Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H bond activation and migratory insertion of alkyne

Article abstract of DOI:10.1016/j.cclet.2016.05.011

A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical or unsymmetrical alkynes using Cu(OAc)₂as oxidant is described. Urea group is shown to be effective as a directing group for initial ortho C–H activation. Two migratory insertion events of alkyne into Rh–C bond occur successively, both with complete regioselectivity. This method is particularly useful for synthesis of polyarenes with different substituents, which has not been reported with conventional protocol. A mechanism has been proposed to explain the observed data.

Full text of DOI:10.1016/j.cclet.2016.05.011

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Chinese Chemical Letters xxx (2016) xxx–xxx
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Chinese Chemical Letters
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1
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Original article
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Rhodium catalyzed regioselective arene homologation of aryl urea via
double C–H bond activation and migratory insertion of alkyne
* *
Q1 Yan Wang, Hao Zhou, Ke Xu, Mei-Hua Shen , Hua-Dong Xu
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School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou 213164, China
A R T I C L E I N F O
A B S T R A C T
Article history:
A convenient rhodium catalyzed oxidative arene homologation of aniline derivatives with symmetrical
or unsymmetrical alkynes using Cu(OAc)2 as oxidant is described. Urea group is shown to be effective as
a directing group for initial ortho C–H activation. Two migratory insertion events of alkyne into Rh–C
bond occur successively, both with complete regioselectivity. This method is particularly useful for
synthesis of polyarenes with different substituents, which has not been reported with conventional
protocol. A mechanism has been proposed to explain the observed data.
Received 21 March 2016
Received in revised form 19 April 2016
Accepted 9 May 2016
Available online xxx
Keywords:
ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Urea
Directing group
C–H Activation
Arene homologation
Asymmetric alkynes
Oxidative cyclization
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8
1. Introduction
electro- and photo-chemical properties [41–45], which very often 28
could be modulated through the introduction of multiple 29
9
Great advancement has been made in transition metal
catalyzed C–H bond activation and functionalization in the past
20 years [1–4]. The merits of direct C–H bond functionalization
could reach its full extension only when site selective is achieved
because there are almost always multiple C–H bonds in any
organic substrate. The most common and successful strategy to
address this selective challenge is using substrates containing
coordinating ligands, namely directing groups [5,6]. By coordinate
to transition metal, the directing group could deliver the catalytic
center to a proximal C–H bond and therefore force the C–H bond-
activating event to occur in a controlled manner. A plenty of
directing groups have been devised for this purpose, and due to its
vast structural diversity, the N-containing directing groups
constitute the major and most important part. These N-containing
directing groups span from various aromatic N-heterocycles,
amines, amides, imides and imines to hydrazones, oximes,
triazoles, and ureas, etc.[7–40].
substituents on the arene core [46–49]. Metal catalyzed coupling 30
of arene with two fold internal alkynes provides an efficient arene 31
homologation method for poly-substituted polycyclic aromatic 32
compounds [50–61]. Direct site selective homologation of un- 33
preactivated arenes, which involves double C–H activation is 34
highly appreciated as this method can provide polycyclic aromatic 35
compounds in both efficient and controlled manner from easily 36
accessible un-functionalized arenes [62–65]. Here, we would like 37
to report a urea group directed arene homologation catalyzed by 38
Rh(III) complex employing either symmetric or unsymmetrical 39
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internal alkynes as coupling partners.
40
2. Experimental
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2.1. General
1H NMR and 13C NMR spectra were recorded using Bruker AV- 43
300/AV-400/AV-500 spectrometers. Analytical thin layer chroma- 44
tography was performed on 0.25 mm extra hard silica gel plates 45
with UV254 fluorescent indicator and/or by exposure to phos- 46
phomolybdic acid followed by brief heating with a heat gun. Liquid 47
Polycyclic aromatic compounds have been found increasing
applications in functional materials in virtue of their excellent
˚
chromatography (flash chromatography) was performed on 60 A 48
(40–60 m) mesh silica gel (SiO2). All reactions were carried out 49
under nitrogen or argon with anhydrous solvents in flame-dried 50
*
Corresponding authors.
