Rhodium-Catalyzed Double Isocyanide Insertion via a Vinylcarbodiimide Intermediate for the Synthesis of 2H-Pyrrol-2-imines

Article abstract of DOI:10.1055/s-0037-1611830

2 H -Pyrrol-2-imine is an important structural motif exhibiting in biologically active compounds and natural products. An efficient rhodium-catalyzed one-pot reaction of one vinyl azide with sequentially with two different isocyanides is reported, which offers an alternative facile access to 3-amino-5-aryl-2 H -pyrrol-2-imines bearing various substitution on the nitrogens in good yields. An unstable vinylcarbodiimide is the key intermediate in this cascade reaction.

Full text of DOI:10.1055/s-0037-1611830

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2019, 51, A–I
paper
A
en
Y. Wang et al.
Paper
Synthesis
Rhodium-Catalyzed Double Isocyanide Insertion via a Vinylcarbo-
diimide Intermediate for the Synthesis of 2H-Pyrrol-2-imines
Yunlong Wanga
Zongyang Lib
Haiying Zhao*a
Zhenhua Zhang*b
R3
HN
[Rh(cod)Cl]2 (2.5 mol%)
DPPE (5 mol%)
R2 NC
R3 NC
+
R1
N3
R1
N
R2
1,4-dioxane, rt to 120 °C
N
N
a Inner Mongolia Key Laboratory of Fine Organic Synthesis, College of
Chemistry and Chemical Engineering, Inner Mongolia University,
Hohhot 010021, China
C
R1
up to 95%
N
via
R
hyzhao@imu.edu.cn
b Department of Applied Chemistry, China Agricultural University,
West Yuanmingyuan Rd. 2, Beijing 100193, P. R. of China
zhangzhh@cau.edu.cn
Received: 29.03.2019
Accepted after revision: 24.04.2019
Published online: 21.05.2019
Organic azides have been developed as a convenient
precursor to N-containing cycles.6 The transition-metal-
catalyzed reaction of an azide with -donor/-acceptor iso-
cyanides has also shown value in the facile access to carbo-
diimide intermediates.7 In 2018, we reported a Rh(I)-cata-
lyzed coupling reaction of vinyl azides with isocyanides at
the azide moiety to form active vinylcarbodiimides, which
gives a new ladder to aza-six-member rings.7h Following
this work, herein we reported a highly efficient one-pot
Rh(I)-catalyzed transformation of vinyl azides with two dif-
ferent isocyanides to synthesize 2H-pyrrol-2-imines with
different N-substituted groups.
DOI: 10.1055/s-0037-1611830; Art ID: ss-2019-f0057-op
Abstract 2H-Pyrrol-2-imine is an important structural motif exhibiting
in biologically active compounds and natural products. An efficient rho-
dium-catalyzed one-pot reaction of one vinyl azide with sequentially
with two different isocyanides is reported, which offers an alternative
facile access to 3-amino-5-aryl-2H-pyrrol-2-imines bearing various sub-
stitution on the nitrogens in good yields. An unstable vinylcarbodiimide
is the key intermediate in this cascade reaction.
Key words vinyl azide, vinylcarbodiimide, 2H-pyrrol-2-imine, isocya-
nide, palladium catalysis
At the outset, the reaction of (1-azidovinyl)benzene
(1a), 1-chloro-4-isocyanobenzene (2a), and tert-butyl iso-
cyanide (3a) was selected as a model. Firstly, 1a was reacted
with 1.07 equiv of isocyanide 2a in the presence of catalyst
[Rh(cod)Cl]2 in 1,4-dioxane at room temperature; after 4
hours, when 1a had been consumed, another isocyanide 3a
was added and the mixture was heated to 120 °C for 40
minutes. To our delight, this process was amenable to the
selective and sequential installation of two different isocya-
nides and the corresponding cross N-substituted 2H-pyrrol-
2-imine 4aa was obtained in 61% yield (Table 1, entry 2). In
addition, no product was obtained in the absence of Rh cat-
alyst and ligand (Table 1, entry 1). In further optimization of
the conditions, we found that phosphine ligands improved
the yield; the addition of PPh3 ligand gave 4aa in 90% yield
(Table 1, entry 3) and different bidentate phosphine ligands
with different bite angles had different effects (Table 1, en-
tries 4–7). The best yield of 4aa was obtained using DPPE as
the ligand.
2H-Pyrrole is an important structural motif present in a
broad range of biologically active compounds and natural
products,1 in which 2H-pyrrol-2-imines possess versatile
applications.2 One strategy to access this aza-five-member
ring is based on the reaction of oximes with two isocya-
nides, which was reported by two different research groups
in 2017. Jiang, Liu, and co-workers reported a redox-neutral
palladium-catalyzed N–O/C(sp3)–H functionalization of one
molecule of an aryl oxime with two molecules of an isocya-
nide to give a 2H-pyrrol-2-imine (Scheme 1a).3 Wang and
co-workers also reported a palladium-catalyzed N–O cleav-
age of O-acetyl oximes with double isocyanide insertion to
obtain 2H-pyrrol-2-imines (Scheme 1b).4 However, the two
isocyanides in these transformations must be the same. In
1988, Capuano and co-workers presented several examples
of 2H-pyrrol-2-imines synthesis via the cyclization of vinyl-
carbodiimides with isocyanides that had different nitrogen-
substituted groups (Scheme 1c).5 Nevertheless, the lack of
convenient access to vinylcarbodiimides and their instabili-
ty in isolation and storage limit its further development.
In one-pot reactions, the conditions need to be suitable
for not only the first coupling step, but also the second cy-
clization step. Screening the conditions for the cyclization
of isolated vinylcarbodiimide 5a with tert-butyl isocyanide
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

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Y. Wang et al.
