Palladium-Catalyzed Synthesis of Benzophenanthrosilines by C?H/C?H Coupling through 1,4-Palladium Migration/Alkene Stereoisomerization

Article abstract of DOI:10.1002/anie.202000217

A new and efficient synthesis of 8H-benzo[e]phenanthro[1,10-bc]silines from 2-((2-(arylethynyl)aryl)silyl)aryl triflates under palladium catalysis has been developed. The reaction mechanism was experimentally investigated and a catalytic cycle involving C

Full text of DOI:10.1002/anie.202000217

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Palladium-Catalyzed Synthesis of Benzophenanthrosilines by
C–H/C–H Coupling through 1,4-Palladium Migration/Alkene
Stereoisomerization
Authors: Tomohiro Tsuda, Yuka Kawakami, Seung-Min Choi, and Ryo
Shintani
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: Angew. Chem. Int. Ed. 10.1002/anie.202000217
Angew. Chem. 10.1002/ange.202000217
Link to VoR: http://dx.doi.org/10.1002/anie.202000217
http://dx.doi.org/10.1002/ange.202000217

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
Palladium-Catalyzed Synthesis of Benzophenanthrosilines by C–
H/C–H Coupling through 1,4-Palladium Migration/Alkene
Stereoisomerization
Tomohiro Tsuda,[a] Yuka Kawakami,[a] Seung-Min Choi,[a] and Ryo Shintani*[a]
Abstract:
A
new
and
efficient
synthesis
from
of
8H-
In 2008, Shimizu and coworkers reported a palladium-catalyzed
synthesis of 5H-dibenzo[b,d]siloles from 2-(arylsilyl)aryl triflates
via intramolecular C–H arylation.[10] This process is highly reliable
and we could also obtain dibenzosilole 2a in 90% yield from
substrate 1a under similar reaction conditions (Table 1, entry 1).
However, we found that the use of substrate 1b having a
phenylethynyl group at the 3-position resulted in no formation of
dibenzosilole 2b, and the major product was found to be
benzophenanthrosiline 3b in 58% yield (entry 2).[11] Reactions
using other ligands such as PPh3 and dppf also gave 3b as the
major product with no 2b (entries 3 and 4), and the same trend
was observed even in the absence of any phosphine ligands
(entry 5).
benzo[e]phenanthro[1,10-bc]silines
2-((2-
(arylethynyl)aryl)silyl)aryl triflates has been developed under
palladium catalysis. The reaction mechanism has been
experimentally investigated and a catalytic cycle involving a C–H/C–
H coupling through a new mode of 1,4-palladium migration with
concomitant alkene stereoisomerization has been proposed.
Silicon-bridged π-conjugated compounds possessing
membered silacycle such as 7H-benzo[e]naphtho[1,8-bc]silines
and 8H-benzo[e]phenanthro[1,10-bc]silines constitute
a 6-
a
potentially useful class of compounds based on the optoelectronic
properties derived from their rigid and extended π-conjugation in
plane (Figure 1).[1] However, in contrast to widely explored 5H-
dibenzo[b,d]siloles and related compounds having a 5-membered
silacycle,[2] these 6-membered silacycles have been significantly
less investigated, which is presumably due to the lack of their
general and efficient synthetic methods. In fact, only a few
approaches have been reported for the synthesis of 7H-
benzo[e]naphtho[1,8-bc]silines, such as dehydrogenative C–C
coupling of methyl(1-naphthyl)(phenyl)silane by pyrolysis[3] and
oxidative Si–C coupling of 1-naphthyltriphenylsilane by a radical
process.[4,5] With regard to the synthesis of 8H-
benzo[e]phenanthro[1,10-bc]silines, only one method has been
reported to date by Wagner and coworkers, where they employed
a conventional multi-step π-extension process through a 5,10-
dihydrodibenzo[b,e]siline as an intermediate.[6] In light of this
methodological deficiency, herein we describe a new and efficient
synthesis of 8H-benzo[e]phenanthro[1,10-bc]silines from easily
Table 1. Palladium-catalyzed reaction of 1.
