Palladium-Catalyzed Cascade Reactions of 2-(Cyanomethoxy)chalcones with Arylboronic Acids: Selective Synthesis of Emissive Benzofuro[2,3- c]pyridines

Article abstract of DOI:10.1021/acs.orglett.9b04185

The Pd(II)-catalyzed cascade reactions of 2-(cyanomethoxy)chalcones with arylboronic acids were demonstrated, allowing the rapid construction of benzofuro[2,3-c]pyridine skeletons with excellent selectivity. These transformations involve the domino-style formation of C-C/C-C/C-N bonds through nitrile carbopalladation, intramolecular Michael addition, cyclization, and aromatization. This chemistry allows for the reactions of 2-(cyanomethoxy)chalcones with thiophen-3-ylboronic acid, providing 3-aryl-1-(thiophen-3-yl)benzofuro[2,3-c]pyridines in moderate to good yields. In addition, the resulting products represent a new class of emissive fluorophores.

Full text of DOI:10.1021/acs.orglett.9b04185

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Palladium-Catalyzed Cascade Reactions of
2‑(Cyanomethoxy)chalcones with Arylboronic Acids: Selective
Synthesis of Emissive Benzofuro[2,3‑c]pyridines
Wenzhang Xiong,† Kun Hu,† Yunxiang Lei,‡ Qianqian Zhen,† Zhiwei Zhao,† Yinlin Shao,†
Renhao Li,§ Yetong Zhang,† and Jiuxi Chen*,†
†College of Chemistry & Materials Engineering, Wenzhou University, Wenzhou 325035, P. R. China
‡School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
§School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, P. R. China
S
* Supporting Information
ABSTRACT: The Pd(II)-catalyzed cascade reactions of 2-
(cyanomethoxy)chalcones with arylboronic acids were dem-
onstrated, allowing the rapid construction of benzofuro[2,3-
c]pyridine skeletons with excellent selectivity. These trans-
formations involve the domino-style formation of C−C/C−
C/C−N bonds through nitrile carbopalladation, intramolec-
ular Michael addition, cyclization, and aromatization. This
chemistry allows for the reactions of 2-(cyanomethoxy)-
chalcones with thiophen-3-ylboronic acid, providing 3-aryl-1-
(thiophen-3-yl)benzofuro[2,3-c]pyridines in moderate to good yields. In addition, the resulting products represent a new class
of emissive fluorophores.
Scheme 1. Reactions Associated with this Study
he development of new transformations to generate high
Tvalue-added synthetic or medicinal products from readily
available starting materials via selective, one-pot domino-style
bond formations is a significant research goal.1 The transition-
metal-catalyzed conjugate addition of arylboronic acids to α,β-
unsaturated carbonyl compounds is emerging as a very
powerful means of accessing a large family of β-aryl substituted
carbonyl molecules.2 Among the reported methods, the well-
established palladium-catalyzed conjugate addition of arylbor-
onic acids to α,β-unsaturated carbonyl compounds (Scheme
1a)3 and the associated mechanism4 have attracted significant
attention over the past several decades. In addition, there has
recently been remarkable progress in the palladium-catalyzed
addition of arylboronic acids to nitriles for the synthesis of
hydrolyzed ketones or further cyclization products.5 This has
evoked a new series of explorations concerning the
carbopalladation of nitriles, with the potential to synthesize
structurally diverse five- or six-membered N-heterocycles, as
demonstrated by our own group6 and others7 (Scheme 1b).
Very recently, our group reported the palladium-catalyzed
cascade reactions of 2′-acetyl-[1,1′-biphenyl]-2-carbonitriles
with arylboronic acids for the synthesis of seven-membered
5H-dibenzo[c,e]azepines.8 However, the selective reaction of
cyano-substituted chalcones with arylboronic acids is still a
significant challenge, because the carbopalladation of nitriles
competes with the conjugate addition of arylboronic acids to
α,β-unsaturated carbonyl compounds. We envisioned that it
might be possible to obtain seven-membered benzo[f ][1,4]-
oxazepines9 via intermediate A (Scheme 1c, right) or
benzo[b]oxepin-3-amines10 through intermediate B (Scheme
1c, left), on the basis of two possible reaction pathways.
