Rhodium-Catalyzed Cascade Annulation of Benzimidates and Nitroalkenes for the Synthesis of Difunctionalized Indenes

Article abstract of DOI:10.1002/adsc.201900427

A facile and expeditious protocol for the synthesis of difunctionalized indenes from readily available benzimidates and nitroalkenes through rhodium-catalyzed C?H activation and cyclization is reported here. The transformation exhibits powerful reactivity

Full text of DOI:10.1002/adsc.201900427

Title: Rhodium-Catalyzed Cascade Annulation of Benzimidates and
Nitroalkenes for the Synthesis of Difunctionalized Indenes
Authors: Ningning Lv, Zhengkai Chen, Yue Liu, Zhanxiang Liu, and
Yuhong Zhang
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201900427
Link to VoR: http://dx.doi.org/10.1002/adsc.201900427

10.1002/adsc.201900427
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Rhodium-Catalyzed Cascade Annulation of Benzimidates and
Nitroalkenes for the Synthesis of Difunctionalized Indenes
Ningning Lv,a Zhengkai Chen,b Yue Liu,a Zhanxiang Liu,a Yuhong Zhang,*a,c
a
Department of Chemistry, ZJU-NHU United R&D Center, Zhejiang University, Hangzhou 310027, People’s Republic
of China
Fax: (+ 86)-571-8795-3244; e-mail: yhzhang@zju.edu.cn
Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, People’s Republic of China
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, People’s Republic of China
b
c
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))
for the assembly of difunctionalized indenones via
Rh-catalyzed multistep cascade reactions of
Abstract: A facile and expeditious protocol for the
synthesis of difunctionalized indenes from readily available
benzimidates and nitroalkenes through rhodium-catalyzed
C-H activation and cyclization is reported here. The
transformation exhibits powerful reactivity, tolerates a
large number of functional groups, and proceeds in
moderate to high yields under an ambient atmosphere,
providing a straightforward method to access structurally
diverse and valuable difunctionalized indene derivatives.
benzimidates and alkenes, which involves
a
completely different reaction pathway compared with
Liu’s work (Scheme 1c).[7c] Shortly after, we realized
the Co-catalyzed spirocycle synthesis between
benzimidates and maleimides by liberation of a
molecule of hydrogen, avoiding the using of external
stoichiometric oxidants (Scheme 1d).[7d] It is found
that benzimidate could be applied as a powerful
directing group, which can reacts with different
alkene substrates through different reaction processes
to obtain a series of useful heterocycles. Inspired by
these instructive works, we envisaged that we could
use nitroalkenes as the coupling partners to enable
novel heterocycle synthesis (Scheme 1e).
Keywords: indene synthesis; cascade annulation; rhodium-
catalyzed; C-H activation; arenes
In the past few decades, transition-metal-catalyzed
directed C-H functionalization reactions have been
applied as an attractive and powerful strategy for the
synthesis of complex and useful molecules without
preactivation of starting materials.[1] In most cases, a
directing group is usually necessary to ensure the
reactivity and selectivity of the transformations.[2]
Therefore, numerous directing groups have been
successfully exploited to realize diverse C-H
activation reactions.[3] Among these transformations,
further removal of the directing groups is inevitable
after completion of the reaction. To streamline the
reaction process, the employment of traceless[4] or
transient directing groups[5] has drawn great attention
and been applied as a versatile tool to assemble
various useful products.
Benzimidate, as a powerful traceless directing
group,[6] has been frequently used for the synthesis of
structurally diverse heterocycles through reacting
with diverse coupling partners,[6] especially with
different kinds of alkenes.[7] In 2016, Liu and co-
workers demonstrated that ruthenium-catalyzed
annulation of benzimidates and acrylates can
construct the lactam derivatives (Scheme 1a).[7a] Later,
Ackermann and co-workers reported the cascade
C−H/N−H allylation of aryl imidates in the presence
of low-cost cobalt(III) catalyst (Scheme 1b).[7b]
Recently, our group disclosed an efficient approach
Scheme 1. Benzimidates reacting with different alkene
substrates.
