Dimethyl Sulfoxide Oxygen Donor-Based Annulation of Ketones and Ammonium Persulfate: Regioselective Synthesis of 2,4-disubstituted Oxazoles

Article abstract of DOI:10.1002/adsc.201801671

An efficient protocol for the synthesis of substituted oxazoles via an annulation of ketones, DMSO, and ammonium is reported. DMSO is first found to serve as oxygen donor in annulation resulting in regioselective synthesis of 2,4-disubstituted oxazoles. With the optimized conditions in hand, 22 examples of 2,4-disubstituted oxazoles are obtained from readily available substrates. The protocol can be also applied in cross-condensation reactions between methyl ketones and non-methyl ketones resulting 4 examples of 2,4,5-trisubstituted oxazoles. Moreover, we have successfully applied the protocol into gram-scale representing good yields, that showing the potential practicality in organic synthesis. Based on control experiments and literature, a plausible reaction mechanism was proposed in our work. (Figure presented.).

Full text of DOI:10.1002/adsc.201801671

Title: Dimethyl Sulfoxide Oxygen Donor-Based Annulation of Ketones
and Ammonium Persulfate: Regioselective Synthesis of 2,4-
disubstituted Oxazoles
Authors: Zhongzhong Cao, Huifang Lv, Yufeng Liu, Zhiwen Nie,
Haiping Liu, Tonglin Yang, Wei-Ping Luo, Liu Qiang, and Can-
Cheng Guo
This manuscript has been accepted after peer review and appears as an
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201801671
Link to VoR: http://dx.doi.org/10.1002/adsc.201801671

10.1002/adsc.201801671
Advanced Synthesis & Catalysis
FULL PAPER
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Dimethyl Sulfoxide Oxygen Donor-Based Annulation of
Ketones and Ammonium Persulfate: Regioselective Synthesis of
2,4-disubstituted Oxazoles
Zhongzhong Cao a, Huifang Lv a, Yufeng Liu a, Zhiwen Nie a, Haiping Liu a, Tonglin
Yang a, Weiping Luo a, Qiang Liu a*, Cancheng Guo a*
aCollege of Chemistry and Chemical Engineering, Advanced Catalytic Engineering Research Center of the Ministry of
Education, Hunan University, Changsha 410082, China
E-mail: fqiangliu@qq.com and ccguo@hnu.edu.cn
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######.
Abstract. An efficient protocol for the synthesis of Based on control experiments and literature, a plausible
substituted oxazoles via an annulation of ketones, DMSO, reaction mechanism was proposed in our work.
and ammonium is reported. DMSO is first found to serve as
oxygen donor in annulation resulting in regioselective
synthesis of 2,4-disubstituted oxazoles. With the optimized
conditions in hand, 22 examples of 2,4-disubstituted
oxazoles are obtained from readily available substrates. The
protocol can be also applied in cross-condensation reactions
between methyl ketones and non-methyl ketones resulting 4
examples of 2,4,5-trisubstituted oxazoles. Moreover, we
have successfully applied the protocol into gram-scale
representing good yields, that showing the potential
practicality in organic synthesis.
Keywords: DMSO, Ketones, Ammonium Persulfate,
Oxazoles, and Annulation.
oxazoles based on multi-components coupling have
been developed in recent years. In this context,
ketone was recognized as the versatile and common
materials in the formation of substituted oxazoles, in
which ketone was employed as both carbon and
oxygen sources.[7-9] Cho et al.[7] reported the cross-
coupling of ketones and benzylamines or amino
acides to synthesis of 2,5-di- or 2,4,5-trisubstituted
Introduction
Regioselective synthesis of the substituted
oxazoles has drawn much attention by researchers,
because the oxazoles bearing the substitution groups
are one of the most important heteroaromatic
compounds that found in natural products and
synthetic pharmaceutical molecules.[1] In past decades, oxazoles (Scheme 1, (1a)). Jiang’s group[8a]
a great number of efforts have been directed towards
developing protocols for the regioselective synthesis
of substituted oxazoles.[2,3]
developed a palladium-catalyzed synthesis of 2,5-di-
or 2,4,5-trisubstituted oxazoles from ketones and
amides (Scheme 1, (1b)). Togo[8b] and Wu[8c] reported
the one-pot preparation of 2,5-di- or 2,4,5-
trisubstituted oxazoles from methyl ketones and
nitriles derivatives, respectively (Scheme 1, (1b)).
