Geometry-Constrained Iminopyridyl Palladium-Catalyzed Hydroarylation of Alkynes to Prepare Tri-substituted Alkenes Using Alcohol as Reductant

Article abstract of DOI:10.1002/adsc.201800423

We developed an efficient and straightforward method to prepare tri-substituted alkenes through palladium-catalyzed hydroarylation of alkynes with aryl bromides. Diarylacetylenes and alkyl(aryl)acetylenes could be well hydroarylated with various aryl bromides in moderate to excellent yields. Mechanistic studies suggested that alcohol was the reductant to provide hydride through β-H elimination. Gram scale reaction further demonstrated the practicality and efficiency of the newly developed strategy. (Figure presented.).

Full text of DOI:10.1002/adsc.201800423

Title: Geometry-Constrained Iminopyridyl Palladium-Catalyzed
Hydroarylation of Alkynes to Prepare Tri-substituted Alkenes
Using Alcohol as Reductant
Authors: Ke Wu, Nan Sun, Baoxiang Hu, Zhenlu Shen, Liqun Jin, and
Xinquan Hu
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.201800423
Link to VoR: http://dx.doi.org/10.1002/adsc.201800423

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
Communication
Very Important Publication
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Geometry-Constrained Iminopyridyl Palladium-Catalyzed
Hydroarylation of Alkynes to Prepare Tri-substituted Alkenes
Using Alcohol as Reductant
Ke Wu,a Nan Sun,a Baoxiang Hu,a Zhenlu Shen,a Liqun Jina,b,* and Xinquan Hua,b,*
a
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032, P.R. China
phone: (+86)-571-88320416; e-mail: liqunjin@zjut.edu.cn; xinquan@zjut.edu.cn.
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, The Chinese
b
Academy of Sciences, Lanzhou 730000, P.R. China
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######.
attentions although it looks like
straightforward.
much more
Abstract. We developed an efficient and straightforward
method to prepare tri-substituted alkenes through
palladium-catalyzed hydroarylation of alkynes with aryl
bromides. Diarylacetylenes and alkyl(aryl)acetylenes
could be well hydroarylated with various aryl bromides
in moderate to excellent yields. Mechanistic studies
suggested that alcohol was the reductant to provide
hydride through -H elimination. Gram scale reaction
further demonstrated the practicality and efficiency of
the newly developed strategy.
Keywords: Hydroarylation; Alkyne; Palladium;
Tri-substituted alkene
Multi-substituted alkenes are prevalent structures in
natural products, drug molecules and organic
materials. They are also important synthetic
intermediates for preparing fine chemicals. Among
different approaches to construct these compounds,
transition metal-catalyzed alkyne hydroarylation has
gained particular attention as for an attractive route
for its potential directly constructing tri-substituted
alkene structures, as well as its fundamentally
challenging transformation.[1-4] Generally, three
strategies have been applied in the hydroarylation of
alkynes (Scheme 1): (a) Addition of arene to
alkyne,[5-12] which usually requires electron-rich
arenes and leads to mixtures of ortho- and
para-alkenylarene isomers; (b) Carbometalation of
alkyne with arylmetallic reagent,[13] such as
aryl-magnesium,[14-18] -zinc,[19-22] -lithium,[23,24] and
-boron[25-32] reagents, and final protodemetalation
giving rise to the hydroarylation product;[33] (c)
Reductive addition of aryl electrophile to alkyne.[34-36]
Overall, an aryl anion / proton provides the
hydroarylation partner in the first two routes, while
the third one employs an aryl cation / hydride, instead.
Great efforts have been devoted to the first two routes,
while surprisingly, the last one received much less
Scheme 1. Three potential strategies for alkyne
hydroarylation.
Among transition metal catalysts for the
hydroarylation of alkynes via reductive strategy,
palladium played an overwhelmed role in this area.
Developed by Cacchi and coworkers,
a
formate-palladium system has been successfully
applied in the hydroarylation of alkynes with aryl
electrophiles.[37-42] In this catalytic system, the
reactions underwent the syn-addition of the in situ
formed arylpalladium intermediate to the C-C triple
bonds, followed by the attack with HCOO-.