Received: November 22, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b04185
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Surprisingly, fused tricyclic benzofuro[2,3-c]pyridines were
obtained from this process. Herein, we report the discovery of
this novel transformation, involving the sequential carbopalla-
dation reaction of the nitrile, an intramolecular Michael
addition, cyclization, and aromatization. This mechanism
proceeds via the one-pot domino-style formation of C−C/
C−C/C−N bonds with excellent selectivity to provide
benzofuro[2,3-c]pyridines that are often difficult to prepare
by traditional routes.11
Scheme 2. Synthesis of 1,3-Diarylbenzofuro[2,3-
c]pyridines
a
We began by screening the reaction conditions using the
readily available reagents 2-(cyanomethoxy)chalcone (1a) and
phenylboronic acid (2a) to determine optimal conditions
(Table 1). The desired product 3a was isolated in 12% yield in
a
Table 1. Reaction Optimization
b
entry
Pd catalyst
ligand
solvent
yield (%)
1
2
3
4
5
6
7
8
Pd(TFA)2
Pd(acac)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
−
L1
L1
L1
L2
L3
L4
L5
L5
L5
L5
L5
−
2-MeTHF
2-MeTHF
2-MeTHF
2-MeTHF
2-MeTHF
2-MeTHF
2-MeTHF
DMA
dioxane
THF
THF
THF
THF
12
21
29
24
21
25
47
21
37
68
9
10
11
12
13
c
81
0
0
L5
a
a
Conditions: 1a (0.2 mmol), 2 (0.4 mmol), Pd(OAc)2 (5 mol %), L5
(10 mol %), TFA (0.4 mmol), THF (1 mL), air, 80 °C, 36 h. Isolated
yield.
Conditions: 1a (0.2 mmol), 2a (0.4 mmol), Pd catalyst (5 mol %),
ligand (10 mol %), TFA (0.4 mmol), solvent (1 mL), 80 °C, 24 h, air.
b
c
Isolated yield. For 36 h.
the presence of Pd(TFA)2 and 2,2′-bipyridine using trifluoro-
acetic acid (TFA) in 2-methyltetrahydrofuran (2-MeTHF) at
80 °C for 24 h under ambient air (entry 1). The 3a yields were
improved to 21% and 29% by using Pd(acac)2 and Pd(OAc)2
as the catalyst, respectively (entries 2−3). A variety of
bidentate N-donor ligands, including 5,5′-dimethyl-2,2′-bipyr-
idine (L2), 6,6′-dimethyl-2,2′-bipyridine (L3), 1,10-phenan-
throline (L4), and 2,9-dimethyl-1,10-phenanthroline (L5),
were examined (entries 4−7), and L5 was found to give the
best results, providing 3a in 47% yield (entry 7). After a brief
screening of solvents, THF was determined to be optimal, as it
afforded 3a in 68% yield (entries 8−10). The yield of 3a was
further improved to 82% by increasing the reaction time to 36
h (entry 11). It is worth noting that both the Pd catalyst and
the ligand are necessary for this reaction to take place (entries
12−13).