Additionally, the regioselective synthesis of 2,5-
disubstituted oxazoles by the cross-coupling between
methyl ketones and ammonium acetate or ammonium
iodide were reported, respectively (Scheme 1, (1c)).[9]
Though, the numerous efforts have focused on the
synthesis of substituted oxazoles using ketones as
starting materials, there are still some problems. As is
known in these works, all products reported were
restricted to 2,5-disubstituted structures because the
oxygen sources are originated from carbonyl (C=O)
of ketones. The ketones-based methods for
In general, the classical methods for preparation of
substituted oxazoles are based on the mono-
component reactions. One of the methods is oxidation
of the unsaturated oxazolines to oxazoles.[4] Another
efficient strategy to synthesize the substituted
oxazoles has been developed via an mono-component
intramolecular annulation of N-alkyl-acylamide
derivatives.[5,6] These mono-component protocols are
reliable and widely employed by many chemists, but
the materials used in these reactions are not readily
available, and most of these strategies have relied on
the promotion of precious metals.[5] Comparing with
the above mono-component reactions, a range of
elegant strategies for synthesizing substituted
1
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
preparation of 2,4-disubstituted oxazoles have not
been reported before. Therefore, we want to report an
efficient strategy via the mutil-components
annulation of readily available ketones and
ammonium to afford 2,4-disubstituted oxazoles. In
contrast to the previous works, this protocol would
use DMSO as oxygen donor to assembly of 2,4-
disubstituted oxazoles (Scheme 1, (2)).
Scheme 2. Screening experiments for C and N source in
oxazole-ring.
obtained (Table 1, entry 2 and 3). The mixed
NH4I/K2S2O8 was failed to improve the yield
comparing with the sole (NH4)2S2O8 (Table 1, entry
4). The reaction was unable to give the product using
solo NH4I (Table 1, entry 5). When the TBAI was
replaced by I2 or KI, the reactions have afforded 2a in
lower yields (Table 1, entry 6 and 7). Notably, no
products could be obtained without any catalyst
(Table 1, entry 8). DMSO was necessary for this
reaction, and the mixed DMSO/H2O would decrease
the yield (Table 1, entry 9). Other solvents, e.g., DMF,
toluene, MeCN, or MeOH, were unable to afford the
desired product (Table 1, entry 10-13). When the
temperature was decreased to 100oC, only 42% yield
has been obtained, and only trace amount of product
could be detected at 80oC (Table 1, entry 14 and 15).
Furthermore, the reactions have been performed in O2
or Ar atmosphere, respectively, and the similar results
were obtained in contrast to in air (Table 1, entry 16
and 17).
Scheme 1. The ketones-based strategies for the synthesis
of substituted oxazoles.
Results and Discussion
The annulation among acetophenone 1a, DMSO
and ammonium persulfate could afford a 2,4-
disubstituted oxazole, (phenyl)(4-phenyloxazol-2-
yl)methanone 2a. The experimental results showed
that DMSO is indispensable for the construction of
oxazole-ring. No desired product was found when
DMSO was replaced by other solvents.[10] Under the
standard condition, the DMSO-d6 labeled experiment
using acetophenone as substrate found the
corresponding deuterium product was not obtained
(Scheme 2, eq. (1)). Additionally, the result obtained
by 18O-DMSO labeled experiment has clearly
revealed the oxygen source in product 2a was from
DMSO (Scheme 2, eq. (2)). As a consequence, the
oxazole-ring is formed by four components, all three
C atoms come from two ketones, N atom is from
ammonium persulfate, and O atom is from DMSO.
To the best of our knowledge, the DMSO have been
widely used as a versatile synthon,[11] nevertheless, it
served as oxygen source in annulation is first found in
this work.