m
E-mail addresses: shenmh@cczu.edu.cn (M.-H. Shen), hdxu@cczu.edu.cn
(H.-D. Xu).
http://dx.doi.org/10.1016/j.cclet.2016.05.011
1001-8417/ß 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Y. Wang, et al., Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H
bond activation and migratory insertion of alkyne, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.011

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Y. Wang et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
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glassware, unless otherwise noted. All reagents were commercially
obtained and, where appropriate, purified prior to use.
and AgSbF6 was a critical additive for this reaction to proceed
smoothly (entries 5–7).
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102
103
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With the optimal conditions in hand, an array of urea substrates
1 were submitted to the reaction with diphenyl acetylene 2a
(Table 2). Meta substituted ureas, such as 1b and 1c were feasible
substrates to give 5, 6, 7, 8-tetraphenyl naphthalene 3ba and 3ca in
yields of more than 60% (entries 2–3). On the other hand, ortho-
and para- substituents decreased the yield dramatically, as both
tetraphenyl naphthalenes 3 da and 3ea were obtain from 1d to 1e
in less than 20% yields (entries 4–5). N,N-diphenyl urea 1f
condensed with diphenyl acetylene to give rise to 3fa in 27%
yield (entry 6). These outcomes may be the results of collective
steric effects of both aryl substituents and bulky Cp* ligand on
metal center, which will be discussed later on.
Further studies using unsymmetrical alkynes as the homologa-
tion partners highlight the virtue of this protocol (Table 3).
Condensation of phenyl methyl acetylene 2b with urea 1a, 1b, 1c
gave related 5,8-dimethyl-6,7-diphenyl naphthalenes 3ab, 3bb,
3cb in 60–70% yields. The structure of 3ab was established by
extensive NMR experiments including, 2D 1H–1H Noesy experi-
ments. The selectivity demonstrated by these reactions is amazing
as only one single regioisomer is produced out of four possible
isomers. Moreover, to our delight, ortho substituted phenyl urea 1e
achieved a much higher yield for 5,8-dimethyl-6,7-diphenyl
naphthale 3eb (Table 3, entry 4, 63%) than the yield for 5,6,7,8-
tetraphenyl naphthalene 3ea (Table 2, entry 5, 18%). Methox-
ymethyl phenyl acetylene 2c is also condensed with 1a to give 3ac
in 51% yield with exclusive regioselectivity, while alkynes 2d and
2e are not feasible coupling partners for this reaction.
53
2.2. General procedure for the homologation of aryl ureas
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65
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A mixture of the diphenylacetylene 2 (1.0 mmol, 2.5 eq.), 1
(0.4 mmol), [Cp*RhCl2]2 (6.2 mg, 0.01 mmol, 2.5 mol%), Cu(OAc)2
(188 mg, 1 mmol, 2.5 eq.), and AgSbF6 (28 mg, 0.08 mmol,
20.0 mmol %) were weighted into a Schlenk tube equipped with
a stir bar. t-AmOH (2 mL) was added and the mixture was stirred at
120 8C for 24 h under N2 atmosphere. The reaction mixture was
extracted with DCM for three times, and the combined organic
layers were then dried over anhydrous Na2SO4, filtered, and the
solvent was removed under reduced pressure. The crude product
was purified by column chromatography on silica gel, eluted by
hexane/EtOAc = 3:1 then 2:1 to afford the desired product 3.
Characterization and spectra for new compounds are compiled
in Supporting information.