We next explored the scope of arylboronic acids that could
be employed, using 1a as the substrate under the optimized
reaction conditions (Scheme 2, 3b−3r). Initially, the reactions
of 1a with tolylboronic acid at the para-, meta-, and ortho-
positions were surveyed, affording the corresponding desired
3b, 3c, and 3d products in 72%, 75%, and 90% yields,
respectively. Dimethyl-, isopropyl-, and tert-butyl-substituted
compounds were also well tolerated, and the corresponding
products were obtained in 70−75% yields (3e−3g). Both
electron-rich substituents, such as methoxy (3h), phenoxy
(3l), and [1,3]dioxolo (3j) groups, and electron-deficient
substituents, such as trifluoromethoxy (3k), fluoro (3l), chloro
(3m), and bromo (3n) groups, were also compatible, giving
the desired products with moderate to good yields. We also
found that the reactions of 2-naphthylboronic acid and 1-
naphthylboronic acid proceeded smoothly to afford the
corresponding products 3o and 3p in 86% and 94% yields,
respectively. Substrates bearing diphenylamino and N-
carbazolyl moieties were well tolerated, providing the
corresponding products 3q and 3r in 50% and 72% yields,
respectively. Subsequently the range of 2-(cyanomethoxy)-
chalcones that could be applied was assessed (Scheme 2, 3s−
4g). A variety of functional groups (R) could be attached to
the chalcone, including electron-donating groups, such as
methyl (3s) and methoxy (3t) moieties, and electron-
withdrawing groups, such as fluoro (3u), chloro (3v), and
bromo (3w) moieties. The effect of the ring position of a single
substituent on the aryl ring (Ar) was evaluated, and the results
indicated that the steric effects of substituents had no obvious
influence on the yield. As an example, substrates with para-,
meta-, and ortho-methyl substituents delivered 3x, 3y, and 3z in
82%, 81%, and 80% yields, respectively. Moderately electron-
B
DOI: 10.1021/acs.orglett.9b04185
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
deficient halogens, such as fluoro (4a), chloro (4b), and
bromo (4c) groups, were well tolerated, giving 86−88% yields.
Highly electron-withdrawing groups (e.g., CF3) could also be
inserted at the para position, although the desired product 4d
was obtained in a slightly lower yield. The structure of 4d was
identified by X-ray diffraction. These transformations were also
efficient when using naphthyl, furyl, and thienyl groups,
affording the desired products 4e, 4f, and 4g in 66−75% yields.
Although the strongly coordinating sulfur atom in the
thiophene ring is known to poison Pd(II) catalysts, we
determined that the reaction with thiophen-3-ylboronic acid
proceeded smoothly to give various 3-aryl-1-(thiophen-3-
yl)benzofuro[2,3-c]pyridines (Scheme 2, 5a−5o). Functional
groups (R) such as methyl (5b), methoxy (5c), fluoro (5d),
chloro (5e), and bromo moieties, could also be applied to
obtain yields ranging from 55% to 72%. In addition, a variety of
substituents (e.g., Me, OMe, F, Cl, Br, CF3, and naphthyl
groups) on the aryl ring of the 2-(cyanomethoxy)chalcone
moiety were well tolerated, affording the desired products 5f−
5o in 66−84% yields. The moderate to good yields obtained
with thiophen-3-ylboronic acid provide further evidence that
our catalytic system can withstand severe sulfur atom
poisoning. Interestingly, furan-2-ylboronic acid was also
compatible with the reaction system, albeit with a lower 36%
yield of the desired 1-(furan-2-yl)-3-phenylbenzofuro[2,3-
c]pyridine (Scheme 2, 5p).
the CN bond is greater than that of the CC bond of the
chalcone in our Pd-catalyzed addition reaction.
On the basis of the above experimental results, we propose a
possible mechanism for the synthesis of benzofuro[2,3-
c]pyridines (Scheme 4). The reaction begins with trans-
Scheme 4. Proposed Mechanism
metalation of the palladium catalyst and aryboronic acids
followed by coordination of a cyano group to the Pd to form
intermediate A. Next, carbopalladation of the cyano group
affords the imine−Pd intermediate B. The protonation of B in
the presence of TFA produces imine intermediate C (or
tautomerization of imine to enamine intermediate D) and
regenerates the palladium catalyst. Intramolecular Michael-
type12 addition of the intermediate C or D gives intermediate
E, followed by cyclization to generate intermediate F. Finally,
the intermediate F could be easily oxidized to a stable π-
conjugated benzofuro[2,3-c]pyridine skeleton.
