Fenton chemistry for Achmatowicz rearrangement

Article abstract of DOI:10.1021/acscatal.1c00219

Achmatowicz rearrangement (AchR) is a very important transformation for the synthesis of various heterocyclic building blocks and natural products. Here, the discovery of Fenton chemistry for AchR using a bifunctional catalyst (FeBr₂ or CeBr

Full text of DOI:10.1021/acscatal.1c00219

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Research Article
Fenton Chemistry for Achmatowicz Rearrangement
Guodong Zhao, Lixin Liang, Eryu Wang, and Rongbiao Tong*
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sı Supporting Information
ABSTRACT: Achmatowicz rearrangement (AchR) is a very
important transformation for the synthesis of various heterocyclic
building blocks and natural products. Here, the discovery of
Fenton chemistry for AchR using a bifunctional catalyst (FeBr or
2
CeBr ), which has environmental friendliness and a broad substrate
3
scope at the same time has been reported. This method addresses
the major limitation of conventional chemical (hazardous) and
enzymatic (limited scope) methods. Mechanistic studies suggested that reactive brominating species (RBS) is the true catalyst for
•
•
AchR and that Fenton chemistry [Fe/Ce (cat.) + H O → HO /HOO + H O] is responsible for the oxidation of bromide into
2
2
2
RBS. Importantly, this in situ RBS generation from M-Br −H O under neutral conditions addresses the long-lasting problem of
x
2
2
many haloperoxidase mimics that require a strong acidic additive/medium for bromide oxidation with H O , which creates
2
2
opportunities for many other brominium-mediated organic reactions.
KEYWORDS: fenton chemistry, Achmatowicz rearrangement, green chemistry, hydrogen peroxide, haloperoxidase mimics
chmatowicz rearrangement (AchR) is a very important
reaction for the construction of six-membered hetero-
cyclic scaffolds (dihydropyranones and dihydropyridinones),
illustrated) and a low reaction concentration (mM). Herein,
we report the discovery of Fenton chemistry for AchR with
A
H O as the terminal oxidant, which is not only green but also
2 2
which are frequently found in bioactive molecules and natural
has a wide scope under a normal concentration (0.2−0.5 M)
1
products. The synthetic utility of AchR has been illustrated by
for organic reactions.
Fenton chemistry (Fe /H
2
II
various transformations of AchR products, including O-
2
O
2
) is widely used for contam-
1
4
3
4
5
glycosylation, [5 + 2] cycloaddition, Kishi reduction, Ferrier
inant or wastewater treatment because (i) Fenton chemistry
has low cost, negligible toxicity, and easy recovery and a (ii)
6
7
8
allylation, ketalization, redox isomerization, and Tsuji−
Trost arylation (Figure 1a). The importance of AchR in
9
•
hydroxyl radical ( OH) generated from Fenton chemistry
15
(
Figure 2a) is a highly strong oxidant that can degrade most
organic synthesis aroused great interest in developing new and
16
organic pollutants into nontoxic oxidized small molecules.
more efficient oxidation protocols, which can be classified into
17
1
0
11
Many iron catalysts have been developed and the Fenton
process can be advantageously performed in many physical
chemical and enzymatic strategies (Figure 1b). The
chemical strategy employs stoichiometric strong oxidants
14,18,19
10m
10n
fields.
such as m-CPBA
and N-bromosuccinimide (NBS),
Fenton chemistry has also been used in organic synthesis for
which are toxic and result in stoichiometric harmful
II
many oxidation reactions. For example, [Fe ]/H O was used
2
2
byproducts (i.e., m-chlorobenzoic acid or succinimide).
