product
be detect by TLC (E/Z > 99/1).
gave the chemoselectivity products such as ethoxyethene 2j, 2-
methyl-1-(vinyloxy)propane 2k, 1-(vinyloxy)butane 2l reacted
with 1c to afford t-butyl (2-(1-ethoxyvinyl)phenyl)carbamate 3j,
t-butyl (2-(1-isobutoxyvinyl)-phenyl)carbamate 3k and t-butyl
(2-(1-butoxyvinyl)phenyl)- carbamate 3l in 62%, 80% and 86%
yields, respectively (Table 2, entries 14-16).2f-2g Furthermore, 2-
halogen-aroyloxycarbamates such as 2-bromo- (1a), 2-chloro-
(1b) and 2-iodine- (1c) substituted substrates were investigated
in the reaction. Fortunately, the 2-bromo-substituted substrates
(1a) reacted with different substitutions of phenyl ring alkenes
2a, 2b, 2c to give the 3a, 3b, 3c with good yields. The reaction
time increased up to 10 h comparing with 1c (Table 2, entries
1-3). Unfortunately, trace of product 3a was detected, when 2-
chloro- (1b) substituted substrates reacted with styrene 2a (Ta-
ble 2, entry 4). As described above, the reactive activity of the
halogeno-substrates can be found as follow order 2-I, 2-Br and
2-Cl.
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stirred for 12 h. From the resulting solution, yellow crystals
suitable for X-ray diffraction grew after leaving the solution to
stand for a week. Yield: 64.3%.21
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3
4
5
6
7
8
9
Synthesis of [Pd(dpa)(acac)]2[V6O11(OMe)8] (C).
VO(acac)2 (0.6 mmol, 159.1 mg) and triethylamine (0.8
mmol) were added to 6 mL of methanol. The resulting solution
was stirred at room temperature for 20 mins, and then 2,2’-di-
pyridine amine (34.3 mg, 0.2 mmol) and Pd(OAc)2 (44.9 mg,
0.2 mmol) were successively added. The reaction mixture was
stirred for 12 h. From the resulting solution, yellow crystals
suitable for X-ray diffraction grew after leaving the solution to
stand for a week. Yield: 62.5%.21
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Representative procedure for the synthesis of O-
aroyloxycarbamates
Figure 2. Reusability of catalyst
General procedure for the preparation of N-hydroxyl car-
bamate (BocNHOH): N-hydroxyl tert-butyl carbamate was
prepared from hydroxylamine hydrochloride with (Boc)2O, ac-
cording to a known procedure. A suspension of NH2OH·HCl
(9.6 g, 0.14 mol, 1.5 equiv) and K2CO3 (7.2 g, 0.07 mol, 1.5
equiv) in Et2O (60 mL) and H2O (2 mL) was stirred for about 1
h at room temperature with evolution of CO2 gas. A solution of
Boc2O (20.0 g, 92 mmol) in Et2O (40 mL) was then added drop-
wise at 0 °C and the suspension was stirred at room temperature
for 12 h. The organic phase was decanted and the solid was
washed with Et2O (30 mL × 2) and the organic layers were com-
bined and concentrated. Recrystallization with a cyclohex-
ane/toluene mixture afforded the desired product.26
General procedure for the preparation of N-hydroxyl car-
bamate (ROCONHOH, R = Me, i-Bu, Bn): N-hydroxyl car-
bamates were prepared from hydroxylamine with the corre-
sponding chloroformates according to a known procedure. Hy-
droxylamine hydrochloride (13.9 g, 200 mmol) was added to
aqueous solution of NaOH (1.5 M, 160 mL, 240 mmol). The
solution was cooled to 0 °C and chloroformate (38 mmol) was
added dropwise. Upon the completion of addition, the mixture
was warmed up to room temperature and stirred for additional
2 h. The reaction was then acidified with aqueous HCl (6 M) till
pH is around 4.5. Then the mixture was extracted with Et2O
(200 mL × 3) and the combined organic layers were washed
with brine and dried over anhydrous Na2SO4. After removal of
the solvent in vacuo, the N-hydroxyl carbamate was used di-
rectly without further purification.26
General procedure for the preparation of N-hydroxyl car-
bamate (ROCONHOH, R = Et, n-Bu, n-penyane, n-hexyl):
To a flame-dried 100 mL round bottom flask equipped with a
stir bar was added CDI (1.78 g, 11 mmol) in anhydrous THF
(30 mL). The flask was cooled to 0 °C and alcohol (10 mmol)
was added dropwise. The mixture was stirred for additional 1 h
at room temperature and then NH2OH·HCl (1.04 g, 15 mmol)
and imidazole (0.82 g, 12 mmol) were added in one portion.