Subsequently, we have performed a series of
experiments to optimize the reaction conditions using
acetophenone 1a as the template (The results were
listed in Table 1). As shown in entry 1, it could give
the desired product 2a with the best 85% yield under
an optimal condition: acetophenone 1a (0.5 mmol),
(NH4)2S2O8 (3.0 equiv), and DMSO (3 ml) in the
presence of 20 mol% TBAI at 120oC for 2 h (Table 1,
entry 1). When the amount of (NH4)2S2O8 was
increased or decreased, the lower yields have been
Table 1. Optimization for reaction conditions. [a]
entry
Ammonium
catalyst
solvent
Yield[b]
(%)
85
72
65
66
0
58
25
1
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
NH4I/K2S2O8
NH4I
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
TBAI
TBAI
TBAI
TBAI
TBAI
I2
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO/H2O 62
DMF
Toluene
MeCN
MeOH
2[c]
3[d]
4
5[e]
6
7
8
KI
-
0
9[f]
10
11
12
13
TBAI
TBAI
TBAI
TBAI
TBAI
0
0
0
0
2
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
14[g]
15[h]
16[i]
17[j]
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
TBAI
TBAI
TBAI
TBAI
DMSO
DMSO
DMSO
DMSO
42
trace
80
81
[a] Reaction condition: acetophenone (0.5 mmol, 60 mg),
ammonium salt (3.0 equiv), catalyst (20 mol%), solvent (3
ml), air, 120oC, 2 h. [b] GC yield. [c] (NH4)2S2O8 (2.0 equiv).
[d] (NH4)2S2O8 (4.0 equiv). [e] NH4I (3.0 equiv).
[f]DMSO/H2O (1:1). [g] 100oC.[h] 80oC. [i] In O2.[j] In Ar.
After confirming the sources of each atom in the
oxazole ring and obtaining the optimized conditions,
we studied the applicability of the protocol with
different scopes of substrates. Initially, the scope of
the substituted acetophenones was tested (Scheme 3).
Acetophenones bearing an electron-donating group,
e.g., -Me, -OMe, and -SMe at para-position of the
benzene ring could afford the corresponding 2,4-
disubstituted oxazoles 2b, 2c, and 2d in 88%, 82%
and 70% yields, respectively (Scheme 3, 2b-2d).
Para-halogen substituted acetophenones have also
[12]
provided the products 2e, 2f, and 2g
in excellent
yields (Scheme 3, 2e, 87%, 2f, 77%, and 2g, 78%). In
addition, the substrates bearing the strong electron-
withdrawing group -CF3 and –CO2Me performed well
giving products 2h and 2i in useful yields,
respectively (Scheme 3, 2h, 78% and 2i, 62%). 2j
was obtained from 3'-methylacetopheone giving in
85% yield. The halogen-groups involving -F, -Cl, and
-Br at meta-position of acetophenones have
transformed smoothly into desired products (Scheme
3, 2k, 80%, 2l, 78%, and 2m, 62%). Similarly, the
strong electron-withdrawing group -NO2 at meta-
position has afforded the product 2n in 47% yield.
Acetophenones bearing the ortho-position substitutes
e.g., -Me, -OMe, -Cl, and -Br could give products 2o
to 2r from 75 to 85% yields, respectively (Scheme 3,
2o-2r). Having investigated the scope of substituted
acetophenones, we further studied the scope of other
aromatic and aliphatic methyl ketones. 2-
acetonapthone could give the product 2r in 75% yield
(Scheme 3, 2s). The heterocyclic methyl ketones, 2-
acetyfuran and 2-acetylthiophene have afforded the
products 2t and 2u in moderate yields, respectively
(Scheme 3, 2t, 58%, and 2u, 52%). To our delight,
the aliphatic substrate pinacolone was successfully
performed providing 2v in 46% yield (Scheme 3, 2v).
The methyl isopropyl ketone could be transformed
into corresponding product 2w which detected by
GC-MS.
Scheme 3. The scope of methyl ketones access to 2,4-
disubstituted oxazoles.
Reaction condition: ketone (0.5 mmol), ammonium
persulfate (3.0 equiv), TBAI (20 mol%), DMSO (3 ml), air,
120oC, 2 h. Isolated yield. [a]The X-ray crystal structure is
shown in the middle of Scheme 3. [b]The reaction was
performed for 6 h. [c]The product was detected by GC-MS.
and 4c, 61%). Furthermore, the cross-condensation
reaction
between
2-phenylacetophenone
and
acetophenone gave the desired product 4d in 53%
isolated yield (Scheme 4, 4d). However, the cross-
coupling between acetophenone and the cyclic
substrate -tetralone or 1,3-indanedione were unable
to transform into corresponding products (Scheme 4,
4e and 4f).