2
0
12
for C−H oxidation [Gif oxidation, Figure 2b(3)], Minisci
Recently, our group reported oxone−KBr as a green catalytic
protocol for AchR. However, as compared to oxygen and
hydrogen peroxide, oxone as a terminal oxidant was not ideal
21 22
reaction [Figure 2b(4)], sulfide oxidation [Figure 2b(5)],
23
and olefin oxidation [Figure 2b(6)]. Notably, well-designed
organic ligands for iron are typically required to tune the
24
1
3
and the E-factor was usually high because of high molar mass
307 g/mol) of oxone (molar mass of H O and O : 34 and 32
oxidation reactivity and selectivity, especially in an olefin
(
2
2
2
25
epoxidation reaction. Nevetheless, the synthetic utility of
g/mol, respectively). Photochemical oxidation with singlet
10p
,
10g
Fenton chemistry in organic synthesis remains very limited due
to poor chemoselectivity of the highly oxidizing hydroxyl
radical. Our continuous interest in AchR drove us to upgrade
oxygen reported by Vassilikogiannakis
was another green
method for AchR, but it requires stoichiometric reducing
agents (Me S or Ph P). Anodic oxidation/rearrangement (2
2
3
10h
steps) as the greenest protocol was reported in 1976
but
Received: January 15, 2021
Revised: February 25, 2021
Published: March 9, 2021
with only three examples and moderate yields (37−73%). The
1
1b
enzymatic strategy reported recently by Beifuss,
2014; 2018),
Deska
1
1c11a
11e
(
and Hollmann and Rutjes uses hydro-
gen peroxide as the stoichiometric terminal oxidant and
produces water as the only byproduct. Enzymatic protocols are
green but suffer from a narrow scope (<10 examples
©
2021 American Chemical Society
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Figure 1. Synthetic utilities of AchR, previous strategies for AchR, and our catalytic protocol.
our previous oxone−halide system and envisioned that Fenton
conditions without an enzyme (haloperoxidase or halogenase)
or a strong acid (AcOH, HBr, H SO , or HClO was required
for haloperoxidase mimics). Remarkably, seven metal salts,
chemistry might be used for AchR [Figure 2c(c1)] through
2
4
4
25
27
epoxidation analogous to the equation (6) [Figure 2b(6)].
Alternatively, Fenton chemistry may oxidize a bromide ion into
reactive brominating species (RBS; Br ) for AchR [Figure
FeCl , CeCl , Sc(OTf) , Cp ZrCl , SnCl , Eu(OTf) , and
2
3
3
2
2
2
3
+
Tm(ClO ) , were found to be efficient catalysts (>40% yield,
4 3
2
c(c2)], which is similar to NBS and oxone−KBr for AchR. If
the detailed information is provided in the Supporting
Information) under this unoptimized condition (Table 1).
Nevertheless, the yield was not high or synthetically useful yet
and needed to be further optimized. Since it was impractical to
simultaneously investigate all of these seven promising metal
salts for the yield improvement, we focused on iron and cerium
for further optimization because of their nontoxicity, low cost,
and environmental friendliness.
successful, it would be the first example of Fenton chemistry
for AchR with H O as the only waste product [Figure 2c(7)]
and greener than our previous oxone−KBr protocol.
Because other transition metals such as chromium, cerium,
copper, cobalt, manganese, ruthenium, and aluminum had
2
•
been used for decomposition of H O into OH and were
2
2
26
classified as iron-free Fenton-like catalysts, we started our
study with a nonselective screening of transition-metal salts
including lanthanides for oxidation of furfuryl alcohol (1a)
with hydrogen peroxide. Disappointingly, no reaction
occurred, which suggested that Fenton chemistry did not
work for AchR through the epoxidation pathway. However,
when 0.1 equiv of KBr was added to the reaction, we were
pleased to find that 16 out of 38 transition-metal salts showed a
positive result and delivered >5% yield of dihydropyranone
The optimization campaign was launched, and the
corresponding results are presented in Table 2. The standard
experiment employed 0.1 equiv of a metal catalyst and we
aimed for >70% yield to verify the good catalytic activity.
Interestingly, we observed that the organic ligands such as
acetylacetone (acac), porphyrin, cyclopentadiene (Cp), and
CO (entry 1−5, Table 2) were inferior to inorganic ligands
such as sulfate, nitrate, and chloride (entry 6−8, Table 2). The
best yield (78% for iron and 91% for cerium) was obtained
with catalytic FeBr (entry 11) and CeBr (entry 16), in which
(2a) in nearly neutral conditions (Table 1). This finding
suggested KBr was mechanistically involved in the AchR and
the Fenton chemistry (Fe /H O ) served as an oxidant for
bromide oxidation, which may follow the bromination
hypothetic pathway [Figure 2c(c2)].
2
3
II
−
bromide (Br ) was not only the ligand of iron and cerium but
also the source of reactive brominating species (RBS) for
AchR. Notably, the reaction using FeBr or CeBr as a catalyst
2
2
2
3
This initial finding was significant because it suggested that
the oxidation of bromide with H O could occur under neutral
was completed within 2 h, which was faster than the other
combinations (metal salt + KBr).