Paper
Synthesis
(3a) showed that temperature is the key, and Rh cata-
lysts/phosphine ligands are not necessary (Table 2). Fur-
thermore, the use of DPPM, DPPE, and 10 mol% of PPh3 de-
creased the yields.
a) Jiang and Liu's work
R2
N
OH
N
N
Pd(PPh3)4/CsF
–
+
R2
NH
R2
C
+
N
R1
toluene, 100 °C
R1
Table 2 Optimization of the Cyclization Reaction of a Vinylcarbodiim-
ide with tert-Butyl Isocyanidea
b) Wang's work
tBu
NH
R3
NH
OAc
N
Catalyst
Pd(PPh3)4
DBU
N
R2
N
Ligand
C
–
+
tBuN
C
+
C
N
R3
R3
Ph
N
N
R1
Ph
+
1,4-dioxane, T
–
+
Cl
R2
C
N
R1
toluene,reflux
N
N
R3
Cl
5a
3a
4aa
Yieldb (%)
c) Capuano's work
Entry Catalyst (mol%)
Ligand (mol%)
T (°C)
1
2
–
–
–
rt
52
>95
58
R1
Ph
R2 yield
NR2
Ph
Ph
Ph
H
N
R2NC
–
120
rt
tBu
45%
NR1
3
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
–
Ph
C
NR1
N
tBu
4-Tol
33%
H
4
–
120
120
120
120
120
120
120
>95
>95
85
5
PPh3 (5)
PPh3 (10)
DPPM (5)
DPPE (5)
DPPP (5)
Xantphos (5)
d) This work
6
R3
NH
7
88
R3 NC
Rh(I)
N
8
>95
81
C
R2
R2 NC
+
R1
N
R1
N3
R1
N
N
R2
9
10
>95
up to 95% isolated yield
a Reaction conditions: 5a (0.15 mmol), 3a (0.18 mmol), catalyst/ligand,
1,4-dioxane (2 mL), rt, 3 h or 120 °C, 40 min.
b Isolated yield.
Scheme 1 Approaches to N-substituted 2H-pyrrol-2-imines
Table 1 Optimization of the Rh-Catalyzed One-Pot Reaction of a Vinyl Azide Sequentially with Two Different Isocyanidesa
tBu
NH
C
Catalyst
Ligand
N
tBuN
C
N
N
+
Ph
1,4-dioxane, rt
120 °C
Ph
N3
Cl
Cl
1a
2a
3a
4aa
Entry
Catalyst (mol%)
Ligand (mol%)
Yieldb (%)
1
2
3
4
5
6
7
–
–
n.r.
61
90
61
94
75
78
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
[Rh(cod)Cl]2 (2.5)
–
PPh3 (5)
DPPM (5)
DPPE (5)
DPPP (5)
Xantphos (5)
a Reaction conditions: 1a (0.15 mmol), 2a (0.16 mmol), catalyst/ligand, 1,4-dioxane (2 mL), rt until complete consumption of 1a, then addition of 3a (0.18
mmol), 120 °C, 40 min.
b Isolated yield. DPPM = bis(diphenylphosphino)methane. DPPP = 1,3-bis(diphenylphosphino)propane. DPPE = 1,2-bis(diphenylphosphino)ethane. Xantphos =
4,5-bis(diphenylphosphino)-9,9-dimethylxanthene.
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With the optimized reaction conditions described
above, an array of functionalized aryl-substituted vinyl
azides 1a–k were subjected to this reaction first with 1-
chloro-4-isocyanobenzene (2a) and then with tert-butyl
isocyanide (3a) in order to investigate the generality
(Scheme 2). As expected, the reaction showed excellent
substrate scope. The steric hindrance of substituent at dif-
ferent positions has little adverse impact on the reactivity
(4ba, 4ca, 4da, 92–96% yield). 1-Arylvinyl azides with dif-
ferent electron-withdrawing/electron-donating groups on
the aryl substituent, such as MeO, F3C, and NC, also gave ex-
cellent isolated yields of products (4ea, 4fa, 4ga, 72–87%
yield). In addition, halogen substituents were well-tolerated
on the aryl ring (4ha, 4ia, 4ja, 84–91% yield), thus offering
an opportunity for further cross-coupling, as well as facili-
tating the expedient synthesis. Furthermore, the use of 1-
benzothiophen-2-ylvinyl azide as the substrate gave the
corresponding product 4ka in 69% yield.
To further explore the diversity of products generated
by this reaction, the generality of different isocyanides was
investigated and the results are presented in Scheme 3. For
the first isocyanide, all of different substituted aryl isocya-
tBu
NH
[Rh(cod)Cl]2 (2.5 mol%)
DPPE (5 mol%)
C
N
N
tBuN
C
N
N3
+
R
R
1,4-dioxane, rt
120 °C
Cl
Cl
1
2a
3a
4
tBu
tBu
NH
tBu
NH
NH
N
N
N
N
N
N
Cl
Cl
Cl
4aa 94%
4ba 96%
4ca 92%
tBu
NH
tBu
NH
tBu
NH
N
N
N
N
N
N
Cl
F3C
Cl
Cl
MeO
4da 95%
4ea 87%
4fa 72%
tBu
tBu
NH
tBu
NH
NH
N
N
N
N
N
N
Cl
Cl
Cl
NC
F
Cl
4ga 85%
4ha 84%
4ia 89%
tBu
tBu
NH
NH
N
N
N
N
S
Cl
Br
Cl
4ja 91%
4ka 69%
Scheme 2 Substrate generality of 1-arylvinyl azides. Reagents and conditions: 1 (0.15 mmol), 2a (0.16 mmol), [Rh(cod)Cl]2 (2.5 mol%), DPPE (5 mol%),
1,4-dioxane (2 mL), rt until complete consumption of 1, then addition of 3a (0.18 mmol), 120 °C, 40 min; all yields are isolated yields.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

D
Y. Wang et al.
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Synthesis
nides used gave 2H-pyrrol-2-imine derivatives (4aa–4af).
Electron-donating aryl isocyanides such as 2c (R2 = 4-
MeOC6H4) gave compound 4ac in 94% yield, the electron-
withdrawing aryl isocyanides such as 2e (R2 = 4-F3CC6H4)
and 2f (R2 = 4-NO2C6H4) gave compounds 4ae and 4af, re-
spectively, in moderate yields (55% and 50%), However,
when alkyl isocyanides were used as the first isocyanide,
R1 = Cy, Bu, and tBu, the corresponding 2H-pyrrol-2-imines
4ag, 4ah, 4ai, 4aj were obtained only in low yields. Accord-
ing to our previous study,7h the reaction of vinyl azides with
alkyl isocyanides could well produce 1-alkyl-3-vinylcarbo-
diimides. We have also tried to use isolated 1-alkyl-3-vinyl-
carbodiimides in the second step of the reaction with isocy-
anides, but the yields of 2H-pyrrol-2-imine were still <30%.