Further, the protocol has been applied in gram-
scale reactions, both the acetophenone and 4’-
chloroacetophenone have been successfully
transformed into corresponding products 2a and
2f, respectively (Scheme 5).
To gain insight into the transform processes
from reactants to the products, a series of control
experiments have been performed as shown in
scheme 6. Initially, the radical inhibition experiments
have been performed using acetophenone 1a as
substrate. The results showed that neither of TEMPO
and BHT added extra in standard conditions have
significantly decreased the yields of 2a, hence, a
radical mechanism could be ruled out (Scheme 6. eq.
a).[13] When the standard condition reaction was
performed with DMSO replacing by toluene in 30
min, the compound A 2-iodo-1-phenylthan-1-one
could be easily detected by GC-MS (Scheme 6. eq. b).
Next, we applied this protocol to the cross-
condensation reactions between the methyl ketone
(acetophenone 1a) and non-methyl ketone. The cross-
coupling between acetophenone and propiophenone,
n-butyrophenone, or valerophenone can afford the
corresponding 2,4,5-trisubstituted oxazoles 4a, 4b
and 4c, respectively (Scheme 4, 4a, 55%, 4b, 52%,
3
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
Scheme 4. Cross-condensation reaction access to 2,4,5-
trisubstituted oxazoles. Reaction condition: 1a (0.25 mmol)
+ 3 (0.25 mmol), (NH4)2S2O8 (0.75 mmol, 3.0 equiv),
TBAI (20 mol%), DMSO (3 ml), air, 120oC, 2 h. Isolated
yield.
Scheme 6. Control experiments.
Standard condition: substrate (0.5 mmol), (NH4)2S2O8 (3.0
equiv), TBAI (20 mol%), DMSO (3 ml), air, 120oC, 2 h.
The reactions were detected by GC-MS.
Scheme 5. Gram-scale reaction.
immediately reacted with ammonium leading to 4.
Then, 4 could convert to 5 underwent tautomerization.
For another part, 7 was formed by another methyl
ketones 6 via the path of Kornblum oxidation. The
coupling between 5 and 7 has resulted in compound 8.
Subsequently, the final product 10 was obtained via
the processes of annulation and aromatization.
Reaction condition: ketone (10.0 mmol), (NH4)2S2O8 (3.0
equiv), TBAI (5 mol%), DMSO (25 ml), air, 120oC, 6 h.
The reactions were performed in a 50 ml round-bottom
flask.
Similarly, the compound B 2-hydroxy-1-phenylthan-
1-one could also be obtained in 30 min under the
standard reaction condition (Scheme 6. eq. c).
Acetophenone 1a can transform into 2a under
standard condition, but none product was obtained in
2-
the absence of TBAI or S2O8 (Scheme 6. eq. d).
Subsequently, compound A was unable to transform
further into B or 2a when the DMSO was replaced by
toluene (Scheme 6. eq. e). However, compound B
would convert to 2a only in the presence of
ammonium source with excellent yields (Scheme 6.
eq. f). The phenylglyoxal failed to afford the desired
product under standard condition (Scheme 6. eq. g).
While, the cross reaction between phenylglyoxal and
2-hydroxy-1-(2-naphthalenyl)-ethanone can afford
the corresponding product successfully (Scheme 6. eq.
h).
Scheme 7. Plausible reaction mechanism.
On the basis of control experiments and literature
precedents, a plausible mechanism is proposed in
Scheme 7. Substrate 1 transformed into 2 via a -
iodination of ketones. Intermediate 3 was obtained by
DMSO providing oxygen atom to replace iodine, and
Conclusion
In summary, a TBAI-promoted annulation of
two ketones, one DMSO, and one ammonium to
4
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
cooled to room temperature, then washed and
extracted with H2O and ethyl acetate (EA). Finally,
extraction liquor was concentrated with rotary
evaporator and purified by column chromatography
using silica gel (200-300 mesh size) with petroleum
ether (PE)/ethyl acetate (EA) as the eluent.
substituted oxazoles is developed. In this work,
DMSO is first found to serve as oxygen donor in
an O-containing annulation. With the optimized
reaction condition in hand, 22 examples of 2,4-
disubstituted oxazoles have been obtained in
useful yields. Moreover, 4 examples of 2,4,5-
trisubstituted oxazoles can also be synthesized by
the cross-condensation reactions between methyl
ketones and non-methyl ketones. The protocols
are further applied in gram-scales reactions that
worked equally well as in general reactions. A
plausible mechanism for the reaction was
proposed based on control experiments and
literature precedents. The further investigation for
the mechanism and applications are in progress in
our laboratory.
