Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light

Article abstract of DOI:10.1002/adsc.201801276

A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O₂ as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).

Full text of DOI:10.1002/adsc.201801276

Title: Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic
Acids under visible Light
Authors: Dong-Ping Luo, Yang-Feng Huang, Xiao-Yi Hong, Dingben
Chen, Guo-Xing Li, Xiaobo Huang, Miaochang Liu, Wenxia
Gao, Yun-Bing Zhou, and Huayue Wu
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content of this Accepted Article.
To be cited as: Adv. Synth. Catal. 10.1002/adsc.201801276
Link to VoR: http://dx.doi.org/10.1002/adsc.201801276

Advanced Synthesis & Catalysis
10.1002/adsc.201801276
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic
Acids under Visible Light
[
a]
[a]
[a]
[b]
Dong-Ping Luo, Yang-Feng Huang, Xiao-Yi Hong, Dingben Chen, Guo-Xing
[
a]
[a]
[a]
[a]
[a],
Li, Xiao-Bo Huang, Wen-Xia Gao, Miao-Chang Liu, Yun-Bing Zhou * and
Hua-Yue Wu *
[
a],
a
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, People’s Republic of China
E-mail: zyb@wzu.edu.cn, huayuewu@wzu.edu.cn
College of Pharmaceutical and Chemical Engineering, Taizhou University, Taizhou 318000, People’s Republic of
b
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######.((Please
delete if not appropriate))
Abstract. A visible-light-promoted aerobic oxidative
During the past decade, photoredox catalysis has
hydroxylation of boronic acids using phthalocyanine zinc as become a research hot topic because of its high
an easily available photosensitizer has been developed. It efficiency and powerful functions in the organic
provided a direct access to synthesize aliphatic alcohols and synthesis. A work from Xiao’s group opened a new
phenols from boronic acids. The advantages of this approach front of introducing photoredox catalysis to aerobic
included the low catalyst loading (0.5 mol %), high efficient,
oxidative hydroxylation of arylboronic acids with
2
the use of O as an oxygen source, wide substrate range, the
simple operational process, and mild conditions.
Ru(bpy)
3
Cl catalyst, providing an efficient access to
2
[17]
phenols from arylboronic acids. Subsequently, an
array of photocatalysts such as metal organic
Keywords: phthalocyanine zinc; visible light; aerobic
oxidative hydroxylation; boronic acids; phenols
[18]
framework (MOF), cationic polycarbazole network
[19]
[20]
[22]
(
CPOP),
porous organic framework (POF),
[21]
organic photocatalysts, and quantum dots (QDs)
have been also demonstrated in the aerobic oxidative
hydroxylation of arylboronic acids. However, most of
these photocatalysts suffered from tedious preparation
of the catalysts, the use of precious metal catalysts,
limited substrate scope and prolonged reaction time.
Therefore, the development of highly efficient visible-
light photocatalytic oxidative hydroxylation of
arylboronic acids remained to be desirable.
Phenols represent an important class of compounds
because they serve as versatile intermediates and are
widely present in natural products and pharmaceutical
compounds.[ Given their great value in many fields,
continuing efforts in the development of efficient
methods for the synthesis of phenols have been
devoted over the past decades. Among various
approaches known, the hydroxylation of arylboronic
acids has emerged as an efficient and appealing
method to access phenols recently. Conventional
conditions of the oxidative hydroxylation of boronic
acids relied on the use of noble transition-metal
1]
Recently, phthalocyanine zinc (ZnPc) and its
derivatives have been prepared and successfully
[2]
[
23]
employed in photovoltaic conversion
and
[24]
photocatalytic H
2
production. Herein, using ZnPc as
an easily available photosensitizer, we developed a
facile and efficient method for the synthesis of
aliphatic alcohols and phenols from a wide range of
boronic acids via visible-light-promoted aerobic
oxidative hydroxylation.
[
3]
[4]
[5]
catalysts such as gold,
palladium, ruthenium,
[6]
[7]
copper and silver, either along with the presence of
a strong base. Other synthetic routes to access phenols
from arylboronic acids via the oxidative hydroxylation
were achieved by using stoichiometric amounts of
In exploratory experiments, PhB(OH) was selected
2
as the model substrate to screen suitable reaction
conditions (Table 1). To our delight, it was found that
by using ZnPc as a photosensitizer and DMFU as an
additive, phenyl boronic acid was successfully
[8]
strong oxidants including hydrogen peroxide,
mCPBA,[
9]
TBHP,
[10]
NaBO ,
[11]
oxone,
[12]
3
benzoquinone,[ PhI(OAc)
13]
[14]
and amine oxide[15].