67
3. Results and discussion
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Our study commenced with urea 1a and diphenyl acetylene 2a
(Table 1). Using an effective protocol disclosed by Fagnou team,
several popular transition metal catalysts for oxidative C–H
functionalization were explored. Pd(OAc)2 and [RuCl2(P-Cym-
ene)]2 failed to promote any reaction (entries 1–3). (Cp*RhCl2)2
activated by AgSbF6 did catalyze the desired arene homologation
reaction and t-AmOH is the solvent of choice for good yield (entries
4 and 5). It was also found that Cu(OAc)2 was a necessary oxidant
Table 1
Condition optimization for oxidative condensation of phenyl urea with alkyne.a
Entry
Catalyst
Oxidant
Additive
Solvent
Yield (%)b
1
2
3
4
5
6
7
Pd(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Air
–
t-AmOH
t-AmOH
DCE
–
[RuCl2(p-Cym)]2
[RuCl2(p-Cym)]2
[Cp*RhCl2]2
[Cp*RhCl2]2
[Cp*RhCl2]2
[Cp*RhCl2]2
–
–
–
–
AgSbF6
AgSbF6
AgSbF6
–
toluene
t-AmOH
t-AmOH
t-AmOH
20
50
–
Cu(OAc)2
complex
a
Reaction conditions: 1a (0.4 mmol, 1.0 eq.), 2a (1.0 mmol, 2.5 eq.), oxidant air or Cu(OAc)2 (1 mmol, 2.5 eq.) and catalyst (0.01 mmol, 2.5 mol%) in t-AmOH (2.5 mL) was
heated to 120 8C in a Schlenk tube for 24 h;
b
Isolated yield.
Table 2
Arene homologation of aryl ureas with dipenyl acetylene.a
Entry
1
R1
R2
R3
Product
Yield (%)b
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
Me
Me
Me
Me
Me
Ph
Me
Me
Me
Me
Me
Pr
H
3aa
3ba
3ca
3 da
3ea
3fa
50
61
63
17
18
27
3-Me
3-Cl
4-Me
2-Cl
H
a
Reaction conditions: 1 (0.4 mmol, 1.0 eq.), 2a (1.0 mmol, 2.5 eq.), Cu(OAc)2 (1 mmol, 2.5 eq.), AgSbF6 (0.02 mmol, 5 mol%), and [Cp*RhCl2]2 (0.01 mmol, 2.5 mol%) in t-
AmOH (2.5 mL) was heated to 120 8C in a Schlenk tube for 24 h under N2;
b
Isolated yield.
Please cite this article in press as: Y. Wang, et al., Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H
bond activation and migratory insertion of alkyne, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.011

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Y. Wang et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
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Table 3
Arene homologation of aryl ureas with unsymmetrical acetylenes.a
Entry
1
R3
2
R4
Product
Yield (%)b
1
2
3
4
5
6
7
1a
1b
1c
1e
1a
1c
1a
H
2b
2b
2b
2b
2c
2d
2e
Me
3ab
3bb
3cb
3eb
3ac
–
60
69
65
63
51
3-Me
3-Cl
2-Cl
H
Me
Me
Me
CH2OMe
COOMe
CH2OH
3-Cl
H
–
a
Reaction conditions: 1 (0.4 mmol, 1.0 eq.), 2 (1.0 mmol, 2.5 eq.), Cu(OAc)2 (1 mmol, 2.5 eq.), AgSbF6 (0.02 mmol, 5 mol%) and [Cp*RhCl2]2 (0.01 mmol, 2.5 mol%) in t-AmOH
(2.5 mL) was heated to 120 8C in a Schlenk tube for 24 h under N2.
b
Isolated yield.
105
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107
108
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112
113
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Based on previous studies [11,66–70] and the data collected in
this research, a mechanism has been proposed as shown in Scheme
1. Pre-catalyst [RhCp*Cl2]2 is initially converted into an active
cationic Rhodium species A by the action of AgSbF6. A is directed to
activate the ortho C–H bond in urea 1 to finish aryl Cp*Rh(III)
species B which coordinates with alkyne 2 followed by migratory
insertion giving alkenyl Cp*Rh(III) intermediate C. A second C–H
bond activation event then took place intramolecularly leading to
Rhodacycle D. A second insertion of alkyne molecule provide two
where electronic effect was raised to explain this intrinsic 121
regioselectivity. For the same reason, the second alkyne insertion 122
will take place at one of the two C–Rh bonds of D to give 123
preferentially E over E’ and F over F’, respectively. After reductive 124
elimination, rhodacycle E will give the observed naphthalene 3aa, 125
whereas F will give its regioisomer 3’aa which is not detected, 126
disproving the intermediacy of rhodacycle F (Scheme 2). These 127
analyses support a pathway B-C-D-E as the operating pathway 128
shown in Scheme 1.