Subsequent decarboxylation and reductive elimination
of vinylpalladium hydride species give rise to the
target hydroarylation product.[35,42] However, only
aryl iodides could serve as the electrophiles in the
above mentioned methods, which might arise to the
relative sluggish oxidative condition step to
alkyne-ligated Pd(0) species. When aryl bromide was
1
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
Initially,
using
the
reaction
between
employed, the reduction adduct of alkyne has been
observed as the major products.[43] Recently,
arenediazonium salts have been successfully applied
in Pd-catalyzed hydroarylation of alkynes with silane
as the reductant.[44] Zhu and coworkers reported a
Pd/PCy3-catalyzed hydroarylation of ynol ethers with
aryl iodides using alcohol as the reductant.[45] Cazin
1,2-diphenylacetylene (1a) and 4-bromo-toluene (2a)
with t-BuOK as base in ethanol as the model
reaction, the catalytic effects of different iminopyridyl
palladium complexes were investigated (Table 1). To
our delight, the desired hydroarylation of
1,2-diphenylacetylene was observed in this catalytic
system. By changing the imino sites of the bidentate
ligands, we found that Pd-2 with the bulky
steric-hindered groups displayed best efficiency
comparing to the one with n-butyl or phenyl group,
which showed consistent with our previous reports
that increasing the steric environment favored for
stabilizing the palladium center.[66] The preliminary
promising results inspired us to further optimize the
reactions using Pd-2 as the catalyst.
and
coworkers
developed
a
cooperative
Pd/Cu-catalyzed system to construct tri-substituted
alkenes from alkynes and aryl bromides in the
presence of B2pin2.[46] To provide a more practical and
accessible protocol to construct multi-substituted
alkene motif, it thus remains of significant importance
in developing novel and efficient palladium catalytic
system for the hydroarylation of alkynes.
Table 1. Initial test of geometry-constrained iminopyridyl
palladium reactivity in alkyne hydroarylation. a
Scheme
2.
Geometry-constrained
iminopyridyl
compounds.
In palladium catalysis, it is no doubt that
phosphorus compounds are the most common ligands,
while, nitrogen ligands are ranked as the second
group and never lost their attention.[47-50] Bidentate
nitrogen ligands, such as bi-pyridine, phenanthroline,
bi-imine, bis-oxazoline, pyridine–oxazoline and
pyridine-benzoxazole etc, have been widely employed
in many Pd-catalyzed transformations for their
relatively thermos stability and exhibited interesting
selectivity and activity, including the excellent work
lately examplified by Sigman,[51-56] Liu,[57-59] Hong[60]
et al. Recently, we have developed a series of
a
Reaction conditions: cat. (2 mol%), 1a (1.0 mmol), 2a
(1.3 mmol), t-BuOK (1.5 mmol), EtOH (6 mL), 90 oC, 12 h.
b GC yields with naphthalene as the internal standard.
Table 2. Optimizing the reaction conditions for
geometry-constrained
iminopyridyl
compounds
Pd-catalyzed hydroarylation of 1,2-diphenylacetylene. a
(Scheme 2).[61-63] Their corresponding palladium
complexes showed satisfied catalytic efficiency for
both Suzuki coupling and Heck coupling involving
aryl bromides and aryl chlorides.[64-66] Compared to
these commonly used bidentate nitrogen ligands, our
developed ligand involved a regulable ring-fused
framework being able to establish a strained
environment for better stability toward the palladium
center. Furthermore, the Csp3 substituent on the
imine site could provide a steric effect, which was not
easily realized with the related bidentate nitrogen
ligands. These properties further inspired us that the
geometry-constrained iminopyridyl-Pd complex
might be suitable to tolerate the less active aryl
electrophiles towards the hydroarylation of alkyne. In
this hence, we herein reported our research in
Pd-catalyzed hydroarylation of alkynes with aryl
bromides to tri-substituted alkenes using alcohol as
the reductant. This newly developed protocol
provides
a
simple strategy for constructing
a
Reaction conditions: cat. (2 mol%), 1a (0.3 mmol), 2a
tri-substituted alkenes with i-PrOH as the reductant.