tBu Ph
Si
tBu Ph
tBu Ph
R
Pd(OAc)2 (5 mol%)
ligand (x mol%)
R
Si
Si
Et2NH (2.0 equiv)
DMF, 100 °C, 24 h
OTf
(0.5 M)
1a (R = H)
1b (R = C CPh)
2a (R = H)
2b (R = C CPh)
3b
Entry
1
Ligand (x)
Yield of 2 [%][a]
Yield of 3 [%][a]
1
2
3
4
5
1a
1b
1b
1b
1b
PCy3[b] (10)
PCy3[b] (10)
PPh3 (10)
Dppf (5.5)
None
90
0
—
58
39
17
59
0
accessible
2-((2-(arylethynyl)aryl)silyl)aryl
triflates
under
0
palladium catalysis, which involves a C–H/C–H coupling[7,8] via a
new mode of 1,4-palladium migration.[8,9]
0
[a] Determined by 1H NMR against internal standard (MeNO2). [b]
PCy3•HBF4/Et2NH was used.
Si
Si
Si
Based on these initial findings, we decided to focus on the
synthesis of benzophenanthrosilines 3. The formation of 3b from
1b presumably goes through a pathway illustrated in Scheme 1.
7H-benzo[e]naphtho- 8H-benzo[e]phenanthro-
[1,8-bc]siline [1,10-bc]siline
5H-dibenzo[b,d]silole
Initial oxidative adduct
I
would undergo 1,5-palladium
migration[11,12] to give arylpalladium species II, and subsequent
insertion of alkyne to the aryl–palladium bond gives
alkenylpalladium intermediate III. If this process is operating, the
same product should be obtained from compound 4b [Eq. (1)] that
can directly generate intermediate II without going through 1,5-
palladium migration. Indeed, as shown in Eq. 1, we found that the
reaction of compound 4b, which is more readily accessible than
1b, efficiently gave benzophenanthrosiline 3b in a much higher
yield of 94% under the same conditions as in Table 1, entry 5.
Figure 1. Structures of representative silicon-bridged π-conjugated compounds.
[a]
T. Tsuda, Y. Kawakami, S.-M. Choi, Prof. Dr. R. Shintani
Division of Chemistry, Department of Materials Engineering Science
Graduate School of Engineering Science
Osaka University, Toyonaka, Osaka 560-8531 (Japan)
E-mail: shintani@chem.es.osaka-u.ac.jp
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
This article is protected by copyright. All rights reserved.

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
The scope of this reaction was found to be reasonably broad as
summarized in Scheme 2. For example, in addition to compound
tBu Ph
3b
having
a
(tert-butyl)phenylsilylene
bridging
unit,
Si
tBu Ph
tBu Ph
benzophenanthrosilines 3c–3e with other silylene units can be
obtained in similarly high yields (92–94% yield). With regard to the
substituents on the aromatic rings, various groups can be installed
at any of them (Ar1, Ar2, and Ar3) with retaining high chemical
yields, including functional groups such as dimethylamino (3g, 3k,
3t), methoxycarbonyl (3n), and nitro (3o) groups. The structures
of products 3f–3j clearly establish that the C–H/C–H couplings
take place exclusively between Ar2 and Ar3 rather than between
Ar1 and Ar3.[13] It is worth mentioning that substrate 4p having 3,5-
dimethylphenyl group as Ar3 can also undergo the C–H/C–H
coupling to give 3p despite its steric hindrance. On the other hand,
the reaction of 4q with 3-tert-butylphenyl group as Ar3 selectively
provides 3q by forming a carbon–carbon bond at the less
hindered position. The present catalysis also accommodates a
heteroaromatic ring as shown for 3s and donor-acceptor-type
benzophenanthrosiline 3t can be synthesized as well.[14]
Furthermore, the reaction of ditriflate 5 gives a new type of π-
3b
Si
Si
Pd
Pd
Pd
OTf
OTf
OTf
I
II
III
Scheme 1. Possible reaction pathway for the production of 3b.