We next turned our attention to mechanistic investigations,
and several control experiments were performed under the
standard conditions (Scheme 3). First, the reaction was
Scheme 3. Control Experiments
Organic luminescent materials have extremely important
applications in probes, biological imaging, therapeutics, and
optoelectronic devices.13 Traditional fluorophores have rela-
tively flat, rigid structures that enhance the conjugation within
the molecule.14 However, this planar configuration can also
result in aggregation of the molecules as a result of relatively
strong π−π interactions. This in turn can cause quenching of
the fluorescence (representing so-called aggregation caused
quenching or ACQ). Therefore, the application of such
materials is limited to the solution state. However, in 2001,
Tang discovered a compound that only exhibits strong
fluorescence in the aggregate state (aggregation induced
emission: AIE). AIE materials have a distorted molecular
configuration and larger spatial structure that prevent strong
interactions between molecules in the aggregated state.15 As
might be expected, the applications of AIE materials are
limited to aggregated states. Thus, fluorophores showing
strong emission in both the solid and solution states have
attracted significant interest. These materials have the
advantages of both ACQ and AIE compounds and show
highly efficient luminescence in both states, thus widening the
range of potential applications.16
attempted in the absence of phenyboronic acid, but 3-(2-oxo-
2-phenylethyl)benzofuran-2-carbonitrile (6a) was not ob-
tained. This result indicates that the tandem transformation
is initiated by the carbopalladation of the nitrile (Scheme 3a).
In addition, an intermolecular competition experiment was
performed under standard conditions (Scheme 3b). Individual
reactions involving chalcone (7a) and 2-phenoxyacetonitrile
(7b) delivered 1,3,3-triphenylpropan-1-one (8a) and 2-
phenoxy-1-phenylethan-1-one (8b) in 82% and 91% yields,
respectively (entries 1−2). A competition reaction incorporat-
ing equimolar amounts of 7a and 7b with phenyboronic acid
showed that the transformation occurred more readily with 7b
(entries 3−4). This observation suggests that the reactivity of
Despite significant research effort, materials which can
exhibit emission in both solution and solid state are still very
rare. Various experimental studies and theoretical calculations
have shown that such compounds should have a configuration
that is both rigid and twisted. In this work, the synthesized
benzofuro[2,3-c]pyridine skeleton is a good candidate which
has strong fluorescence in solution and solid state. This
structure exhibits a level of planarity that ensures the intrinsic
C
DOI: 10.1021/acs.orglett.9b04185
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
luminescence of the compound. Moreover, the aromatic
groups attached to the 1 and 3 positions of the pyridine ring
distort the spatial configuration of the molecule to produce
strong fluorescence in the solid state. To verify the properties
of benzofuro[2,3-c]pyridine derivatives, we selected nine
compounds and examined their luminescence. As shown in
Figure 1a, these derivatives exhibited strong blue fluorescence
produced strong fluorescence emissions (Figures 1c, S1 and
S2). These results provide further evidence that these
derivatives have strong emission in solution and solid state.
The effects of solvent polarity were examined by assessing the
fluorescence emissions of the above-mentioned three com-
pounds in toluene, dichloromethane (DCM), ethyl acetate
(EA), and DMSO. The emission wavelengths of benzofuro-
[2,3-c]pyridine with either an electron-donating group (e.g.,
3i) or an electron-withdrawing group (e.g., 3l) in different
solvents were almost constant, indicating that the fluorescence
of these materials is relatively unaffected by the polarity of the
solvent (Figures 1d, S3 and S4). Density functional theory
calculations were performed to obtain additional information
regarding the optical properties of these compounds at the
molecular level, using a suite of the Gaussian 09 program. The
highest occupied molecular orbital (HOMO) and lowest
unoccupied molecular orbital (LUMO) energy levels of the
derivatives were calculated using the B3LYP/6-31+G*
method. Because pyridine is electron-withdrawing, the
LUMO of each compound was primarily distributed on the
benzofuro[2,3-c]pyridine skeleton, while the HOMO was
distributed over almost the entire molecule (Figure 1e).
In summary, we successfully demonstrated the Pd(II)-
catalyzed cascade reactions of (cyanomethoxy)chalcones with
arylboronic acids, providing a new strategy for the synthesis of
a diverse array of valuable benzofuro[2,3-c]pyridines that are
often difficult to prepare by traditional routes. This chemistry
can also be applied to the synthesis of 1-(thiophen-3-
yl)benzofuro[2,3-c]pyridines by using thiophen-3-ylboronic
acid as the coupling partner. Benzofuro[2,3-c]pyridines have
great practical significance in terms of expanding the types and
applications of fluorescent materials.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.9b04185.