Nitroalkenes are valuable and commonly used
synthons, which can react with a broad range of
different nucleophiles and employed as dienophiles in
1
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10.1002/adsc.201900427
Advanced Synthesis & Catalysis
Diels−Alder reactions.[8] However, applications of
substituted nitroalkenes in transition-metal-catalyzed
C-H activation reactions have been rarely
reported.[9,10] Herein, we communicate the first
example of Rh(III)-catalyzed C-H activation and
cascade annulation of benzimidates and nitroalkenes
for the formation of difunctionalized indenes, which
constitute a kind of important synthetic intermediates
and biologically active molecules.[11]
(Table 1, entry 10). The effect of solvents upon the
reaction was examined and TFE (CF3CH2OH) was
regarded as the optimal solvent to deliver the target
product 3a in the highest yield (Table 1, entries 11-
13). Furthermore, lowering or raising the temperature
results in a decrease in the reaction yield; the optimal
temperature is 80 °C (see Supporting Information for
details). Other common metal catalysts in the field of
C-H functionalization, such as Pd(OAc)2, [Ru(p-
cymene)Cl2]2, and Cp*Co(CO)I2, appear to be invalid
in the reaction (Table 1, entries14-16). No reaction
was observed in the absence of [Cp*RhCl2]2 (Table 1,
entry 17). Additionally, reducing the loading of the
Rh catalyst resulted in lower reaction yield (see
Supporting Information for details).
Table 1. Optimization of Reaction Conditions.[a]
Entry
Additive
Solvent
Yield (%)[b]
Table 2. Scope of Benzimidates.
1
2
3
4
5
6
7
8
AgOAc
Cu(OAc)2
NaOAc
KOAc
CsOAc
CsOPiv
PhCOOK
AdCOOK
HOAc
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
THF
DCE
MeOH
CF3CH2OH
CF3CH2OH
CF3CH2OH
CF3CH2OH
41
nr
77
82
75
72
80
87
49
68
nr
nr
nr
nr
nr
9
10
11
12
13
14[c]
15[d]
16[e]
17[f]
-
AdCOOK
AdCOOK
AdCOOK
AdCOOK
AdCOOK
AdCOOK
AdCOOK
nr
nr
[a]
Reactions were carried out by using 1a (0.2 mmol), 2a
(0.3 mmol), [Cp*RhCl2]2 (5 mol %), additive (50 mol %),
solvent (2.0 mL), 80 °C, air, 16 h; AdCOOK = potassium
adamantanecarboxylate.
[a]
Reaction conditions:1 (0.2 mmol), 2a (0.3 mmol),
[b] Isolated yield; nr = no reaction.
[c] Pd(OAc)2 was used.
[Cp*RhCl2]2 (5 mol %), AdCOOK (50 mol %), TFE (2.0
ml), 80 °C, air, 16 h.
[d] [Ru(p-cymene)Cl2]2 was used.
[e] Cp*Co(CO)I2 was used.
[b] Isolated yield.
[c] 2 mmol scale.
[f] Without [Cp*RhCl2]2.
With the optimized reaction conditions in hand, we
investigated the generality and limitation of the
protocol with a variety of benzimidates as shown in
Table 2. The effect of diverse alkoxy groups in the
benzimidate was first tested, which demonstrated that
different alkoxy groups could all smoothly afford the
desired product 3a in good yield, and the ethoxy
group gave the superior result in 87% yield. The
structure of 3a was determined by single-crystal X-
ray diffraction analysis.[12] The reaction could be
performed on 2 mmol scale with no obvious
efficiency decrease. The transformation showed
broad substrate scope, as illustrated by the good
tolerance of a wide variety of functional groups, fur-
nishing the corresponding 2-nitro-3-aminoindene in
good to excellent yields (3b-3j). The survival of
halogen substituents provides the possibility for
further derivatization through various coupling
reactions. With regard to meta-OMe substituted
We initiated our investigation by choosing
benzimidate 1a and nitroalkene 2a as model
substrates to optimize the reaction conditions. To our
delight, the reaction proceeded smoothly upon the
commonly
used
catalytic
combination
of
[Cp*RhCl2]2/AgOAc in TFE and the desired 2-nitro-
3-aminoindene 3a was obtained in 41% yield (Table
1, entry 1). Then, different additives, including
Cu(OAc)2, NaOAc, KOAc, CsOAc, CsOPiv,
PhCOOK, AdCOOK and HOAc, were tested to
examine the reactivity of the transformation (Table 1,
entries 2-9). The result revealed that the above
additives could lead to the moderate to high
efficiency except for Cu(OAc)2, among which
AdCOOK was proven to be the best candidate to give
the desired product in 87% yield. Noteworthy was
that the reaction could also occur in the absence of
additive, affording the product 3a in acceptable yield
2
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10.1002/adsc.201900427
Advanced Synthesis & Catalysis
benzimidate, a mixture of regioselective products was
isolated with the ratio of 1.37:1 (3k, 3k’). However,
the single isomer was obtained in reasonable yield as
for meta-F substituted benzimidate (3l). Significantly,
the ethyl 2-naphthimidate could also serve as a viable
substrate in the reaction to afford the corresponding
product 3m in 66% yield. Indole-substituted imidate
was also compatible with the reaction system to give
the fused indene product 3n in a reasonable yield.