2
2
3
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Figure 2. Fenton chemistry and its synthetic utilities in organic synthesis, and our mechanistic hypothesis for AchR through Fenton chemistry.
With the discovery and optimized condition (FeBr −H O
(2h), Piv (2k), and Boc (2j), unusual substituents on 3- and/
or 4-position of furan (2z−2ac), and sterically hindered
furfuryl tertiary alcohols (2m and 2n). The scalability of these
two catalytic methods was demonstrated by a 10 mmol scale
2
2
2
and CeBr −H O ) in hand, we set out to examine and expand
3
2
2
the scope of furfuryl alcohol for AchR (Table 3a). It was
noteworthy that some substrates (2a, 2e, 2n, 2q, etc.) were
12
chosen according to our published literatures using the
oxone−KBr protocol to make a systematic green chemistry
metrics comparison with this M-Br −H O protocol. To our
reaction of 2b (R = t-Bu, 1.54 g) at room temperature under
1
an open-air condition, which gave excellent yields (FeBr : 77%;
2
CeBr : 92%) comparable to the yields of 0.4 mmol scale (81
x
2
2
3
delight, the oxidative rearrangement proceeded with high
efficiency for a variety of furfuryl alcohols under this catalytic
neutral condition. The mild reaction conditions tolerated
common functional groups such as ester (2g and 2w), alkene
and 93%, respectively). It was noted that a relatively lower
catalyst loading was needed for CeBr (0.03 equiv) vs FeBr
3
2
(0.15 equiv), which means that CeBr is more efficient than
3
FeBr for the large-scale synthesis. Furthermore, there were no
2
(
2e and 2t), electron-rich arenes (2o−2r), and furan/
potentially competing side reactions like arene bromination,
alkene dibromination, and alcohol oxidation for the above
substrates. Interestingly, the more hydrophobic substrates
always gave a higher yield. Consequently, our Fenton protocol
thiophene (2x and 2y), commonly used protecting groups
like triisopropylsilyl (TIPS) (2p and 2aa), tert-butyldimethyl-
silyl (TBS) (2l and 2r), Bn (2i and 2v), Ac (2o and 2u), Bz
3
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a
Table 1. Nonselective Screening of a Metal Catalyst for AchR for 1a Using H O as an Oxidant
2
2
a
Reaction was carried out at rt: 1a (0.1 mmol) was dissolved in a solvent (tetrahydrofuran (THF)/H O 10/1, 0.55 mL), and then transition-metal
2
salt (0.01 mmol), KBr (0.01 mmol), and H O (30%, 22 μL, 0.22 mmol) were added and stirred at rt for 8 h. The reaction was quenched using a
2
2
dilute Na S O aqueous solution. The detailed procedure is given in the Supporting Information.
2
2
3
Table 2. Optimization of AchR for 1a
chose AchR of furfuryl alcohols to 2a, 2e, 2n, and 2q as
representative examples to analyze their green chemistry
metrics. We performed the calculation of four green metrics,
13
28
environmental factor (E-factor), atom economy (AE),
29
reaction mass efficiency (RME), and process mass intensity
3
0
(
(
PMI), for FeBr −H O , CeBr −H O , and oxone−KBr
2
2
2
3
2
2
Table 3b). The lower value of the E-factor (ideal: 0.00) and
a
d
entry
1
2
MXn (0.1 equiv) + KBr (0.1 equiv)
solvent
yield (%)
PMI (ideal: 1.0) means that less waste is generated or less total
Ferroceneacetic acid + KBr
Cp Fe (CO) + KBr
THF/H O
<5
<5
<5
<5
<5
37
30
58
68
30
78
61
80
81
77
91
mass of material is needed for per mass of the desired
2
b
13,30
THF/H O
product,
while the higher value of AE (ideal: 100%) and
2
2
4
2
28,29
3
4
Fe(acac) + KBr
THF/H O
RME (100%) reveals better atom and resource efficiency.
