Rh(III)-catalyzed chelation-assisted intermolecular carbenoid functionalization of α-imino Csp3-H bonds

Article abstract of DOI:10.1039/c5cc06428g

A Rh(iii)-catalyzed cross-coupling/cyclization cascade of α-imino Csp³-H bonds with donor/acceptor α-acyl diazocarbonyl compounds has been developed. This novel transformation involves ligand-directed Csp³-H bond functionalization with carbenoids under the pyridine-chelation assistance, and offered an efficient access to synthetically versatile polysubstituted N-(2-pyridyl)pyrroles with a broad range of functional group tolerance.

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DOI: 10.1039/C5CC06428G
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ARTICLE TYPE
Rh(III)-Catalyzed Chelation-Assisted Intermolecular Carbenoid
Functionalization of -Imino Csp3-H Bonds
Xun Chen,a Ying Xie,a Xinsheng Xiao,a Guoqiang Li,b Yuanfu Deng,a Huanfeng Jiang, a and Wei Zeng*, a
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/co000000x
We recently focus on developing transition metal-catalyzed
C-C and C-N bond cross-coupling reaction involving imines
A Rh(III)-catalyzed cross-coupling/cyclization cascade of -
imino Csp3-H bonds with donor/acceptor -acyl
diazocarbonyl compounds has been developed. This novel
transformation involves ligand-directed Csp3-H bond
functionalization with carbenoids under the pyridine-
chelation assistance, and offered an efficient access to
synthetically versatile polysubstituted N-(2-pyridyl)pyrroles
with broad range of functional group tolerance.
to construct kinds of -amino carboxylic acids and
13
heterocycles.
Very recently, we further found a six-
membered cyclopalladium species which derived from N-(2-
pyridyl)-ketoimines A (Scheme 1b) through Csp3-H activation
process, could be trapped by unsaturated alkynes and CO to
furnish heteroarenes, respectively. 14 These results inspired us
to envision that Rh salts could possibly activate saturated -
imino alkyl Csp3-H bonds to form rhodacycle intermediate (B)
(Scheme 1b) with the assistance of Rh(III)/pyridine nitrogen-
chelation, then followed by resulting in C-C coupling with
diazo ketones via rhodium carbene complexes (C) (Scheme
1b). To identify this hypothesis, herein we report a novel
Rh(III)-catalyzed pyridine-directed cross-coupling cascade of
-imino alkyl Csp3-H bonds with -acyldiazoacetates to
rapidly assemble N-(2-pyridyl)pyrrole (N-PPR) library, these
compounds are ubiquitous in synthetic building blocks and
biological molecules (Scheme 2). 15
Introduction
Carbon-carbon bond-forming reactions are most important
1
transformation in modern organic chemistry.
A single-step
chemical process involving diverse C-C and C-X bond
formations (X = C, N, and O etc.) provides a step-economic
approach to assembling complex molecules. Over the past
decades, transition metal-catalyzed C-H insertion of carbenoids
represents a powerful tool for constructing C-C and C-X bonds. 2
In this regard, various carbene precursors have been extensively
3
explored to allow for efficient cross-coupling with alkanes,
a) Previous Work: Ketoimine-directed Rh(III)-catalyzed ArCsp2-H functionalization with diazo compounds
(Ref. 11c)
alkenes, 4 alkynes, 5 arenes 6 and carbonyl compounds.7 However,
despite enormous progress in this field, there are very rare
examples about transition metal-catalyzed cross-coupling of
carbenoids with imines,8 albeit the method will provide a novel
approach to versatile nitrogen-containing compounds. To date,
the pioneering report by Doyle ever described Rh(II) or Cu(II)-
catalyzed synthesis of dihydropyrroles through a [3 + 2]
Me
O
Me
R1
R3
R1
Me
R
Me
R2
R1
N
R3
R1
N
R
R
N
cat. [Rh(III)]
MeOH, heat
N
N2
R2
Rh(III)
R3
O
R2
R = H, or OMe
b) This Work: Pyridine-directed Rh(III)-catalyzed Imino Csp3-H functionalization with diazo compounds
R3
O
O
R3
R2
R3
Rh
R2
Ar
R2
Me
N
N
N
Rh
R1
N
9
N2
Rh(III)
cycloaddition of vinyldiazoacetates with imines. Recently, Hu
N
Ar
N
N
Ar
N
3
A
B
C
also developed a novel Rh(II) and chiral phosphoric acid co-
catalyzed C-H insertion/C-C coupling cascade of N-aryl
diazoamides with imines, in which imines were acted as an
electrophilic reagent to trap zwitterionic rhodium carbenes.10
More recently, prompted by many achievements of C-H
activation, several breakthroughs about chelation-assisted Csp2-H
Scheme 1. Rh(III)-Catalyzed C-C Coupling Cascade Involving Imines and
Diazo compounds
R1
R
O
O
N
N
O
O
R2
insertions of carbenoids have been made for site-selectively
R3
NEt2
11
N
N
N
N
N
N
forming C-C bonds.