The reaction is sensitive to steric hindrance of the
benzimidate, as demonstrated by the fact that ortho-
substituted substrates did not participate in the
transformation (3o,p).
After examining the compatibility of the various
benzimidates, the generality of the present
transformation were further explored by the
employment of various alkenes (Table 3). A variety
of phenylsubstituted nitroalkenes proved to be
effective coupling partners under current catalytic
system. Different electron-withdrawing and electron-
donating substituents on the para or meta position of
the aromatic β-nitrostyrenes were well tolerated to
lead to the corresponding products in moderate to
Scheme 2. Mechanistic investigations.
To gain further insight into the reaction mechanism,
a set of control experiments were conducted as shown
in Scheme 2. The benzimidate 1a was subjected into
the standard conditions in the presence of 20 equiv
D2O, and the deuterium in corporation at the dual
ortho-carbon of substrate 1a was obtained at a level
of 26%, which suggest that the rhodium-catalyzed C-
H cleavage is reversible (Scheme 2, eq 1). The
excellent
yields
(4a-4j).
(E)-1-(2-nitrovinyl)
naphthalene can also couple with benzimidate under
the standard conditions, giving the mixture of double
bond migration products with the ratio of 5:1
(4k+4k’). With respect to aliphatic nitroalkenes, the
reaction proceeded well to provide the coupling
products in moderate to excellent yields (4l-4m). To
further extend the reaction scope, chalcone and ethyl
3-benzoylacrylate were examined in the current
reaction, and the corresponding products could be
yielded with moderate efficiency (4n-4o), greatly
underscoring the good compatibility and utility of the
protocol.
intermolecular
competition
experiment
of
electronically differentiated 1b and 1i with 2a was
performed, and the result revealed that the more
electron-donating benzimidate showed preferable
reactivity (Scheme 2, eq 2), implying C-H activation
probably occurs through an electrophilic aromatic
substitution (SEAr) process. It is observed that
electronic effect of nitroalkenes have no apparent
impact the reaction (Scheme 2, eq 3). The kinetic
isotope effect (KIE) value of 2.0 was observed from
the competitive reactions of 1a and 1a-D5 with 2a at a
low conversion (Scheme 2, eq 4). Moreover, a similar
value of 1.27 was obtained from two parallel
reactions (Scheme 2, eq 5). The above results
indicated that the cleavage of the C-H bond might not
be involved in the turnover-limiting step.
Table 3. Scope of alkenes.
Scheme 3. The proposed mechanism
[a]Reaction conditions:1a (0.2 mmol), 2 (0.3 mmol),
[Cp*RhCl2]2 (5 mol %), AdCOOK (50 mol %), TFE (2.0
ml), 80 °C, air, 16 h.
On the basis of the preliminary mechanistic studies
and previous literature reports,[7c,9a,9b,10a,10b] a plausible
3
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10.1002/adsc.201900427
Advanced Synthesis & Catalysis
reaction mechanism is proposed as outlined in
Wencel-Delord, F. Glorius, Angew. Chem., Int. Ed.
2012, 51, 10236–10254; Angew. Chem. 2012, 124,
10382–10401; e) C. S. Yeung, V. M. Dong, Chem. Rev.
2011, 111, 1215–1292; f) L. McMurray, F. O’Hara, M.