The reaction was monitored by TLC, until the starting material
disappeared (about 1 h). Then the mixture was filtered and con-
centrated in vacuo. The residue was dissolved in EtOAc (40 mL)
and washed with aqueous HCl (1 M, 20 mL × 3). The organic
layer was dried over anhydrous Na2SO4 and concentrated to af-
ford the crude product (85-88% yield), which can be used di-
rectly for next step.26
In conclusion, we have developed a new approach for the
regioselective synthesis of 2-vinylanilines using Pd-POVs cat-
alyst system from aryl carboxylic acids. The route is the first
example for 2-vinylanilines through sequential approach by se-
quential decarboxylation/amination/Heck Reaction from
aroyloxycarbamates and alkenes. Using an in situ generated
aroyloxycarbamates from inexpensive aromatic acid with
carbamates, various substituted of vinylanilines were site-selec-
tively synthesized. Given the excellent functional group
compatibility and the ubiquity of amine functional groups, the
Pd-POVs catalyst system will streamline the synthesis of vinyl-
anilines. This method opens many opportunities for
regioselective C-N bonds construction using carboxylic acids
by creating alternatives to conventional synthetic routes.
EXPERIMENTAL SECTION
General Remarks
All commercially available reagents were used without fur-
ther purification. Unless stated otherwise, all reactions were
carried out in Schlenk Tube under a dry argon or nitrogen at-
mosphere. All solvents were purified and dried according to
standard methods prior to use. Column chromatography was
performed on silica gel (200-400 mesh). GC-MS data were per-
formed on Agilent 7890A. GC analyses were performed on a
Shimadzu GC-2014 equipped with a capillary column (HP-5 30
m × 0.25 μm) using a flame ionization detector. Melting points
were determined using an X-4 apparatus and are uncorrected.
The FTIR spectra were recorded from KBr pellets in the range
4000–400 cm-1 on Nicolet 170 SXFT/IR spectrometer. NMR
spectra were taken with a Bruker 400 spectrometer at 400 MHz
(1H) and 101 MHz (13C) using CDCl3 as the solvent with TMS
as internal standard. Chemical shifts were reported in ppm ref-
erenced to the center of a triplet at 77.0 ppm of chloroform-d.
HRMS was performed on TOF LC-MS in ESI mode.
Synthesis of [Pd(DMAP)2(acac)]2[V6O11(OMe)8]·H2O (A).
VO(acac)2 (0.6 mmol, 159.1 mg) and triethylamine (0.8
mmol) were added to 6 mL of methanol. The resulting solution
was stirred at room temperature for 20 mins, and then DMAP
2,2’-dipyridine amine (48.0 mg, 0.4 mmol) and Pd(OAc)2 (44.9
mg, 0.2 mmol) were successively added. The reaction mixture
was stirred for 12 h. From the resulting solution, yellow crystals
suitable for X-ray diffraction grew after leaving the solution to
stand for a week. Yield: 65.6%.21
General procedure for the preparation of O-aroyloxycarba-
mates (1a): To a 250 mL flame-dried round bottom flask
equipped with a stir bar, an N-hydroxyl tert-butyl carbamate (20
mmol, 1.0 equiv.), 2-bromobenzoic acid (4.22 g, 21 mmol) and
anhydrous CH2Cl2 (80 mL) were added. The flask was cooled
Synthesis of [Pd(dpa)(acac)]2[V6O13(OMe)6] (B).
VO(acac)2 (0.6 mmol, 159.1 mg) and triethylamine (0.6
mmol) were added to 6 mL of methanol. The resulting solution
was stirred at room temperature for 20 mins, and then 2,2’-di-
pyridine amine (34.3 mg, 0.2 mmol) and Pd(OAc)2 (44.9 mg,
0.2 mmol) were successively added. The reaction mixture was
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The Journal of Organic Chemistry
to -15 °C. DCC (4.53 g, 22 mmol, dissolved in 20 mL of anhy-
(d, J = 8.0 Hz), 126.7, 124.3, 123.3 (d, J = 2.0 Hz), 122.4, 115.6
(d, J = 22.2 Hz), 80.7, 28.3; HRMS (ESI-TOF) m/z: [M + H]+
Calcd for C19H20FNO2 314.1551; found 314.1559.