Figure 1. (a) Fluorescence spectra of compounds in the solution state
(THF as solvent, concentration: 1.0 × 10−4 mol/L). (b) Fluorescence
spectra of compounds in the solid state. (c) Fluorescence spectra of
3a in THF/H2O with varying H2O percentages (inset: fluorescent
photographs of the compound at 0% and 99% water content in the
mixed solvent; concentration: 1.0 × 10−4 mol/L). (d) Emission
spectra of 3a in different solvents. (e) LUMOs and HOMOs of 3a, 3i,
and 3l.
Experimental procedures, characterization data, NMR
spectra, and X-ray data for product 4d (PDF)
Accession Codes
CCDC 1971013 contains 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 Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
emissions in solution, with wavelengths in the range 484 to 492
nm and absolute quantum yields from 33% to 70% (Table S1).
The fluorescence wavelengths in the solid state were in the
range 405 to 440 nm, and the fluorescence quantum yields
were from 20% to 40% (Figure 1b, Table S1). These results
confirm that the benzofuro[2,3-c]pyridine derivatives can emit
fluorescence in solution and solid state. Compared to the
solution state, the wavelengths of the solid materials are red-
shifted and the fluorescence intensity is decreased. These
effects can possibly be attributed to weak intermolecular
interactions between molecules in the aggregated state.12a,14b
The luminescence properties of compounds 3a, 3i, and 3l in
different THF/H2O mixtures were also investigated. In pure
THF solutions, these materials showed intense fluorescence
emissions. However, the compounds changed from mono-
molecular to an aggregated state when the proportion of the
poor solvent (water) was increased to 80%. Despite the red
shift of wavelengths and change in fluorescence intensity, the
compounds in both the solution state and the aggregate state
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: jiuxichen@wzu.edu.cn.
ORCID
Yinlin Shao: 0000-0003-1935-0345
Renhao Li: 0000-0003-2451-2142
Jiuxi Chen: 0000-0001-6666-9813
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China
(No. 21572162) and the Natural Science Foundation of
■
D
DOI: 10.1021/acs.orglett.9b04185
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Zhang, Y.; Yu, S.; Yang, F.; Yuan, D.; Guo, H.; Zhang, C. Adv. Synth.
Catal. 2019, 361, 3582−3587.
Zhejiang Province (Nos. LY20B020015 and LQ18B020006)
for financial support.
(10) (a) Stopka, T.; Marzo, L.; Zurro, M.; Janich, S.; Wurthwein, E.-
U.; Daniliuc, C.; Aleman, J.; Mancheno, O. Angew. Chem., Int. Ed.
2015, 54, 5049−5053. (b) Xia, Y.; Liu, Z.; Xiao, Q.; Qu, P.; Ge, R.;
Zhang, Y.; Wang, J. Angew. Chem., Int. Ed. 2012, 51, 5714−5717.
(c) Matsuda, T.; Sato, S. J. J. Org. Chem. 2013, 78, 3329−3335.
(d) Ouyang, L.; Qi, C.; He, H.; Peng, Y.; Xiong, W.; Ren, Y.; Jiang, H.
J. Org. Chem. 2016, 81, 912−919. (e) Stockerl, S.; Danelzik, T.;
Piekarski, D.; Mancheno, O. Org. Lett. 2019, 21, 4535−4539.
(11) For synthesis of benzofuro[2,3-c]pyridines, see: (a) Dhiman, S.;
Mishra, U. K.; Ramasastry, S. S. V. Angew. Chem., Int. Ed. 2016, 55,
7737−7741. (b) Sun, P.; Wu, Y.; Yang, T.; Wu, X.; Xu, J.; Lin, A.;
Yao, P. Adv. Synth. Catal. 2015, 357, 2469−2473. (c) Rao, Y.; Li, Z.;
Yin, G. Green Chem. 2014, 16, 2213−2218. (d) Zhu, D.; Wu, Z.; Luo,
B.; Du, Y.; Liu, P.; Chen, Y.; Hu, Y.; Huang, P.; Wen, S. Org. Lett.