The bidentate geometry-constrained iminopyridyl
ligand played an important role in stabilizing the
palladium center for promoting this transformation.
o
(0.39 mmol), base (0.45 mmol), solvent (2 mL), 90 C, 12
h. GC yields with naphthalene as the internal standard.
b
c
d
Isolated yield. 1a (1 mmol), 2a (1.3 mmol), KOH (1.5
mmol), cat. (2 mol%), solvent (6 mL), 90 oC, 12 h.
2
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
a
Alcohol has been widely employed as a mild
Reaction conditions: Pd-2 (2 mol%), 1a (1.0 mmol ), 2
reductant in many transformations.[45, 67-70] We first (1.3 mmol), KOH (1.5 mmol), i-PrOH (6 mL), 90 oC, 12 h.
b
c
tested different alcohols, including EtOH, n-BuOH,
Isolated yields. E/Z ratios were determined by GC
i-PrOH and cyclohexanol (CyOH) (Table 2). analysis or 1H NMR spectra. The isolated yield was
Obviously, the secondary alcohols gave better results obtained from 0.3 mmol scale reaction.
than the primary ones, and the reaction yield was
d
significantly improved from 55% to 77% when
i-PrOH was used instead of EtOH (Table 2, entries 1
With the optimal conditions in hand, aryl bromides
and 3). Base also played important role in this with different substituents were applied to react with
transformation and was then subsequently evaluated. symmetrical diarylacetylenes in this hydroarylation
Strong bases, t-BuOK, t-BuONa, NaOH and KOH, reaction (Table 3). The hydroarylation products of
could efficiently promote the conversion, while KOH diphenylacetylene with various aryl bromides were
provided an obviously advantage and was thus chosen isolated in moderate to excellent yields, especially the
in the final protocol (Table 2, entry 11). To further steric ones with ortho substituents (Table 2, 3ac, 3ae
confirm the superiority that the geometry-constrained and 3ag), which were rather problematic in the
iminopyridyl ligand generated towards the palladium reported with the corresponding aryl iodides.[44] The
center, ligand-free Pd(OAc)2 and PdCl2(CH3CN)2 reaction could well tolerate
a
variety of
catalyzed hydroarylation of 1a under the identical electron-donating and electron-withdrawing
reaction conditions were performed and moderate substituents, including amino (3ah) and halides (3ai
yields and poor selectivity were obtained (Table 2, and 3aj). When p-bromoacetophenone (2l) was used
entries 14 and 15). Using PdCl2(PPh3)2 instead, only as the substrate, only 24% of the desired product 3al
11% of the desired product was observed (Table 2, was isolated. It was postulated that the carbonyl group
entry 16).
was reduced to the hydroxyl group under strong basic
environment and thus elimination to generate a vinyl
group. However, when the carbonyl group was
Table 3. Pd-catalyzed hydroarylation of diarylacetylene converted to the protected form (2s) (eqn 1), the
with different aryl bromides.
reaction proceeded smoothly, and subsequently
performing de-protection during work-up allowed
us to obtain the corresponding hydroarylation product
3al in 82% isolated yield. It is noteworthy that
heteroaryl bromides can be able to form the desired
products, although the isolated yields were lower than
others. We noted that the competitive reductive
de-bromination side reactions were dominant for
these electron-deficient aryl and heteroaryl bromides,
which was frequently observed under the ROH/base
conditions.[71,72] Besides, high stereoselectivities for
the tested substrates were attained and most E/Z ratios
are up to or higher than 99:1 except the one with –
NH2 group (2h). Methoxy and trifluoromethyl
substituted diarylacetylenes (1b and 1c) were also
examined under the standard conditions. Similar to
diphenylacetylene, the hydroarylation products were
achieved in 82% and 86% isolated yields, respectively
(3bf and 3cf) when using electron-rich aryl bromides
(2f). When electron-deficient aryl bromide was
employed, for example, para-trifluoromethylphenyl
bromide (2k), no matter hydroarylation with 1b or 1c,
only moderate yields were obtained.