These results showed that 1-alkyl-3-vinylcarbodiimides
were unsuitable for the cyclization with isocyanide.
To our delight, when the first isocyanide was an aryl iso-
cyanide (via 1-aryl-3-vinylcarbodiimides), regardless of
whether the second isocyanide was an alkyl isocyanide or
aryl isocyanide, the reactions all gave 2H-pyrrol-2-imine
products in moderate to high yields (4ak–4ap), Further-
more, we also utilized the same isocyanide for both steps
and obtained 2H-pyrrol-2-imine derivatives 4aq (83% yield)
and 4ar (45% yield).
R2
NH
[Rh(cod)Cl]2 (2.5 mol%)
DPPE (5 mol%)
R2
N C
N
R1
N
C
N3
R1
N
+
1,4-dioxane, rt
120 °C
1a
tBu
2
3
4
tBu
tBu
tBu
NH
NH
NH
N
NH
N
N
N
N
N
N
Ph
Ph
Ph
N
Ph
CF3
CN
OMe
4ab 61%
4ac 94%
4ad 85%
4ae 55%
tBu
NH
tBu
NH
tBu
NH
N
NH
N
Ph
N
N
Cy
nBu
N
N
N
Ph
Ph
Ph
N
tBu
NO2
4ag 21%
4ah trace
4ai 16%
4af 50%
Cy
Bu
F3C
Cy
NH
NH
NH
N
N
N
NH
N
N
N
N
Ph
Ph
Ph
N
tBu
Ph
Cl
Cl
4aj trace
4ak 94%
4al 35%
4am 90%
MeO
NC
NH
NH
NH
NH
N
N
N
N
N
Ph
N
N
N
Ph
Ph
Ph
Cl
Cl
Cl
4aq 83%
4an 50%
4ao 52%
4ap 64%
Scheme 3 Substrate generality of isocyanides. Reagents and conditions: 1a (0.15 mmol), 2 (0.16 mmol), [Rh(cod)Cl]2 (2.5 mol%), DPPE (5 mol%), 1,4-
dioxane (2 mL), rt until complete consumption of 1a then addition of 3 (0.18 mmol), 120 °C, 40 min; all yields are isolated yields.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

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Synthesis
R1
N
N
R1
C
C
Ar
N
L
N
L
D
Ar
Rh
C
R2
NC
Cl
R2
N
L
Cl
Rh(I)
Rh
B
R1
N
N
R
NC
R1
N
Ar
Ar
N
E
R2
N
NH
N2
Cl
Ar
N3
L
Rh
N
N
Ar
N
R1
R1
N2
Ar
products
A
Scheme 4 Plausible mechanism
A plausible mechanism for the one-pot sequential reac-
tion of vinyl azide with two different isocyanides is shown
in Scheme 4, which generally involves two processes in-
cluding Rh(I)-catalyzed cross-coupling of vinyl azide with
the first isocyanide, and the cyclization of the vinylcarbo-
diimide intermediate with the second isocyanide. Initially,
the key intermediate vinylcarbodiimide D is generated via a
Rh–nitrene pathway with only release of N2. Next, the ther-
mal cyclization of the second isocyanide gives the 2H-pyr-
rol-2-imine as the product. According to the condition
screening in Table 2, which could also be considered as con-
trolled experiments, the cyclization does not go through a
Rh(I)-mediated pathway, and isocyanide reacted with vinyl
azide prior to the vinylcarbodiimide.
In summary, we have reported an efficient rhodium-
catalyzed one-pot reaction of one vinyl azide with two se-
quential isocyanides, which offers an alternative facile ap-
proach to cross N-substituted 2H-pyrrol-2-imines in good
yields. In addition, this transformation also features good
functional group tolerance. From the perspective of the re-
action pathway, the unstable vinylcarbodiimide is the key
intermediate in this cascade reaction. The further applica-
tions of 2H-pyrrol-2-imines are currently underway in our
laboratories.
ters Auto Purification LC/MS system. HRMS were obtained on a
Bruker Apex IV FTMS spectrometer. All catalysts and ligands were
purchased from Sigma-Aldrich. All alkyl and aryl isocyanides and aryl
isocyanides are commercially available, unless stated otherwise.
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-phenyl-2H-pyrrol-3-
amine (4aa); Typical Procedure
To a dry 5-mL tube equipped with a magnetic stir bar, [Rh(cod)Cl]2
(1.8 mg, 0.004 mmol), and DPPE (3 mg, 0.008 mmol) was added to
freshly distilled 1,4-dioxane (2 mL). The tube was sealed, evacuated
and refilled with N2. Then, vinyl azide 1a (22 mg, 0.15 mmol) and iso-
cyanide 2a (22 mg, 0.16 mmol) were added and the mixture was
stirred at rt until 1a disappeared (TLC monitoring). Then 0.1 M t-BuNC
(3a) in 1,4-dioxane (15 mg, 0.18 mmol) was added and the mixture
was stirred at 120 °C for 40 min. When the reaction was complete, the
mixture was concentrated under reduced pressure. The resulting
crude residue was purified via column chromatography (silica gel,
PE/EtOAC 30:1) to afford the desired product 4aa (48 mg, 94%).
(1-Azidovinyl)benzene (1a); Typical Procedure7h
In a flask with a magnetic bar, Ag2CO3 (0.2 mmol) was suspended in
DMSO (4 ml). Phenylacetylene (2 mmol), TMSN3 (4 mmol), and H2O (4
mmol) were added to flask, respectively. Then the mixture was heat
to 80 °C. After 1 h, the mixture was partitioned between Et2O and
H2O, and the organic phase was separated, dried (Na2SO4), and con-
centrated. The residue was chromatographed (PE) to afford (1-azi-
dovinyl)benzene (1a); yield: 232 mg (1.6 mmol, 80%).