3
2
b
Fe (CO) + KBr
THF/H O
As shown in Table 3b, the average E-factors of AchR using
2
9
2
5
6
7
8
9
Heme B + KBr
THF/H O
oxone−KBr, FeBr −H O , and CeBr −H O were 5.46, 0.98,
2
2
2
2
3
2
2
Fe(NO ) + KBr
THF/H O
and 0.69, respectively, which suggested that M-Br −H O
3
3
2
x
2
2
FeSO + KBr
THF/H O
could be reduced six to eight times of mass waste than
oxone−KBr and was closely approaching to the ideal metrics
(E-factor: 0.00). The average AE value of FeBr −H O and
4
2
FeCl + KBr
THF/H O
3
2
FeBr2
MeCN/H O
2
2
2
2
10
11
12
13
14
15
16
FeBr2
FeBr2
DMF/H O
CeBr −H O was 91.2%, which suggested more than 50%
2
3
2
2
c
THF/H O
increase from 39.9% for oxone−KBr. The average 60% RME of
M-Br −H O indicated the reaction’s mass advantage over
2
b
Ce (C O ) + KBr
THF/H O
2
2
4
3
2
x
2
2
Ce(NO ) + KBr
Ce(SO ) + KBr
THF/H O
3
3
2
oxone−KBr (RME: 16.8%). Finally, the PMI value ratio of
oxone−KBr (PMI: 6.46) and M-Br −H O (PMI: ∼1.8) was
THF/H O
4
2
2
x
2
2
CeCl + KBr
THF/H O
3
2
∼3.5, which means nearly 4-fold materials were needed using
the oxone−KBr method. The analysis of these green metrics
clearly demonstrated that our new M-Br −H O was greener,
c
CeBr3
THF/H O
2
a
Reaction was carried out at rt: 1a (0.1 mmol) was dissolved in a
solvent (organic solvent/H O 10/1, 0.55 mL), and then [Fe] or [Ce]
x
2
2
2
more efficient, and environmentally friendly (sustainable) than
our previous oxone−KBr and other existing approaches. It was
noteworthy that oxone was synthesized industrially from H O
(
0.01 mmol), KBr (0.01 mmol), and H O (30%, 22 μL, 0.22 mmol)
2 2
were added and stirred at rt for 8 h. The reaction was quenched using
b
2
2
a dilute Na S O aqueous solution. Metal catalyst (0.005 mmol) was
31
2
2
3
c
d
1
in two steps (first concentrated H SO and then KOH).
2
4
added. Reaction time was 2 h. Yield was determined by H NMR
Taking this fact and the stoichiometric waste generated into
analysis of the crude reaction mixture using CH Br as the internal
reference.
2
2
consideration, our new M-Br −H O method was greener and
x
2
2
should be preferably used over the oxone−KBr protocol (H O
2
vs K SO + Na SO + CO ).
2
4
2
4
2
(
FeBr /H O and CeBr /H O ) holds great promise for
To shed light on the mechanism of Fenton chemistry for
AchR, we designed and performed a series of controlled
experiments and characterizations of AchR (Figure 3). First,
controlled experiments (Figure 3a) were divided into two sets
(S-1 and S-2); S-1 was designed to investigate the role of metal
and bromide (Figure 3a, entries 1−17). It was found that both
2
2
2
3
2
2
commercialization and medicinal chemistry with the following
advantages: (1) H O as the green oxidant, (2) low-toxic
catalyst (FeBr and CeBr ), (3) scalable operation without
special equipment, (4) very mild condition (RT), and (5) a
wide substrate scope with high yields and tolerence of multiple
functional groups.
To evaluate the greenness of our new system and make a
comparison with our previous oxone−halide protocol, we
2
2
2
3
2
+
3+
metal (Fe or Ce ) and bromide were indispensable for
AchR, which suggested that (1) RBS was generated from the
reaction of M-Br (FeBr or CeBr ) and H O and served as the
2
3
2
2
3
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a
Table 3. Fenton Chemistry for Achmatowicz Rearrangement
a
Reaction conditions for AchR: furfuryl alcohol (0.4 mmol), FeBr (0.1 equiv) or CeBr (0.08 equiv), H O (2.2 equiv), THF/H O (10/1, 2.2
2
3
2
2
2
b
c
mL), and room temperature for 2−3 h. FeBr (0.2 equiv) and H O (4.4 equiv) were needed. Yield obtained from 1.54 g of 1b using FeBr (0.15
equiv) or CeBr (0.03 equiv).