According to the previous hydroarylation of aryl
iodides and related palladium-catalyzed additions of
“arylpalladium halides” to alkynes, a lack of
regioselectivity was observed when applying the
approach to unsymmetrical diarylacetylene. Under
our optimized conditions, we also carefully studied
the hydroarylation of unsymmetrical diarylacetylenes
(Scheme 3). The role of electronic effects from
3
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
alkynes and aryl bromides on the regioselectivity of controlled by the steric hindrance. Regarding to this,
this hydroarylation process was explored. To our we then applied 1-phenyl-1-butyne in this chemistry
disappointment, the results obtained were almost (Table 4). For the tested aryl bromides, the
same as those in the previous reports, and suggested hydroarylation products 4 could be produced in
that the electronic effects either from the alkyne or moderate to excellent yields. The strategy is indeed
from the aryl bromides, could not obviously influence more efficient for electron-rich aryl bromides. For the
the ratio of the regioisomeric products.[35]
regioselectivity, as we expected, the addition of aryl
group from Ar-Pd-X species to the carbon-carbon
triple bonds was favorable for the less steric sides,
finally delivering the -arylated products in 82-96%
regioselectivity. Increasing the steric hindrance of
aryl bromides slightly decreased the regioselectivities
(4dc and 4de). Extending the alkyl chain to
1-phenyl-1-decyne (1e), to our delight, the reactions
still proceeded well with identical regiochemical
outcomes. When the alkyl group is t-Bu (1f), good
yields were obtained while with obvious decreases in
the regioselectivity.
Scheme 3. Pd-catalyzed hydroarylations of unsymmetrical
diarylacetylene with different aryl bromides (The
regioisomers were not assigned)
In addition, the developed palladium system was
also tested with a dialkylacetylene. When using
4-octyne to react with 2b, the hydroarylated product
was isolated in 61% yield (eqn 2). Noteworthy, a
small amount (<5%) of double alkyne insertion side
Table 4. Pd-catalyzed hydroarylation of aryl(alkyl)
acetylenes with different aryl bromides. a
product
was
also
observed.[73]
Moreover,
phenylacetylene was also examined to react with 2b,
in which no hydroarylation occurred.
Scheme 4. Deuterium-Labelling Experiments
To gain some insights into the mechanism for this
Pd-catalyzed hydroarylation of alkynes, the reactions
between 1a and 2c were carried out under the
standard conditions in (CD3)2CDOD (Scheme 4). The
deuterated hydroarylation product 3ac-d was obtained
in 71% NMR yield. In contrast, when the reaction
was performed in t-BuOH instead, no desired
hydroarylation product was observed. These results
indicated that i-PrOH played a reductant role as a
hydride donor through -H elimination process after
the syn-addition of arylpalladium intermediate to the
C-C triple bonds.
a Reaction conditions: Pd-2 (2 mol%), 1 (1.0 mmol), 2 (1.3
mmol), KOH (1.5 mmol), i-PrOH (6 mL), 90 C, 12 h.
o
b
Isolated yields. Only trace amount of anti-addition product
c
was observed from GC-MS analysis. / products ratios
1
d
were determined by GC and H NMR analysis, NMR
yield was obtained with 1,2-dibromoethane as the internal
standard.
The previous Pd-catalyzed hydroarylation of
unsymmetrical
di-substituted
alkynes
also
demonstrated that the regioselectivity was greatly
4
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
[8]C. Jia, D. Piao, J. Oyamada, W. Lu, T. Kitamura, Y.
Fujiwara, Science (Washington, D. C.) 2000, 287,
1992-1995.
[9]T. Tsuchimoto, T. Maeda, E. Shirakawa, Y. Kawakami,
Chem. Commun. (Cambridge) 2000, 1573-1574.
[10] A. Biffis, C. Tubaro, G. Buscemi, M. Basato, Adv.
Synth. Catal. 2008, 350, 189-196.
[11] K. Gao, P.-S. Lee, T. Fujita, N. Yoshikai, J. Am.
Chem. Soc. 2010, 132, 12249-12251.
Finally, to further demonstrate the practicality and
efficiency of the developed system, we performed a
scale-up reaction (eqn 3). 1 mol% amount of Pd-2
was used and the reaction time was elongated to 15 h.