2
However, from environmentally friendly and
economic viewpoints, the use of molecular oxygen or
air instead of these strong oxidants would be more
appealing. On the other hand, phenols could be also
accessible via the electrochemical hydroxylation of
boronic acids.[
converted to phenol in 35% yield in CH
visible light (Table 1, entry 1). However, replacement
of DMFU with other additives such as NEt , iPr NEt,
3
OH under
3
2
DME and Py led to no formation of the desired product
(Table 1, entries 2-5). When the reaction was
performed in the absence of a photosensitizer or an
16]
1
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Advanced Synthesis & Catalysis
10.1002/adsc.201801276
Table 1. Reaction optimization.[a]
beneficial for this transformation (Table 1, entry 20).
Hence, the optimum conditions involved performing
the reaction in THF at room temperature under O
2
atmosphere using ZnPc as a photosensitizer and
DMFU as an additive in the presence of visible light.
With the optimum conditions in hand, we set out to
investigate the substrate scope of the photocatalytic
oxidative hydroxylation by testing a diverse range of
substituted boronic acids (Table 2). Various
electronically different substituents on the aromatic
ring have proved to be compatible with this reaction
conditions, from electron-rich methyl, methoxy,
methylthio and hydroxyl groups to electron-withdraw
halogens, cyanoyl, acyl, and nitro groups (Table 2,
products 2b-2x). Substituents at the ortho position of
the aromatic ring resulted in a subtle decrease in yields
in comparison with these at para position (T
able 2, products 2b vs 2e, 2c vs 2f, 2d vs 2g). To our
delight, the gram-scale reaction of substrate 1g was
successfully achieved with a slightly lower yield
compared to the small-scale reaction, implying the
potential practicability of this protocol. In the case of
sulfur-containing substrate 1k, moderate yield was
obtained (Table 2, product 2k). Notably, a marked
[
b
Entr Photosensitize Additiv Solvent Yield %
]
y
1
r
e
ZnPc
DMFU CH
3
3
3
3
3
3
3
3
3
3
3
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
35
0
0
0
0
0
0
0
0
0
0
0
0
2
3
4
5
6
ZnPc
ZnPc
ZnPc
ZnPc
---
NEt
3
CH
iPr NEt CH
2
DME
Py
CH
CH
DMFU CH
--- CH
DMFU CH
DMFU CH
DMFU CH
DMFU CH
7
ZnPc
ZnPc
ZnPc
CoPc
CuPc
ZnPc
ZnPc
8[
c]
9[d]
1
1
1
1
0
1
2
3
DMFU Ethanol
DMFU
Toluen
e
Table 2. Scope of Reaction.[a]
1
1
1
1
4
5
6
7
ZnPc
ZnPc
ZnPc
ZnPc
DMFU DMSO
26
29
93
78
DMFU
DMFU
DMFU
DMF
THF
1,4-
dioxane
1
1
8
9
ZnPc
ZnPc
DMFU CH
3
CN
25
45
DMFU Aceton
e
2 [
0
e]
ZnPc
DMFU
THF
98
[
a]
Reaction conditions: PhB(OH)
2
(0.4 mmol), MPc (0.5
(1 atm),
mol %), additive (0.8 mmol), THF (5 mL), O
filament lamp (100 W), rt, 3 h. Isolated yield. In the
2
[
b]
[c]
[
d]
[e]
absence of light. Under N
.5 h.