129
possible Rhodacycles
E
or/and
F
and consequent reductive
The low yield associated with meta- and para-substituted 130
phenyl ureas when diphenyl acetylene 2a was used as condensa- 131
tion partner may derive from the serious steric repulsions in the 132
intermediates along the pathway, such as indicated in G and H 133
(Fig. 1). Those steric interactions can be relieved when diphenyl 134
acetylene 2a was replaced by methyphenyl acetylene 2b to afford 135
elimination delivers the homologated arene 3 and the reduced
Cp*Rh(I) species is oxidized by Cu(II) to regenerate Cp*Rh(III)
complex A ready for a second catalytic circle.
According to this mechanism, it can be deduced from the
product structure of 3ab-3eb that D is formed favorably over D’
from B and this is also in line with Fagnou’s observations [11],
increased yield.
136
Scheme 1. Proposed mechanism for the arene homologation (RS stands for small group, RL stands for large group).
Please cite this article in press as: Y. Wang, et al., Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H
bond activation and migratory insertion of alkyne, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.011

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Y. Wang et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
Scheme 2. Discrimination of two possible pathways.
References
156
[1] J.Q. Yu, Z.J. Shi, C-H Activation, Top. Curr. Chem., 292, Springer GmbH, 2010.
[2] O. Baudoin, Transition metal-catalyzed arylation of unactivated C(sp3)–H bonds,
Chem. Soc. Rev. 40 (2011) 4902–4911.
[3] L. McMurray, F. O’Hara, M.J. Gaunt, Recent developments in natural product
synthesis using metal-catalysed C-H bond functionalisation, Chem. Soc. Rev.
40 (2011) 1885–1898.
[4] G. Yan, X. Wu, M. Yang, Transition-metal-catalyzed additions of C–H bonds to C–X
(X = N, O) multiple bonds via C–H bond activation, Org. Biomol. Chem. 11 (2013)
5558–5578.
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
Fig. 1. The steric repulsions in intermediates G and H leading to low yields.
[5] L. Cuesta, E.P. Urriolabeitia, Coordination-directed metallation strategy for C–H
functionalization, RSC Catal. Ser. 11 (2013) 262–309.
[6] T.W. Lyons, M.S. Sanford, Palladium-catalyzed ligand-directed CÀH functionali-
zation reactions, Chem. Rev. 110 (2010) 1147–1169.
[7] N. Guimond, K. Fagnou, Isoquinoline synthesis via rhodium-catalyzed oxidative
cross-coupling/cyclization of aryl aldimines and alkynes, J. Am. Chem. Soc. 131
(2009) 12050–12051.
[8] N. Guimond, S.I. Gorelsky, K. Fagnou, Rhodium(III)-catalyzed heterocycle synthe-
sis using an internal oxidant: improved reactivity and mechanistic studies, J. Am.
Chem. Soc. 133 (2011) 6449–6457.
[9] N. Guimond, C. Gouliaras, K. Fagnou, Rhodium(III)-catalyzed isoquinolone syn-
thesis: the NÀO bond as a handle for CÀN bond formation and catalyst turnover, J.
Am. Chem. Soc. 132 (2010) 6908–6909.
[10] S. Rousseaux, S.I. Gorelsky, B.K.W. Chung,K. Fagnou, Investigationofthe mechanism
of C(sp3)ÀH bond cleavage in Pd(0)-catalyzed intramolecular alkane arylation
adjacent to amides and sulfonamides, J. Am. Chem. Soc. 132 (2010) 10692–10705.