1.97 g of hydroarylated product 3aa (73%) was
successfully isolated from 10 mmol of 1a.
[12] D. J. Schipper, M. Hutchinson, K. Fagnou, J. Am.
Chem. Soc. 2010, 132, 6910-6911.
[13] P. Knochel, in Comprehensive Organic Synthesis
(Ed.: I. Fleming), Pergamon, Oxford, 1991, pp. 865-911.
[14] E. Shirakawa, T. Yamagami, T. Kimura, S.
Yamaguchi, T. Hayashi, J. Am. Chem. Soc. 2005, 127,
17164-17165.
[15] T. Yamagami, R. Shintani, E. Shirakawa, T. Hayashi,
Org. Lett. 2007, 9, 1045-1048.
[16] K. Murakami, H. Ohmiya, H. Yorimitsu, K. Oshima,
Org. Lett. 2007, 9, 1569-1571.
[17] J. G. Duboudin, B. Jousseaume, J. Organomet. Chem.
1978, 162, 209-222.
[18] F. Xue, J. Zhao, T. S. A. Hor, Chem. Commun. 2013,
49, 10121-10123.
[19] K. Murakami, H. Yorimitsu, K. Oshima, Org. Lett.
2009, 11, 2373-2375.
In summary, we developed an efficient
Pd-catalyzed hydroarylation of alkynes with aryl
bromides using i-PrOH as the reductant. The
geometry-constrained iminopyridyl ligand played an
important role in stabilizing the Pd center. Different
internal alkynes, involving symmetrical or
unsymmetrical
diarylacetylenes
and
alkyl(aryl)acetylenes, could be well tolerated to react
with various aryl bromides in moderate to excellent
yields. The regioselectivity for unsymmetrical alkynes
was demonstrated to be controlled by steric hindrance.
Further investigations for improving this chemistry
via modifying ligands are ongoing in our group.
[20] K. Shimizu, M. Takimoto, M. Mori, Y. Sato, Synlett
2006, 3182-3184.
Experimental Section
[21] B.-H. Tan, J. Dong, N. Yoshikai, Angew. Chem., Int.
Ed. 2012, 51, 9610-9614.
[22] M. Corpet, C. Gosmini, Chem. Commun. 2012, 48,
11561-11563.
[23] E. Shirakawa, S. Masui, R. Narui, R. Watabe, D.
Ikeda, T. Hayashi, Chem. Commun. 2011, 47,
9714-9716.
To a Young tube, was added 1,2-diphenylacetylene (178
mg, 1 mmol), 4-bromo-toluene (222 mg, 1.3 mmol), Pd-2
(14.9 mg, 2 mol%), KOH (84 mg, 1.5 mmol) and
isopropanol (6 mL). The mixture was stirred at 90 oC for 12
hours. Then,
solvent was removed in vacuo. 216 mg of
3aa (80%) was isolated by column chromatography on
silica gel (petroleum ether as the eluent ).
[24] E. Shirakawa, D. Ikeda, T. Ozawa, S. Watanabe, T.
Hayashi, Chem. Commun. 2009, 1885-1887.
[25] C. H. Oh, H. H. Jung, K. S. Kim, N. Kim, Angew.
Chem., Int. Ed. 2003, 42, 805-808.
[26] T. Hayashi, K. Inoue, N. Taniguchi, M. Ogasawara, J.
Am. Chem. Soc. 2001, 123, 9918-9919.
[27] M. Lautens, M. Yoshida, Org. Lett. 2002, 4, 123-125.
[28] N. Kim, K. S. Kim, A. K. Gupta, C. H. Oh, Chem.
Commun. 2004, 618-619.
[29] E. Shirakawa, G. Takahashi, T. Tsuchimoto, Y.
Kawakami, Chem. Commun. 2001, 2688-2689.
[30] H. Zeng, R. Hua, J. Org. Chem. 2008, 73, 558-562.
[31] Y. Yang, L. Wang, J. Zhang, Y. Jin, G. Zhu, Chem.
Commun. 2014, 50, 2347-2349.
[32] X. Xu, J. Chen, W. Gao, H. Wu, J. Ding, W. Su,
Tetrahedron 2010, 66, 2433-2438.