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2
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drous CH2Cl2) solution was then added dropwise. The reaction
mixture was stirred at the same temperature for additional 30
min until the N-hydroxyl carbamate was fully consumed (mon-
itored by TLC). The white precipitate (N,N’-dicyclohexylurea)
was removed by filtration and the filtrate was concentrated in
vacuo and dissolved again in Et2O (30 mL). The solution was
cooled to -20 oC for 2 h and filtered again to remove additional
precipitate. The organic layer was then concentrated in vacuo
and the residue was recrystallized from hexanes and EtOAc to
afford corresponding acyloxyl carbamate 1a as a white solid
(yield 90%).26
tert-butyl-(2-(2-chlorostyryl)phenyl)carbamate (3e, Table 2,
entry 9). White solid (122 mg, 74% yield); mp: 111-113 oC; Rf
= 0.39 (hexane:EtOAc = 10:1); IR (film) 3414, 2972, 1686,
1
1459, 1156, 1035, 747 cm-1; H NMR (400 MHz, CDCl3): δ
7.79-7.78 (m, 1H), 7.69 (dd, J = 7.6, 1.6 Hz, 1H), 7.55-7.54 (m,
1H), 7.42-7.38 (m, 2H), 7.33-7.28 (m, 2H), 7.26-7.21 (m, 1H),
7.16-7.11 (m, 2H), 6.46 (s, 1H), 1.53 (s, 9H); 13C NMR (101
MHz, CDCl3): δ 153.1, 135.4, 135.3, 133.5, 129.8, 129.0, 128.9,
128.7, 128.3, 127.2, 126.9, 126.7, 126.4, 124.3, 122.4, 80.7,
28.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C19H20ClNO2
330.1255; found 330.1264.
tert-butyl-(2-(3-chlorostyryl)phenyl)carbamate (3f, Table 2,
entry 10). White solid (135 mg, 82% yield); mp: 138-139 oC; Rf
= 0.40 (hexane:EtOAc = 10:1); IR (film) 3411, 1689, 1444,
1165, 1021, 773 cm-1; 1H NMR (400 MHz, CDCl3): δ 7.75 (d,
J = 7.6 Hz, 1H), 7.50-7.48 (m, 2H), 7.38-7.36 (m, 1H), 7.31-
7.24 (m, 3H), 7.18-7.10 (m, 2H), 6.92 (d, J = 16.0 Hz, 1H), 6.41
(s, 1H), 1.53 (s, 9H); 13C NMR (101 MHz, CDCl3): δ 153.2,
139.0, 135.4, 134.7, 130.6, 129.9, 129.0, 128.7, 127.8, 126.8,
126.4, 125.1, 124.9, 124.5, 122.6, 80.8, 28.3; HRMS (ESI-TOF)
m/z: [M + H]+ Calcd for C19H20ClNO2 330.1255; found
330.1266.
tert-butyl-(2-(4-methoxystyryl)phenyl)carbamate (3g, Table
2, entry 11). White solid (124 mg, 76% yield); mp: 117-118 oC;
Rf = 0.37 (hexane:EtOAc = 10:1); IR (film) 3422, 1639, 1506,
1247, 1156, 956 cm-1; 1H NMR (400 MHz, CDCl3): δ 7.78 (d,
J = 6.8 Hz, 1H), 7.48-7.44 (m, 3H), 7.27-7.22 (m, 1H), 7.09 (t,
J = 7.6 Hz, 1H), 7.01 (d, J = 16.0 Hz, 1H), 6.94-6.90 (m, 3H),
6.44 (s, 1H), 3.83 (s, 3H), 1.52 (s, 9H); 13C NMR (101 MHz,
CDCl3): δ 159.6, 153.1, 135.2, 131.9, 130.0, 129.5, 128.0, 127.9,
126.7, 124.2, 122.0, 121.4, 114.2, 80.6, 55.3, 28.3; HRMS (ESI-
TOF) m/z: [M + H]+ Calcd for C20H23NO3 326.1751; found
326.1748.
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60
General Procedure for the Synthesis of 2-vinylanilines (3a-
3l and 3aa-3ak)
To
a
solution
of
1
(0.5
mmol),
[Pd(DMAP)2(acac)]2[V6O11(OMe)8] · H2O (0.025 mmol, 5
mol %), styrene (0.6 mmol) and Cs2CO3 (0.5 mmol) in chloro-
benzene (5 ml) in a Schlenk Pressure Tube (10 ml) under a dry
argon atmosphere. The reaction mixture was vigorously stirred
at 100 oC for 8-14 h, quenched by ethyl acetate, and purified by
silica gel chromatography using a mixture of hexanes and
EtOAc to provide the desired 3 (hexane:EtOAc = 10:1 for 3a-
3h, 3aa-3ak; hexane:EtOAc = 5:1 for 3i; hexane:EtOAc = 20:1
for 3j-3l; note: neutral alumina column for 3j-3l).
tert-butyl-(2-styrylphenyl)carbamate (3a, Table 2, entry 1).27
White solid (116 mg, 78% yield); mp: 130-132 oC; C; Rf = 0.43
(hexane:EtOAc = 10:1); 1H NMR (400 MHz, CDCl3): δ 7.78 (d,
J = 6.4 Hz, 1H), 7.50 (t, J = 7.6 Hz, 3H), 7.37 (t, J = 7.2 Hz,
2H), 7.30-7.23 (m, 2H), 7.15 (d, J = 16.4 Hz, 1H), 7.15 (t, J =
7.6 Hz, 1H), 6.98 (d, J = 16.4 Hz, 1H), 6.45 (s, 1H), 1.52 (s,
9H); 13C NMR (101 MHz, CDCl3): δ 153.2, 137.2, 135.4, 132.3,
129.3, 128.8, 128.4, 128.0, 126.9, 126.7, 124.3, 123.6, 122.3,
80.7, 28.4.