2
2
2
2
3
active catalyst for AchR, and (2) without a bromide ion,
(entries 20−21), m-CPBA (entries 22−23), and oxone−KBr
(entries 24−25). Clearly, only FeBr −H O and CeBr −H O
14,32
Fenton chemistry (FeSO −H O )
could not affect AchR
Figure 3a, entries, 2, 4, 6, 8, 10, 12, 14, and 16). The second
4
2
2
2
2
2
3
2
2
(
were significantly suppressed by ABTS, which suggested that
•
set (S-2) of controlled experiments (Figure 3a, entries 18−25)
they involved the hydroxyl radical (HO ). To further support
•
was designed to explore the possible presence of a hydroxyl
the generation of the hydroxyl radical (HO ), we recorded the
•
33
34
radical (HO ) from Fenton chemistry. ABTS [2,2′-Azino-
bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt]
as a Fenton scavenger was added to the AchR reaction
UV−visible spectra for the reaction of M-Br (FeBr or CeBr )
2
3
and H O in the presence of ABTS (λ = 340 nm) (Figure
2
2
max
35
3b). Chromagen ABTS (λmax = 340 nm) was widely used to
35
promoted by FeBr −H O (entries 18−19), CeBr −H O
trap the short-lived hydroxyl radical, and the resulting cation
2
2
2
3
2
2
3
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Figure 3. Mechanistic studies and hypothesis. (a) RBS-promoted AchR and the presence of a hydroxyl radical from Fenton chemistry. For the first
set, light blue bars represent the controls using either M or Br, while the orange ones use both M and Br. Compared with the green bars in set 2, the
red ones represent the controls with the addition of ABTS to trap the hydroxyl radical. Note: 5% yield was used in the chart for the yields lower
+
than 5%. (b) UV−vis spectral experiments with ABTS to confirm the generation of the hydroxyl radical. (c) Br -trapping experiment by the
intramolecular bromocyclization of alkenyl carboxylic acid 3 and bromination of arene 5 using FeBr −H O or CeBr −H O . (d) Proposed
2
2
2
3
2
2
mechanism for generation of reactive brominating species (RBS). (e) Hypothesis of a tight ion−radical pair that might exhibit higher efficiency in
generating RBS from oxidation of bromide with the fleeting hydroxyl radical. (f) Proposed mechanism for catalytic oxidation of furans.
radical ABTS+ (λmax = 415 nm) was far more stable and
•
34
According to these mechanistic studies, we proposed a
plausible mechanism for AchR (Figure 3d−f). Fenton
chemistry occurred to generate a hydroxyl radical and/or a
could be characterized by UV−visible spectroscopy. It was
observed that absorbance of ABTS at 415 nm increased with
increasing concentration of FeBr and CeBr , which corrobo-
+•
•
hydroperoxyl radical (HOO ) as a strong oxidant, which can
2
3
37
•
oxidize a bromide ion into hypobromous acid (HO−Br) as
the RBS for various oxidations (Figure 3d). To account for this
observation that FeBr and CeBr were consistently more
rated the generation of the hydroxyl radical (HO ) from
FeBr −H O and CeBr −H O (Figure 3b). It was interesting
2
2
2
3
2
2
+
•
to note that the absorbance of ABTS at 415 nm in a CeBr −
2
3
3
efficient than the corresponding combination of metal salts and
H O solution was considerably lower than that in a FeBr −
2
2
2
potassium bromide (i.e., FeSO + KBr, Ce(OAc) + KBr in
4
3
H O solution. This difference might suggest that the
2
2
•
Table 2), we proposed the concept of an ion−radical pair:
generation of the hydroxyl radical (HO ) from CeBr −H O
3
2
2
•
33,36
short-lived hydroxyl radical (HO )
released from the metal
was slower than that from FeBr −H O . The slow release of
2
2
2
35
•
33,36
(Fe or Ce) was more efficiently reacting with bromide
bonded to the metal because they formed a tight ion−radical
pair such as complex I or II (Figure 3e). However, if KBr was
used as the source of bromide in the combination with metal
salts, the bromide would be surrounded by solvents as a
the fleeting hydroxyl radical (HO )
from the CeBr −H O
3
2
2
solution might well explain our observation that CeBr −H O
generally outperformed the FeBr −H O system in the AchR
3
2
2
2
2
2
(Table 3).
To further support the generation of RBS from FeBr −H O
2
2
2
solvated bromide, which disfavored the reaction with the
and CeBr −H O , we performed two oxidative bromination, as
33,36
3
2
2
fleeting hydroxyl radical.