2
atmosphere. Reaction time:
1
additive, no desired product was obtained (Table 1,
entries 6 and 7). Furthermore, the reaction failed to
provide phenol in the absence of light or under a N
2
atmosphere (Table 1, entries 8 and 9). These control
reactions suggested that photositizer, additive, visible
light and O are all indispensable for this reaction
2
system. Neither CoPc nor CuPc was able to facilitate
this transformation (Table 1, entries 10 and 11). The
screening of solvents showed that THF was the
optimal solvent, providing the desired product in 93%
yield (Table 1, entries 12-19). Notably, only 0.5 mol %
of catalyst enabled the reaction to complete with high
efficiency. Shortening the reaction time to 1.5 h is
[
a]
Reaction conditions: ArB(OH)
2
(0.4 mmol), MPc (0.5
mol %), additive (0.8 mmol), THF (5 mL), DMFU (0.8
mmol), O
[
b]
2
(1 atm), filament lamp (100 W), rt, 3 h. The
2
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Advanced Synthesis & Catalysis
10.1002/adsc.201801276
reaction was performed on 20 mmol scale. [c]Adding 10
acids including aromatic boronic acids and alkyl
boronic acids. The advantages including the low
catalyst loading (0.5 mol %), high efficient, the use of
[
d]
[e]
mol % citric acid.
Reaction time: 2 h.
Adding 30 mol % citric acid.
O as an oxygen source, wide substrate range, the
2
simple
increase in yield of 2k was observed when 10 mol %
citric acid was added. 2, 6-disubstituted substrate
failed to afford the desired product, which could be
attributed to large steric hindrance (Table 2, product
2
u). However, the addition of 30 mol % citric acid
successfully enabled 1u to give the desired product 2u
in 93% yield. The boronic acids bearing a heterocyclic
ring were also amenable to the reaction conditions, and
a slight extension of time would be beneficial for this
transformation (Table 2, product 2x). Interestingly, the
hydroxylation of benzo[b]thiophen-2-ylboronic acid
gave product 2y' in 75% yield instead of the desired
product 2y (Table 2, products 2y and 2y').
Unfortunately, the hydroxylation of boronic acids
bearing a quinoline ring or a benzofuran ring led to no
formation of the desired products (Table 2, products
Scheme 2. Proposed mechanism.
2z, 2z' and 2aa). Remarkably, alkylboronic acids
which were investigated rarely or incompatible with
previous reported catalytic systems, have proved to be
a type of suitable substrates under the optimum
conditions, providing aliphatic alcohols in excellent
yields (Table 2, products 2bb and 2cc).
operational process and mild conditions enable an
attracting approach. However, the need for relatively
high power filament lamp may be a major obstacle to
the successful industrial application of this method,
and further improvement is underway in our laboratory.
To determine the ultimate source of oxygen, the
1
8
18
O-labeling experiment was performed under the O
2
atmosphere (Scheme 1). It was found that the control
experiment provided 18O-labeling product in 95%
yield, demonstrating that the oxygen in phenol was
Experimental Section
derived from O .
2
Under oxygen atmosphere, a mixture of the benzoboronic
acid (0.4 mmol, 48.8 mg), phthalocyanine zinc (0.5 mol %,
1
2
.2 mg), 2, 5- dimethylfuran (0.8 mmol, 85 μL) was put into
5 mL Schlenk tube, followed by addition of 5 mL THF
before seal. After stirring at 25 ℃ for 1.5 h in the presence
of a 100 W filament lamp (note that the reaction temperature
was maintained by circulating cooling water), the reaction
was detected by TLC and GC-MS. When the reaction was
completed, the resultant mixture was concentrated under
reduced pressure and then purified by flash chromatography
on silica gel to provide the desired products.
18
Scheme 1. O-labeling experiment.
On the basis of 18O-labeling experiment, together
with the relevant literature,[ a possible mechanism
for aerobic oxidative hydroxylation of boronic acids
was proposed (Scheme 2). Initially, ground state ZnPc
was converted to excited state *ZnPc via absorption of
visible-light energy. Triplet oxygen took energy from
Acknowledgements
25]
We are grateful for financial support from the National Natural
Science Foundation of China (21472140 and 21572165), Zhejiang
Provincial Natural Science Foundation (LY16B020011,
LY18B020003) and the Wenzhou Science & Technology Bureau
Program (No. G20170021).
*
ZnPc and was subsequently converted to singlet
oxygen while *ZnPc returned back into ground state
ZnPc. Next, DMFU underwent [4+2] cycloaddition
with singlet oxygen to afford intermediate A, which
References
reacted with PhB(OH) to deliver intermediate B. The
2
[
1] a) S. Quideau, D. Deffieux, C. Douat-Casassus, L.
Pouysꢀgu, Angew. Chem. Int. Ed. 2011, 50, 586; b) Z.
Rappoport, The Chemistry of Phenols; Wiley-VCH:
Weinheim, 2003.
in-situ generated intermediate B was further converted
to intermediate C, followed by hydrolysis to provide
the final product.
