Synthesis of 2-(3-Arylallylidene)-3-oxindoles via Dirhodium(II)-Catalyzed Reaction of 3-Diazoindolin-2-imines with 1-Aryl-Substituted Allylic Alcohols and Computational Insights

Article abstract of DOI:10.1002/adsc.201901160

A straightforward approach for the synthesis of 2-(3-arylallylidene)-3-oxindoles has been achieved by the dirhodium(II)-catalyzed reaction of 3-diazoindolin-2-imines with 1-aryl-substituted allylic alcohols. This protocol employs easily accessible feedsto

Full text of DOI:10.1002/adsc.201901160

Title: Synthesis of 2-(3-Arylallylidene)-3-oxindoles via Dirhodium(II)-
Catalyzed Reaction of 3-Diazoindolin-2-imines with 1-Aryl-
Substituted Allylic Alcohols and Computational Insights
Authors: Ke Gao, Luyao Kou, Rui Fu, and Xiaoguang Bao
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: Adv. Synth. Catal. 10.1002/adsc.201901160
Link to VoR: http://dx.doi.org/10.1002/adsc.201901160

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Synthesis of 2-(3-Arylallylidene)-3-oxindoles via Dirhodium(II)-
Catalyzed Reaction of 3-Diazoindolin-2-imines with 1-Aryl-
Substituted Allylic Alcohols and Computational Insights
Ke Gao, Luyao Kou, Rui Fu, Xiaoguang Bao*
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P. R. of China
E-mail: xgbao@suda.edu.cn
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
imines to react with aryl imidates through Rh(III)-
catalyzed C−H activation and C−C/C−N coupling
processes. Moreover, Jiang’s group[7] realized an
efficient copper-catalyzed P−H insertions of α-imino
carbenes using 3-diazoindolin-2-imines as carbene
precursors.
Abstract. A straightforward approach for the synthesis
of 2-(3-arylallylidene)-3-oxindoles has been achieved
by the dirhodium(II)-catalyzed reaction of 3-
diazoindolin-2-imines with 1-aryl-substituted allylic
alcohols. This protocol employs easily accessible
feedstocks to produce oxindole derivatives, which might
be applicable in the dye industry. DFT calculations were
carried out to gain a mechanistic insight into the
reaction.
In particular, 2-(3-arylallylidene)-3-oxindoles,
being important oxindole derivatives present in
merocyanine dyes, are often applied in the dye
industry.[8] The reported methodology to construct 2-
allylidene-3-oxindoles usually employs indolin-3-
one as feedstock (Scheme 1).[9,10] Nevertheless, the
development of the synthetic approach in a more
efficient manner with readily available reagents is
still desirable. Inspired by the chemistry of 3-
diazoindolin-2-imine, herein we report a convenient
approach to synthesize 2-(3-arylallylidene)-3-
oxindoles via the Rh(II)2-catalyzed reaction of 3-
diazoindolin-2-imine with 1-aryl-substituted allylic
alcohols, which may undergo sequential hydroxyl
addition, Claisen rearrangement,[11] and the
elimination of TsNH2[5b] to finally afford the desired
product.
Keywords: Rhodium catalysis; α-Imino carbene;
Oxindole; DFT calculation.
Indoline and oxindole skeletons exist widely in
natural products, bioactive molecules, and
industrially useful compounds.[1] Thus, significant
research attention has been devoted to developing
new synthetic methods to functionalize indole
scaffolds in a concise and efficient manner.[2]
Recently, the employment of 3-diazoindolin-2-imine,
which can be produced by direct 1,3-dipolar
cycloaddition of indoles with tosyl azide, has
emerged as a powerful tool to synthesize indole
derivatives via transition metal carbene chemistry. In
comparison with diazo compounds being commonly
employed as precursors to generate transition metal
carbene intermediates,[3] using 3-diazoindolin-2-
imine as precursor can lead to the formation of α-
imino transition metal carbenoid, which could further
convert to N-containing heterocycles with appropriate
nucleophiles. For instance, Wang and co-workers[4]
reported that 3-diazoindolin-2-imines could be easily
transferred to α-imino rhodium carbene intermediates
in the presence of appropriate rhodium catalyst and
subsequently react with alkynes, furans, indoles, and
others, enabling efficient construction of the
molecular complexity for cyclic compounds. Lee et
al.[5] described that 3-diazoindolin-2-imines could be
employed as rhodium carbene precursors to couple
with 1,3-dienes, azirines and sulfoximines. Li and co-
workers[6] successfully utilized 3-diazoindolin-2-
Scheme 1. Synthesis of 2-(3-arylallylidene)-3-oxindoles.