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-phenyl-2H-pyrrol-3-
amine (4aa)
All reactions were performed in a glass vial under N2 atmosphere. An-
hydrous solvents were distilled on a small scale with CaH2 or Na and
stored under N2. Petroleum ether bp 60–90 °C (PE) was used. For
chromatography, 200–300 mesh silica gel (Qingdao, China) was em-
ployed. 1H and 13C NMR spectra were recorded on Varian 300 or Vari-
an Mercury 400 spectrometer in CDCl3 referenced to TMS (1H  = 0;
13C  = 77.00) or in DMSO-d6 referenced to residual DMSO-d5 (1H  =
2.50; 13C  = 39.52). IR spectra were recorded with a Nicolet AVATAR
330 FT-IR spectrophotometer. Mass spectra were obtained on a Wa-
Following the typical procedure gave the product as a dark red solid;
yield: 47 mg (94%).
IR (neat): 3353, 2975, 2930, 1629, 1607, 1576, 1508, 1455, 1422,
1354, 1228, 842, 728 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.12 (d, J = 7.4 Hz, 2 H), 7.75 (dd, J = 8.8,
2.1 Hz, 2 H), 7.55–7.44 (m, 4 H), 7.35 (dd, J = 8.8, 2.1 Hz, 2 H), 6.27 (s,
1 H), 5.71 (s, 1 H), 1.46 (s, 9 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

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Y. Wang et al.
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13C NMR (101 MHz, CDCl3):  = 187.94, 165.09, 155.43, 145.61,
133.98, 132.77, 131.97, 128.89, 128.61, 127.93, 89.64, 52.47, 28.70.
HRMS (ESI): m/z [M + H]+ calcd for C20H21ClN3: 338.1419; found:
338.1403.
1H NMR (300 MHz, CDCl3):  = 8.10 (d, J = 8.9 Hz, 2 H), 7.73 (d, J = 8.7
Hz, 2 H), 7.34 (d, J = 8.7 Hz, 2 H), 6.97 (d, J = 8.9 Hz, 2 H), 6.17 (s, 1 H),
5.68 (s, 1 H), 3.88 (s, 3 H), 1.46 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 187.05, 165.36, 163.67, 155.10,
145.91, 131.57, 131.20, 128.74, 127.86, 126.54, 114.04, 89.30, 55.60,
52.30, 28.67.
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-(p-tolyl)-2H-pyrrol-3-
amine (4ba)
HRMS (ESI): m/z [M + H]+ calcd for C21H23ClN3O: 368.1524; found:
368.1507.
Following the typical procedure gave the product as a dark red solid;
yield: 51 mg (96%).
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-[4-(trifluorometh-
yl)phenyl]-2H-pyrrol-3-amine (4fa)
IR (neat): 3351, 2972, 2926, 1628, 1596, 1572, 1346, 1227, 1089, 742
cm–1
.
Following the typical procedure gave the product as a dark red solid;
yield: 44 mg (72%).
1H NMR (400 MHz, CDCl3):  = 8.02 (d, J = 8.1 Hz, 2 H), 7.74 (d, J = 8.7
Hz, 2 H), 7.34 (d, J = 8.7 Hz, 2 H), 7.27 (d, J = 8.2 Hz, 2 H), 5.70 (s, 1 H),
2.42 (s, 3 H), 1.46 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 187.82, 165.30, 155.23, 145.76,
143.69, 131.79, 131.24, 129.39, 129.09, 128.78, 127.92, 89.58, 52.38,
28.69, 21.99.
IR (neat): 3349, 2974, 2928, 1617, 1601, 1577, 1417, 1319, 1167,
1089, 841 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.20 (d, J = 8.1 Hz, 2 H), 7.76–7.73 (m, 2
H), 7.71 (d, J = 8.5 Hz, 2 H), 7.36 (d, J = 8.7 Hz, 2 H), 6.36 (s, 1 H), 5.70
(s, 1 H), 1.48 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 164.46, 156.06, 145.22, 137.38,
133.85, 133.53, 132.44, 128.99, 127.92, 125.49, 122.62, 89.54, 77.48,
77.16, 76.84, 52.79, 28.75.
HRMS (ESI): m/z [M + H]+ calcd for C21H23ClN3: 352.1575; found:
352.1560.
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-(m-tolyl)-2H-pyrrol-3-
amine (4ca)
HRMS (ESI): m/z [M + H]+ calcd for C21H20ClF3N3: 406.1292; found:
406.1276.
Following the typical procedure gave the product as a dark red solid;
yield: 49 mg (92%).
4-{3-(tert-Butylamino)-2-[(4-chlorophenyl)imino]-2H-pyrrol-5-
yl}benzonitrile (4ga)
IR (neat): 3354, 2973, 2928, 1630, 1600, 1568, 1342, 1225, 1089, 735
cm–1
.
Following the typical procedure gave the product as a dark red solid;
yield: 46 mg (85%).
1H NMR (400 MHz, CDCl3):  = 7.76 (d, J = 7.9 Hz, 1 H), 7.69–7.65 (m, 2
H), 7.32 (d, J = 8.7 Hz, 3 H), 7.27 (d, J = 7.6 Hz, 2 H), 6.14 (s, 1 H), 5.51
(s, 1 H), 2.66 (s, 3 H), 1.44 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 165.08, 154.35, 145.55, 138.98,
134.43, 131.88, 131.07, 129.70, 128.77, 127.63, 125.77, 93.26, 52.42,
28.70, 22.28.
IR (neat): 3348, 2957, 2925, 2228, 1628, 1598, 1569, 1414, 1347,
1283, 1226, 1089, 843 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.19 (d, J = 8.3 Hz, 2 H), 7.76 (d, J = 1.7
Hz, 1 H), 7.75–7.73 (m, 2 H), 7.72 (s, 1 H), 7.37 (d, J = 8.6 Hz, 2 H), 6.41
(s, 1 H), 5.68 (s, 1 H), 1.48 (s, 9 H).
HRMS (ESI): m/z [M + H]+ calcd for C21H23ClN3: 352.1575; found:
352.1561.
