Gold(I)-Catalyzed Dimerization of 3-Diazooxindoles towards Isoindigos

Article abstract of DOI:10.1002/ejoc.201800809

A gold-catalyzed dimerization of 3-diazooxindoles was developed, delivering isoindigos as products. The reaction shows broad substrate scope and functional group tolerance by affording various substituted isoindigos. Moreover, the method also exhibited high efficiency on a gram-scale reaction.

Full text of DOI:10.1002/ejoc.201800809

A Journal of
Accepted Article
Title: Gold(I)-Catalyzed Dimerization of 3-Diazooxindoles Towards
Isoindigos
Authors: Xinbo Yao, Tao Wang, and Zunting Zhang
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201800809
Link to VoR: http://dx.doi.org/10.1002/ejoc.201800809
Supported by

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
Gold(I)-Catalyzed Dimerization of 3-Diazooxindoles Towards
Isoindigos
Xinbo Yao,[a] Tao Wang,*[a] and Zunting Zhang*[a]
Abstract: A gold-catalyzed dimerization of 3-diazooxindoles was
developed, delivering isoindigos as products. The reaction shows
broad substrate scope and functional group tolerance by affording
various substituted isoindigos. Moreover, the method also exhibited
high efficiency on a gram-scale reaction.
stereoselective gold-catalyzed coupling of diazo reagents and
fluorinated enol silyl ethers, delivering tetrasubstituted alkenes
as products.[9] To make our efforts on gold catalysis,[10] in 2015
we reported the gold-catalyzed synthesis of 2,5-dihydrofurans
via a formal [4 + 1] cycloaddition of α-diazoesters and propargyl
alcohols (Scheme 1a).[10a] The reaction worked well for aryl
diazoacetates, however, no expected spiro dihydrofuran product
was obtained when diazooxindole was subjected to the standard
conditions. Instead, a dimerization product, isoindigo, was
obtained in moderate yield (Scheme 1a). As literature present,
isoindigos play important roles in both pharmaceuticals and
material science. For example, meisoindigo (Figure 1) shows
anti-angiogenesis effects on chronic myelogenous leukemia in
vitro.[11] Natura is proved to be an cyclin-dependent kinases
(CDKs) inhibitor.[12] In addition, isoindigo-based materials were
also wildly used in organic solar cells (OSCs) and field-effect
transistors (FETs).[13] For an example, Figure 1 shows the first
application of isoindigo-based materials ((iI)TT2) to OPVs.[14] The
importance of isoindigos in pharmaceuticals and material
science inspired us to investigate the dimerization of
diazooxindoles. Herein, we want to report the preparation of
isoindigos via the dimerization of 3-diazooxindoles under gold
catalysis.
Introduction
Benefited from the explosive development of gold catalysis[1] in
the last decade, a variety of transformations based on diazo
compounds[2] has been achieved under gold catalysis. There
have been reports on the gold-catalyzed cycloaddition,[3]
cyclopropenation,[4] cyclopropanation,[5] C−H insertion[6] and
O−H insertion[7] of diazo compounds. Recent results showed the
advantage of gold catalysis in the carbene transfer from diazo
compounds. For example, Zhang and Liu reported the gold-
catalyzed chemoselective aryl C-H insertion over O-H insertion
Figure 1. Representative examples of isoindigos in pharmaceuticals and
organic photovoltaics (OPVs).
Scheme 1. Our previous work and this exploration.
of phenol derivatives with diazo compounds.[6d] Sun and co-
workers made great efforts on the gold-catalyzed coupling of
diazo compounds.[8] Very recently, Zhou reported the
Results and Discussion
In our previous work, it was found that unprotected 3-
diazooxindole completely decomposed in the presence of a gold
catalyst while 1-benzyl-3-diazoindolin-2-one (1a) afforded 2a in
45% yield (Scheme 1a).[10a] Based on this result, we optimized
the reaction conditions for the dimerization by using 1a as model
substrate. The results were summarized in Table 1. Firstly, a
variety of gold catalyst was examined. A gold catalyst with a
[a]
Ms.C X. Yao, Dr. T. Wang, Prof. Dr. Z. Zhang
Key Laboratory of Applied Surface and Colloid Chemistry, Ministry
of Education, School of Chemistry and Chemical Engineering,
Shaanxi Normal University,
No.620 West Chang’an Avenue, Xi’an 710119, China
E-mail: chemtao@snnu.edu.cn; zhangzunting@sina.com
http://www.chem.snnu.edu.cn/teach_show.aspx?id=1563
steric
bulk
ligand,
2-dicyclohexylphosphino-2',4',6'-
triisopropylbiphenyl (XPhos), was found highly efficiency for the
dimerization of 1a, delivering isoindigo 2a in 60% isolated yield
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
dimerization. [d] 2.5 mol % of BinapAu2Cl2 was added in combination
with 5 mol % of AgNTf2. [e] The conversion rate of 1a was less than
90%.