1
This article is protected by copyright. All rights reserved.

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
Initially, substrates 3-diazoindolin-2-imine (1a)
(entries 13-17). Furthermore, other solvent, such as
DCE, PhCl, and THF, was screened. However, no
any improvement of the yield was obtained (entries
18-20). In addition, the yield was not enhanced when
the reaction was performed under nitrogen or argon
atmosphere (entries 21-22). The yield remained at 59%
when 1a was added in portions in three batches (entry
23). When palladium catalysts such as Pd(OAc)2,
[Pd(PPh3)2Cl2]2, PdCl2, and Pd(PPh3)4 were tried, the
yield was in the range of 28-41% (entry 24-27). No
desired product was detected when Cu(OTf)2,
[Cu(MeCN)4]BF4, AgOTf (entries 28-30), and other
catalysts[13] were used. It turned out that the
Rh2(OAc)4 catalyst shows the best performance in
driving this reaction.
and 1-(4-nitrophenyl)prop-2-en-1-ol (2a) were used
to obtain the optimized reaction conditions (Table 1).
A variety of dirhodium(II) catalysts were screened,
such as Rh2(TFA)4, Rh2(Oct)4, Rh2(OAc)4 and
Rh2(OPiv)4 in toluene at 85 °C for 6 hours. Among
these catalysts, Rh2(OAc)4 demonstrates better
efficiency in catalyzing this reaction to afford the
product 3aa (entries 1-4). The structure of 3aa was
confirmed by single-crystal X-ray diffraction
analysis.[12] Next, the temperature of the reaction was
screened (entries 5-8). However, the yield was not
Table 1. Optimization of the reaction conditions. [a]
Table 2. Substrate scope of 1-aryl-substituted allylic
alcohols.[a]
[a]
Reaction conditions: 1a (0.14 mmol, 1.4 equiv), 2a (0.1
mmol), catalyst (4 mol%), toluene (2 mL), isolated yield.
[b]
1a (0.28 mmol, 2.8 equiv), 2a (0.1 mmol). [c] 1a (0.5
mmol, 5 equiv), 2a (0.1 mmol). [d] Under N2 atmosphere. [e]
Under Argon atmosphere. [f] 1a was added in portions in
three batches. n. d. = not detected.
improved by either lowering or increasing
temperature. When reaction time was extended to 13
hours, the yield can be improved slightly to 54%.
However, further prolonging reaction time cannot
lead to higher yield (entries 9-10). Subsequently, the
amount of 1a was increased to 2.8 equiv, and the
yield can be improved slightly to 60%. Further
increasing 1a to 5 equiv, however, no any
improvement of the yield was found (entries 11-12).
Moreover, the addition of additives, such as base,
acid, and 4Å molecular sieves, was also tried.
Unfortunately, the yield was not improved further
[a]
Reaction conditions: 1a (0.28 mmol, 2.8 equiv) and 2
(0.1 mmol), toluene (2 mL), 4 mol% Rh2(OAc)4, 85 °C, 13
h. The yields were given in isolated yields.
With the optimal reaction conditions in hand, we
next explored the scope of the substrates. Firstly, the
allylic alcohols with various substituents at the aryl
moiety were examined (Table 2). When the nitro
group is present at the ortho-position of phenyl
moiety of the 1-aryl-substituted allylic alcohols (2b),
the yield of the desired product (3ab) is 66%. For
substrates
with
other
electron-withdrawing
2
This article is protected by copyright. All rights reserved.

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
Computational studies[15] were carried out to gain a
mechanistic insight into the dirhodium(II)-catalyzed
reaction of 1a with 2a (Figure 1). The reaction may
start with the coordination of 1a with the catalyst,
Rh2(OAc)4, to form an initial complex INT1.