13C NMR (101 MHz, CDCl3):  = 164.08, 156.33, 145.01, 138.17,
132.58, 132.27, 129.03, 127.88, 118.60, 115.29, 89.45, 52.93, 28.76.
HRMS (ESI): m/z [M + H]+ calcd for C21H20ClN4: 363.1371; found:
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-(o-tolyl)-2H-pyrrol-3-
amine (4da)
363.1356.
Following the typical procedure gave the product as a purple solid;
yield: 50 mg (95%).
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-(4-fluorophenyl)-2H-
pyrrol-3-amine (4ha)
IR (neat): 3351, 2974, 2926, 1631, 1596, 1578, 1340, 1227, 1088, 737
cm–1
.
Following the typical procedure gave the product as a dark red solid;
yield: 45 mg (84%).
1H NMR (400 MHz, CDCl3):  = 7.94 (s, 1 H), 7.89 (d, J = 4.3 Hz, 1 H),
7.73 (d, J = 8.5 Hz, 2 H), 7.36 (s, 2 H), 7.34 (d, J = 2.4 Hz, 2 H), 6.22 (s, 1
H), 5.71 (s, 1 H), 2.43 (s, 3 H), 1.46 (s, 9 H).
IR (neat): 3347, 2975, 2931, 1632, 1591, 1507, 1416, 1228, 1153, 843,
751 cm–1
.
13C NMR (101 MHz, CDCl3):  = 188.19, 165.15, 155.27, 145.67,
138.33, 133.89, 133.68, 131.91, 129.42, 128.83, 128.49, 127.89,
126.26, 89.80, 52.44, 28.71, 21.52.
1H NMR (400 MHz, CDCl3):  = 8.14 (dd, J = 8.9, 5.6 Hz, 2 H), 7.74–7.70
(m, 2 H), 7.37–7.33 (m, 2 H), 7.19–7.12 (m, 2 H), 6.27 (s, 1 H), 5.67 (s,
1 H), 1.47 (s, 9 H).
HRMS (ESI): m/z [M + H]+ calcd for C21H23ClN3: 352.1575; found:
13C NMR (101 MHz, CDCl3):  = 164.92, 155.60, 145.58, 132.04,
352.1559.
131.32, 130.28, 128.85, 127.88, 115.93, 115.71, 89.29, 52.53, 28.71.
HRMS (ESI): m/z [M + H]+ calcd for C20H20ClFN3: 356.1324; found:
356.1308.
N-tert-Butyl-2-[(4-chlorophenyl)imino]-5-(4-methoxyphenyl)-
2H-pyrrol-3-amine (4ea)
Following the typical procedure gave the product as a dark red solid;
yield: 48 mg (87%).
N-tert-Butyl-5-(4-chlorophenyl)-2-[(4-chlorophenyl)imino]-2H-
pyrrol-3-amine (4ia)
IR (neat): 3351, 2974, 2932, 1628, 1594, 1574, 1417, 1352, 1257, 1167
Following the typical procedure gave the product as a dark red solid;
yield: 50 mg (89%).
cm–1
.
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IR (neat): 3348, 2973, 2927, 1628, 1605, 1590, 1568, 1408, 1343,
1225, 1089, 1012, 840, 745 cm–1
N-tert-Butyl-2-[(4-methoxyphenyl)imino]-5-phenyl-2H-pyrrol-3-
amine (4ac)
.
1H NMR (400 MHz, CDCl3):  = 8.05 (d, J = 8.7 Hz, 2 H), 7.75–7.69 (m, 2
H), 7.46–7.42 (m, 2 H), 7.37–7.33 (m, 2 H), 6.27 (s, 1 H), 5.66 (s, 1 H),
1.46 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 186.58, 164.79, 155.73, 145.48,
138.85, 132.49, 132.15, 130.22, 128.90, 127.89, 89.31, 52.59, 28.72.
Following the typical procedure gave the product as a dark red solid;
yield: 47 mg (94%).
IR (neat): 3352, 2975, 2930, 1607, 1508, 1455, 1273, 1109, 728 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.09 (d, J = 7.5 Hz, 4 H), 7.68 (s, 2 H),
7.51 (d, J = 27.3 Hz, 3 H), 6.29 (s, 1 H), 5.75 (s, 1 H), 3.93 (s, 3 H), 1.49
(s, 9 H).
HRMS (ESI): m/z [M + H]+ calcd for C20H20Cl2N3: 372.1029; found:
13C NMR (101 MHz, CDCl3):  = 167.16, 155.42, 151.34, 133.86,
132.93, 130.30, 129.07, 128.64, 127.05, 125.26, 89.93, 52.77, 52.14,
28.78.
372.1030.
5-(4-Bromophenyl)-N-tert-butyl-2-[(4-chlorophenyl)imino]-2H-
pyrrol-3-amine (4ja)
HRMS (ESI): m/z [M + K]+ calcd for C21H23N3OK: 372.1473; found:
Following the typical procedure gave the product as a dark red solid;
yield: 57 mg (91%).
372.1456.
IR (neat): 3347, 2974, 2930, 1628, 1605, 1566, 1508, 1480, 1404,
N-tert-Butyl-2-[(2,6-dimethylphenyl)imino]-5-phenyl-2H-pyrrol-
3-amine (4ad)
1341, 1225, 1088, 1009, 839, 742 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.97 (d, J = 8.5 Hz, 2 H), 7.72 (d, J = 8.7
Hz, 2 H), 7.59 (d, J = 8.5 Hz, 2 H), 7.35 (d, J = 8.7 Hz, 2 H), 6.33 (s, 1 H),
5.65 (s, 1 H), 1.46 (s, 9 H).
Following the typical procedure gave the product as a dark red solid;
yield: 42 mg (85%).
IR (neat): 2963, 2126, 1367, 1239, 1183, 841 cm–1
.
13C NMR (101 MHz, CDCl3):  = 186.68, 164.76, 155.73, 145.47,
132.90, 132.14, 131.87, 130.33, 128.85, 127.88, 127.50, 89.25, 52.58,
28.70.