tert-butyl-(2-(4-methylstyryl)phenyl)carbamate (3b, Table 2,
entry 2). White solid (125 mg, 81% yield); mp: 120-121 oC; Rf
= 0.45 (hexane:EtOAc = 10:1); IR (film) 3428, 1733, 1521,
1
1447, 1359, 1230, 1153, 1050, 806 cm-1; H NMR (400 MHz,
tert-butyl-(2-(3-phenoxyprop-1-en-1-yl)phenyl)carbamate
(3h, Table 2, entry 12). White solid (127 mg, 78% yield); mp:
CDCl3): δ 7.80 (d, J = 6.4 Hz, 1H), 7.50 (dd, J = 8.0, 1.2 Hz,
1H), 7.43 (d, J = 8.0 Hz, 2H), 7.29-7.25 (m, 1H), 7.20 (d, J =
8.0 Hz, 2H), 7.13-7.09 (m, 2H), 6.97 (d, J = 16.0 Hz, 1H), 6.45
(s, 1H), 2.38 (s, 3H), 1.53 (s, 9H); 13C NMR (101 MHz, CDCl3):
δ 153.1, 138.0, 135.2, 134.3, 132.3, 129.4, 128.1, 126.8, 126.5,
124.1, 122.5, 122.0, 80.6, 28.3, 21.2; HRMS (ESI-TOF) m/z:
[M + H]+ Calcd for C20H23NO2 310.1802; found 310.1803.
tert-butyl-(2-(4-chlorostyryl)phenyl)carbamate (3c, Table 2,
entry 3). White solid (143 mg, 87% yield); mp: 159-160 oC; Rf
= 0.40 (hexane:EtOAc = 10:1); IR (film) 3440, 1701, 1444,
o
65-67 C; Rf = 0.44 (hexane:EtOAc = 10:1); IR (film) 3437,
1721, 1486, 1221, 1150, 741 cm-1; 1H NMR (400 MHz, CDCl3):
δ 7.76 (d, J = 8.0 Hz, 1H), 7.38 (dd, J = 7.6, 1.2 Hz, 1H), 7.33-
7.24 (m, 3H), 7.07 (t, J = 7.6 Hz, 1H), 6.99-6.95 (m, 3H), 6.81
(d, J = 15.6 Hz, 1H), 6.35 (s, 1H), 6.33-6.26 (m, 1H), 4.72 (dd,
J = 5.6, 1.6 Hz, 2H), 1.51 (s, 9H); 13C NMR (101 MHz, CDCl3):
δ 158.4, 153.0, 135.2, 129.5, 128.6, 128.3, 127.9, 127.2, 124.1,
122.0, 121.1, 114.8, 80.6, 68.4, 28.3; HRMS (ESI-TOF) m/z:
[M + H]+ Calcd for C20H23NO3 326.1751; found 326.1759.
methyl-3-(2-((tert-butoxycarbonyl)amino)phenyl)acrylate
(3i, Table 2, entry 13).28 White solid (76 mg, 55% yield); mp:
83-85 oC; Rf = 0.33 (hexane:EtOAc = 5:1); 1H NMR (400 MHz,
CDCl3): δ 7.84 (d, J = 16.0 Hz, 1H), 7.46 (d, J = 8.0 Hz, 1H),
7.50 (dd, J = 8.0, 1.5 Hz, 1H), 7.35 (t, J = 8.0 Hz, 1H), 7.11 (t,
J = 8.0 Hz, 1H), 6.54 (s, 1H), 6.38 (d, J = 16.0 Hz, 1H), 3.81 (s,
3H), 1.52 (s, 9H); 13C NMR (101 MHz, CDCl3): δ 167.2, 153.0,
139.6, 136.6, 130.8, 127.1, 126.2, 124.4, 123.0, 120.0, 81.0,
51.8, 28.2.
1
1383, 1162, 1015, 809 cm-1; H NMR (400 MHz, CDCl3): δ
7.75 (d, J = 7.2 Hz, 1H), 7.50 (dd, J = 7.6, 1.0 Hz, 1H), 7.44 (d,
J = 8.4 Hz, 2H), 7.34 (d, J = 8.8 Hz, 2H), 7.31-7.27 (m, 1H),
7.16-7.11 (m, 2H), 6.94 (d, J = 16.0 Hz, 1H), 6.43 (s, 1H), 1.53
(s, 9H); 13C NMR (101 MHz, CDCl3): δ 153.2, 135.6, 135.3,
133.6, 130.7, 129.2, 128.9, 128.5, 127.8, 126.7, 124.4, 124.2,
122.6, 80.7, 28.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for
C19H20ClNO2 330.1255; found 330.1263.