Table 1. Reaction Optimization. [a]
(Table
Bis(diphenylphosphino)-1,1'-binaphthalene),
C6H3O)3PAuCl and IPrAuCl [IPr
1,
entry
4).
BinapAu2Cl2
(Binap
=
=
2,2'-
(2,4-tBu-
1,3-bis(2,6-
Entry
1
Catalyst (5 mol %)
PPh3AuCl/AgNTf2
JohnPhosAuCl/AgNTf2
SPhosAuCl/AgNTf2
XPhosAuCl/AgNTf2
BinapAu2Cl2/AgNTf2
(2,4-tBu-PhO)3PAuCl/AgNTf2
IPrAuCl/AgNTf2
XPhosAuCl/AgSbF6
XPhosAuCl/AgOTf
XPhosAuCl/AgBF4
XPhosAuCl/AgPF6
XPhosAuCl/AgPF6
XPhosAuCl/AgPF6
XPhosAuCl/AgPF6
XPhosAuCl/AgPF6
AgNTf2
Solvent/Time
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCM/0.5 h
DCE/0.5 h
Toluene/0.5 h
THF/2 h
Yield[b]
14%[c]
30%[c]
30%[c]
60%[c]
15%[c]
35%[c]
41%[c]
69%[c]
60%[c]
65%[c]
80%
diisopropylphenyl)imidazol-2-ylidene)] were also tested together
with AgNTf2 (entries 5-7), respectively. However, no
improvement was observed for the dimerization. A main reason
accounting for the low yield was the decomposition of 1a. By
replacing AgNTf2 with other silver salts to active the gold catalyst
by chloride abstraction, the reaction was improved in some
degree.[15] For example, when XPhosAuCl was used in
combination with AgSbF6, the reaction afforded 2a in 69% yield
(entry 8). When AgPF6 was added to active XPhosAuCl, the
reaction was dramatically improved affording 2a in 80% yield
(entry 11). A subsequent solvent screening revealed that the use
of acetonitrile as solvent could further improved the
transformation by preventing 1a from decomposition (entry 15).
AgNTf2 was also capable of catalyzing this reaction, but only
gave 2a in 23% yield (entry 16). The addition of ligands (XPhos)
in a 1:1 ratio to AgNTf2 resulted in incompletely conversion of 1a,
delivering just trace amount of 2a (entry 17). Other Lewis acids
which were reported to be effective in the transformation of
diazo compounds were examined (entries 18-24). The use of
rhodium octanoate dimmer as catalyst also gave trace amount
of 2a due to the decomposition of 1a (entry 18). Copper salts
were also tested, among which Cu(OTf)2, Cu(CH3CN)4BF4 and
2
3
4
5[d]
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
66%
74%
73%
Cu(CH3CN)4PF4 exhibited
a
similarly catalytic efficiency,
CH3CN/6 h
DCM/0.5 h
DCM/12 h
DCM/12 h
DCM/12 h
DCM/2 h
84%
delivering 2a in moderate yields (entries 19-24).