Representative work by Glorious took
O
H
advantage of the directing character of ketoimines to enable a
Antimalarial drugs
Biological PBR ligands
HIV-1 RT inhibitors
Rh(III)-catalyzed tandem Csp2-H activation/cyclization of N-
Scheme 2. Selected Examples of Biological N-PPR-Containing Molecules
substituted acetophenone imines with -diazo ketones for rapidly
11c
assembling isoquinolines (Scheme 1a),
in which insertion of
Results and Discussion
carbenoids into -imino alkyl Csp3-H bonds could not be
accessed through imine/enamine-isomerization and C-H
activation process, 12 and such a useful cross-coupling is believed
to be of great importance for organic synthetic chemistry.
To begin, the cross-coupling of N-(2-pyridyl)-ketoimine (1a)
and -acyldiazoacetate (2a) was investigated for screening
various transition-metal Pd(II), Ir(III) and Rh(III) salts etc. in
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DOI: 10.1039/C5CC06P42a8gGe 2 of 4
o
o
in solvent (2.0 mL) at 80 C for 8 h under Ar in a sealed reaction tube,
the presence of AgClO4 (10 mol %) in THF at 80 C under Ar
b
c
followed by flash chromatography on SiO2. Isolated yield. The reaction
temperature is 60 oC. dThe reaction temperature is 100 oC.
atmosphere for 8 h (Table, entries 1-8). We were pleased to
find that catalyst (Cp*IrCl2)2 and (Cp*RhCl2)2 could give us
the desired polysubstituted N-PPR 3a in 21% and 27% yield
(entries 5 and 8), respectively. With a promising Rh(III)
catalyst in hand, we then turned our attention to evaluating
various silver additives such as AgBF4, AgOAc and AgNTf2
etc. For further increasing the reaction conversion (entries 8-
12), and we found that a slightly improved yield (36%) was
obtained by employing AgSbF6 as additive (compare entries
8-11 with 12). To maximize the yield of the reaction, the
additional optimization of the solvent system revealed that 1,
2-dichloroethane (DCE) and acetonitrile could result in
excellent yields (entries 14 and 17), and acetonitrile proved to
be the optimal solvent (90% yield of 3a, entry 17). Moreover,
directly employing Cp*Rh(SbF6)2 (5 mol %) as catalyst could
also afford 92% yield of 3a (compare entry 17 with 19). It
should be noted that the yield of 3a would decrease to 59% in
absence of AgSbF6 (compare entry 17 with 18); Moreover,
lowering or increasing the reaction temperature also led to
poorer yield (compare entries 21 and 22 with 17) (see ESI for
the more details about screening of reaction conditions).