tert-butyl-(2-(4-fluorostyryl)phenyl)carbamate (3d, Table 2,
entry 8). White solid (133 mg, 85% yield); mp: 143-144 oC; Rf
= 0.41 (hexane:EtOAc = 10:1); IR (film) 3440, 1653, 1506,
tert-butyl (2-(1-ethoxyvinyl)phenyl)carbamate (3j, Table 2,
entry 14). Oil (82 mg, 62% yield); Rf = 0.57 (hexane:EtOAc =
20:1); IR (film) 3402, 2987, 1721, 1521, 1439, 1241, 1177,
1038, 765 cm-1; 1H NMR (700 MHz, CDCl3): δ 8.08 (d, J = 4.9
Hz, 1H), 7.93 (s, 1H), 7.32 (dd, J = 7.7, 1.4 Hz, 1H), 7.31-7.29
(m, 1H), 6.99-6.96 (m, 1H), 4.41 (d, J = 2.8 Hz, 1H), 4.38 (d, J
= 2.1 Hz, 1H), 3.96 (q, J = 7.0 Hz, 2H), 1.51 (s, 9H), 1.43 (t, J
1
1362, 1227, 1150, 815 cm-1; H NMR (400 MHz, CDCl3): δ
7.76 (d, J = 7.2 Hz, 1H), 7.50-7.49 (m, 3H), 7.30-7.25 (m, 1H),
7.14-7.05 (m, 4H), 6.95 (d, J = 16.4 Hz, 1H), 6.42 (s, 1H), 1.53
(s, 9H); 13C NMR (101 MHz, CDCl3): δ 162.5 (d, J = 251.3 Hz),
153.1, 135.3, 133.3 (d, J = 3.0 Hz), 130.9, 129.3, 128.4, 128.2
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1
= 7.0 Hz, 3H); 13C NMR (176 MHz, CDCl3) δ 160.2, 152.8,
1044, 753 cm-1; H NMR (400 MHz, CDCl3): δ 7.79 (s, 1H),
1
2
3
4
5
6
7
8
136.3, 129.4, 129.1, 125.9, 122.3, 119.3, 87.4, 80.0, 63.6, 28.3,
14.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C15H21NO3
264.1594; found 264.1595.
7.53-7.51 (m, 3H), 7.40-7.36 (m, 2H), 7.32-7.27 (m, 2H), 7.18-
7.12 (m, 2H), 7.00 (d, J = 16.4 Hz, 1H), 6.55 (s, 1H), 4.19 (t, J
= 6.4 Hz, 2H), 1.70-1.63 (m, 2H), 1.46-1.37 (m, 2H), 0.97-0.93
(m, 3H); 13C NMR (101 MHz, CDCl3): δ 154.1, 137.0, 134.9,
132.6, 129.0, 128.7, 128.4, 128.1, 126.9, 126.7, 124.6, 123.3,
65.3, 31.0, 19.1, 13.7; HRMS (ESI-TOF) m/z: [M + H]+ Calcd
for C19H21NO2 296.1645; found 296.1649.
tert-butyl (2-(1-isobutoxyvinyl)phenyl)carbamate (3k, Table
2, entry 15). Oil (116 mg, 80% yield); Rf = 0.58 (hexane:EtOAc
= 20:1); IR (film) 3405, 2975, 1721, 1515, 1447, 1162, 1018,
1
756 cm-1; H NMR (700 MHz, CDCl3): δ 8.12 (d, J = 7.0 Hz,
1H), 7.92 (s, 1H), 7.33-7.29 (m, 2H), 6.99-6.96 (m, 1H), 4.39
(d, J = 2.8 Hz, 1H), 4.37 (d, J = 2.1 Hz, 1H), 3.66 (d, J = 6.3 Hz,
2H), 2.10 (9, J = 7.0 Hz, 1H), 1.50 (s, 9H), 1.06 (d, J = 7.0 Hz,
6H); 13C NMR (176 MHz, CDCl3) δ 160.6, 152.7, 136.4, 129.4,
129.3, 126.1, 122.2, 119.1, 87.3, 80.0, 74.6, 28.3, 28.0, 19.5;
HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C17H25NO3
292.1907; found 292.1911.
tert-butyl (2-(1-butoxyvinyl)phenyl)carbamate (3l, Table 2,
entry 16). Oil (125 mg, 86% yield); Rf = 0.58 (hexane:EtOAc =
20:1); IR (film) 3405, 2966, 1727, 1518, 1447, 1247, 1153,
1024, 762 cm-1; 1H NMR (400 MHz, CDCl3): δ 8.11 (d, J = 8.0
Hz, 1H), 7.90 (s, 1H), 7.32-7.26 (m, 2H), 6.97 (t, J = 7.6 Hz,
1H), 4.39 (d, J = 2.4 Hz, 1H), 4.37 (d, J = 2.4 Hz, 1H), 3.89 (t,
J = 6.4 Hz, 2H), 1.81-1.74 (m, 2H), 1.57-1.52 (m, 2H), 1.51 (s,
9H), 0.99 (t, J = 8.2 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ
160.6, 152.8, 136.3, 129.4, 129.2, 126.0, 122.2, 119.2, 87.2,
80.0, 67.9, 31.0, 28.3, 19.6, 13.9; HRMS (ESI-TOF) m/z: [M +
H]+ Calcd for C17H25NO3 292.1907; found 292.1914.
isobutyl-(2-styrylphenyl)carbamate (3af, Table 3, entry 6).