tBu Ph
Si
tBu Ph
Si
Pd(OAc)2 (5 mol%)
(1)
TfO
Et2NH (2.0 equiv)
DMF, 100 °C, 20 h
4b (0.5 M)
3b: 94% yield
R1 R2
R1 R2
extended silicon-bridged
compound
6
possessing
a
Si
Si
Ar1
Ar2
benzo[k]tetraphene moiety through the two-fold present reaction
sequence [Eq. (2)]. In our preliminary experiment, we have also
found that the present catalysis can be extended to the synthesis
of a nitrogen-bridged analogue, 8H-naphtho[1,2,3-kl]acridine 8,
under slightly modified conditions [Eq. (3)].
Ar1
Ar2
Pd(OAc)2 (5 mol%)
TfO
H
Et2NH (2.0 equiv)
DMF, 100 °C, 20 h
H
H
13
Ar3
Ar3
4 (0.5 M)
3
iPr iPr
R1 R2
Si
iPr iPr
iPr iPr
iPr iPr
Si
R
Si
Si
OMe
Si
TfO
Pd(OAc)2 (10 mol%)
(2)
Et2NH (4.0 equiv)
DMF, 100 °C, 20 h
3b (R1, R2 = tBu, Ph): 94% yield
3c (R1, R2 = Me, Ph): 92% yield
3d (R1 = R2 = Me): 94% yield
3e (R1 = R2 = iPr): 93% yield
3f (R = Me): 96% yield
3g (R = NMe2): 92% yield
3h: 91% yield
OTf
Si
iPr iPr
Si
iPr iPr
iPr iPr
iPr iPr
Si
iPr iPr
5 (0.25 M)
Si
Si
6: 72% yield
F
Ph
N
Ph
N
Pd(OAc)2 (5 mol%)
PCy3•HBF4 (10 mol%)
R
(3)
TfO
3i: 78% yield (120 °C)
3j: 75% yield (120 °C)
3k (R = NMe2): 73% yield
3l (R = OMe): 94% yield
3m (R = Me): 96% yield
3n (R = CO2Me): 93% yield
3o (R = NO2): 85% yield
Et2NH (2.1 equiv)
DMF, 120 °C, 20 h
iPr iPr
iPr iPr
Si
Si
7 (0.5 M)
8: 47% yield
iPr iPr
In the present catalysis, two C–H bonds on Ar2 and Ar3 of
substrate 4 (see Equation in Scheme 2) are cleaved to form a
carbon–carbon bond between them, and a new C–H bond is
generated at the 13-position of resulting benzophenanthrosiline 3.
To understand the fate and origin of these hydrogen atoms for
elucidation of the reaction mechanism, we conducted several
deuterium labeling experiments. The reaction of 4e-d having a
deuterium at the 6-position of Ar2 was found to give product 3e
with almost no deuterium incorporation at the 13-position [Eq. (4)],
and the reaction of 4e-d5 having pentadeuteriophenyl group as
Ar3 gave the same result [Eq. (5)]. These results indicate that H
at the 13-position of compound 3 is not directly derived from either
C–H bond that engages in the carbon–carbon bond formation. In
Me
Si
Me
tBu
3q: 89% yield
3p: 94% yield
Me
iPr iPr
iPr iPr
3r: 89% yield
Me2N
Si
Si
N
NO2
3s: 81% yield
3t: 85% yield
(10 mol% Pd, 120 °C)
Scheme 2. Scope of palladium-catalyzed synthesis of benzophenanthrosilines.
This article is protected by copyright. All rights reserved.