The generality of the reaction was then explored (Table 2),
and it was found that common functional groups on the imino
phenyl rings were well tolerated in this transformation to
provide the corresponding polysubstituted pyrroles in good to
excellent yields (entries 1-8), including electron-donating
methyl (1b), methoxyl (1c), and acetal group (1i), and
electron-withdrawing halogen (1d-1f), ester (1g), and nitro
group (1h). Notably, meso or ortho-substituted phenyl rings
resulted in a decreased yield possibly because of the increased
steric hindrance around the ketoimine (1d-1f). 16 Moreover, 2-
furan and 2-thiophene substituted ketoimines also allowed for
this transformation and furnished the desired 2-heteroaryl-
substituted pyrroles (3j and 3k) in 61% and 58% yields,
respectively (entries 9 and 10). Subsequently, the substitution
effects from pyridine ring on this transformation was
evaluated, and we found electron–rich or electron-deficient
pyridines could provide good to excellent yields of 3l-3o
regardless of the electronical properties of substituents
(entries 11-14). In addition, N-(2-pyrimidyl)ketoimine (1p)
was also a suitable substrate for this transformation and
provided 78% yield of the desired pyrrole 3p (entry 15).
Meanwhile, the present carbenoid functionalization of -imino
Csp3-H bonds could also be successfully applied to a wide range
of -acyldiazo compounds with particular N-(2-pyridyl)
ketoimine 1a. Remarkably, -alkylacyl, -arylacyl, -
homoallylic acyl, and -alkoxymethylacyl substituted
diazoacetates could easily enable assembling the desired N-PPR
3q-3v in 72-92% yields (Table 2, entries 16-21). Moreover, when
-acyl diazoketone 2h was employed as the substrate in this
reaction system, the desired 3-acetyl group-substituted pyrrole 3w
was obtained in 76% yield (entry 22). More importantly, -acyl
diazophosphonate 2i and -acyl diazosulfone 2j could also be
rapidly converted to 3-phosphonyl and 3-sulfonyl-containing N-
PPR 3x and 3y in 55% and 63% yields (entries 23 and 24),
respectively. Existing synthetic approaches to these pyrrole
derivatives generally need tedious reaction steps and harsh
reaction conditions.17 By the way, the structures of pyrrole 3r and
3y were already unambiguously assigned by their single crystal
X-ray analysis (see ESI for more details).
Table 1. Reaction Optimization a
EtO C
2
O
O
Catalysts (2.5 mol %)
additives (10 mol %)
Me
Ph
N
+
N
N
OEt
o
solvent, 80 C, 8 h
N
N
1a
3a
2a
2
Ph
entry
1
catalysts
Pd(OAc)2
Cu(OAc)2
CuI
additives solvent
yield (%) b
AgClO4
AgClO4
AgClO4
AgClO4
AgClO4
AgClO4
AgClO4
AgClO4
AgBF4
AgNTf2
AgOAc
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
--
THF
0
2
THF
0
3
THF
0
4
[Ru(p-cymene)Cl2]
(Cp*IrCl2)2
THF
0
5
THF
21
0
6
RhCl3
THF
7