White solid (97 mg, 66% yield); mp: 70-72 oC; Rf = 0.44 (hex-
ane:EtOAc = 10:1); IR (film) 3446, 2955, 1704, 1453, 1218,
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
1038, 759 cm-1; H NMR (400 MHz, CDCl3): δ 7.79 (s, 1H),
7.52 (d, J = 7.6 Hz, 3H), 7.39 (t, J = 7.2 Hz, 2H), 7.30 (t, J =
7.2 Hz, 2H), 7.20-7.13 (m, 2H), 7.00 (d, J = 16.0 Hz, 1H), 6.56
(s, 1H), 3.97 (d, J = 6.8 Hz, 2H), 1.99 (sep, J = 6.8 Hz, 1H),
0.97 (d, J = 6.4 Hz, 6H); 13C NMR (101 MHz, CDCl3): δ 154.2,
137.0, 134.9, 132.6, 128.8, 128.4, 128.1, 126.9, 126.7, 124.6,
123.3, 71.6, 27.9, 19.1; HRMS (ESI-TOF) m/z: [M + H]+ Calcd
for C19H21NO2 296.1645; found 296.1647.
pentyl-(2-styrylphenyl)carbamate (3ag, Table 3, entry 7).
White solid (97 mg, 63% yield); mp: 76-78 oC; Rf = 0.45 (hex-
ane:EtOAc = 10:1); IR (film) 3423, 2955, 1671, 1530, 1444,
1
1032, 765 cm-1; H NMR (400 MHz, CDCl3): δ 7.80 (s, 1H),
7.54-7.51 (m, 3H), 7.41-7.31 (m, 2H), 7.32-7.28 (m, 2H), 7.19-
7.13 (m, 2H), 7.00 (d, J = 16.0 Hz, 1H), 6.56 (s, 1H), 4.18 (t, J
= 6.8 Hz, 2H), 1.72-1.65 (m, 2H), 1.39-1.34 (m, 4H), 1.93-0.89
(m, 3H); 13C NMR (101 MHz, CDCl3): δ 154.1, 137.0, 134.9,
132.6, 129.5, 128.7, 128.4, 128.1, 126.9, 126.7, 124.6, 123.3,
122.3, 65.6, 28.6, 28.0, 22.3, 13.9; HRMS (ESI-TOF) m/z: [M
+ H]+ Calcd for C20H23NO2 310.1802; found 310.1804.
benzyl-(2-styrylphenyl)carbamate (3aa, Table 3, entry 1).27
White solid (115 mg, 70% yield); mp: 83-85 oC; Rf = 0.43 (hex-
ane:EtOAc = 10:1); 1H NMR (400 MHz, CDCl3): δ 7.82 (s, 1H),
7.53-7.48 (m, 3H), 7.43-7.27 (m, 9H), 7.18-7.12 (m, 2H), 6.99
(d, J = 16.0 Hz, 1H), 6.64 (s, 1H), 5.23 (s, 2H); 13C NMR (101
MHz, CDCl3): δ 153.8, 136.9, 136.0, 134.7, 132.7, 128.7, 128.6,
128.4, 128.4, 128.4, 128.1, 126.9, 126.7, 124.8, 123.1, 67.2.
methyl-(2-styrylphenyl)carbamate (3ab, Table 3, entry 2).29
White solid (78 mg, 62% yield); mp: 82-83 oC; Rf = 0.38 (hex-
ane:EtOAc = 10:1); 1H NMR (400 MHz, CDCl3): δ 7.79 (s, 1H),
7.53-7.51 (m, 3H), 7.38 (t, J = 7.2 Hz, 2H), 7.30 (t, J = 7.2 Hz,
2H), 7.19-7.15 (m, 2H), 7.00 (d, J = 16.0 Hz, 1H), 6.61 (s, 1H),
3.80 (s, 3H); 13C NMR (101 MHz, CDCl3): δ 154.5, 136.9,
134.8, 132.7, 129.5, 128.8, 128.4, 128.1, 126.9, 126.7, 124.7,
123.2, 122.4, 52.5.
hexyl-(2-styrylphenyl)carbamate (3ah, Table 3, entry 8).