[11] D.R. Stuart, P. Alsabeh, M. Kuhn, K. Fagnou, Rhodium(III)-catalyzed arene and
alkene CÀH bond functionalization leading to indoles and pyrroles, J. Am. Chem.
Soc. 132 (2010) 18326–18339.
[12] D.R. Stuart, M. Bertrand-Laperle, K.M.N. Burgess, K. Fagnou, Indole synthesis via
rhodium catalyzed oxidative coupling of acetanilides and internal alkynes, J. Am.
Chem. Soc. 130 (2008) 16474–16475.
[13] B. Lie´gault, K. Fagnou, Palladium-catalyzed intramolecular coupling of arenes and
unactivated alkanes in air, Organometallics 27 (2008) 4841–4843.
[14] D. Zhao, Z. Shi, F. Glorius, Indole synthesis by rhodium(III)-catalyzed hydrazine-
directed C-H activation: redox-neutral and traceless by N-N bond cleavage,
Angew. Chem. Int. Ed. 52 (2013) 12426–12429.
[15] Z. Shi, D.C. Koester, M. Boultadakis-Arapinis, F. Glorius, Rh(III)-Catalyzed synthe-
sis of multisubstituted isoquinoline and pyridine N-oxides from oximes and diazo
compounds, J. Am. Chem. Soc. 135 (2013) 12204–12207.
[16] H.H. Al Mamari, E. Diers, L. Ackermann, Triazole-assisted ruthenium-catalyzed
C[n.63743]H arylation of aromatic amides, Chem. Eur. J. 20 (2014) 9739–9743.
[17] J. Li, M. John, L. Ackermann, Amidines for versatile ruthenium(II)-catalyzed
oxidative C-H activations with internal alkynes and acrylates, Chem. Eur. J. 20
(2014) 5403–5408.
137
4. Conclusion
138
139
140
141
142
143
144
In summary, we have established a facile method for arene
homologation of aryl urea with internal alkyne. This rhodium
catalyzed transformation features a double C–H activation process
and two successive completely regioselctive migratory insertions
of unsymmetrical alkynes into Rhodium–carbon bonds enable this
method particularly useful for poly-substituted polyarenes.
Furthermore, a mechanism proposal has been discussed.
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Acknowledgments
146
147
148
149
150
151
We are grateful for the National Natural Science Foundation of
China (No. 21272077), the Natural Science Foundation of Jiangsu
Province (No. BK20131143), Jiangsu Key Laboratory of Advanced
Catalytic Materials & Technology and the Priority Academic
Program Development of Jiangsu Higher Education Institutions
(PAPD) for financial support.
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Appendix A. Supplementary data
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Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.cclet.2016.05.
011.
Please cite this article in press as: Y. Wang, et al., Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H
bond activation and migratory insertion of alkyne, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.011

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201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
[18] L. Ackermann, E. Diers, A. Manvar, Ruthenium-catalyzed C-H bond arylations of
arenes bearing removable directing groups via six-membered ruthenacycles, Org.
Lett. 14 (2012) 1154–1157.
[19] W. Liu, L. Ackermann, Ortho- and para-selective ruthenium-catalyzed C(sp2)-H
oxygenations of phenol derivatives, Org. Lett. 15 (2013) 3484–3486.
[20] W. Ma, K. Graczyk, L. Ackermann, Ruthenium-catalyzed alkyne annulations with
substituted 1H-pyrazoles by C-H/N-H bond functionalizations, Org. Lett. 14
(2012) 6318–6321.
[21] M. Schinkel, L. Wang, K. Bielefeld, L. Ackermann, Ruthenium(II)-catalyzed C(sp3)-
H a-alkylation of pyrrolidines, Org. Lett. 16 (2014) 1876–1879.
[22] C.L. Ciana, R.J. Phipps, J.R. Brandt, F.M. Meyer, M.J. Gaunt, A highly para-selective
copper(II)-catalyzed direct arylation of aniline and phenol derivatives, Angew.
Chem. Int. Ed. 50 50 (2011) 458–462.