Rh2(COD)2Cl2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
Cp*Rh(SbF6)2
(Cp*RhCl2)2
(Cp*RhCl2)2
(Cp*RhCl2)2
THF
0
8
THF
27
31
34
29
36
23
85
trace
52
90
59
92
26
81 c
87 d
9
THF
10
11
12
13
14
15
16
17
18
19
20
21
22
THF
THF
THF
Table 2. Substrate Scope a
EtOH
DCE
R3
R2
X
R1
O
[Cp*RhCl2]2 (2.5 mol %)
AgSbF6 (10 mol %)
CH3CN, 80 oC, 8 h
Ar
R3
N
+
toluene
dioxane
MeCN
MeCN
MeCN
DMSO
MeCN
MeCN
N
N
R2
X
N
N2
Ar
X = CH or N
R1
1
2
3
entry
ketoimine (1)
diazocompd. (2)
prod./yield (%) b
EtO C
2
--
Ar
O
O
N
AgSbF6
AgSbF6
AgSbF6
N
N
N
OEt
N2
Ar
1
2a
3
aUnless otherwise noted, all the reactions were carried out using
ketoimine (1a) (0.10 mmol) and diazocompound (2a) (0.20 mmol) with
catalysts (2.5 mol %) in the presence of silver salts additives (10 mol %)
1
1b, Ar = 4-Me-Ph
2a
3b, Ar = 4-Me-Ph
82
2
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MeO2C
2
1c, Ar = 4-MeO-Ph
1d, Ar = 4-Cl-Ph
2a
2a
2a
2a
2a
2a
3c, Ar = 4-MeO-Ph
3d, Ar = 4-Cl-Ph
72
MeO
O
O
Ph
N
3
4
5
6
7
91
21
MeO
92
76
OMe
N
N2
1e, Ar = 3-Cl-Ph
3e, Ar = 3-Cl-Ph
85
62
1a
1a
2g
3v
Me
1f, Ar = 2-Cl-Ph
3f, Ar = 2-Cl-Ph
O
1g, Ar = 4-CO2Me-Ph
1h, Ar = 4-NO2-Ph
3g, Ar = 4-CO2Me-Ph
3h, Ar = 4-NO2-Ph
86
O
O
Me
Ph
N
22
Me
Me
N
95
N
2
2h
3w
EtO C
2
O
MeO
N
N
OMe
N
P
O
O
8
O
O
N
O
O
P
Me
Ph
N
N
OMe
OMe
23
61
55
63
1i
2a
3i
N
2
EtO C
2
1a
1a
2i
3x
O
O
Ts
N
N
N
OEt
X
N2
N
O
Me
Ph
N
X
Ts
24
1
2a
2a
2a
3
N
N
2
2j
3y
9
1j, X = O
1k, X = S
3j, X = O
3k, X = S
61
a
All the reactions were carried out using ketoimines (1) (0.10 mmol)
and diazocompounds (2) (0.2 mmol) with (Cp*RhCl2)2 (2.5 mol %) in
the presence of AgSbF6 (10 mol %) in CH3CN (2.0 mL) at 80 C for 8
10
58
EtO2C
o
Ph
N
1
h under Ar in a sealed reaction tube, followed by flash chromatography
R
O
O
on SiO2. b Isolated yield.
N
N
N
OEt
N
2
1
Ph
To better understand the -imino Csp3-H functionalization
process, the cross-coupling/cyclization cascade of N-phenyl
ketoimine (1q) with -acyl diazoacetate (2a) was performed
under our standard conditions, and no desired N-phenyl
substituted pyrrole 3z was observed by the 1H NMR and GC-MS
methods (Scheme 3-1). This result remarkably implied that
pyridyl group played a key chelation in this transformation.
Subsequently, when N-(2-pyridyl) ketoimine 1a was subjected to
Rh(III)/CD3OD/Ar system for 24 h in the absence of diazoacetate
2a, 82% deuterium incorporation was detected at the imino
methyl group of 1a (Scheme 3-2) (see SI for more details), 18 this
experiment indicated that imine-enamine tautomerization could
efficiently occur with the assistance of the Rh(III)/pyridine
nitrogen-chelation. In addition, the KIE value (KH/KD = 2.3) from
kinetic isotope effect experiments further indicated that -imino
C-H bond cleavage possibly dominate the reaction rate (see ESI
for more details).