1H NMR (400 MHz, CDCl3):  = 8.01 (d, J = 8.2 Hz, 2 H), 7.51–7.46 (m, 1
H), 7.43–7.37 (m, 2 H), 7.05 (d, J = 7.4 Hz, 2 H), 6.98–6.93 (m, 1 H),
6.14 (s, 1 H), 5.69 (d, J = 1.2 Hz, 1 H), 2.14 (s, 6 H), 1.47 (d, J = 1.2 Hz, 9
H).
HRMS (ESI): m/z [M + H]+ calcd for C20H20BrClN3: 418.0503; found:
13C NMR (101 MHz, CDCl3):  = 187.48, 165.06, 153.29, 146.73,
134.10, 132.59, 128.95, 128.47, 127.76, 123.98, 120.97, 90.33, 52.33,
28.70, 18.95.
418.0484.
5-(Benzo[b]thiophen-2-yl)-N-tert-butyl-2-[(4-chlorophenyl)imi-
no]-2H-pyrrol-3-amine (4ka)
HRMS (ESI): m/z [M + H]+ calcd for C22H26N3: 332.2121; found:
Following the typical procedure gave the product as a dark red solid;
yield: 41 mg (69%).
332.3112.
IR (neat): 3353, 2975, 2930, 1629, 1601, 1523, 1439, 1365, 1224,
(Z)-N-tert-Butyl-5-phenyl-2-[(4-(trifluoromethyl)phenyl)imino]-
2H-pyrrol-3-amine (4ae)
1088, 842, 748 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.06 (s, 1 H), 7.87 (t, J = 6.3 Hz, 2 H),
7.80–7.76 (m, 2 H), 7.45–7.38 (m, 2 H), 7.38–7.35 (m, 2 H), 6.24 (s, 1
H), 5.70 (d, J = 1.8 Hz, 1 H), 1.47 (s, 9 H).
Following the typical procedure gave the product as a black solid;
yield: 31 mg (55%).
IR (neat): 3356, 2975, 2928, 1610, 1510, 1455, 1321, 1118, 853 cm–1
.
13C NMR (101 MHz, CDCl3):  = 164.42, 155.20, 145.46, 142.70,
139.72, 132.21, 129.09, 128.86, 128.25, 126.93, 125.20, 124.89,
122.89, 89.74, 52.50, 28.68.
HRMS (ESI): m/z [M + H]+ calcd for C22H21ClN3S: 394.1139; found:
394.1123.
1H NMR (300 MHz, CDCl3):  = 8.15–8.06 (m, 2 H), 7.67 (dd, J = 24.0,
8.5 Hz, 4 H), 7.49 (dt, J = 8.5, 7.1 Hz, 3 H), 6.28 (s, 1 H), 5.74 (s, 1 H),
1.48 (s, 9 H).
13C NMR (75 MHz, CDCl3):  = 188.78 (s), 166.22 (s), 155.39 (s), 150.32
(s), 133.90 (s), 132.98 (s), 129.11 (s), 128.66 (s), 125.76 (dd, J = 9.3, 5.4
Hz), 89.98 (s), 52.73 (s), 28.78 (s).
4-{[3-(tert-Butylamino)-5-phenyl-2H-pyrrol-2-ylidene]ami-
no}benzonitrile (4ab)
HRMS (ESI): m/z [M + H]+ calcd for C21H21F3N3: 372.1682; found:
372.1673.
Following the typical procedure gave the product as a dark red solid;
yield: 30 mg (61%).
(Z)-N-tert-Butyl-2-[(4-nitrophenyl)imino]-5-phenyl-2H-pyrrol-3-
IR (neat): 3349, 2973, 2930, 2223, 1609, 1508, 1455, 1422, 1355,
amine (4af)
1281, 1026, 829 cm–1
.
Following the typical procedure gave the product as a black solid;
yield: 26 mg (50%).
IR (neat): 3348, 2925, 2853, 1609, 1509, 1455, 1337, 1025, 864 cm–1
1H NMR (300 MHz, CDCl3):  = 8.25 (d, J = 9.0 Hz, 2 H), 8.10 (dd, 2 H),
7.68 (d, J = 9.0 Hz, 2 H), 7.57 (s, 1 H), 7.53–7.45 (m, 2 H), 5.75 (s, 1 H),
1.49 (s, 9 H).
13C NMR (75 MHz, CDCl3):  = 189.69 (s), 166.78 (s), 155.55 (s), 153.38
(s), 145.07 (s), 133.65 (s), 133.33 (s), 129.23 (s), 128.74 (s), 125.64 (s),
124.39 (s), 90.05 (s), 52.98 (s), 28.79 (s).
1H NMR (400 MHz, CDCl3):  = 8.10 (d, J = 8.1 Hz, 2 H), 7.67 (q, J = 8.6
Hz, 4 H), 7.59–7.53 (m, 1 H), 7.47 (t, J = 7.6 Hz, 2 H), 6.28 (s, 1 H), 5.74
(s, 1 H), 1.48 (s, 9 H).
13C NMR (101 MHz, CDCl3):  = 166.35, 155.29, 151.18, 133.47,
133.10, 132.57, 129.01, 128.55, 125.93, 119.39, 108.47, 89.76, 52.69,
28.58.
.
HRMS (ESI): m/z [M + H]+ calcd for C21H21N4: 329.1761; found:
329.1746.
HRMS (ESI): m/z [M + H]+ calcd for C20H21N4O2: 349.1659; found:
349.1650.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

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N-tert-Butyl-2-(cyclohexylimino)-5-phenyl-2H-pyrrol-3-amine
HRMS (ESI): m/z [M + H]+ calcd for C24H28N3: 358.2278; found:
(4ag)
358.2263.
Following the typical procedure gave the product as a dark red solid;
yield: 9 mg (21%).
N-Butyl-2-[(4-chlorophenyl)imino]-5-phenyl-2H-pyrrol-3-amine
(4am)
IR (neat): 3232, 2930, 2855, 1685, 1597, 1453, 1328, 1060, 728 cm–1
.
Following the typical procedure gave the product as a dark red solid;
yield: 46 mg (90%).