2018, 20, 4815−4818. (e) Fu, X.; Yang, J.; Deng, K.; Shao, L.; Xia, C.;
Ji, Y. Org. Lett. 2019, 21, 3505−3509. (f) Lai, L.; Lin, P.; Huang, W.;
Shiao, M.; Ru Hwu, J. Tetrahedron Lett. 1994, 35, 3545−3546.
(g) Black, M.; Cadogan, J.; McNab, H. Org. Biomol. Chem. 2010, 8,
2961−2967. (h) Abramovitch, R.; Inbasekaran, M.; Kato, S.;
Radzikowska, T.; Tomasik, P. J. Org. Chem. 1983, 48, 690−695.
(i) Liu, J.; Fitzgerald, A.; Mani, N. J. Org. Chem. 2008, 73, 2951−
2954. (j) Yue, W.; Li, J. Org. Lett. 2002, 4, 2201−2203.
REFERENCES
■
(1) For selected reviews, see: (a) Dimakos, V.; Taylor, M. S. Chem.
Rev. 2018, 118, 11457−11517. (b) Eisenstein, O.; Milani, J.; Perutz,
R. N. Chem. Rev. 2017, 117, 8710−8753. (c) Afewerki, S.; Cordova,
́
A. Chem. Rev. 2016, 116, 13512−13570. (d) Dai, C.; Zhang, J.;
Huang, C.; Lei, Z. Chem. Rev. 2017, 117, 6929−6983. (e) Liang, Y.;
Wei, J.; Qiu, X.; Jiao, N. Chem. Rev. 2018, 118, 4912−4945.
(f) Waldvogel, S. R.; Lips, S.; Selt, M.; Riehl, B.; Kampf, C. J. Chem.
Rev. 2018, 118, 6706−6765. (g) Chen, S.; Wojcieszak, R.; Dumeignil,
F.; Marceau, E.; Royer, S. Chem. Rev. 2018, 118, 11023−11117.
(2) (a) Alexakis, A. The conjugate addition reaction. In Transition
Metals for Organic Synthesis: Building Blocks and Fine Chemicals, 2nd
ed.; Beller, M., Bolm, C., Eds.; Wiley-VCH: Weinheim, 2004.
(b) Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis;
Pergamon Press: Oxford, U.K., 1992. (c) Hawner, C.; Alexakis, A.
Chem. Commun. 2010, 46, 7295−7306. (d) Harutyunyan, S. R.; den
Hartog, T.; Geurts, K.; Minnaard, A. J.; Feringa, B. L. Chem. Rev.
2008, 108, 2824−2852. (e) Hayashi, T.; Yamasaki, K. Chem. Rev.
2003, 103, 2829−2844. (f) Fagnou, K.; Lautens, M. Chem. Rev. 2003,
103, 169−196. (g) Rossiter, B. E.; Swingle, N. M. Chem. Rev. 1992,
92, 771−806. (h) For a review on Pd-catalyzed conjugate addition,
see: Liu, Y.; Han, S.-J.; Liu, W.-R.; Stoltz, B. M. Acc. Chem. Res. 2015,
48, 740−751.
(3) (a) Lu, X.; Lin, S. H. J. Org. Chem. 2005, 70, 9651−9653.
(b) Liu, R.; Yang, Z.; Ni, Y.; Song, K.; Shen, K.; Lin, S.; Pan, Q. J. Org.
Chem. 2017, 82, 8023−8030. (c) Lin, S.; Lu, X. Org. Lett. 2010, 12,
2536−2539. (d) He, P.; Lu, Y.; Dong, C.-G.; Hu, Q.-S. Org. Lett.
2007, 9, 343−346. (e) Nishikata, T.; Yamamoto, Y.; Miyaura, N.