[23] B. Haffemayer, M. Gulias, M.J. Gaunt, Amine directed Pd(ii)-catalyzed C-H bond
functionalization under ambient conditions, Chem. Sci. 2 (2011) 312–315.
[24] S.R. Neufeldt, M.S. Sanford, Asymmetric chiral ligand-directed alkene dioxygena-
tion, Org. Lett. 15 (2012) 46–49.
[25] G. Yang, P. Lindovska, D. Zhu, et al., Pd(II)-catalyzed meta-C–H Olefination,
arylation, and acetoxylation of indolines using a U-shaped template, J. Am. Chem.
Soc. 136 (2014) 10807–10813.
[26] M. Shang, H.L. Wang, S.Z. Sun, H.X. Dai, J.Q. Yu, Cu(II)-mediated ortho C–H
alkynylation of (hetero)arenes with terminal alkynes, J. Am. Chem. Soc. 136
(2014) 11590–11593.
[27] R.Y. Tang, G. Li, J.Q. Yu, Conformation-induced remote meta-C-H activation of
amines, Nature 507 (2014) 215–220.
[28] S.L. ChanKelvin, M. Wasa, L. Chu, et al., Ligand-enabled cross-coupling of C(sp3)–H
bonds with arylboron reagents via Pd(II)/Pd(0) catalysis, Nat. Chem. 6 (2014)
146–150.
[29] G. Zhang, L. Yang, Y. Wang, Y. Xie, H. Huang, An Efficient Rh/O2 catalytic system for
oxidative C–H activation/annulation: evidence for Rh(I) to Rh(III) oxidation by
molecular oxygen, J. Am. Chem. Soc. 135 (2013) 8850–8853.
[30] C. Wang, Y. Huang, Traceless directing strategy: efficient synthesis of N-alkyl
indoles via redox-neutral C–H activation, Org. Lett. 15 (2013) 5294–5297.
[31] W.W. Chan, S.F. Lo, Z. Zhou, W.Y. Yu, Rh-catalyzed intermolecular carbenoid
functionalization of aromatic C–H bonds by a-diazomalonates, J. Am. Chem. Soc.
134 (2012) 13565–13568.
[32] B. Liu, C. Song, C. Sun, S. Zhou, J. Zhu, Rhodium(III)-catalyzed indole synthesis
using N–N bond as an internal oxidant, J. Am. Chem. Soc. 135 (2013) 16625–
16631.
[33] X.C. Huang, X.H. Yang, R.J. Song, J.H. Li, Rhodium-catalyzed synthesis of isoqui-
nolines and indenes from benzylidenehydrazones and internal alkynes, J. Org.
Chem. 79 (2014) 1025–1031.
[34] N.J. Wang, S.T. Mei, L. Shuai, Y. Yuan, Y. Wei, Aerobic oxidative C–H olefination of
cyclic N-sulfonyl ketimines catalyzed by a rhodium catalyst, Org. Lett. 16 (2014)
3040–3043.
[35] H. Sun, C. Wang, Y.F. Yang, et al., Synthesis of indolo[2,1-a]isoquinolines via a
triazene-directed C–H annulation cascade, J. Org. Chem. 79 (2014) 11863–11872.
[36] W. Han, G. Zhang, G. Li, H. Huang, Rh-catalyzed sequential oxidative C–H and N–N
bond activation: conversion of azines into isoquinolines with air at room tem-
perature, Org. Lett. 16 (2014) 3532–3535.
[37] S.C. Chuang, P. Gandeepan, C.H. Cheng, Synthesis of isoquinolines via Rh(III)-
catalyzed C–H activation using hydrazone as a New oxidizing directing group,
Org. Lett. 15 (2013) 5750–5753.
[38] G. Li, Z. Ding, B. Xu, Rhodium-catalyzed oxidative annulation of sulfonylhydra-
zones with alkenes, Org. Lett. 14 (2012) 5338–5341.
[45] M. Watanabe, K.Y. Chen, Y.J. Chang, T.J. Chow, Acenes generated from precursors 271
and their semiconducting properties, Acc. Chem. Res. 46 (2013) 1606–1615.