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
contrast, when the reaction of 4f is conducted in the presence of
excess D2O, resulting product 3f showed 78% deuterium
incorporation at the 13-position [Eq. (6)], indicating that the H at
this position is derived from an external hydrogen donor (H
derived from Et2NH and/or residual water in solvent DMF under
the standard anhydrous conditions).[15] This reaction was carried
out in the presence of non-deuterated benzophenanthrosiline 3e
and no deuterium incorporation to 3e was observed under these
conditions, confirming that the deuterium is incorporated during
the formation of compound 3 from substrate 4 and no C–H/C–D
exchange occurs once compound 3 is produced.
cycle for the present reaction is illustrated in Scheme 3. Thus,
oxidative addition of aryl triflate
4 to palladium(0) gives
arylpalladium species A. Intramolecular insertion of alkyne to the
aryl–palladium bond takes place to give alkenylpalladium B. C–H
bond activation on Ar2 then leads to alkenyl(aryl)palladium
intermediate C, which undergoes protonation by an external
proton donor to give cationic alkyl(aryl)palladium D. Cleavage of
alkyl–palladium bond with concomitant formation of (Z)-alkene
gives arylpalladium E, which possesses the right stereochemistry
toward subsequent C–H bond activation to give diarylpalladium F.
Finally, carbon–carbon bond-forming reductive elimination gives
product 3 along with regeneration of palladium(0). The alkyl–
palladium bond cleavage of intermediate D could also lead to
arylpalladium G with (E)-alkene moiety, which can reenter the
catalytic cycle by alkenyl C–H bond activation to give intermediate
C. Interconversion between complexes B and G represents a
standard 1,4-palladium migration, which has been well explored
in the literature.[8,9] On the other hand, the presently proposed
conversion from B to E can be regarded as a new mode of 1,4-
palladium migration that involves concomitant alkene
stereoisomerization.
iPr iPr
iPr iPr
Si
Si
Pd(OAc)2 (5 mol%)
6
(4)
TfO
D
Et2NH (2.0 equiv)
DMF, 100 °C, 20 h
H
13
92% D
~95% H
3e: 79% yield
4e-d (0.5 M)
iPr iPr
iPr iPr
Si
Si
Pd(OAc)2 (5 mol%)
To probe the feasibility of the involvement of intermediate E, we
prepared aryl triflate 9 with (Z)-alkene geometry and conducted
the present palladium-catalyzed reaction to find that desired
product 3d was obtained in a high yield [Eq. (7)]. When this
reaction was conducted in the presence of excess D2O, 15%
deuterium incorporation was observed at the 13-position,
indicating the reversible conversion from E to D (and to C). In
addition, to confirm that complex G can enter the present catalytic
cycle toward benzophenanthrosiline 3, compound (E)-9[13] was
also prepared and subjected to this reaction to find that the same
product 3d was indeed obtained as expected [Eq. (8)]. It is worth
noting that the degree of deuterium incorporation is significantly
higher for the reaction of (E)-9 than that of (Z)-9, which is
consistent with the proposed reaction pathway where complex G
generated from (E)-9 undergoes the alkenyl C–H bond cleavage
to generate intermediate C followed by subsequent reprotonation.
(5)
TfO
≥99% D
D4
Et2NH (2.0 equiv)
DMF, 100 °C, 20 h
H
~95% H
D5
≥99% D
4e-d5 (0.5 M)
3e-d4: 88% yield
iPr iPr
iPr iPr
Me
Si
Me
Si
Pd(OAc)2 (10 mol%)
(6)
TfO
3e (1.0 equiv)
Et2NH (4.0 equiv)
D2O (44 equiv)
(H)D
DMF, 100 °C, 20 h
78% D
3f-d: 84% yield
4f (0.25 M)
3e: 95% recovery
no D incorporation
On the basis of these experiments and the fact that the C–H/C–
H coupling takes place between Ar2 and Ar3, a proposed catalytic
Si
Si
Ar1
Ar2
Ar1
Ar2
Ar3
X
H
H
H
4
3
Si
Ar3
Si
Ar1
Ar2
Ar1
Ar2
PdII
Pd0
PdII
H
– H X
H
X
H
Ar3
Ar3
F
A
Si
Si
Si
Ar1
Ar3
Ar2
Ar1
Ar2
PdII
Ar1
Ar3
Ar2
standard
1,4-palladium migration
PdII
H
X
H
PdII
X
H
H
– HX
Ar3
G
X
H
B
E
H
Si
Si
Ar1
Ar2
Ar1
Ar3
Ar2
– H X
H
PdII
H
PdII
HX
X
Ar3
C
1,4-palladium migration
with alkene stereoisomerization
H
D
Scheme 3. Proposed catalytic cycle for the reaction of 4 to 3 (X = OTf; amine base is omitted for clarity).