Angew. Chem., Int. Ed. 2003, 42, 2768−2770. (f) Cho, C. S.;
Motofusa, S.; Ohe, K.; Uemura, S.; Shim, S. C. J. Org. Chem. 1995, 60,
883−888. (g) Nishikata, T.; Yamamoto, Y.; Miyaura, N. Adv. Synth.
Catal. 2007, 349, 1759−1764. (h) Holder, J. C.; Zou, L.; Marziale, A.
N.; Liu, P.; Lan, Y.; Gatti, M.; Kikushima, K.; Houk, K. N.; Stoltz, B.
M. J. Am. Chem. Soc. 2013, 135, 14996.
(12) (a) Chintala, P.; Ghosh, S.; Long, E.; Headley, A.; Ni, B. Adv.
́
Synth. Catal. 2011, 353, 2905−2909. (b) Avila, E.; de Mello, A.;
Diniz, R.; Amarante, G. Eur. J. Org. Chem. 2013, 2013, 1881−1883.
(c) Maity, R.; Sahoo, S.; Pan, S. Eur. J. Org. Chem. 2019, 2019, 2297−
2304. (d) Sato, Y.; Hosoya, Y.; Kobayashi, I.; Adachi, K.; Nakada, M.
Asian J. Org. Chem. 2019, 8, 1033−1036.
(13) (a) Kim, H. N.; Guo, Z.; Zhu, W.; Yoon, J.; Tian, H. Chem. Soc.
Rev. 2011, 40, 79−93. (b) Cai, Z. X.; Zhang, N.; Awais, M. A.; Filatov,
A. S.; Yu, L. P. Angew. Chem., Int. Ed. 2018, 57, 6442−6448. (c) Nie,
H.; Hu, K.; Cai, Y.; Peng, Q.; Zhao, Z.; Hu, R.; Chen, J.; Su, S. J.; Qin,
A.; Tang, B. Z. Mater. Chem. Front. 2017, 1, 1125−1129. (d) Mei, J.;
Hong, Y.; Lam, J. W. Y.; Qin, A. J.; Tang, Y. H.; Tang, B. Z. Adv.
Mater. 2014, 26, 5429−5479. (e) Cai, Z. X.; Lo, W. Y.; Zheng, T. Y.;
Li, L. W.; Zhang, N.; Hu, Y. B.; Yu, L. P. J. Am. Chem. Soc. 2016, 138,
10630−10635.
(14) (a) Lei, Y. X.; Zhou, Y. Z.; Guo, Y.; Huang, X. B.; Qian, L. B.;
Wu, H. Y.; Liu, M. C.; Cheng, Y. X. J. Phys. Chem. C 2015, 119,
23138−23148. (b) Sturala, J.; Etherington, M. K.; Bismillah, A. N.;
Higginbotham, H. F.; Bromley, E. H. C.; Monkman, A. P.;
McGonigal, P. R. J. Am. Chem. Soc. 2017, 139, 17882−17889.
(c) Li, K.; Liu, Y. Y.; Li, Y. Y.; Feng, Q.; Hou, H. W.; Tang, B. Z.
Chem. Sci. 2017, 8, 7258−7267.
(15) (a) Luo, J.; Xie, Z.; Lam, J. W. Y.; Cheng, L.; Chen, H.; Qiu, C.;
Kwok, H. S.; Zhan, X.; Liu, Y.; Zhu, D.; Tang, B. Z. Chem. Commun.
2001, 1740−1741. (b) Mizoshita, N.; Tani, T.; Inagaki, S. Adv. Mater.
2012, 24, 3350−3355. (c) Lawrence, J. R.; Shim, G. H.; Jiang, P.;
Han, M. G.; Ying, Y. R.; Foulger, S. H. Adv. Mater. 2005, 17, 2344−
2349. (d) Suzuki, T.; Shinkai, S.; Sada, K. Adv. Mater. 2006, 18,
1043−1046.