Subsequently, the Rh(II)2-catalyzed decomposition of
INT1 via the extrusion of N2 to form the key
intermediate INT2 may occur and the transition state
was located as TS1. The predicted free energy barrier
is 16.1 kcal/mol. After the formation of INT2, the
intermolecular nucleophilic attack of substrate 2a to
the carbenoid moiety may follow. Both the additions
of hydroxyl group and alkenyl group of 2a to the
substituents at the para-position, such as, –F (2c,
57%), –Cl (2d, 50%), –Br (2e, 44%), and –CN (2f,
55%), moderate yields of the desired product were
obtained (3ab~3af). Substrates with multiple
substituents on the phenyl moiety were also
considered in this reaction. When halogen group is
present with the –NO2 group at the aryl moiety , such
as 5-fluoro-2-nitro- (2g), 4-fluoro-2-nitro- (2h), 5-
chloro-2-nitro- (2i), 5-bromo-2-nitro-(2j), 4-methoxy-
2-nitro- (2k) and 5-methoxy-2-nitro- (2l), moderate to
excellent yields (3ag~3al) were obtained. A gram-
scale reaction for the Rh(II)2-catalyzed reaction of 1a
with 2l was tested and 61% yield of 3al was
obtained.[14] For substrate 2m, in which no any
substituent is present on the phenyl ring, lower yield
of 3am (40%) was obtained. When the electron-
donating groups are attached to the phenyl moiety at
the para-position, such as para-tbutyl (3an, 42%),
para-ethyl (3ao, 36%), para-methyl (3ap, 31%) and
para-methoxy (3aq, 18%), the yields of the desired
product are not good. A possible reason responsible
for the low yield for substrate with electron-donating
group was provided based on computational studies
(see below). In addition, heterocyclic substituted
groups including thienyl (3ar) and naphthyl (3as)
were also tested, giving yields of 23% and 31%,
respectively. No desired product (3at) was observed
for 2-alkyl-substituted allylic alcohol.
Subsequently, the substrate scope of 3-
diazoindolin-2-imines (1) were investigated under the
optimal reaction conditions (Table 3). For 1b (R2=H;
R3=H), the Rh(II)2-catalyzed reaction with 2a is less
reactive and only 42% yield of the product (3ba) is
obtained. When 1c is employed (R2=Et and R3=H),
moderate yield of the desired product 3ca is obtained
by 56%. For 3-Diazoindolin-2-imine derivatives with
5-F and 5-Br substituted groups, moderate yields of
the corresponding products 3da, 3em and 3fm are
isolated in 43%, 55% and 51% yields, respectively.
Only 30% yield of the desired product (3cm) is
isolated when 1c is used to react with 2m.
carbene site
of
INT2
were considered.
Computational results show that the nucleophilic
addition of hydroxyl group via TS2 to form an ylide
intermediate INT5 is much more favorable than the
[2+1] cycloaddition with the alkenyl group (Figure 1).
Next, the formed INT5 could undergo intramolecular
proton migration from O atom to N atom via TS3 to
form intermediate INT6 and regenerate the catalyst.
It should be noteworthy that INT6 could undergo
Claisen rearrangement via TS4 to afford intermediate
INT7. The predicted free energy barrier for this step
is 24.9 kcal/mol. Finally, the elimination of TsNH2
from INT7 was considered, which might proceed in
the assistance of the rhodium(II) catalyst. The allylic
sp3 C-H bond could be activated by one of the acetate
groups of Rh2(OAc)4 to form INT9. The β-
elimination of the amido group of INT9 might follow
to yield the desired product 3aa and the formed
amido moiety is ready to be protonated from the
yielded acetic acid to form a complex INT10. The
catalyst can be regenerated after the release of TsNH2.
A plausible mechanistic pathway is shown in Scheme
2.
Computational results suggested that the rate-
limiting step for the formation of the desired product
is the allylic C−H bond activation of INT7, leading to
the elimination of TsNH2. When a substrate with
electro-withdrawing group at the para position of the
aryl moiety, such as 2a, was employed, it is relatively
advantageous for the formed complex INT8 to
undergo such C−H bond activation. The formed
allylic carbon centered anion could be stabilized by
the electro-withdrawing group at the para position of
the aryl moiety via conjugated effect. For the
substrate with electron-donating group, such as OMe
at the para position (2q), the corresponding C−H
bond activation, however, becomes more challenging
because of the destabilizing effect caused by the
electron-donating group to the formed carbon anion.