This article is protected by copyright. All rights reserved.

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
Support has been provided in part by JSPS KAKENHI Grant
Number JP18H04653 (Hybrid Catalysis) and the Sumitomo
Foundation. We thank Prof. Takeshi Naota and Dr. Soichiro
Kawamorita at Osaka University for the measurement of
fluorescence spectra.
Me Me
Me Me
Si
Si
Pd(OAc)2 (30 mol%)
(7)
Et2NH (6.0 equiv)
OTf
D2O (20 equiv)
DMF, 100 °C, 20 h
H
(D)H
15% D
3d: 85% yield
(w/o D2O: 89% yield)
(Z)-9 (0.17 M)
Keywords: palladium • C–H coupling • 1,4-migration • silicon •
π-conjugated compounds
Me Me
Si
Me Me
Si
[1]
Appropriately substituted 7H-benzo[e]naphtho[1,8-bc]silines and 8H-
benzo[e]phenanthro[1,10-bc]silines could be used as light-emitting
materials: a) M. Jun, S. Kim, Y. Kim, S. Hwang, S. Yang, US 2016/019-
449 A1, 2016; b) M. Jun, S. Ko, H. Kim, Y. Kim, S. Hwang, US
2016/0365521 A1, 2016.
Pd(OAc)2 (30 mol%)
(8)
Et2NH (6.0 equiv)
D2O (20 equiv)
DMF, 100 °C, 20 h
OTf
H
H/D
49% D
3d: 84% yield
(w/o D2O: 92% yield)
(E)-9 (0.17 M)
[2]
For reviews: a) H. Fu, Y. Cheng, Curr. Org. Chem. 2012, 16, 1423–1446;
b) J. Y. Corey, Adv. Organomet. Chem. 2011, 59, 181–328; c) W. W. H.
Wong, J. F. Hooper, A. B. Holmes, Aust. J. Chem. 2009, 62, 393–401;
d) J. Chen, Y. Cao, Macromol. Rapid Commun. 2007, 28, 1714–1742.
J. D. Citron, J. Organomet. Chem. 1975, 86, 359–367.
We have also briefly examined the optical properties of
benzophenanthrosilines 3 obtained by the present catalysis. As
summarized in Table S1,[16] we chose some of these compounds
for comparison (3e: parent, 3g: 10-NMe2, 3o: 3-NO2, 3t: 10-NMe2-
3-NO2). In both UV-vis absorption (Figure S1) and fluorescence
spectra (Figure S2),[16] introduction of an electron-donating group
at 10-position (3g) or an electron-withdrawing group at 3-position
(3o) led to a red-shift in their UV-vis absorption and emission band
[3]
[4]
a) D. Leifert, A. Studer, Org. Lett. 2015, 17, 386–389; b) C. Yang, J.
Wang, J. Li, W. Ma, K. An, W. He, C. Jiang, Adv. Synth. Catal. 2018, 360,
3049–3054.
[5]
[6]
For other synthetic approach: V. M. Hertz, H.-W. Lerner, M. Wagner, Org.
Lett. 2015, 17, 5240–5243.