[33] K. Murakami, H. Yorimitsu, Beilstein J. Org. Chem.
2013, 9, 278-302.
[34] S. C. M. Dorn, A. K. Olsen, R. E. Kelemen, R.
Shrestha, D. J. Weix, Tetrahedron Lett. 2015, 56,
3365-3367.
[35] S. Cacchi, Pure Appl. Chem. 1990, 62, 713-722.
[36] G. D. Kortman, K. L. Hull, ACS Catal. 2017, 7,
6220-6224.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (21773210, 21603190, 21473160, and
21376224). Jin also thanks the support from Zhejiang University
of Technology and Qianjiang Scholar Program funded by
Zhejiang Province.
References
[1]V. P. Boyarskiy, D. S. Ryabukhin, N. A. Bokach, A. V.
Vasilyev, Chem. Rev. 2016, 116, 5894-5986.
[2]Y. Yamamoto, Chem. Soc. Rev. 2014, 43, 1575-1600.
[3]R. Manikandan, M. Jeganmohan, Org. Biomol. Chem.
2015, 13, 10420-10436.
[4]T. de Haro, C. Nevado, in: Comprehensive Organic
Synthesis (Eds.: P. Knochel, G. A. Molander), Elsevier:
Amsterdam, 2014, pp 1621-1659.
[5]A. Biffis, C. Tubaro, M. Baron, Chem. Rec. 2016, 16,
1742-1760.
[6]T. Kitamura, Eur. J. Org. Chem. 2009, 2009,
1111-1125.
[7]C. Jia, W. Lu, J. Oyamada, T. Kitamura, K. Matsuda, M.
Irie, Y. Fujiwara, J. Am. Chem. Soc. 2000, 122,
7252-7263.
[37] S. Cacchi, M. Felici, B. Pietroni, Tetrahedron Lett.
1984, 25, 3137-3140.
5
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
[38] A. Arcadi, S. Cacchi, F. Marinelli, Tetrahedron Lett. [67] Y. Tsuchiya, Y. Hamashima, M. Sodeoka, Org. Lett.
1986, 27, 6397-6400. 2006, 8, 4851-4854.
[39] S. Cacchi, G. Fabrizi, F. Marinelli, L. Moro, P. Pace, [68] K. M. Gligorich, S. A. Cummings, M. S. Sigman, J.
Tetrahedron 1996, 52, 10225-10240. Am. Chem. Soc. 2007, 129, 14193-14195.
[40] A. Arcadi, S. Cacchi, G. Fabrizi, F. Marinelli, P. Pace, [69] B. Ding, Z. Zhang, Y. Liu, M. Sugiya, T. Imamoto, W.
Eur. J. Org. Chem. 1999, 3305-3313. Zhang, Org. Lett. 2013, 15, 3690-3693.
[41] S. Cacchi, G. Fabrizi, L. M. Parisi, Heterocycles 2002, [70] R. J. DeLuca, B. J. Stokes, M. S. Sigman, Pure Appl.
58, 667-682. Chem. 2014, 86, 395-408.
[42] M. Ahlquist, G. Fabrizi, S. Cacchi, P.-O. Norrby, J. [71] S. D. Friis, M. T. Pirnot, L. N. Dupuis, S. L.
Am. Chem. Soc. 2006, 128, 12785-12793. Buchwald, Angew. Chem., Int. Ed. 2017, 56, 7242-7246.
[43] M. J. Wu, L. M. Wei, C. F. Lin, S. P. Leou, L. L. Wei, [72] Y. Hu, J. Liu, Z. Lü, X. Luo, H. Zhang, Y. Lan, A.
Tetrahedron 2001, 57, 7839-7844. Lei, J. Am. Chem. Soc. 2010, 132, 3153-3158.
[44] S. Cacchi, G. Fabrizi, A. Goggiamani, D. Persiani, [73] C. Zhou, R. C. Larock, J. Org. Chem. 2005, 70,
Org. Lett. 2008, 10, 1597-1600.
3765-3777
[45] W. Cui, J. Yin, R. Zheng, C. Cheng, Y. Bai, G. Zhu, J.