The calculated ΔGǂ of the rate-limiting step for 2q is
ca. 2 kcal/mol higher than that of 2a (Figure S2).
Thus, the 1-aryl-substituted allylic alcohols with
electron-donating group are less reactive than those
with electro-withdrawing group in the dirhodium(II)-
catalyzed reaction with 1a, which might account for,
at least partially, the low yield of the product 3aq.
Table 3. Substrate scope of 3-diazoindolin-2-imine. [a]
[a]
Reaction conditions: 1 (0.28 mmol, 2.8 equiv) and 2a
(0.1 mmol), toluene (2 mL), 4 mol% Rh2(OAc)4, 85 °C, 13
h. The yields were given in isolated yields.
3
This article is protected by copyright. All rights reserved.

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
Figure 1. Energy profile for the formation of the final product 3aa. Bond lengths are shown in Å.
1.0
(a)
CH3OH
CH3CN
0.8
0.6
0.4
0.2
0.0
EtOH
AcOEt
CH2Cl2
DMSO
300
400
500
600
700
Wavelength (nm)
1.0
0.8
0.6
0.4
0.2
0.0
(b)
CH3OH
CH3CN
Scheme 2. Proposed reaction mechanism.
EtOH
AcOEt
CH2Cl2
Subsequently, the photophysical properties of 3aa
were investigated by UV/vis and photoluminescence
(PL) spectroscopy at room temperature. The normalized
UV/vis absorption and emission spectra of 3aa in
various organic solvents are shown in Figure 2.
Compound 3aa features two low-energy absorption
bands centered at ~540 and ~380 nm, respectively. With
increasing solvent polarity, slight red-shift for the
absorption band centered at ca. 540 nm was observed.
Interestingly, 3aa exhibits solvent-dependent emission
spectrum. The emission bands of 3aa in DMSO
demonstrate two peaks centered at ca. 420 and 450 nm
while these emissive regions are not observed in AcOEt.
By contrast, a strong emission band of 3aa centered at
ca. 600 nm is found in AcOEt while such emission band
is absent in DMSO. The formation of an excimer, which
is more likely in less polar solvent, is tentatively
proposed to account for the solvent-dependent emission
spectrum. More details about the photophysical
properties of the synthesized compounds and potential
applications are currently being working on in our lab.
DMSO
400
450
500
550
600
650
700
Wavelength (nm)
Figure 2. The normalized UV/vis absorption (a) and
emission spectra (b) of 3aa (10-5 M) in various organic
solvents.
In conclusion, we disclosed a reaction of
dirhodium(II)-catalyzed 3-diazoindolin-2-imine with
1-aryl-substituted allylic alcohols to synthesize 2-(3-
arylallylidene)-3-oxindoles.
This
methodology
provides convenient approach from easily
a
accessible feedstock to synthesize oxindole
derivatives, which might be applicable in the dye
industry. DFT calculations suggest that the reaction
may proceed via the hydroxyl addition of allylic
alcohols to the formed Rh-carbenoid intermediate
4
This article is protected by copyright. All rights reserved.

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
followed by sequential Claisen rearrangement and the
elimination of TsNH2 to afford the desired product.
C. Wang, P. Lu, Y. Wang, Org. Lett. 2017, 19, 1630-
1633; h) Z. Du, Y. Xing, P. Lu, Y. Wang, Org. Lett.
2015, 17, 1192-1195; i) H. Ding, S. Bai, P. Lu, Y.
Wang, Org. Lett. 2017, 19, 4604-4607; j) J. Qi, Z.
Wang, B. Lang, P. Lu, Y. Wang, J. Org. Chem. 2017,
82, 12640-12646; k) G. Sheng, S. Ma, S. Bai, J. Mao, P.
Lu, Y. Wang, Chem.Commun. 2018, 54, 1529-1532; l)
Y. Zhou, Z. Li, F. Ma, C. Zhao, P. Lu, Y. Wang, J. Org.
Chem. 2019, 84, 6655-6668; m) J. Qian, Z. Lin, Z.