1
2a
R3
11
12
13
14
1l, R1 = Me
1m, R1 = Cl
1n, R1 = Br
1o, R1 = CN
2a
3l, R1 = Me
3m, R1 = Cl
3n, R1 = Br
81
78
75
79
2a
2a
2a
3o, R1 = CN
EtO2C
Ph
N
N
15
N
N
N
N
Ph
1p
2a
3p
78
EtO2C
R2
O
O
Ph
N
2
N
N
R
OEt
N
N
Ph
2
1a
2
3
16
17
18
1a
1a
1a
2b, R2 = Et
2c, R2 = Ph
2d, R2 = Cy
3q, R2 = Et
3r, R2 = Ph
87
72
74
EtO C
2
O
[Cp*RhCl ] (2.5 mol %)
2 2
N
AgSbF (10 mol %)
CO Et
2
Me
Ph
+
6
N
(1)
o
CH CN, 80 C, 8 h
3
H C
3
Ph
N
2
3s, R2 = Cy
2a
1q
(not observed)
3z
EtO2C
[Cp*RhCl ] (2.5 mol %)
2 2
AgSbF (10 mol %)
6
Ph
N
N
Ph
(2)
(3)
O
O
N
N
N
N
CD OD (2.0 equiv)
3
o
19
20
84
71
CH CN (2. 0 mL), 80 C, 8 h
3
D C
Ph
3
H C
3
1a
Ph
Ph
OEt
N
d-1a
82% D
EtO C
N2
EtO C
D
2
2
1a
1a
2e
3t
[Cp*RhCl ] (2.5 mol %)
78% D
Ph
2 2
AgSbF (10 mol %)
6
H
C
Ph
H C
3
N
N
or
or
Ph
3
EtO2C
N
N
N
2a (2.0 equiv)
CH CN, 80 C, 24 h
3
o
D C
3
Ph
N
N
H C
3
Ph
O
O
N
N
KIE = 2.3
82% D
1a
3a
d-1a
d-3a
OEt
N2
Scheme 3. Preliminary Mechanism Studies
2f
3u
Based on the above-mentioned results, a plausible reaction
mechanism is shown in Figure 1. Firstly, enamine A-1
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DOI: 10.1039/C5CC06P42a8gGe 4 of 4
12
2008, 47, 9749; (b) C. Qin, H. M. L. Davies, J. Am. Chem. Soc. 2014,
136, 9792; (c) D. M. Guptill, H. M. L. Davies, J. Am. Chem. Soc. 2014,
136, 17718.
derived from imine/enamine-isomerization
could be
electrophilically attacked by Rh(III) to produce a rhodacycle
intermediate B-1, and B-1 could isomerize to form rhodacycle
intermediate C-1. Subsequently, the coordination of the
diazoestate (2) was followed by the denitrogenation to form
Rh-carbene D-1, which would undergo migratory insertion to
4 For the selected examples, see: (a) D. D. Schwarzer, P. J. Gritsch, T.
Gaich. Angew. Chem., Int. Ed. 2012, 51, 11514; (b) V. N. G. Lindsay,
D. Fiset, P. J. Gritsch, S. Azzi, A. B. Charette. J. Am. Chem. Soc. 2013,
135, 1463; (c) S. I. Lee, G. S. Hwang, D. H. Ryu. J. Am. Chem. Soc.
2013, 135, 7126; (d) Z. Y. Cao, X. Wang, C. Tan, X. L. Zhao, J. Zhou,
K. Ding. J. Am. Chem. Soc. 2013, 135, 8197.
5 For the selected examples, see: (a) L. H. Phun, J. Aponte-Guzman, S.
France. Angew. Chem., Int. Ed. 2012, 51, 3198; (b) X. Cui, X. Xu, L.
Wojtas, M. M. Kim, X. P. Zhang. J. Am. Chem. Soc. 2012, 134, 19981.
6 For the selected examples, see: (a) D. F. Chen, F. Zhao, Y. Hu, L. Z.
Gong. Angew. Chem., Int. Ed. 2014, 53, 10763; (b) S. Muthusamy, C.
Gunanthan, S. A. Babu, E. Suresh, P. Dastidar. Chem. Commun. 2002,
824; (c) H. L. Wang, Z. Li, G. W. Wang, S. D. Yang. Chem. Commun.
2011, 47, 11336; (d) F. Ye, S. Qu, L. Zhou, C. Peng, C. Wang, J.
Cheng, M. L. Hossain, Y. Liu, Y. Zhang, Z. X. Wang, J. Wang. J. Am.
Chem. Soc. 2015, 137, 4435; (e) Z. Yu, B. Ma, M. Chen, H. H. Wu, L.
Liu, J. Zhang. J. Am. Chem. Soc. 2014, 136, 6904.
7 For the selected examples, see: (a) C. Wang, D. Xing, D. Wang, X. Wu,
W. Hu. J. Org. Chem. 2014, 79, 3909; (b) R. Kumar, D. Verma, S. M.
Mobin, I. N. N. Namboothirl. Org. Lett. 2012, 14, 4070; (c) S.
Muthusamy, C. Gunanathan, M. Nethaji. Synlett 2004, 4, 639.