J. Gaunt, Chem. Soc. Rev. 2011, 40, 1885–1898; g) S.
H. Cho, J. Y. Kim, J. Kwak, S. Chang, Chem. Soc. Rev.
2011, 40, 5068–5083; h) I. A. I. Mkhalid, J. H. Barnard,
T. B. Marder, J. M. Murphy, J. F. Hartwig, Chem. Rev.
2010, 110, 890–931; i) T. Satoh, M. Miura, Chem. -Eur.
J. 2010, 16, 11212–11222.
Scheme
3.
Initially,
the
active
catalyst
Cp*Rh(AdCOO)2 A is generated through ligand
exchange between [Cp*RhCl2]2 and AdCOOK, which
underwent coordination with 1a and C-H metallation
process to form rhodacycle complex B with the loss
of AdCOOH. The H/D exchange experiment revealed
that the activation process is reversible (Scheme 2, eq
1). Then, the coordination of complex B and
nitroalkene gave a rhodium species C, which
occurred the migratory insertion into the nitroalkene
to afford intermediate D, followed by protonation
process, leading to alkylated product E. Subsequently,
the intramolecular ester condensation of E generated
the intermediate F, which eventually isomerized to
the thermodynamically more stable product 3a.
[2] For selected reviews: a) D. A. Colby, A. S. Tsai, R. G.
Bergman, J. A. Ellman, Acc. Chem. Res. 2012, 45,
814–825; b) P. B. Arockiam, C. Bruneau, P. H.
Dixneuf, Chem. Rev. 2012, 112, 5879–5918; c) Y.
Yang, J. Lan, J. You, Chem. Rev. 2017, 117, 8787–
8863; d) Y. Hu, B. Zhou, C. Wang, Acc. Chem.
Res. 2018, 51, 816–827.
In summary, we have developed a mild and
powerful approach for the assembly of structurally
diverse indenes scaffolds via rhodium(III)-catalyzed
C-H activation and annulation reaction from readily
available benzimidates and nitroalkenes. The
transformation showed broad substrate scope and
good functional group compatibility under mild
conditions. The reaction could be easily scaled up to
gram scale. This methodology may offer an efficient
tool for the synthesis of biologically or
pharmaceutically useful molecules. Further studies on
the synthesis of other valuable cyclic compounds via
C-H activation are underway.
[3] Z. Chen, B. Wang, J. Zhang, W. Yu, Z. Liu, Y. Zhang,
Org. Chem. Front. 2015, 2, 1107–1295.
[4] a) K. Ueura, T. Satoh, M. Miura, Org. Lett. 2007, 9,
1407–1409; b) Q. Lu, S. Gressies, S. Cembellin, F. J. R.
Klauck, C. G. Daniliuc, F. Glorius, Angew. Chem., Int.
Ed. 2017, 56, 12778–12782; Angew. Chem. 2017, 129,
12954–12958; c) A. Mandal, H. Sahoo, S. Dana, M.
Baidya, Org. Lett. 2017, 19, 4138–4141; d) C. Kuai, L.
Wang, B. Li, Z. Yang, X. Cui, Org. Lett. 2017, 19,
2102–2105; e) F. Xie, S. Yu, Z. Qi, X. Li, Angew.
Chem., Int. Ed. 2016, 55, 15351–15355; Angew. Chem.
2016, 128, 15577–15581; f) B. Li, H. Xu, H. Wang, B.
Wang, ACS Catal. 2016, 6, 3856–3862; g) L. Li, W. W.
Brennessel, W. D. Jones, J. Am. Chem. Soc. 2008, 130,
12414–12419; h) N. Guimond, C. Gouliaras, K. Fagnou,
J. Am. Chem. Soc. 2010, 132, 6908–6909; i) F. W.
Patureau, T. Besset, N. Kuhl, F. Glorius, J. Am. Chem.
Soc. 2011, 133, 2154–2156; j) K. Muralirajan, K.
Parthasarathy, C.-H. Cheng, Angew. Chem. Int. Ed.
2011, 50, 4169–4172; Angew. Chem. 2011, 123, 4255–
4258; k) B.-J. Li, H.-Y. Wang, Q.-L. Zhu, Z.-J. Shi,
Angew. Chem.,Int. Ed. 2012, 51, 3948–3952; Angew.
Chem. 2012, 124, 4014–4018; l) J. H. Kim, T. Gensch,
D. Zhao, L. Stegemann, C. A. Strassert, F. Glorius,
Angew. Chem. Int. Ed. 2015, 54, 10975–10979; Angew.