Wang, Z. Peng, L. Wu, P. Lu, Y. Wang, J. Org. Chem.
2019, 84, 6395-6404.
Experimental Section
General procedure
To a 10-mL oven-dried test tube was added in a magnetic
stirring stone. Then, 4.0 mol% Rh2(OAc)4, 0.28 mmol 3-
diazoindolin-2-imine compound 1, 0.1 mmol 1-aryl-
substituted allylic alcohols compound 2 and 2 mL
toluene were added. The reaction mixture was stirred for
13 hours at 85 °C. After the reaction finished, 2 mL EtOAc
was added. Then, adding 1g silicon gel and evaporating the
solvent in vacuo. The residue was purified by flash column
chromatography on silica gel. (gradient eluent: Petroleum
ether/EtOAc/ Dichloromethane = 30:1:1~8:1:1)
[5] a) S. Kim, H, Kim, K. Um, P. H. Lee, J. Org. Chem.
2017, 82, 9808-9815; b) G. Ko, J. Son, H. Kim, C.
Maeng, Y. Baek, B. Seo, K. Um, P. H. Lee, Adv. Synth.
Catal. 2017, 359, 3362-3370; c) Y. Baek, C. Maeng, H.
Kim, P. H. Lee, J. Org. Chem. 2018, 83, 2349-2360. d)
Y. Baek, Y. Kwon, C. Maeng, J. H. Lee, H. Hwang, K.
M. Lee, P. H. Lee, J. Org. Chem. 2019, 84, 3843-3852.
[6] H. Wang, L. Li, S.Yu, Y. Li, X. Li, Org. Lett. 2016, 18,
2914-2917.
Acknowledgements
We are grateful to the National Natural Science Foundation of
China (21642004) and the Priority Academic Program
Development of Jiangsu Higher Education Institutions (PAPD)
for financial support. We thank Prof. Bo Song for helpful
discussion on the photophysical results.
[7] L. Wang, Y. Wu, Y. Liu, H. Yang, X. Liu, J. Wang, X.
Li, J. Jiang, Org. Lett. 2017, 19, 782-785.
[8] a) F. Sieber, Photochem. Photobiol. 1987, 46, 1035-
1042; b) K. Sayama, K. Hara, N. Mori, M. Satsuki, S.
Suga, S. Tsukagoshi, Y. Abe, H. Sugihara, H. Arakawa,
Chem. Commun. 2000, 1173-1174; c) F. Würthner, S.
Yao, T. Debaerdemaeker, R. Wortmann, J. Am. Chem.
Soc. 2002, 124, 9431-9447; d) A. Kulinich, A.
Ishchenko, Russ. Chem. Rev. 2009, 78, 141-164; e) L.
Brooker, G. Keyes, R. Sprague, R. Vandyke, E. Vanlare,
G. Vanzandt, F. White, J. Am. Chem. Soc. 1951, 73,
5326-5332.
References
[1] a) J. Wilson, R. Kurukulasuriya, M. Reibarkh, M.
Reiter, A. Zwicker, K. Zhao, F. Zhang, R. Anand, V.
Colandrea, A. Cumiskey, A. Crespo, R. Duffy, B.
Murphy, K. Mitra,D. Johns, J. Duffy, P. Vachal, ACS
Med. Chem. Lett. 2016, 7, 261-265; b) W. Yang, Y.
Wang, A. Lai, J. Qiao, T. Wang, J. Hua, L. Price, H.
Shen, X. Chen, P. Wong, E. Crain, C. Watson, C.
Huang, D. Seiffert, R. Rehfuss, R. Wexler, P. Lam, J.
Med. Chem. 2014, 57, 6150-6164; c) J. F. M. da Silva,
S. J. Garden, A. C. Pinto, J. Braz. Chem. Soc. 2001, 12,
273-324; d) F. Zhou, Y. Liu, J. Zhou, Adv. Synth. Catal.
2010, 352, 1381-1407.
[2] a) S. Cacchi ， G. Fabrizi, Chem. Rev. 2005, 105,
2873-2920; b) L. Joucla, L. Djakovitch, Adv. Synth.