In conclusion, we have developed a visible-light-
promoted aerobic oxidative hydroxylation of boronic
acids using phthalocyanine zinc as an easily available
photosensitizer, providing a direct access to synthesize
aliphatic alcohols and phenols. This method displayed
very high efficiency toward a broad range of boronic
[
2] a) K. W. Anderson, T. Ikawa, R. E. Tundel, S. L.
Buchwald, J. Am. Chem. Soc. 2006, 128, 10694; b) T.
Schulz, C. Torborg, B. Schꢁffner, J. Huang, A. Zapf, R.
Kadyrov, A. Bꢂrner, M. Beller, Angew. Chem. Int. Ed.
2
009, 48, 918; c) A. Tlili, N. Xia, F. Monnier, M.
3
This article is protected by copyright. All rights reserved.

Advanced Synthesis & Catalysis
10.1002/adsc.201801276
Taillefer, Angew. Chem. Int. Ed. 2009, 48, 8725; d) G.
Shan, X. Yang, L. Ma, Y. Rao, Angew. Chem. Int. Ed.
012, 51, 13070; e) J. W. Han, J. Jung, Y.-M. Lee, W.
Nam, S. Fukuzumi, Chem. Sci. 2017, 8, 7119; f) L. Yang,
Z. Huang, G. Li, W. Zhang, R. Cao, C. Wang, J. Xiao,
D. Xue, Angew. Chem. Int. Ed. 2018, 57, 1968.
H. Jiang, L. Lykke, S. U. Pedersen, W.-J. Xiao, K. A.
Jørgensen, Chem. Commun. 2012, 48, 7203.
2
[
[
17] Y.-Q. Zou, J.-R. Chen, X.-P. Liu, L.-Q. Lu, R. L. Davis,
K. A. Jørgensen, W.-J. Xiao, Angew. Chem. Int. Ed.
2
012, 51, 784.
18] a) T. Toyao, N. Ueno, K. Miyahara, Y. Matsui, T.-H.
Kim, Y. Horiuchi, H. Ikeda, M. Matsuoka, Chem.
Commun. 2015, 51, 16103; b) X. Yu, S. M. Cohen,
Chem. Commun. 2015, 51, 9880; c) J. A. Johnson, J. Luo,
X. Zhang, Y.-S. Chen, M. D. Morton, E. Echeverría, F.
E. Torres, J. Zhang, ACS Catal. 2015, 5, 5283.
[
[
3] a) J. Zheng, S. Lin, X. Zhu, B. Jiang, Z. Yang, Z. Pan,
Chem. Commun. 2012, 48, 6235; b) L. Wang, W. Zhang,
D. Sheng Su, X. Meng, F.-S. Xiao, Chem. Commun.
2
012, 48, 5476.
4] A. D. Chowdhury, S. M. Mobin, S. Mukherjee, S.
Bhaduri, G. K. Lahiri, Eur. J. Inorg. Chem. 2011, 2011,
[
19] H.-P. Liang, Q. Chen, B.-H. Han, ACS Catal. 2018, 8,
3
232.
5
313.
[
[
5] N. Gogoi, P. K. Gogoi, G. Borah, U. Bora, Tetrahedron
Lett. 2016, 57, 4050.
[
[
20] J. Luo, X. Zhang, J. Zhang, ACS Catal. 2015, 5, 2250.
21] a) S. P. Pitre, C. D. McTiernan, H. Ismaili, J. C. Scaiano,
J. Am. Chem. Soc. 2013, 135, 13286; b) H.-Y. Xie, L.-S.
Han, S. Huang, X. Lei, Y. Cheng, W. Zhao, H. Sun, X.
Wen, Q.-L. Xu, J. Org. Chem. 2017, 82, 5236; c) I.
Kumar, R. Sharma, R. Kumar, R. Kumar, U. Sharma,
Adv. Synth. Catal. 2018, 360, 2013.
6] a) H. Yang, Y. Li, M. Jiang, J. Wang, H. Fu, Chem. -
Eur. J. 2011, 17, 5652; b) A. Affrose, I. A. Azath, A.
Dhakshinamoorthy, K. J. Pitchumani, Mol. Catal. A:
Chem. 2014, 395, 500; c) J. Xu, X. Wang, C. Shao, D.