White solid (99 mg, 61% yield); mp: 72-74 oC; Rf = 0.45 (hex-
ane:EtOAc = 10:1); IR (film) 3414, 2949, 1659, 1450, 1047,
753 cm-1; 1H NMR (400 MHz, CDCl3): δ 7.73 (s, 1H), 7.44 (d,
J = 7.6 Hz, 3H), 7.31 (t, J = 7.6 Hz, 2H), 7.25-7.20 (m, 2H),
7.11-7.05 (m, 2H), 6.93 (d, J = 16.4 Hz, 1H), 6.48 (s, 1H), 4.10
(t, J = 6.8 Hz, 2H), 1.64-1.57 (m, 2H), 1.31-1.89 (m, 6H), 0.82
(t, J = 6.8 Hz, 3H); 13C NMR (101 MHz, CDCl3): δ 153.1, 135.9,
133.9, 131.5, 127.7, 127.4, 127.0, 125.9, 125.6, 123.5, 122.3,
121.2, 64.6, 30.4, 27.8, 24.5, 21.5, 12.9; HRMS (ESI-TOF) m/z:
[M + H]+ Calcd for C21H25NO2 324.1958; found 324.1964.
tert-butyl-(3-styrylphenyl)carbamate (3ai, Table 3, entry 9).
ethyl-(2-styrylphenyl)carbamate (3ac, Table 3, entry 3).27
White solid (93 mg, 70% yield); mp: 66-71 oC; Rf = 0.40 (hex-
ane:EtOAc = 10:1); 1H NMR (400 MHz, CDCl3): δ 7.79 (s, 1H),
7.52-7.50 (m, 3H), 7.39-7.36 (m, 2H), 7.31-7.27 (m, 2H), 7.18-
7.12 (m, 2H), 6.99 (d, J = 16.0 Hz, 1H), 6.58 (s, 1H), 4.23 (q, J
= 7.2 Hz, 2H), 1.31 (t, J = 7.2 Hz, 3H); 13C NMR (101 MHz,
CDCl3): δ 154.0, 137.0, 134.9, 132.6, 129.3, 128.8, 128.4, 128.1,
126.9, 126.7, 124.6, 123.3, 122.3, 61.4, 14.5.
isopropyl-(2-styrylphenyl)carbamate (3ad, Table 3, entry 4).
White solid (94 mg, 67% yield); mp: 76-77 oC; Rf = 0.41 (hex-
ane:EtOAc = 10:1); IR (film) 3411, 2978, 1689, 1444, 1035,
750 cm-1; 1H NMR (400 MHz, CDCl3): δ 7.83 (s, 1H), 7.52 (t,
J = 7.2 Hz, 3H), 7.39 (t, J = 7.6 Hz, 2H), 7.32-7.28 (m, 2H),
7.19-7.12 (m, 2H), 7.00 (d, J = 16.0 Hz, 1H), 6.53 (s, 1H), 5.05
(sep, J = 6.4 Hz, 1H), 1.31 (d, J = 6.0 Hz, 6H); 13C NMR (101
MHz, CDCl3): δ 153.6, 137.0, 135.1, 132.6, 129.1, 128.7, 128.4,
128.1, 126.9, 126.7, 124.4, 123.4, 122.1, 69.0, 22.1; HRMS
(ESI-TOF) m/z: [M + H]+ Calcd for C18H19NO2 282.1489; found
282.1488.
o
White solid (109 mg, 74% yield); mp: 123-125 C; Rf = 0.38
(hexane:EtOAc = 10:1); IR (film) 2927, 1701, 1530, 1444, 1235,
1156, 1050, 1009 cm-1; 1H NMR (400 MHz, CDCl3): δ 7.62 (s,
1H), 7.50 (d, J = 8.0 Hz, 2H), 7.36 (t, J = 8.0 Hz, 2H), 7.29-7.24
(m, 2H), 7.20-7.17 (m, 2H), 7.13 (d, J = 16.4 Hz, 1H), 7.08 (d,
J = 16.4 Hz, 1H), 6.49 (s, 1H), 1.54 (s, 9H); 13C NMR (101 MHz,
CDCl3): δ 152.7, 138.7, 138.2, 137.2, 129.2, 129.1, 128.6, 128.4,
127.6, 126.5, 121.3, 117.7, 116.3, 80.6, 28.3; HRMS (ESI-TOF)
m/z: [M + H]+ Calcd for C19H21NO2 296.1645; found 296.1654.
tert-butyl-(3-(4-methylstyryl)phenyl)carbamate (3aj, Table 3,
entry 10). White solid (116 mg, 75% yield); mp: 76-78 oC; Rf =
0.40 (hexane:EtOAc = 10:1); IR (film) 3440, 1701, 1439, 1162,
1
1041, 962, 876 cm-1; H NMR (400 MHz, CDCl3): δ 7.60 (s,
1H), 7.40 (d, J = 8.0 Hz, 2H), 7.28-7.24 (m, 1H), 7.19-7.16 (m,
4H), 7.09 (d, J = 16.4 Hz, 1H), 7.02 (d, J = 16.0 Hz, 1H), 6.50
(s, 1H), 2.36 (s, 3H), 1.54 (s, 9H); 13C NMR (101 MHz, CDCl3):
δ 152.7, 138.7, 138.4, 137.6, 134.4, 129.4, 129.1, 129.0, 127.4,
126.4, 121.2, 117.5, 116.2, 80.6, 28.38, 21.2; HRMS (ESI-TOF)
m/z: [M + H]+ Calcd for C20H23NO2 310.1802; found 310.1810.
tert-butyl-(3-(4-chlorostyryl)phenyl)carbamate (3ak, Table
3, entry 11). White solid (125 mg, 76% yield); mp: 148-150 oC;
butyl-(2-styrylphenyl)carbamate (3ae, Table 3, entry 5).