Procedures for gram-scale reaction. Ketone
(10.0 mmol), (NH4)2S2O8 (3.0 equiv, 3.42g), TBAI (5
mol%, 90 mg), DMSO (25 ml) were added to a 50 ml
round-bottom flask with sealed vinolok. The reaction
was stirred vigorously at 120 °C for 6 h and
monitored by TLC and GC-MS. After completion of
the reaction, the mixture was cooled to room
temperature, then washed and extracted with H2O and
ethyl acetate (EA) for thrice. Finally, extraction
liquor was concentrated with rotary evaporator and
purified by column chromatography using silica gel
(200-300 mesh size) with petroleum ether
(PE)/ethyl acetate (EA) as the eluent
Experimental Section
NMR data of title products.
General Methods. All solvents and reactants were
purchased from commercial sources. The exact
structure of 2g was determined by single-crystal-
diffraction. All target compounds were characterized
on the basis of HRMS and NMR (1H and 13C)
spectroscopic data. NMR measurements were
performed on Bruker AV400MHz, and all data were
reported in ppm relative to trimethylsilane ( = 0)
and measured relative to the signals for residual
chloroform (7.26 ppm for H and 77.00 ppm for C)
in the deuterated solvent. GC-MS analyses were
performed on Shimadzu GC-MS (QP-2010). The
reactions were performed in the sealed tube (25 ml)
with threaded end.
(phenyl)(4-phenyloxazol-2-yl)methanone (2a) [16]
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
30:1 as the eluent. 53.1 mg, 85% yield, deep yellow
solid, melting point: 117.8-119.5 C. H NMR (400
MHz, CDCl3) δ 8.60 (d, J = 7.6 Hz, 2H), 8.15 (s, 1H),
7.85 (d, J = 7.6 Hz, 2H), 7.68 (t, J = 7.6 Hz, 1H),
7.56 (t, J = 7.2 Hz, 2H), 7.45 (t, J = 7.6 Hz, 2H), 7.39
(t, J = 7.2 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ
178.71, 157.52, 142.68, 136.22, 134.94, 134.03,
131.03, 129.91, 128.89, 128.86, 128.49, 125.83.
HRMS (ESI) (M+H)+ Calcd. for C16H12NO2:
250.0862, Found: 250.0862.
o
1
1
13
Method for preparation of 18O labeled
DMSO:[14,15] Dimethylsulfur dibromide (5.0 g, 22.5
mmoles) was prepared using the reported methods.[16]
Then it was added portion wise over 15 min to a
vigorously stirred solution of triethylamine (6.3 ml,
45 mmoles, freshly distilled from KOH) and 18O-
(4-methylphenyl)(4-(4-methylphenyloxazol)-2-
yl)methanone (2b)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
15:1 as the eluent. 61.1 mg, 88% yield, orange solid,
18
labeled water (97 atom % O) (0.20 ml, 11 mmoles)
o
1
melting point: 104.8-107.5 C. H NMR (400 MHz,
CDCl3) δ 8.50 (d, J = 7.6 Hz, 2H), 8.10 (s, 1H), 7.73
(d, J = 6.8 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 7.25 (d,
in 15 ml of tetrahydrofuran (freshly distilled from
Na). The temperature of the reaction was maintained
15 min below 50oC and then occasional cooling in ice.
The precipitate of triethylamine hydrobromide was
removed by filtration and washed twice with ice ether.
The combined yellow supernatant and washings were
dried on high vacuum pressure pump at room
temperature to remove the solvent and gave a pale
yellow liquid. The obtained liquid was direct used
without further purification.
13
J = 5.2 Hz, 2H), 2.47 (s, 3H), 2.40(s, 3H). C NMR
(101 MHz, CDCl3) δ 178.39, 157.61, 145.07, 142.65,
138.77, 135.65, 132.53, 131.17, 129.54, 129.22,
127.21, 125.74, 21.82, 21.33. HRMS (ESI) (M+H)+
Calcd. for C18H16NO2: 278.1176, Found: 278.1175.