V. M. Hertz, M. Bolte, H.-W. Lerner, M. Wagner, Angew. Chem. Int. Ed.
2015, 54, 8800–8804. Patents in Ref. [1] do not describe the synthetic
maxima compared to the parent compound (3e), and
a
significantly higher quantum yield was obtained for 3g (FF = 0.66
vs. FF = 0.10 for 3e and 3o). Even more significant red-shifts of
UV-vis absorption and emission band maxima were observed for
donor-acceptor compound 3t. Furthermore, while pyridine-
containing compound 3s had very similar absorption and
emission spectra compared with the parent compound (3e), N-
methylated derivative 10, which can be readily synthesized from
3s [Eq. (9)], showed red-shifts for both UV-vis absorption and
emission band maxima with a high quantum yield (FF = 0.83).[17]
These results demonstrate that the optical properties can be
effectively tuned by changing the substituents or derivatization of
these benzophenanthrosilines.
methods
of
8H-benzo[e]phenanthro[1,10-bc]siline
(and
7H-
benzo[e]naphtho[1,8-bc]siline) skeletons.
[7]
[8]
For reviews: a) Y. Yang, J. Lan, J. You, Chem. Rev. 2017, 117, 8787–
8863; b) B. V. Varun, J. Dhineshkumar, K. R. Bettadapur, Y. Siddaraju,
K. Alagiri, K. R. Prabhu, Tetrahedron Lett. 2017, 58, 803–824; c) G. P.
Chiusoli, M. Catellani, M. Costa, E. Motti, N. D. Ca, G. Maestri, Coord.
Chem. Rev. 2010, 254, 456–469.
For examples involving 1,4-palladium migration: a) M. A. Campo, Q.
Huang, T. Yao, Q. Tian, R. C. Larock, J. Am. Chem. Soc. 2003, 125,
11506–11507; b) Q. Huang, A. Fazio, G. Dai, M. A. Campo, R. C. Larock,
J. Am. Chem. Soc. 2004, 126, 7460–7461; c) J. Zhao, R. C. Larock, Org.
Lett. 2005, 7, 701–704; d) J. Zhao, D. Yue, M. A. Campo, R. C. Larock,
J. Am. Chem. Soc. 2007, 129, 5288–5295; e) Z. Lu, Y. Cui, Y. Jia,
Synthesis 2011, 2595–2599; f) T. Piou, A. Bunescu, Q. Wang, L. Neuville,
J. Zhu, Angew. Chem. Int. Ed. 2013, 52, 12385–12389; g) M. Wang, X.
Zhang, Y.-X. Zhuang, Y.-H. Xu, T.-P. Loh, J. Am. Chem. Soc. 2015, 137,
1341–1347; h) C.-W. Lee, E.-C. Liu, Y.-T. Wu, J. Org. Chem. 2015, 80,
10446–10456; i) S. K. Bhunia, A. Polley, R. Natarajan, R. Jana, Chem.
Eur. J. 2015, 21, 16786–16791; j) R. Rocaboy, O. Baudoin, Org. Lett.
2019, 21, 1434–1437; k) R. Rocaboy, I. Anastasiou, O. Baudoin, Angew.
Chem. Int. Ed. 2019, 58, 14625–14628.
iPr iPr
iPr iPr
Si
Si
MeOTf (1.2 equiv)
CH2Cl2, RT, 3 h
(9)
OTf
Me
N
N
10: 89% yield
3s
[9]
For reviews: a) F. Shi, R. C. Larock, Top. Curr. Chem. 2010, 292, 123–
164; b) S. Ma, Z. Gu, Angew. Chem. Int. Ed. 2005, 44, 7512–7517; For
selected examples: c) M. A. Campo, R. C. Larock, J. Am. Chem. Soc.
2002, 124, 14326–14327; d) A. Singh, P. R. Sharp, J. Am. Chem. Soc.