(16) (a) Beppu, T.; Tomiguchi, K.; Masuhara, A.; Pu, Y. J.; Katagiri,
H. Angew. Chem., Int. Ed. 2015, 54, 7332−7335. (b) Huang, M. N.;
Yu, R. N.; Ye, S. X.; Kang, S.; Zhu, X. H.; Wan, Y. Q. Chem. Sci. 2016,
7, 4485−4491. (c) Suenaga, K.; Tanaka, K.; Chujo, Y. Eur. J. Org.
Chem. 2017, 2017, 5191−5196. (d) Li, M.; Niu, Y. L.; Zhu, X. Z.;
Peng, Q.; Lu, H. Y.; Xia, A. D.; Chen, C. F. Chem. Commun. 2014, 50,
2993−2995.
(4) (a) Lan, Y.; Houk, K. N. J. Org. Chem. 2011, 76, 4905−4409.
(b) Peng, Q.; Yan, H.; Zhang, X.; Wu, Y.-D. J. Org. Chem. 2012, 77,
7487−7496.
(5) (a) Zhou, C.; Larock, R. C. J. Am. Chem. Soc. 2004, 126, 2302−
2303. (b) Zhou, C.; Larock, R. C. J. Org. Chem. 2006, 71, 3551−3558.
(c) Zhao, B.; Lu, X. Org. Lett. 2006, 8, 5987−5990. (d) Wang, X.; Liu,
M.; Xu, T.; Wang, Q.; Chen, J.; Ding, J.; Wu, H. J. Org. Chem. 2013,
78, 5273−5281. (e) Yu, S.; Qi, L.; Hu, K.; Gong, J.; Cheng, T.; Wang,
Q.; Chen, J.; Wu, H. J. Org. Chem. 2017, 82, 3631−3638. (f) Yousuf,
M.; Das, T.; Adhikari, S. New J. Chem. 2015, 39, 8763−8770. (g) Xu,
T.; Shao, Y.; Dai, L.; Yu, S.; Cheng, T.; Chen, J. J. Org. Chem. 2019,
84, 13604−13614.
(6) (a) Qi, L.; Hu, K.; Yu, S.; Zhu, J.; Cheng, T.; Wang, X.; Chen, J.;
Wu, H. Org. Lett. 2017, 19, 218−221. (b) Hu, K.; Qi, L.; Yu, S.;
Cheng, T.; Wang, X.; Li, Z.; Xia, Y.; Chen, J.; Wu, H. Green Chem.
2017, 19, 1740−1750. (c) Zhang, Y.; Shao, Y.; Gong, J.; Hu, K.;
Cheng, T.; Chen, J. Adv. Synth. Catal. 2018, 360, 3260−3265. (d) Hu,
K.; Zhen, Q.; Gong, J.; Cheng, T.; Qi, L.; Shao, Y.; Chen, J. Org. Lett.
2018, 20, 3083−3087.
(7) (a) Yu, H.; Xiao, L.; Yang, X.; Shao, L. Chem. Commun. 2017,
53, 9745−9748. (b) Yousuf, M.; Adhikari, S. Org. Lett. 2017, 19,
2214−2217.
(8) (a) Yao, X.; Shao, Y.; Hu, M.; Xia, Y.; Cheng, T.; Chen, J. Org.
Lett. 2019, 21, 7697−7701. (b) Yao, X.; Shao, Y.; Hu, M.; Zhang, M.;
Li, S.; Xia, Y.; Cheng, T.; Chen, J. Adv. Synth. Catal. 2019, 361,
4707−4713.
(9) (a) Kamei, K.; Maeda, N.; Nomura, K.; Shibata, M.; Katsuragi-
Ogino, R.; Koyama, M.; Nakajima, M.; Inoue, T.; Ohno, T.;
Tatsuoka, T. Bioorg. Med. Chem. 2006, 14, 1978−1992. (b) De
Munck, L.; Sukowski, V.; Mun
2017, 4, 1624−1628. (c) Deng, H.; Meng, Z.; Wang, S.; Zhang, Z.;
̃
oz, M.-C.; Pedro, J. Org. Chem. Front.
E
DOI: 10.1021/acs.orglett.9b04185
Org. Lett. XXXX, XXX, XXX−XXX