This hypothesis also explained
shown in Figure 3c. Bromolactonization of alkenyl carboxylic
acid 3 using FeBr −H O or CeBr −H O in acetonitrile
that organic ligands were ineffective for metal (entry 1−5,
Table 2). Taking all of the mechanistic studies and hypothesis
together, we could depict the overall mechanism for AchR
(Figure 3f). For catalytic cycle 1 (c-1), Fenton chemistry
2
2
2
3
2
2
provided lactone 4 in 53 and 62% yields, respectively.
Bromination of TBS-protected phenol (5) with FeBr −H O
3
2
2
•
•
and CeBr −H O gave TBS-protected 4-bromophenol (6) in
generated an oxygen-based radical (HO and HOO ) from
3
2
2
II
III 14,32,35
high yields (FeBr :76%; CeBr :94%). These experiments
H O by the Fenton catalyst (Fe or Ce ),
oxidized bromide to RBS (HOBr). For catalytic cycle 2 (c-
2), the in situ generated RBS catalyzed the oxidation of furfuryl
which
2
3
2
2
+
37
conclusively confirmed the generation of RBS ([Br ]) from
FeBr −H O and CeBr −H O .
2
2
2
3
2
2
3
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alcohols (AchR) and released the bromide ion that could be
reoxidized by the hydroxyl/hydroperoxyl radical generated
from Fenton chemistry. Clearly, Fenton chemistry and
bromide redox work in a synergistic way (Figure 3f c-1 and
c-2), and FeBr (or CeBr ) serves as a bifunctional catalyst for
Department of Chemistry, The Hong Kong University of
Science and Technology, Kowloon, Hong Kong, China
Lixin Liang − Department of Chemistry, The Hong Kong
University of Science and Technology, Kowloon, Hong Kong,
China
Eryu Wang − Department of Chemistry, The Hong Kong
University of Science and Technology, Kowloon, Hong Kong,
China
2
3
AchR (Figure 3f). The detailed hypothesis for the catalytic
cycles (c-1 and c-2) of Fenton metal (Fe2 or Ce ) and RBS
+
3+
in our system (M-Br −H O ) is provided in the SI, which
x
2
2
further demonstrated that M-Brx serves as a bifunctional
catalyst: iron (or cerium) as a catalyst for Fenton chemistry to
generate hydroxyl/hydroperoxyl radical oxidants and bromide
as a precatalyst for RBS-promoted Achmatowicz rearrange-
ment. Notably, the stepwise mechanisms of AchR using RBS
were similar to those that employed NBS or oxone−KBr,
Complete contact information is available at:
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Notes
The authors declare no competing financial interest.
1
a
which have been well established in the literature.
ACKNOWLEDGMENTS
In summary, we discovered that Fenton chemistry can be
used for Achmatowicz rearrangement, which represents a new
■
This research was financially supported by the Hong Kong
Branch of Southern Marine Science and Engineering
Guangdong Laboratory (Guangzhou) (SMSEGL20Sc01-B),
the Research Grant Council of Hong Kong (C6026-19G,
and greenest catalytic protocol (FeBr −H O and CeBr −
2
2
2
3
H O ) for AchR with H O as the only byproduct. Four green
2
2
2
chemistry metrics, environmental factor (E-factor), atom
economy (AE), reaction mass efficiency (RME), and process
mass intensity (PMI), were used to evaluate the greenness of
our new M-Br −H O method as compared to our previous
1
6307219, 16304618, and 16303617), and the National
Natural Science Foundation of China (NSFC 21772167).
x
2
2
oxone−KBr protocol and revealed that the new M-Br −H O
x
2
2
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ASSOCIATED CONTENT
sı Supporting Information
■
*
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acscatal.1c00219.
(
+)-Brevisamide. Org. Lett. 2011, 13, 3636−3639.
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AUTHOR INFORMATION
■
Corresponding Author
Rongbiao Tong − Department of Chemistry and Hong Kong
Branch of the Guangdong Southern Marine Science and
Engineering Laboratory (Guangzhou), The Hong Kong
University of Science and Technology, Kowloon, Hong Kong,
China; HKUST Shenzhen Research Institute, Shenzhen
18057, China; orcid.org/0000-0002-2740-5222;
Phone: +(852) 23587357; Email: rtong@ust.hk
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Authors
Guodong Zhao − School of Chinese Pharmacy, Beijing
University of Chinese Medicine, Beijing 102488, China;
3
746
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ACS Catal. 2021, 11, 3740−3748

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