Chem. 2015, 127, 11126–11130.
Experimental Section
General procedure for
difunctionalized indenes
the synthesis of
To a test tube with a stir bar was added benzimidates (1,
0.20 mmol), nitroalkenes (2, 0.30 mmol), [Cp*RhCl2]2
(0.01 mmol, 6.0 mg), AdCOOK (0.1 mmol, 21.8 mg) in
TFE (2.0 mL) was stirred at 80 °C for 16 h, cooled to room
temperature, filtered through a pad of celite, and then
washed with CH2Cl2 (10 mL × 3). Organic solvents were
removed under reduced pressure and the crude reaction
mixture was purified by column chromatography on silica
gel column with EtOAc/petroleum ether (1:5~1:2, v/v) as
an eluent to afford the desired product 3 or 4.
[5] For a recent review and representative examples, see:
a) D.-S. Kim, W.-J. Park, C.-H. Jun, Chem. Rev. 2017,
117, 8977–9015; b) P. Gandeepan, L. Ackermann,
Chem. 2018, 4, 199–222; c) S. S. John-Campbell, J. A.
Bull, Org. Biomol. Chem. 2018, 16, 4582–4595; d) C.-
H. Jun, H. Lee, J.-B. Hong, J. Org. Chem. 1997, 62,
1200–1201; e) R. B. Bedford, S. J. Coles, M. B.
Hursthouse, M. E. Limmert, Angew. Chem. Int. Ed.
2003, 42, 112–114; Angew. Chem. 2003, 115, 116–118;
f) F. Mo, G. Dong, Science. 2014, 345, 68–72; g) F.-L.
Zhang, K. Hong, T.-J. Li, H. Park, J.-Q. Yu, Science.
2016, 351, 252–256; h) Y. Xu, T. Su, Z. Huang, G.
Dong, Angew. Chem. Int. Ed. 2016, 55, 2559–2563;
Angew. Chem. 2016, 128, 2605–2609; i) Y. Liu, H. Ge,
Nat. Chem. 2017, 9, 26–32; j) K. Yang, Q. Li, Y. Liu,
G. Li, H. Ge, J. Am. Chem. Soc. 2016, 138, 12775–
12778; k) Q.–J. Yao, S. Zhang, B.–B. Zhan, B.–F. Shi,
Angew. Chem. Int. Ed. 2017, 56, 6617–6621; Angew.
Chem. 2017, 129, 6717–6721.
Acknowledgements
Funding from Natural Science Foundation of China (Nos.
21472165, 21672186, 21602202) and Important Project of
Zhejiang province (2017C03049) is highly acknowledged
References
[1] For selected reviews: a) L. Ackermann, Acc. Chem.
Res. 2014, 47, 281–295; b) S. R. Neufeldt, M. S.
Sanford, Acc. Chem. Res. 2012, 45, 936–946; c) K. M.
Engle, T.-S. Mei, M. Wasa, J.-Q. Yu, Acc. Chem. Res.
2012, 45, 788–802; d) N. Kuhl, M. N. Hopkinson, J.
4
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10.1002/adsc.201900427
Advanced Synthesis & Catalysis
[6] a) D.-G. Yu, M. Suri, F. Glorius, J. Am. Chem. Soc.
2013, 135, 8802–8805; b) Q. Wang, X. Li, Org. Lett.
2016, 18, 2102–2105; c) H. Li, H. Wang, S. Yu, X.
Yang, X. Li, Org. Lett. 2016, 18, 3662–3665; d) S. Yu,
G. Tang, Y. Li, X. Zhou, Y. Lan, X. Li, Angew. Chem.
Int. Ed. 2016, 55, 8696–8700; Angew. Chem. 2016, 128,
8838–8842; e) F. Wang, H. Wang, Q. Wang, S. Yu, X.
Li, Org. Lett. 2016, 18, 1306–1309; f) J. Wang, S. Zha,
K. Chen, F. Zhang, C. Song, J. Zhu, Org.
Lett. 2016, 18, 2062–2065; g) X. Wang, N. Jiao, Org.