Org. Chem. 2014, 79, 3487-3493.
[46] M. Lesieur, Y. D. Bidal, F. Lazreg, F. Nahra, C. S. J.
Cazin, ChemCatChem 2015, 7, 2108-2112.
[47] A. Togni, L. M. Venanzi, Angew. Chem., Int. Ed.
1994, 33, 497-526.
[48] G. Desimoni, G. Faita, K. A. Jorgensen, Chem. Rev.
(Washington, DC, U. S.) 2006, 106, 3561-3651.
[49] L. Milhau, P. J. Guiry, Top. Organomet. Chem. 2011,
38, 95-154.
[50] F. Shibahara, T. Murai, Asian. J. Org. Chem. 2013, 2,
624-636.
[51] L. Xu, M. J. Hilton, X. Zhang, P.-O. Norrby, Y.-D.
Wu, M. S. Sigman, O. Wiest, J. Am. Chem. Soc. 2014,
136, 1960-1967.
[52] M. S. McCammant, M. S. Sigman, Chem. Sci. 2015, 6,
1355-1361.
[53] Z.-M. Chen, M. J. Hilton, M. S. Sigman, J. Am. Chem.
Soc. 2016, 138, 11461-11464.
[54] Z.-M. Chen, C. S. Nervig, R. J. De Luca, M. S.
Sigman, Angew. Chem., Int. Ed. 2017, 56, 6651-6654.
[55] H. H. Patel, M. B. Prater, S. O. Squire, M. S. Sigman,
J. Am. Chem. Soc. 2018, 140, 5895-5898.
[56] Q. Yuan, M. S. Sigman, J. Am. Chem. Soc. 2018, 140,
6527-6530.
[57] Z. Yuan, H.-Y. Wang, X. Mu, P. Chen, Y.-L. Guo, G.
Liu, J. Am. Chem. Soc. 2015, 137, 2468-2471.
[58] G. Yin, X. Mu, G. Liu, Acc. Chem. Res. 2016, 49,
2413-2423.
[59] W. Zhang, P. Chen, G. Liu, Angew. Chem., Int. Ed.
2017, 56, 5336-5340.
[60] J. Kim, S. H. Hong, ACS Cat. 2017, 3336-3343.
[61] Y. Xie, H. Huang, W. Mo, X. Fan, Z. Shen, Z. Shen,
N. Sun, B. Hu, X. Hu, Tetrahedron: Asymmetry 2009,
20, 1425-1432.
[62] J. Yu, X. Hu, Y. Zeng, L. Zhang, C. Ni, X. Hao, W.-H.
Sun, New J. Chem. 2011, 35, 178-183.
[63] F. Huang, Z. Sun, S. Du, E. Yue, J. Ba, X. Hu, T.
Liang, G. B. Galland, W.-H. Sun, Dalton Trans. 2015,
44, 14281-14292.
[64] B. Ye, L. Wang, X. Hu, C. Redshaw, W.-H. Sun,
Inorg. Chim. Acta 2013, 407, 281-288.
[65] Y. Tang, Y. Zeng, Q. Hu, F. Huang, L. Jin, W. Mo, N.
Sun, B. Hu, Z. Shen, X. Hu, W.-H. Sun, Adv. Synth.
Catal. 2016, 358, 2642-2651.
[66] Y. Lai, Z. Zong, Y. Tang, W. Mo, N. Sun, B. Hu, Z.
Shen, L. Jin, W.-h. Sun, X. Hu, Beilstein. J. Org. Chem.
2017, 13, 213-221.
6
This article is protected by copyright. All rights reserved.

10.1002/adsc.201800423
Advanced Synthesis & Catalysis
COMMUNICATION
Geometry-Constrained Iminopyridyl
Palladium-Catalyzed Hydroarylation of Alkynes to
Prepare Tri-substituted Alkenes Using Alcohol as
Reductant
T
O
C
G
r
Adv. Synth. Catal. Year, Volume, Page – Page
a
p
h
i
Ke Wu, Nan Sun, Baoxiang Hu, Zhenlu Shen,
Liqun Jin,* and Xinquan Hu*
c
7
This article is protected by copyright. All rights reserved.