Su, G. Cheng, Y. Hu, Org. Lett. 2010, 12, 1964; d) K.
Inamoto, K. Nozawa, M. Yonemoto, Y. Kondo, Chem.
Commun. 2011, 47, 11775.
[22] A. K. Simlandy, B. Bhattacharyya, A. Pandey, S.
Mukherjee, ACS Catal. 2018, 8, 5206.
[
[
7] T. Begum, A. Gogoi, P. K. Gogoi, U. Bora, Tetrahedron
Lett. 2015, 56, 95.
[23] a) M.-E. Ragoussi, J.-J. Cid, J.-H. Yum, G. Torre, D. D.
Censo, M. Grꢁtzel, M. K. Nazeeruddin, T. Torres,
Angew. Chem. Int. Ed. 2012, 51, 4375; b) M. García-
Iglesias, J. Yum, R. Humphry-Baker, S. Zakeeruddin, P.
Pꢀchy, P. Vꢃzquez, E. Palomares, M. Grꢁtzel, M.
Nazeeruddin, T. Torres, Chem. Sci. 2011, 2, 1145.
8] a) A. Gogoi, U. Bora, Tetrahedron Lett. 2013, 54, 1821;
b) S. Gupta, P. Chaudhary, V. Srivastava, J. Kandasamy,
Tetrahedron Lett. 2016, 57, 2506.
[
[
[
9] D.-S. Chen, J.-M. Huang, Synlett 2013, 24, 499.
10] S. Guo, L. Lu, H. Cai, Synlett 2013, 24, 1712.
[24] a) X. Zhang, L. Yu, C. Zhuang, T. Peng, R. Li, X. Li,
RSC Adv. 2013, 3, 14363; b) X. Zhang, T. Peng, L. Yu,
R. Li, Q. Li, Z. Li, ACS Catal. 2015, 5, 504; c) X. Zhang,
L. Yu, C. Zhuang, T. Peng, R. Li, X. Li, ACS Catal. 2014,
4, 162; d) A. Tiwari, N. V. Krishna, L. Giribabu, U. Pal,
J. Phys. Chem. C 2018, 122, 495.
11] G. W. Kabalka, T. M. Shoup, N. M. Goudgaon,
Tetrahedron Lett. 1989, 30, 1483.
[
12] a) G. A. Molander, L. N. J. Cavalcanti, J. Org. Chem.
2
011, 76, 623; b) J. J. Molloy, T. A. Clohessy, C. Irving,
N. A. Anderson, G. C. Lloyd-Jones, A. J. B. Watson,
Chem. Sci. 2017, 8, 1551.
[
25]a) C. S. Foote, S. Wexler, W. Ando, R. Higgins, J. Am.
Chem. Soc. 1968, 90, 975; b) F. Cermola, M. R. Iesce,
G. Buonerba, J. Org. Chem. 2005, 70, 6503; c) A.
Astarita, F. Cermola, M. DellaGreca, M. R. Iesce, L.
Previtera, M. Rubino, Green Chem. 2009, 11, 2030.
[
[
13] G. Cheng, X. Zeng, X. Cui, Synthesis 2014, 46, 295.
14] N. Chatterjee, A. Goswami, Tetrahedron Lett. 2015, 56,
1
524.
[
[
15] C. Zhu, R. Wang, J. R. Falck, Org. Lett. 2012, 14, 3494.
16] a) K. Hosoi, Y. Kuriyama, S. Inagi, T. Fuchigami,
Chem. Commun. 2010, 46, 1284; b) H.-L. Qi, D.-S. Chen,
J.-S. Ye, J.-M. Huang, J. Org. Chem. 2013, 78, 7482; c)
4
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Advanced Synthesis & Catalysis
10.1002/adsc.201801276
COMMUNICATION
Phthalocyanine Zinc-catalyzed Hydroxylation of
Aryl Boronic Acids under visible Light
Adv. Synth. Catal. Year, Volume, Page – Page
[
a]
[a]
Dong-Ping Luo, Yang-Feng Huang, Xiao-
[
a]
[b]
[a]
Yi Hong, Dingben Chen, Guo-Xing Li,
[
a]
[a]
Xiao-Bo Huang, Wen-Xia Gao, Miao-
[
a]
[a],
Chang Liu, Yun-Bing Zhou * and Hua-Yue
[
a],
Wu *
5
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