272
[46] C. Kitamura, T. Ohara, A. Yoneda, et al., Synthesis and solid-state optical properties 273
of 2,3-dialkyl- and 2,3,8,9-tetraalkyltetracenes, Chem. Lett. 40 (2011) 58–59.
[47] A.S. Paraskar, A.R. Reddy, A. Patra, et al., Rubrenes: planar and twisted, Chem. Eur. 275
J. 14 (2008) 10639–10647.
[48] X. Qiao, M.A. Padula, D.M. Ho, et al., Octaphenylnaphthalene and decaphenylan- 277
thracene, J. Am. Chem. Soc. 118 (1996) 741–745.
[49] T. Takahashi, S. Li, W. Huang, et al., Homologation method for preparation of 279
substituted pentacenes and naphthacenes, J. Org. Chem. 71 (2006) 7967–7977.
274
276
278
280
[50] W. Huang, X. Zhou, K.I. Kanno, T. Takahashi, Pd-Catalyzed reactions of o-diio- 281
doarenes with alkynes for aromatic ring extension, Org. Lett. 6 (2004) 2429–2431. 282
[51] H. Pellissier, M. Santelli, The use of arynes in organic synthesis, Tetrahedron 59 283
(2003) 701–730.
284
[52] D. Pena, D. Perez, E. Guitian, L. Castedo, Palladium-catalyzed cocyclization of 285
arynes with alkynes: selective synthesis of phenanthrenes and naphthalenes, J. 286
Am. Chem. Soc. 121 (1999) 5827–5828.
287
[53] T. Seri, H. Qu, L. Zhou, K.i. Kanno, T. Takahashi, Substituent effects in the 288
preparation of naphthacenes by the coupling reaction of diyne-derived zircona- 289
cyclopentadienes with tetraiodobenzene, Chem. Asian J. 3 (2008) 388–392.
290
[54] T. Takahashi, Y. Li, P. Stepnicka, et al., Coupling reaction of zirconacyclopenta- 291
dienes with dihalonaphthalenes and dihalopyridines: a new procedure for the 292
preparation of substituted anthracenes, quinolines, and isoquinolines, J. Am. 293
Chem. Soc. 124 (2002) 576–582.
[55] E. Yoshikawa, K.V. Radhakrishnan, Y. Yamamoto, Palladium-catalyzed controlled 295
carbopalladation of benzyne, J. Am. Chem. Soc. 122 (2000) 7280–7286.
294
296
[56] L. Adak, N. Yoshikai, Iron-catalyzed annulation reaction of arylindium reagents 297
and alkynes to produce substituted naphthalenes, Tetrahedron 68 (2012) 298
5167–5171.
299
[57] A. Bej, A. Chakraborty, A. Sarkar, Solvent free, phosphine free Pd-catalyzed 300
annulations of aryl bromides with diarylacetylenes, RSC Adv. 3 (2013) 15812– 301
15819.
302
[58] T. Fukutani, K. Hirano, T. Satoh, M. Miura, Synthesis of highly substituted acenes 303
through rhodium-catalyzed oxidative coupling of arylboron reagents with 304
alkynes, J. Org. Chem. 76 (2011) 2867–2874.
305
[59] S. Kawasaki, T. Satoh, M. Miura, M. Nomura, Synthesis of tetrasubstituted 306
naphthalenes by palladium-catalyzed reaction of aryl iodides with internal 307
alkynes, J. Org. Chem. 68 (2003) 6836–6838.
[60] K. Komeyama, T. Kashihara, K. Takaki, Cobalt-catalyzed annulation of aryl iodides 309
with alkynes, Tetrahedron Lett. 54 (2013) 5659–5662.
308
310
[61] M.V. Pham, N. Cramer, Aromatic homologation by non-chelate-assisted Rh(III)- 311
catalyzed C-H functionalization of arenes with alkynes, Angew. Chem. Int. Ed. 53 312
(2014) 3484–3487.