23%[c]
trace[e]
trace[c]
45%[c]
NR
With the optimized conditions in hand, the scope of the
substrates was explored (Scheme 2). At first, the protecting
group on the nitrogen atom was explored. A methyl protected
substrate gave 2b in 75% yield, while a tosyl (Ts) protected
product 2c was obtained in only 56% yield. To our delight, when
a t-butyloxy carbonyl (Boc) group was installed to nitrogen atom,
the reaction worked smoothly affording 2d in quantitative yield
(98%). It was found that the existing of a Boc group dramatically
increase the solubility of both the starting material and the
product. In addition, as a protecting group, Boc is facile to be
installed and removed. When unprotected 3-diazooxindole was
subjected to the standard conditions, the corresponding
isoindigo (2e) was obtained in only 40% yield. The substrate
suffered from decomposition, resulting the poor yield of the
product. Various of Boc protected 3-diazooxindoles were
prepared and was subjected to the standard conditions to further
explore the scope of the dimerization reaction. Firstly, a variety
of substituents was introduced to the 5-position of 3-
diazooxindole. Under standard conditions, the substrates
afforded corresponding isoindigos in good to excellent yields (2f-
2l). It was found that the substrates with electron-donating group
in their 5-positions gave corresponding isoindigos in better yields
than those with electron-withdrawing groups (for example 2g Vs
AgNTf2/XPhos
[Rh(CH3(CH2)6CO2)2]2
Cu(OTf)2
Cu(acac)2
CuI
DCM/2 h
NR
Cu(CH3CN)4BF4
Cu(CH3CN)4PF6
CuCl2
DCM/4 h
45%[c]
43%[c]
NR
DCM/4 h
DCM/12 h
[a] Reaction conditions: For entries 1-15 and entry 17, 1a (49.9 mg, 0.2
mmol) was added to the stirring solution of the corresponding catalyst
(0.01 mmol) in 2 mL of solvent at room temperature. For entries 18-24
and entry 16, the corresponding catalyst (0.01 mmol) was added to the
solution of 1a (49.9 mg, 0.2 mmol) in 2 mL of dichloromethane. After 1a
was fully consumed (monitored by TLC) or the time mentioned in each
entry, the solvent was removed via rotary evaporation. The residue was
purified by column chromatography on silica gel (dichloromethane was
used as the eluting solvent) to afford 2a as product. [b] Yields of isolated
products. [c] The decomposition of 1a is the main competing process of
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
R'
O
N2
N
XPhosAuCl (5 mol %)/AgPF6 (5 mol %)
CH3CN, rt, 12 h
R
O
R
R
N
R'
N
O
R'
1
2
Me
N
Ts
N
Boc
N
H
N
O
O
O
O
O
O
O
O
N
N
N
N
Me
Ts
Boc
H
2b, 75%
2c, 56%[b]
2d, 98%
2e, 40%[b]
Boc
N
Boc
N
Boc
N
2f, R = OMe, 69%
2g, R = Me, 91%
2h, R = F, 67%
2I, R = Cl, 74%
2j, R = Br, 70%
2k, R = I, 75%
O
O
F
F
O
Cl
R
R
F
F
Cl
O
O
N
O
N
N
Boc
Boc
Boc
2l, R = NO2, 40%[b]
2n, 74%
2m, 53%[b]
R
Bn
Boc
N
N
2r, R = Me, 96%
2s, R = CF3, 98%
2t, R = F, 80%
O
O
N
R
2o, R = F, 96%
2p, R = Cl, 98%
2q, R = Br, 88%
2u, R = Cl, 64%[b]
R
O
O
N
2v, R = Br, 72%
Bn
Boc
R
Scheme 2. Reaction Scope for the Synthesis of isoindigos. [a] Unless otherwise noted, reactions were performed on 0.3 mmol scale in 3 mL of CH3CN with
[b]
XPhosAuCl (5 mol %) and AgPF6 (5 mol %) at room temperature for 12 h; the yields given are isolated yields. The decomposition of the corresponding 3-
diazooxindole resulted in the relatively lower yield of the product.
2l). 3-Diazooxindoles bearing substituents in 4-positions were
also explored, which afforded corresponding isoindigos in good
yields (2m and 2n). 2p and 2q are often used starting materials
for the preparation of isoindigo-based conjugated polymers,
which could be obtained in good to excellent yields via the
dimerization of corresponding 3-diazooxindoles under gold
catalysis. In case of 3-diazooxindoles bearing substituents in 7-
positions, because N-Boc protected substrates were difficult to
prepared, N-Bn protected substrates were explored. The
reactions worked well to deliver corresponding isoindigo
products in good to excellent yields (2r-2v).