Catal. 2009, 351, 673-714; c) M. Bandini, A.
Eichholzer, Angew. Chem., Int. Ed. 2009, 48, 9608-
9644; d) G. Bartoli, G. Bencivenni, R. Dalpozzo, Chem.
Soc. Rev. 2010, 39, 4449-4465; e) R. Dalpozzo, Chem.
Soc. Rev. 2015, 44, 742-778; f) J. Leitch, Y. Bhonoah,
C. Frost, ACS Catal. 2017, 7, 5618-5627.
[9] A. Buzas, J. Merour, Synthesis. 1989, 6, 458-461.
[10] Z. Krasnaya, T. Stytsenko, Russ. Chem. Bull. 1987, 36,
748-754.
[11] a) A. Wetzel, F. Gagosz, Angew. Chem. Int. Ed. 2011,
50, 7354-7358; b) T. Miura, T. Tanaka, T. Biyajima, A.
Yada, M. Murakami, Angew. Chem. Int. Ed. 2013, 52,
3883-3886; c) J. Wood, G. Moniz, D. Pflum, B. Stoltz,
A. Holubec, H. Dietrich, J. Am. Chem. Soc. 1999, 121,
1748-1749; d) J. Wood, G. Moniz, Org. Lett., 1999, 1,
371-374; e) T. Miura, T. Tanaka, K. Matsumoto, M.
Murakami, Chem. Eur. J. 2014, 20, 16078-16082.
[12] CCDC-1947908 (3aa) contains the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge
[3] a) Q. Q. Cheng, Y. Deng, M. Lankelma, M. P. Doyle,
Chem. Soc. Rev. 2017, 46, 5425-5443; b) H. D. Khanal,
R. S. Thombal, S. M. B. Maezono, Y. R. Lee, Adv.
Synth. Catal. 2018, 360, 3185-3212; c) R. S. Thombal,
S. T. Kim, M. H. Baik, Y. R. Lee, Chem. Commun.
2019, 55, 2940—2943; d) H. D. Khanal, S. H. Kim, Y.
R. Lee, RSC Adv. 2016, 6, 58501-58510.
Crystallographic
www.ccdc.cam.ac.uk/data_request/cif.
[13] More catalysts screening was shown in Table S1.
Data
Centre
via
[14] The Rh(II)-catalyzed reaction of 1a with 2l could be
scaled up to gram scale with 61% yield of 3al.
[4] a) Y. Xing, G. Sheng, J. Wang, P. Lu, Y. Wang, Org.
Lett. 2014, 16, 1244-1247; b) G. Sheng, K. Huang, Z.
Chi, H. Ding, Y. Xing, P. Lu, Y. Wang, Org. Lett. 2014,
16, 5096-5099; c) C. Wang, H. Zhang, B. Lang, A. Ren,
P. Lu, Y. Wang, Org. Lett. 2015, 17, 4412-4415; d) G.
Sheng, K. Huang, S. Ma, J. Qian, P. Lu, Y. Wang,
Chem.Commun. 2015, 51, 11056-11059; e) J. Qian, G.
Sheng, K. Huang, S. Liu, P. Lu, Y. Wang, Org. Lett.
2016, 18, 3682-3685; f) Z. Li, X. Zhou, P. Lu, Y. Wang,
J. Org. Chem. 2016, 81, 9433-9437; g) B. Lang, H. Zhu,
[15] See Supporting Information for computational details.
[16] A distortion/interaction analysis for TS2 and TS2’
was performed to gain an insight on the chemo-
selectivity (Figure S1).
[17] Molecular orbitals of 3aa are shown in Figure S3.
5
This article is protected by copyright. All rights reserved.

10.1002/adsc.201901160
Advanced Synthesis & Catalysis
COMMUNICATION
Synthesis of 2-(3-Arylallylidene)-3-oxindoles via
Dirhodium(II)-Catalyzed Reaction
of
3-
Diazoindolin-2-imines with 1-Aryl-Substituted
Allylic Alcohols and Computational Insights
Adv. Synth. Catal. Year, Volume, Page – Page
Ke Gao, Luyao Kou, Rui Fu, Xiaoguang Bao*
6
This article is protected by copyright. All rights reserved.