313
[62] L.C. Misal Castro, A. Obata, Y. Aihara, N. Chatani, Chelation-assisted nickel- 314
catalyzed oxidative annulation via double C À H activation/alkyne insertion 315
reaction, Chem. Eur. J. 22 (2016) 1362–1367.
316
[63] Z. Shi, C. Tang, N. Jiao, Chemoselective synthesis of naphthylamides and iso- 317
quinolinones via rhodium-catalyzed oxidative dehydrogenative annulation of 318
benzamides with alkynes, Adv. Synth. Catal. 354 (2012) 2695–2700.
319
[64] J. Wu, X. Cui, X. Mi, Y. Li, Y. Wu, Palladium catalyzed synthesis of highly 320
substituted naphthalenes via direct ring construction from amides with alkynes, 321
Chem. Commun. 46 (2010) 6771–6773.
322
[65] M. Yamashita, H. Horiguchi, K. Hirano, T. Satoh, M. Miura, Fused ring construction 323
around pyrrole, indole, and related compounds via palladium-catalyzed oxidative 324
coupling with alkynes, J. Org. Chem. 74 (2009) 7481–7488.
325
[39] Z. Song, R. Samanta, A.P. Antonchick, Rhodium(III)-catalyzed direct regioselective
synthesis of 7-substituted indoles, Org. Lett. 15 (2013) 5662–5665.
[40] C.E. Houlden, C.D. Bailey, J.G. Ford, et al., Distinct reactivity of Pd(OTs)2: the
intermolecular Pd(II)-catalyzed 1,2-carboamination of dienes, J. Am. Chem. Soc.
130 (2008) 10066–10067.
[41] J.E. Anthony, Functionalized acenes and heteroacenes for organic electronics,
Chem. Rev. 106 (2006) 5028–5048.
[42] M. Bendikov, F. Wudl, D.F. Perepichka, Tetrathiafulvalenes, oligoacenenes, and
their buckminsterfullerene derivatives: the brick and mortar of organic electron-
ics, Chem. Rev. 104 (2004) 4891–4945.
[43] F. Cicoira, C. Santato, Organic light emitting field effect transistors: advances and
perspectives, Adv. Funct. Mater. 17 (2007) 3421–3434.
[44] V.C. Sundar, J. Zaumseil, V. Podzorov, et al., Elastomeric transistor stamps:
reversible probing of charge transport in organic crystals, Science 303 (2004)
1644–1647.
[66] D.R. Stuart, M. Bertrand-Laperle, K.M.N. Burgess, K. Fagnou, Indole synthesis via 326
rhodium catalyzed oxidative coupling of acetanilides and internal alkynes, J. Am. 327
Chem. Soc. 130 (2008) 16474–16475.
328
[67] R.C. Larock, E.K. Yum, M.D. Refvik, Synthesis of 2,3-disubstituted indoles via 329
palladium-catalyzed annulation of internal alkynes, J. Org. Chem. 63 (1998) 330
7652–7662.
331
[68] L. Li, W.W. Brennessel, W.D. Jones, C-H activation of phenyl imines and 2- 332
phenylpyridines with [Cp*MCl2]2 (M = Ir, Rh): regioselectivity, kinetics, and 333
mechanism, Organometallics 28 (2009) 3492–3500.
334
[69] K. Ueura, T. Satoh, M. Miura, Rhodium- and iridium-catalyzed oxidative coupling 335
of benzoic acids with alkynes via regioselective C-H bond cleavage, J. Org. Chem. 336
72 (2007) 5362–5367.
337
[70] K. Ueura, T. Satoh, M. Miura, An efficient waste-free oxidative coupling via 338
regioselective C–H Bond Cleavage: Rh/Cu-catalyzed reaction of benzoic acids 339
with alkynes and acrylates under air, Org. Lett. 9 (2007) 1407–1409.
340
Please cite this article in press as: Y. Wang, et al., Rhodium catalyzed regioselective arene homologation of aryl urea via double C–H
bond activation and migratory insertion of alkyne, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.05.011