Two different 3-diazooxindoles, 1g and 1h, were subjected
to the standard conditions (eq 1). By HPLC analysis, three
products were observed in a 1:2.9:2.8 ratio (2h:2hg:2g). A
cross-coupling product 2hg and a homocoupling product 2g
were found as main products. The result suggests that the
relatively electron-rich 3-diazooxindole 1g is prior to the
relatively electron-deficient 3-diazooxindole 1h to attack the
gold-carbenoid generated from 1g and 1h in the presence of a
gold catalyst. This result is consistent with previous
investigations of Davies[16] and Sun.[8a]
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
A gram-scale reaction of 1d afforded 2d in 88% yield when 5
mol % of catalyst was added. When the catalyst loading
decreased to 3 mol %, 2d was obtained in a slight lower yield
(eq 2). The Boc group was easily removed when 2d was
subjected to LiBr or HCl conditions. Especially when 2d was
treated with HCl in ethyl acetate (EA), 2e was obtained in nearly
quantitative yield (95%, eq 3).
(GK201703022) are greatly appreciated. We thank Xuetong Li
for reproducing the preparation of 2d, 2j and 2p (Scheme 2).
Keywords: gold catalysis • diazo compounds • dimerization •
isoindigo • coupling
[1]
For recent published reviews on gold catalysis, see: a) J. Xie, H. Jin, A.
S. K. Hashmi, Chem. Soc. Rev. 2017, 46, 5193-5203; b) Z. Zheng, Z.
Wang, Y. Wang, L. Zhang, Chem. Soc. Rev. 2016, 45, 4448-4458; c) M.
Asiri, A. S. K. Hashmi, Chem. Soc. Rev. 2016, 45, 4471-4503; d) F.
Pan, C. Shu, L.-W. Ye, Org. Biomol. Chem. 2016, 14, 9456-9465; e) L.
Liu, J. Zhang, Chem. Soc. Rev. 2016, 45, 506-516; f) M. R. Fructos, M.
M. Díaz-Requejo, P. J. Pérez, Chem. Commun. 2016, 52, 7326-7335;
g) M. Jia, M. Bandini, ACS Catal. 2015, 5, 1638-1652; h) R. Dorel, A. M.
Echavarren, Chem. Rev. 2015, 115, 9028-9072; i) F. Wei, C. Song, Y.
Ma, L. Zhou, C.-H. Tung, Z. Xu, Sci. Bull. 2015, 60, 1479-1492; j) J. Xie,
C. Pan, A. Abdukader, C. Zhu, Chem. Soc. Rev. 2014, 43, 5245-5256;
k) A. Fürstner, Acc. Chem. Res. 2014, 47, 925-938; l) W. Yang, A. S. K.
Hashmi, Chem. Soc. Rev. 2014, 43, 2941-2955; m) L. Fensterbank, M.
Malacria, Acc. Chem. Res. 2014, 47, 953-965; n) L.-P. Liu, G. B.
Hammond, Chem. Soc. Rev. 2012, 41, 3129-3139; o) D. Garayalde, C.
Nevado, ACS Catal. 2012, 2, 1462-1479.
Boc
O
N
N2
XPhosAuCl/AgPF6
CH3CN, rt.
O
(2)
N
N
Boc
O
Boc
2d
1d
0.8177 g, 88% yield (5 mol % catalyst)
0.7489 g, 81% yield (3 mol % catalyst)
1.037 g (4 mmol)
Boc
H
O
O
N
N
Conditions
(3)
N
N
O
O
[2]
[3]
For recent published reviews on diazo compounds, see: a) Y. Xia, D.
Qiu, J. Wang, Chem. Rev. 2017, 117, 13810-13889; b) A. Ford, H. Miel,
A. Ring, C. N. Slattery, A. R. Maguire, M. A. McKervey, Chem. Rev.
2015, 115, 9981-10080; c) M. Marinozzi, F. Pertusati, M. Serpi, Chem.
Rev. 2016, 116, 13991-14055; d) N. R. Candeias, R. Paterna, P. M. P.
Gois, Chem. Rev. 2016, 116, 2937-2981.
Boc
H
2d
2e
Condition A: LiBr (3 equiv), CH3CN, 65 oC, 5 h, 76% yield
Condition B: HCl, EA, rt, 6 h, 95% yield
a) Q.-Q. Cheng, Y. Deng, M. Lankelma, M. P. Doyle, Chem. Soc. Rev.
2017, 46, 5425-5443; b) B. S. Kale, H.-F. Lee, R.-S. Liu, Adv. Synth.