(4-methoxylphenyl)(4-(4-methoxylphenyloxazol)-
2-yl)methanone (2c)
General Procedures for Synthesis of substituted
oxazoles. All the reagents were using direct unless
otherwise noted, and solvents were kept with
molecular sieve. Ketone (2 * 0.25 mmol), (NH4)2S2O8
(3.0 equiv, 0.75 mmol), TBAI (20 mol%, 18 mg),
DMSO (3.0 ml) were added to sealed tube. The
reaction was stirred vigorously at 120 °C for 2 to 6 h.
After completion of the reaction, the mixture was
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
10:1 as the eluent. 63.4 mg, 82% yield, dark yellow
o
1
solid, melting point: 98.8-101.5 C. H NMR (400
MHz, CDCl3) δ 8.64 (d, J = 7.6 Hz, 2H), 8.04 (s, 1H),
7.78 (d, J = 7.6 Hz, 2H), 7.02 (d, J = 7.6 Hz, 2H),
5
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
6.97 (d, J = 7.6 Hz, 2H), 3.91 (s, 3H), 3.85 (s, 3H).
13C NMR (101 MHz, CDCl3) δ 177.14, 164.40,
160.06, 157.70, 142.32, 134.91, 133.58, 131.68,
127.19, 122.74, 114.30, 113.83, 55.55, 55.35. HRMS
(ESI) (M+H)+ Calcd. for C18H16NO4: 310.1074,
Found: 310.1072.
MHz, CDCl3) δ 8.29 (d, J = 8.4 Hz, 2H), 8.16 (s, 1H),
7.93 (d, J = 8.4 Hz, 2H), 7.79 (d, J = 8.1 Hz, 2H),
7.56 (d, J = 8.2 Hz, 2H). 13C NMR (101 MHz, CDCl3)
δ 177.78, 157.36, 141.94, 138.09, 137.94, 136.60,
134.11, 132.24, 129.31, 127.48, 102.89, 94.63.
HRMS (ESI) (M+H)+ Calcd. for C16H10NO2I2:
501.8796, Found: 501.8794.
(4-sulfurmethylphenyl)(4-(4-
sulfurmethylphenyloxazol)-2-yl)methanone (2d)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
10:1 as the eluent. 59.8 mg, 70% yield, yellow solid,
melting point: 129.8-132.3 C. H NMR (400 MHz,
CDCl3) δ 8.54 (d, J = 8.0 Hz, 2H), 8.10 (s, 1H), 7.75
(d, J = 8.0 Hz, 2H), 7.33 (t, J = 8.8 Hz, 4H), 2.56 (s,
3H), 2.53 (s, 3H). 13C NMR (101 MHz, CDCl3) δ
177.43, 157.61, 147.68, 142.16, 139.60, 135.76,
131.36, 131.11, 126.67, 126.57, 126.17, 124.71,
15.57, 14.63. HRMS (ESI) (M+H)+ Calcd. for
C18H16NO2S2: 342.0617, Found: 342.0615.
(4-trifluoromethyl)(4-(4-
trifluoromethylphenyloxazol)-2-yl)methanone (2h)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
10:1 as the eluent. 74.9 mg, 78% yield, wine red solid,
o
1
o
1
melting point: 157.9-161.0 C. H NMR (400 MHz,
CDCl3) δ 8.70 (d, J = 8.1 Hz, 1H), 8.27 (s, 1H), 7.96
(d, J = 8.0 Hz, 1H), 7.84 (d, J = 8.1 Hz, 1H), 7.73 (d,
J = 8.0 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ
177.43, 157.34, 141.69, 137.59, 137.46, 135.23 (d, J
= 32.7 Hz), 133.10, 131.30, 130.96 (d, J = 32.7 Hz),
126.10, 126.00 (dd, J = 7.6, 3.8 Hz), 125.55 (q, J =
3.7 Hz), 125.06 (d, J = 37.6 Hz), 122.35 (d, J = 38.3
Hz).13C NMR (101 MHz, CDCl3) δ 177.44, 157.36 ,
141.71, 137.54 (d, J = 11.5 Hz), 135.25 (d, J = 32.9
Hz), 133.11, 131.31, 126.11, 126.01 (d, J = 3.8 Hz),
125.56 (d, J = 3.8 Hz), 123.90 (d, J = 272.7 Hz),
123.53 (d, J = 274.1 Hz). HRMS (ESI) (M+H)+ Calcd.
for C16H10NO2I2: 386.0611, Found: 386.0608.