8 (a) A. M. Jadhav, V. V. Pagar, R. S. Liu. Angew. Chem., Int. Ed. 2012,
51, 11809; (b) X. Qi, X. Xu, C. M. Park. Chem. Commun. 2012, 48,
3996.
afford
enamine
intermediate
E-1.
Finally,
protonolysis/intramocular cyclization cascade generated the
desired pyrrole product 3 and the active Rh catalyst.
1/2[Cp*RhCl2]2
Py
AgSbF6
AgCl
O
HN
N
A-1
NH
Ar
N
N
EtO2C
Ar
Cp*Rh(SbF6)2
F-1
1
-H2O
Ar
rate-limiting
protonolysis
C-H cleavage
CO2Et
Me
N
N
N
NH
Ar
Ar
N
Rh
B-1
C-1
Rh
3
Py
Ar
CO2Et
O
E-1
N
NH
Ar
CO2Et
1, 2-alkenyl shift
N
NH
Rh
O
Rh
O
Ar
CO2Et
D-1
2
N2
Figure 1. Possible Mechanism for the Transformation
9 M. P. Doyle, M. Yan, W. Hu, L. S. Gronenberg. J. Am. Chem. Soc.
2003, 125, 4692.
10 H. Qiu, M. Li, L. Q. Jiang, F. P. Lv, L. Zan, C. W. Zhai, M. P. Doyle,
W. H. Hu. Nat. Chem. 2012, 4, 733.
Conclusions
In conclusion, we have disclosed for the first time that -
dicarbonyl -Rh-carbene could cross-couple with -imino Csp3-
H bonds through migratory insertion process. This transformation
offered an efficient access to synthetically versatile
polysubstituted N-(2-pyridyl)pyrroles from readily available
ketoimines and -acyl diazocompounds with tolerance of a broad
range of functional groups. Further exploration about ligand-
assisted remote unactive Csp3-H functionzalization with
carbenoids is underway in our laboratory.
11 (a) W. W. Chan, S. F. Lo, Z. Zhou, W. Yu. J. Am. Chem. Soc. 2012,
134, 13565; (b) X. Yu, S. Yu, J. Xiao, B. Wan, X. W. Li. J. Org. Chem.
2013, 78, 5444; (c) Z. Shi, D. C. Koester, M. Boultadakis-Arapinis, F.
Glorious. J. Am. Chem. Soc. 2013, 135, 12204; (d) T. K. Hyster, K. E.
Ruhl, T. Rovis. J. Am. Chem. Soc. 2013, 135, 5364; (e) S. Yu, S. Liu,
Y. Lan, B. Wan, X. Li. J. Am. Chem. Soc. 2015, 137, 1623; (f) X. Yu,
S. Yu, J. Xiao, B. Wan, X. Li. J. Org. Chem. 2013, 78, 5444; (g) Y.
Xia, Z. Liu, S. Feng, Y. Zhang, J. Wang. J. Org. Chem. 2015, 80, 223.
12 Y. Wei, I. Deb, N. Yoshikai. J. Am. Chem. Soc. 2012, 134, 9098.
13 (a) S. J. Zhu, J. Dong, S. M. Fu, H. F. Jiang, W. Zeng. Org. Lett. 2011,
13, 4914; (b) Y. Luo, X. X. Lu, Y. Ye, Y. Guo, H. F. Jiang, W. Zeng.
Org. Lett. 2012, 14, 5640; (c) J. Y. Chen, X. X. Lu, W. Y. Lou, Y. Ye,
H. F. Jiang, W. Zeng. J. Org. Chem., 2012, 77, 8541; (d) S. J. Zhu, X.
X. Lu, Y. T. Luo, W. Zhang, H. F. Jiang, M. Yan, W. Zeng. Org. Lett.
2013, 15, 1440; (e) L. Dang, L. B. Liang, C. Qian, M. Q. Fu, T. M. Ma,
D. G. Xu, H. F. Jiang, W. Zeng. J. Org. Chem. 2014, 79, 769; (f) M. Y.
Li,; Y. Xie, Y. Ye, Y. Zou, H. F. Jiang, W. Zeng. Org. Lett. 2014, 16,
6232.