Catal. 2017, 359, 402 -409; c) S. Liu, P. Yang, S. Peng, C. Zhu, S. Cao,
J. Li, J. Sun, Chem. Commun. 2017, 53, 1152-1155; d) C. Zhu, G. Xu, J.
Sun, Angew. Chem. 2016, 128, 12046-12050; Angew. Chem. Int. Ed.
2016, 55, 11867-11871; e) E. Lopez, J. Gonzalez, L. A. Lopez, Adv.
Synth. Catal. 2016, 358, 1428-1432; f) G. Lonzi, L. A. López, Adv.
Synth. Catal. 2013, 355, 1948-1954; g) S. K. Pawar, C.-D. Wang, S.
Bhunia, A. M. Jadhav, R.-S. Liu, Angew. Chem. 2013, 125, 7707-7711;
Angew. Chem. Int. Ed. 2013, 52, 7559-7563; h) V. V. Pagar, A. P.
Jadhav, R.-S. Liu, J. Am. Chem. Soc. 2011, 133, 20728-20731.
J. F. Briones, H. M. L. Davies, J. Am. Chem. Soc. 2012, 134, 11916-
11919.
Conclusions
In conclusion, a highly efficient gold-catalyzed dimerization of 3-
diazooxindoles was developed. The reaction shows its
advantage in rapid construction of various substituted isoindigos
in gram-scale under mild conditions. Taking the importance of
isoindigos into account, the reaction shows its potent application
in both pharmaceuticals and material science.
[4]
[5]
a) M. R. Fructos, T. R. Belderrain, P. de Fremont, N. M. Scott, S. P.
Nolan, M. M. Diaz-Requejo, P. J. Perez, Angew. Chem. 2005, 117,
5418-5422; Angew. Chem. Int. Ed. 2005, 44, 5284-5288; b) Z.-Y. Cao,
X. Wang, C. Tan, X.-L. Zhao, J. Zhou, K. Ding, J. Am. Chem. Soc. 2013,
135, 8197-8200.
Experimental Section
General procedure for the gold-catalyzed dimerization of 3-
Diazooxindoles
[6]
a) K. Liu, G. Xu, J. Sun, Chem. Sci. 2018, 9, 634-639; b) B. Ma, J. Wu,
L. Liu, J. Zhang, Chem. Commun. 2017, 53, 10164-10167; c) B. Ma, Z.
Chu, B. Huang, Z. Liu, L. Liu, J. Zhang, Angew. Chem. 2017, 129,
2793-2797; Angew. Chem. Int. Ed. 2017, 56, 2749-2753; d) Z. Yu, H.
Qiu, L. Liu, J. Zhang, Chem. Commun. 2016, 52, 2257-2260; e) Z. Yu,
B. Ma, M. Chen, H.-H. Wu, L. Liu, J. Zhang, J. Am. Chem. Soc. 2014,
136, 6904-6907; f) Y. Xi, Y. Su, Z. Yu, B. Dong, E. J. McClain, Y. Lan,
X. Shi, Angew. Chem. 2014, 126, 9975-9979; Angew. Chem. Int. Ed.
2014, 53, 9817-9821; g) F. Zhao, N. Li, T. Zhang, Z.-Y. Han, S.-W. Luo,
L.-Z. Gong, Angew. Chem. 2017, 129, 3295-3299; Angew. Chem. Int.
Ed. 2017, 56, 3247-3251.
3-Diazooxindole (0.3 mmol) was added successively to
a stirring
suspension of XPhosAuCl (10.6 mg, 15.0 µmol) and AgPF6 (3.8 mg, 15.0
µmol) in acetonitrile (3.0 mL) at room temperature. The solution was then
stirred at room temperature for 12 hours. After evaporation, the residue
was purified by column chromatography on silica gel (dichloromethane
was used as the eluting solvent) affording the desired product.
(E)-1,1'-Dibenzyl-[3,3'-biindolinylidene]-2,2'-dione (2a)[17] : Yield: 75%, 1H
NMR (CDCl3, 400 MHz): δ = 9.23 (d, 2 H, J = 7.8 Hz), 7.33-7.25 (m, 12
H), 7.04 (t, 2 H, J = 7.8 Hz), 6.71 (d, 2 H, J = 7.8 Hz), 5.02 (s, 4 H) ppm.