2006, 128, 5998–5999; e) T. Kesharwani, R. C. Larock, Tetrahedron
2008, 64, 6090–6102; f) T.-J. Hu, G. Zhang, Y.-H. Chen, C.-G. Feng, G.-
Q. Lin, J. Am. Chem. Soc. 2016, 138, 2897–2900.
In summary, we have developed a new and efficient synthesis
of 8H-benzo[e]phenanthro[1,10-bc]silines, silicon-bridged π-
conjugated compounds having a 6-membered silacycle, from 2-
((2-(arylethynyl)aryl)silyl)aryl triflates under simple palladium
catalysis. The reaction involves a C–H/C–H coupling via a 1,4-
palladium migration with concomitant alkene stereoisomerization,
which has been supported by
a series of experimental
[10] a) M. Shimizu, K. Mochida, T. Hiyama, Angew. Chem. Int. Ed. 2008, 47,
9760–9764; For an asymmetric variant: b) R. Shintani, H. Otomo, K. Ota,
T. Hayashi, J. Am. Chem. Soc. 2012, 134, 7305–7308.
mechanistic investigations. Future studies will be directed toward
further development of synthetic methods for various functional
organic compounds.
[11] For the reaction of related aryl triflates having an amino group at the 3-
position: a) Y. Sato, C. Takagi, R. Shintani, K. Nozaki, Angew. Chem. Int.
Ed. 2017, 56, 9211–9216; b) N. Misawa, T. Tsuda, R. Shintani, K.
Yamashita, K. Nozaki, Chem. Asian J. 2018, 13, 2566–2572.
Acknowledgements
[12] a) C. Bour, J. Suffert, Org. Lett. 2005, 7, 653–656; b) A. J. Mota, A.
Dedieu, C. Bour, J. Suffert, J. Am. Chem. Soc. 2005, 127, 7171–7182;
This article is protected by copyright. All rights reserved.

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
c) A. J. Mota, A. Dedieu, Organometallics 2006, 25, 3130–3142; d) A. J.
Mota, A. Dedieu, J. Org. Chem. 2007, 72, 9669–9678.
substrate having 2-benzothienyl group as Ar3 is not applicable in the
present catalysis, resulting in almost no reaction.
[13] The structures of compounds 3f and (E)-9 were determined by X-ray
crystallographic analysis. CCDC 1973920 and 1973921 contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336033.
[15] See the Supporting Information for kinetic isotope effect using H2O/D2O.
[16] See the Supporting Information.
[17] a) H. Wang, R. Helgeson, B. Ma, F. Wudl, J. Org. Chem. 2000, 65, 5862–
5867; b) I. Richter, M. R. Warren, J. Minari, S. A. Elfeky, W. Chen, M. F.
Mahon, P. R. Raithby, T. D. James, K. Sakurai, S. J. Teat, S. D. Bull, J.
S. Fossey, Chem. Asian J. 2009, 4, 194–198; c) M. T. Gabr, F. C. Pigge,
RSC Adv. 2015, 5, 90226–90234; d) R. Shintani, N. Misawa, R. Takano,
K. Nozaki, Chem. Eur. J. 2017, 23, 2660–2665.
[14] Notes: (1) Substrates having Br instead of OTf show much lower
reactivity (e.g., 10% yield of 3d from the corresponding bromide). (2) A
This article is protected by copyright. All rights reserved.

10.1002/anie.202000217
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 2:
COMMUNICATION
Tomohiro Tsuda, Yuka Kawakami,
Seung-Min Choi, Ryo Shintani*
R1 R2
Si
R1 R2
Si
Ar1
Ar2
Ar1
Ar2
Ar3
Pd(OAc)2 (5 mol%)
Page No. – Page No.
TfO
H
H
Et2NH (2.0 equiv)
DMF, 100 °C, 20 h
Palladium-Catalyzed Synthesis of
Benzophenanthrosilines by C–H/C–H
Coupling through 1,4-Palladium
73–96% yield
Ar3
Migration/Alkene Stereoisomerization
A new and efficient synthesis of 8H-benzo[e]phenanthro[1,10-bc]silines has been
developed under palladium catalysis. The reaction mechanism has been
experimentally investigated and a catalytic cycle involving a C–H/C–H coupling
through a new mode of 1,4-palladium migration with concomitant alkene
stereoisomerization has been proposed.
This article is protected by copyright. All rights reserved.