Lett. 2016, 18 , 2150–2153; h) H. Wang, L. Li, S. Yu,
Y. Li, X. Li, Org. Lett. 2016, 18, 2914–2917.
T. Xu, Q. Zhang, F. Wu, C. Ma, B. Liu, J. Chang, X. Li,
J. Org. Chem. 2017, 82, 9877–9884; c) T. J. Potter, Y.
Li, M. D. Ward, J. A. Ellman, Eur. J. Org. Chem. 2018,
2018, 4381–4388; d) A. Mishra, U. Mukherjee, W.
Sarkar, S. L. Meduri, A. Bhowmik, I. Deb, Org. Lett.
2019, 21, 2056-2059.
[10] During preparation of the manuscript, similar
reactions were reported by the Cui and Sharma groups.
a) B. Wu, Z. Yang, H. Zhang, L. Wang, X. Cui, Chem.
Commun. 2019, 55, 4190-4193; b) B. Chaudhary, P.
Auti, S. D. Shiinde, P. A. Yakkala, D. Giri, S. Sharma,
Org. Lett. 2019, 21, 2763-2767.
[7] a) X.-G. Li, M. Sun, K. Liu, P.-N. Liu, Adv. Synth.
Catal. 2015, 357, 395-399; b) H. Wang, M. M. Lorion,
L. Ackermann, ACS Catal. 2017, 7, 3430–3433; c) N.
Lv, Z. Chen, Y. Liu, Z. Liu, Y. Zhang, Org. Lett. 2017,
19, 2588–2591; d) N. Lv, Y. Liu, C. Xiong, Z. Liu, Y.
Zhang, Org. Lett. 2017, 19, 4640–4643.
[8] For select reviews on nitroalkenes and their use, see: (a)
A. G. M. Barrett, G. G. Graboski, Chem. Rev. 1986, 86,
751–762; b) S. E. Denmark, A. Thorarensen, Chem.
Rev. 1996, 96, 137–166; c) O. M. Berner, L. Tedeschi,
D. Enders, Eur. J. Org. Chem. 2002, 2002, 1877–1894;
d) A. G. Doyle, E. N. Jacobsen, Chem. Rev. 2007, 107,
5713–5743; e) A. Z. Halimehjani, I. N. N. Namboothiri,
S. E. Hooshmand, RSC Adv. 2014, 4, 31261–31299; f)
A. Z. Halimehjani, I. N. N. Namboothiri, S. E.
Hooshmand, RSC Adv. 2014, 4, 48022–48084.
[11] a) T. George, R. Tahilramani, C. L. Kaul, R. S.
Grewal, J. Pharm. Sci. 1969, 58, 47–50; b) J. Augstein,
A. L. Ham, P. R. Leeming, J. Med. Chem. 1972, 15,
466–470; c) K. P. Bogeso, J. Med. Chem. 1983, 26,
935–947; d) K. P. Bogeso, A. V. Christensen, J. Hyttel,
T. Liljefors, J. Med. Chem. 1985, 28, 1817–1828; e) M.
Pan, T. J.Mabry, J. M. Beale, B. M. Mamiya,
Phytochemistry, 1997, 45, 517–519; f) M. Froimowitz,
K.-M. Wu, A. Moussa, R. M. Haidar, J. Jurayj, C.
George, E. L.Gardner, J. Med. Chem. 2000, 43, 4981–
4992; g) H. Minegishi, Y. Futamura, S. Fukashiro, M.
Muroi, M. Kawatani, H. Osada, H. Nakamura, J. Med.
Chem. 2015, 58, 4230–4241.
[12] CCDC-1873798 and -1873799 (3a) contain the
supplementary crystallographic data for this paper.
These data can be obtained free of charge from The
[9] a) T. Potter, D. N. Kamber, B. Q. Mercado, J. A.
Ellman, ACS Catal. 2017, 7, 150–153; b) D. Bai, Q. Jia,
Cambridge
via www.ccdc.cam.ac.uk/data_request/cif.
Crystallographic
Data
Centre
5
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Advanced Synthesis & Catalysis
COMMUNICATION
Rhodium-Catalyzed Cascade Annulation of
Benzimidates and Nitroalkenes for the Synthesis
of Difunctionalized Indenes
Adv. Synth. Catal. 2019, Volume, Page – Page
Ningning Lv, Zhengkai Chen, Yue Liu, Zhanxiang
Liu, Yuhong Zhang*
6
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