[7]
[8]
a) G. Xu, K. Liu, Z. Dai, J. Sun, Org. Biomol. Chem. 2017, 15, 11, 2345-
2348; b) D. Huang, G. Xu, S. Peng, J. Sun, Chem. Commun. 2017, 53,
3197-3200; c) L. Ricard, F. Gagosz, Organometallics, 2007, 26, 4704-
4707.
Acknowledgements
Financial support by the National Natural Science Foundation of
China (21502110, 21542002), the 111 Project (B14041) and the
Fundamental Research Funds for the Central Universities
a) D. Zhang, G. Xu, D. Ding, C. Zhu, J. Li, J. Sun, Angew. Chem. 2014,
126, 11250-11254; Angew. Chem. Int. Ed. 2014, 53, 11070-11074; b)
G. Xu, C. Zhu, W. Gu, J. Li, J. Sun, Angew. Chem. 2015, 127, 897-901;
Angew. Chem. Int. Ed. 2015, 54, 883-887; c) P. Liu; J. Sun, Org. Lett.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
2017, 19, 3482-3485; d) C. Zhu, G. Xu, K. Liu, L. Qiu, S. Peng, J. Sun,
Chem. Commun. 2015, 51, 12768-12770.
[13] for reviews, please see: a) T. Lei, J.-Y. Wang, J. Pei, Acc. Chem. Res.
2014, 47, 1117-1126; b) R. Stalder, J. Mei, K. R. Graham, L. A. Estrada,
J. R. Reynolds, Chem. Mater. 2014, 26, 664-678.
[9]
F.-M. Liao, Z.-Y. Cao, J.-S. Yu, J. Zhou, Angew. Chem. 2017, 129,
2499-2503; Angew. Chem. Int. Ed. 2017, 56, 2459-2463.
a) J. Wang, X. Yao, T. Wang, J. Han, J. Zhang, X. Zhang, P. Wang, Z.
Zhang, Org. Lett. 2015, 17, 5124-5127; b) X. Yao, T. Wang, X. Zhang,
P. Wang, B. Zhang, J. Wei, Z. Zhang, Adv. Synth. Catal. 2016, 358,
1534-1539; c) B. Zhang, T. Wang, Z. Zhang, J. Org. Chem. 2017, 82,
11644-11654.
[14] J. Mei, K. R. Graham, R. Stalder, J. R. Reynolds, Org. Lett. 2010, 12,
660-663.
[10]
[15]
a) D. Wang, R. Cai, S. Sharma, J. Jirak, S. K. Thummanapelli, N. G.
Akhmedov, H. Zhang, X. Liu, J. L. Petersen, X. Shi, J. Am. Chem. Soc.
2012, 134, 9012-9019; b) A. Homs, I. Escofet, A. M. Echavarren, Org.
Lett. 2013, 15, 5782-5785
[11] a) X. M. Liu, L. G. Wung, H. Y. Li, X. I. Ji, Biochem. Pharmacol. 1996,
51, 1545-1551; b) Z. Xiao, Y. Hao, B. Liu, L. Qian, Leukocyte Lymph.
2002, 43, 1763-1768.
[16] J. H. Hansen, B. T. Parr, P. Pelphrey, Q. Jin, J. Autschbach, H. M. L.
Davies, Angew. Chem. 2011, 123, 2592-2596; Angew. Chem. Int. Ed.
2011, 50, 2544-2548.
[12]
a) F. Bouchikhi, F. Anizon, P. Moreau, Eur. J. Med. Chem. 2008, 43,
755-762; b) X. K. Wee, W. K. Yeo, B. Zhang, V. Tan, K. M. Lim, T. E.
Tay, M. L. Go, Bioorg. Med. Chem. 2009, 17, 7562-7571.
[17]
G. Li, G. Zhou, D. Zhang-Negrerie, Y. Du, J. Huang, K. Zhao, Adv.
Synth. Catal. 2016, 358, 3534-3540.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201800809
European Journal of Organic Chemistry
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Gold Catalysis
Xinbo Yao, Tao Wang,* and Zunting
Zhang*
Page No. – Page No.
Gold(I)-Catalyzed Dimerization of 3-
Diazooxindoles Towards Isoindigos
Isoindigos were prepared via a gold-catalyzed dimerization of 3-diazooxindoles.
Besides broad substrate scope and functional group tolerance, the reaction also
exhibited high efficiency on a gram-scale reaction.
This article is protected by copyright. All rights reserved.