1H NMR (400 MHz, CDCl3):  = 7.94–7.84 (m, 2 H), 7.59 (m, 3 H), 6.03
(s, 1 H), 3.93 (m, 1 H), 1.95 (m, 2 H), 1.78–1.62 (m, 4 H), 1.53 (s, 9 H),
1.45-1.26 (m, 3 H).
13C NMR (101 MHz, CDCl3):  = 163.96, 159.84, 153.15, 133.71,
129.73, 127.68, 127.48, 94.38, 77.48, 77.16, 76.84, 58.97, 58.73, 33.52,
30.47, 24.98, 24.68.
IR (neat): 3350, 2959, 2931, 1635, 1596, 1558, 1492, 1404, 1314,
1091, 829, 753 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.14–8.08 (m, 2 H), 7.79–7.73 (m, 2 H),
7.52 (d, J = 7.2 Hz, 1 H), 7.47 (dd, J = 8.1, 6.5 Hz, 2 H), 7.37–7.34 (m, 2
H), 6.04 (s, 1 H), 5.70 (s, 1 H), 3.37 (t, J = 7.1 Hz, 2 H), 1.72 (dt, J = 19.9,
7.4 Hz, 2 H), 1.47 (dt, J = 15.0, 7.4 Hz, 2 H), 0.99 (t, J = 7.4 Hz, 3 H).
HRMS (ESI): m/z [M + H]+ calcd for C22H28N3: 310.2278; found:
310.2265.
13C NMR (101 MHz, CDCl3):  = 159.95, 132.60, 128.79, 127.24 (s),
122.89, 88.93, 46.41, 31.41, 20.41, 13.95.
HRMS (ESI): m/z [M + H]+ calcd for C20H21ClN3: 338.1419; found:
2-(tert-Butylimino)-N-(2,6-dimethylphenyl)-5-phenyl-2H-pyrrol-
3-amine (4ai)
338.1400.
Following the typical procedure gave the product as a dark red solid;
yield: 8 mg (16%).
2-[(4-Chlorophenyl)imino]-N-(4-methoxyphenyl)-5-phenyl-2H-
pyrrol-3-amine (4an)
IR (neat): 2963, 2126, 1367, 1239, 1184, 841 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.97 (dd, J = 6.7, 1.6 Hz, 2 H), 7.38 (d, J =
6.4 Hz, 3 H), 7.06 (d, J = 7.4 Hz, 2 H), 6.99–6.95 (m, 1 H), 5.38 (d, J = 1.1
Hz, 1 H), 2.07 (s, 6 H), 1.62 (d, J = 0.9 Hz, 9 H).
13C NMR (101 MHz, CDCl3):  = 166.52 (s), 160.30 (s), 133.22 (s),
129.98 (s), 128.10 (s), 127.44 (s), 126.97 (d, J = 6.1 Hz), 125.82 (s),
122.99 (s), 90.89 (s), 51.86 (s), 27.93 (s), 17.45 (s).
Following the typical procedure gave the product as a dark red solid;
yield: 29 mg (50%).
IR (neat): 3350, 2948, 1715, 1595, 1456, 1278, 841, 768 cm–1
1H NMR (400 MHz, CDCl3):  = 8.15 (d, J = 7.1 Hz, 2 H), 8.09 (d, J = 8.5
Hz, 2 H), 7.85 (d, J = 8.7 Hz, 2 H), 7.56 (d, J = 7.1 Hz, 1 H), 7.50 (dd, J =
10.0, 4.8 Hz, 2 H), 7.43–7.37 (m, 2 H), 7.28–7.22 (m, 2 H), 6.38 (s, 1 H),
3.93 (s, 3 H).
13C NMR (101 MHz, CDCl3):  = 166.64, 133.21, 132.42, 131.41,
130.94, 129.61, 129.29–128.67, 128.40, 126.76, 125.12, 122.85,
118.41, 95.39, 52.23.
HRMS (ESI): m/z [M + H]+ calcd for C22H26N3: 332.2121; found:
332.3112.
2-[(4-Chlorophenyl)imino)]-N-cyclohexyl-5-phenyl-2H-pyrrol-3-
amine (4ak)
HRMS (ESI+): m/z [M + H]+ calcd for C23H19ClN3O: 388.1211; found:
388.1372.
Following the typical procedure gave the product as a dark red solid;
yield: 51 mg (94%).
IR (neat): 3364, 2930, 2854, 1735, 1609, 1595, 1481, 1356, 1227,
2-[(4-Chlorophenyl)imino]-N-(4-cyanophenyl)-5-phenyl-2H-pyr-
rol-3-amine (4ao)
1089, 1011, 842, 725 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.10 (d, J = 7.3 Hz, 2 H), 7.76 (d, J = 8.5
Hz, 2 H), 7.55–7.42 (m, 3 H), 7.37–7.33 (m, 2 H), 5.69 (s, 1 H), 3.43–
3.32 (m, 1 H), 2.07 (s, 2 H), 1.83 (dd, J = 8.3, 4.0 Hz, 2 H), 1.69 (d, J =
12.3 Hz, 1 H), 1.40 (t, J = 9.8 Hz, 5 H).
Following the typical procedure gave the product as a dark red solid;
yield: 30 mg (52%).
IR (neat): 3319, 2925, 2222, 1594, 1530, 1456, 1351, 1089, 828 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.20–8.11 (m, 2 H), 8.05 (s, 1 H), 7.86
(d, J = 8.7 Hz, 2 H), 7.70 (d, J = 8.6 Hz, 2 H), 7.52 (t, J = 7.5 Hz, 2 H),
7.43–7.38 (m, 2 H), 7.31–7.25 (m, 3 H), 6.38 (s, 1 H).
13C NMR (101 MHz, CDCl3):  = 185.90, 163.84, 158.58, 144.87,
133.96, 132.55, 131.63, 128.86, 128.72, 127.20, 88.80, 55.49, 32.76,
25.64, 24.84.
13C NMR (101 MHz, CDCl3):  = 133.84, 133.23, 132.52, 129.95,
HRMS (ESI): m/z [M + H]+ calcd for C22H23ClN3: 364.1575; found:
129.47, 129.23, 128.98, 126.69, 126.17, 122.79, 122.19, 119.06, 95.85.
364.1560.