Acknowledgments
The authors thank the NSFC (No. 21372085) and the GNSF
(No. 10351064101000000) for financial support.
Notes and references
a School of Chemistry and Chemical Engineering, South China Unversity
14 (a) Y. Xie, T. Chen, S. M. Fu, X. S. Li, Y. Deng, H. F. Jiang, W. Zeng.
Chem. Commun. 2014, 50, 10699; (b) Y. Xie, T. Chen, S. M. Fu, H. F.
Jiang, W. Zeng. Chem. Commun. 2015, 51, 9377.
of Technology, Guangzhou, 510641, China.
E-mail: zengwei@scut.edu.cn
b Analysis and Testing Center, Jinan University, Guangzhou 510632,
China
15 For selected examples, see: (a) J. Guillon, P. Grellier, M. Labaied, P.
Sonnet, J. M. Leger, R. Deprez-Poulain, I. Forfar-bares, P. Dallemagne,
N. Lemaitre, F. Pehourcq, J. Rochette, C. Sergneraert, C. Jarry, J. Med.
Chem. 2004, 47, 1997; (b) G. Campiani, E. Morelli, M. Fabbrini, V.
Nacci, G. Greco, E. Novellino, A. Ramunno, G. maga, S. Spadari, G.
Caliendo, A. Bergamini, E. Faggioli, I. Uccella, F. Bolacchi, S. Marini,
M. Coletta, A. nacca, S. Caccia, J. Med. Chem. 1999, 42, 4462; (c) S.
Butini, M. Brindisi, S. Cosconati, L. Marinelli, G. Borrelli, S. S.
Coccone, A. Ramunno, G. Campiani, E. Novellino, S. Zanoli, A.
Samuele, G. Giorgi, A. Bergamini, M. D. Mattia, S. Lalli, B. Galletti,
S. Gemma, G. Maga, J. Med. Chem. 2009, 52, 1224.
† Electronic Supplementary Information (ESI) available: Experimental
details and compound data, including 1H NMR spectrum and X-ray
crystallographic data of 3r and 3y. See DOI: 10.1039/c000000x/ :
1 For selected reviews, see: (a) M. Pena-Lopez, A. Rosas-Hernandez, M.
Beller. Angew. Chem., Int. Ed. 2015, 54, 5006; (b) G. C. Micalizio, S.
B. Hale. Acc. Chem. Res. 2015, 48, 663; (c) S. Roscales, A. G. Csaky.
Chem. Soc. Rev. 2014, 43, 8215; (d) S. A. Girard, T. Knauber, C. J. Li.
Angew. Chem., Int. Ed. 2014, 53, 74; (e) M. Garcia-Melchor, A. A. C.
Braga, A. Lledos, G. Ujaque, F. Maseras. Acc. Chem. Res. 2013, 46,
2626.
2 For the selected reviews and examples, see: (a) D. Gillingham, N. Fei.
Chem. Soc. Rev. 2013, 42, 4918; (b) H. M. L. Davies, J. R. Denton.
Chem. Soc. Rev. 2009, 38, 3061; (c) H. M. L. Davies, J. R. Manning.
Nature 2008, 451, 417; (d) V. F. Ferreira. Curr. Org. Chem. 2007, 11,
177.
16 α-Substituted aryl ketoimines such as N-(1-phenylpropylidene)-2-
pyridinamine could not provide the desired pyrroles.
17 (a) A. Padwa, B. H. Norman. J. Org. Chem. 1990, 55, 4801; (b) C. Y.
Chen, D. F. Bocian, J. S. Lindsey. J. Org. Chem. 2014, 79, 1001; (c)
W. Debrouwer, T. S. A. Heugebaert, C. V. Stevens. J. Org. Chem.
2014, 79, 4322; (d) A. S. Demir, S. Tural. Tetrahedron 2007, 63, 4156.
18 For the 1H NMR spectrum of d-1a, please see ESI.
3 For the selected examples, see: (a) H. Y. Thu, G. S. M. Tong, J. S.
Huang, S. L. F. Chan, Q. H. Deng, C. M. Che. Angew. Chem., Int. Ed.
4
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