White solid (108 mg, 73% yield); mp: 47-49 oC; Rf = 0.43 (hex-
ane:EtOAc = 10:1); IR (film) 3428, 2955, 1692, 1450, 1218,
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The Journal of Organic Chemistry
Rf = 0.35 (hexane:EtOAc = 10:1); IR (film) 3434, 1721, 1450,
AUTHOR INFORMATION
Corresponding Author
1
1380, 1153, 1026, 809 cm-1; H NMR (400 MHz, CDCl3): δ
1
2
3
4
5
6
7
8
7.65 (s, 1H), 7.43 (d, J = 8.4 Hz, 2H), 7.31 (d, J = 8.4 Hz, 2H),
7.29-7.25 (m, 1H), 7.17 (t, J = 7.6 Hz, 2H), 7.05 (s, 2H), 6.49
(s, 1H), 1.54 (s, 9H); 13C NMR (101 MHz, CDCl3): δ 152.7,
138.8, 137.9, 135.7, 133.2, 129.2, 129.1, 128.8, 127.8, 127.7,
121.4, 117.9, 116.3, 80.6, 28.3; HRMS (ESI-TOF) m/z: [M +
H]+ Calcd for C19H20ClNO2 330.1255; found 330.1269.
General procedure for preparation of 2-substituted indole
4a:
To a solution of substrate 3a (0.147 g, 0.5 mmol) in CH2Cl2
(1.0 mL) was added NIS (0.173 g, 1.0 mmol) under air. The
resulting mixture was stirred at rt for the 50 h, then the mixture
was concentrated under reduced pressure. The residue was pu-
rified by column chromatography on silica gel (hexane:EtOAc
= 10:1 as an eluent) to give the corresponding product 4a. tert-
butyl 2-phenyl-1H-indole-1-carboxylate (4a).22 White solid (73
mg, 50% yield); mp: 76-77 oC; 1H NMR (400 MHz, CDCl3): δ
8.21 (d, J = 8.4 Hz, 1H), 7.54 (d, J = 7.6 Hz, 1H), 7.43-7.30 (m,
6H), 7.26-7.22 (m, 1H), 6.55 (s, 1H), 1.30 (s, 9H); 13C NMR
(101 MHz, CDCl3): δ 150.2, 140.5, 137.4, 135.0, 129.2, 128.7,
127.8, 127.5, 124.3, 122.9, 120.4, 115.2, 109.9, 83.4, 27.5.
General procedure for preparation of t-butyl (Z)-(2-
styrylphenyl)carbamate 5a:
To a solution of substrate 3a (0.147 g, 0.5 mmol) in CH3CN
(1.0 mL) under air. The resulting mixture was stirred at rt for
the 36 h under the high pressure mercury lamp (500 W) as the
light resource, then the mixture was concentrated under reduced
pressure. The residue was purified by column chromatography
on silica gel (hexane:EtOAc = 20:1 as an eluent) to give the
corresponding product 5a. tert-butyl (Z)-(2-styrylphenyl)carba-
mate(5a).23a White solid (66 mg, 90% yield); mp: 77-79 oC; 1H
NMR (400 MHz, CDCl3): δ 8.00 (d, J = 8.4 Hz, 1H), 7.26 (t, J
= 8.8 Hz, 1H), 7.19-7.12 (m, 6H), 6.97 (t, J = 7.6 Hz, 1H), 6.76
(d, J = 12.0 Hz, 1H), 6.53 (d, J = 12.0 Hz, 1H), 6.52 (s, 1H),
1.42 (s, 9H); 13C NMR (101 MHz, CDCl3): δ 152.8, 136.0,
135.6, 133.3, 129.1, 128.8, 128.4, 127.7, 126.7, 125.6, 123.3,
119.2, 80.4, 28.3.
*daiqipu@bit.edu.cn.
*cwhu@bit.edu.cn.
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
9
This work was financially supported by the National Natural Sci-
ence Foundation of China (21231002, 21276026), the 973 Program
(2014CB932103) and the Excellent Young Scholars Research
Fund of Beijing Institute of Technology (3190012331518,
3190012331523)
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website.
1H and 13C NMR spectra of all the compounds 3.
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