HRMS (ESI): m/z [M + H]+ calcd for C23H16ClN4: 383.1058; found:
N-Cyclohexyl-2-[(2,6-dimethylphenyl)imino]-5-phenyl-2H-pyr-
383.1041.
rol-3-amine (4al)
Following the typical procedure gave the product as a dark red solid;
yield: 19 mg (35%).
2-[(4-Chlorophenyl)imino]-N-(2,6-dimethylphenyl)-5-phenyl-2H-
pyrrol-3-amine (4ap)
Following the typical procedure gave the product as a dark red solid;
yield: 37 mg (64%).
IR (neat): 3371, 2928, 2853, 1614, 1509, 1455, 1358, 1292, 1015, 727
cm–1
.
IR (neat): 3352, 2975, 1607, 1508, 1455, 1273, 1109, 728 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.00 (d, J = 7.2 Hz, 2 H), 7.48 (d, J = 7.4
Hz, 1 H), 7.40 (t, J = 7.5 Hz, 2 H), 7.05 (d, J = 7.4 Hz, 2 H), 6.97 (d, J = 6.8
Hz, 1 H), 5.63 (s, 1 H), 3.36 (s, 1 H), 2.14 (s, 6 H), 1.74 (dd, J = 41.9, 19.6
Hz, 5 H), 1.43 (t, J = 8.8 Hz, 4 H).
1H NMR (400 MHz, CDCl3):  = 8.02 (d, J = 6.4 Hz, 2 H), 7.95 (d, J = 8.8
Hz, 2 H), 7.45 (dd, J = 9.1, 6.1 Hz, 3 H), 7.42–7.39 (m, 2 H), 7.10 (t, J =
9.6 Hz, 3 H), 5.53 (s, 1 H), 2.42 (s, 1 H), 2.15 (s, 6 H).
13C NMR (101 MHz, CDCl3):  = 167.96, 155.74, 152.64, 146.45,
133.92, 133.03, 132.36, 128.49, 128.34, 127.69, 127.60, 127.01, 89.27,
54.29, 32.44, 29.68, 25.53, 24.66, 18.74.
13C NMR (101 MHz, CDCl3):  = 159.32, 133.34, 131.67, 129.68,
129.12, 128.53, 128.38, 127.61, 125.07, 122.40, 92.74, 18.36.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I

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HRMS (ESI): m/z [M + H]+ calcd for C24H21ClN3: 386.1419; found:
386.1403.
Lymphoma Myeloma 2010, 10, 285. (c) Hernández, P. I.; Moreno,
D.; Javier, A. A.; Torroba, T.; Pérez-Tomás, R.; Quesada, R. Chem.
Commun. 2012, 48, 1556.
(2) For examples, see: (a) Gorman, A.; Killoran, J.; O’Shea, C.; Kenna,
T.; Gallagher, W. M.; O’Shea, D. F. J. Am. Chem. Soc. 2004, 126,
10619. (b) Coskun, A.; Yilmaz, M. D.; Akkaya, E. U. Org. Lett.
2007, 9, 607. (c) Amin, A. N.; El-Khouly, M. E.; Subbaiyan, N. K.;
Zandler, M. E.; Fukuzumi, S.; D’Souza, F. Chem. Commun. 2012,
48, 206. (d) Liu, S.; Shi, Z.; Xu, W.; Yang, H.; Xi, N.; Liu, X.; Zhao,
Q.; Huang, W. Dyes Pigm. 2014, 103, 145.
N-(2,6-Dimethylphenyl)-2-[(2,6-dimethylphenyl)imino]-5-phe-
nyl-2H-pyrrol-3-amine (4aq)4
Following the typical procedure gave the product as a dark red solid;
yield: 47 mg (83%).
IR (neat): 3352, 2975, 1607, 1508, 1455, 1273, 1109, 728 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.93 (d, J = 7.5 Hz, 1 H), 7.40 (d, J = 2.2
Hz, 3 H), 7.15–7.05 (m, 7 H), 6.99 (dd, J = 12.6, 7.5 Hz, 3 H), 6.41 (s, 1
H), 5.47 (s, 1 H), 2.24 (s, 6 H), 2.17 (s, 6 H).
(3) Hu, W.; Li, J.; Xu, Y.; Li, J.; Wu, W.; Liu, H.; Jiang, H. Org. Lett.
2017, 19, 678.
(4) Senadi, G. C.; Lu, T.-Y.; Dhandabani, G. K.; Wang, J.-J. Org. Lett.
2017, 19, 1172.
(5) Capuano, L.; Dahm, B.; Port, V.; Schnur, R.; Schramm, V. Chem.
Ber. 1988, 121, 271.
13C NMR (101 MHz, CDCl3):  = 160.72, 155.85, 149.86, 146.10,
131.74, 129.17, 128.54, 128.33, 127.85, 127.59, 126.56, 125.97,
123.81, 123.44, 94.85, 18.21.
HRMS (ESI): m/z [M + H]+ calcd for C26H26N3: 380.2121; found:
380.2112.
(6) For selected reviews, see: (a) Bräse, S.; Gil, C.; Knepper, K.;
Zimmermann, V. Angew. Chem. Int. Ed. 2005, 44, 5188. (b) Bräse,
S.; Banert, K. Organic Azides: Syntheses and Applications; Wiley-
VCH: Weinheim, 2010. (c) Driver, T. G. Org. Biomol. Chem. 2010,
8, 3831. (d) Intrieri, D.; Zardi, P.; Caselli, A.; Gallo, E. Chem.
Commun. 2014, 50, 11440. (e) Shin, K.; Kim, H.; Chang, S. Acc.
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Funding Information
This project is supported by the Inner Mongolia University (Enhanc-
ing Comprehensive Strength Foundation, Grant No. 10000-
1601010981), and National Natural Science Foundation of China
(Grants No. 21672256 and 21562032).
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Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1611830.
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References
(1) For examples, see: (a) Furstner, A. Angew. Chem. Int. Ed. 2003,
42, 3582. (b) Parikh, S. A.; Kantarjian, H.; Schimmer, A.; Walsh,
W.; Asatiani, E.; El-Shami, K.; Winton, E.; Verstovsek, S. Clin.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–I