(4-fluorophenyl)(4-(4-fluorolphenyloxazol)-2-
yl)methanone (2e)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
20:1 as the eluent. 62.1 mg, 87% yield, yellow solid,
o
1
melting point: 105.5-108.0 C. H NMR (400 MHz,
CDCl3) δ 8.81-8.74 (m, 2H), 8.21 (s, 1H), 7.97-7.86
(m, 2H), 7.37-7.35 (m, 1H), 7.33 (s, 1H), 7.32-7.27
Methyl 4-(2-(4-(methoxycarbonyl)benzoyl)oxazol-
4-yl)benzoate (2i)
13
(m, 1H), 7.24 (m, 1H). C NMR (101 MHz, CDCl3)
δ 176.90, 166.47 (d, J = 257.1 Hz), 163.08 (d, J =
248.8 Hz), 157.41, 141.88, 135.94, 133.89 (d, J =9.5
Hz), 131.25 (d, J = 2.9 Hz), 127.68 (d, J = 8.3 Hz),
126.07, 116.02 (d, J = 22.4 Hz), 115.79 (d, J = 22.4
Hz). HRMS (ESI) (M+H)+ Calcd. for C16H10NO2F2:
286.0675, Found: 286.0675.
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
8:1 as the eluent. 56.7 mg, 62% yield, dark yellow
o
1
solid, melting point: 157.9-161.0 C. H NMR (400
MHz, CDCl3) δ 8.64 (d, J = 8.4 Hz, 2H), 8.27 (s, 1H),
8.23 (d, J = 8.4 Hz, 2H), 8.14 (d, J = 8.3 Hz, 2H),
7.92 (d, J = 8.3 Hz, 2H). 13C NMR (101 MHz, CDCl3)
δ 178.00, 166.56, 166.17, 138.09, 137.62, 134.68,
134.01, 130.91, 130.49, 130.31, 130.02, 129.66,
125.74 124.47, 52.57, 52.29. HRMS (ESI) (M+H)+
Calcd. for C20H16NO6: 366.0973, Found: 366.0970.
(4-chlorophenyl)(4-(4-chlorophenyloxazol)-2-
yl)methanone (2f)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
15:1 as the eluent. 61.3 mg, 77% yield, yellowish
o
1
white solid, melting point: 144.7-146.5 C. H NMR
(400 MHz, CDCl3) δ 8.55 (d, J = 8.0 Hz, 2H), 8.14 (s,
1H), 7.76 (d, J = 8.4 Hz, 2H), 7.53 (d, J = 8.0 Hz,
(3-methylphenyl)(4-(3-methylphenyloxazol)-2-
yl)methanone (2j)
It is synthesized basing on General Procedure and
purified by column chromatography with PE/EA =
15:1 as the eluent. 58.9 mg, 85% yield, dark yellow
13
2H), 7.43 (d, J = 8.4 Hz, 2H). C NMR (101 MHz,
CDCl3) δ 177.16, 157.31, 141.75, 140.86, 136.47,
134.79, 133.09, 132.39, 129.17, 128.90, 128.25,
127.07. HRMS (ESI) (M+H)+ Calcd. for
C16H10NO2Cl2: 319.0083, Found: 319.0082.
o
1
solid, melting point: 118.8-121.0 C. H NMR (400
MHz, CDCl3) δ 8.44 (d, J = 7.6 Hz, 1H), 8.30 (s, 1H),
8.13 (s, 1H), 7.71 – 7.60 (m, 2H), 7.46 (q, J = 7.9 Hz,
2H), 7.35 (t, J = 7.6 Hz, 1H), 7.20 (d, J = 7.6 Hz, 1H),
2.48 (s, 3H), 2.43 (s, 3H). 13C NMR (101 MHz,
CDCl3) δ 179.02, 157.60, 142.77, 138.62, 138.32,
136.14, 134.99, 134.86, 131.16, 129.84, 129.63,
128.79, 128.49, 128.37, 126.46, 122.96. HRMS (ESI)
(M+H)+ Calcd. for C18H16NO2: 278.1176, Found:
278.1176.
(4-iodophenyl)(4-(4-iodophenyloxazol)-2-
yl)methanone (2g)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
15:1 as the eluent. 97.4 mg, 78% yield, dark yellow
o
1
solid, melting point: 160.9-163.5 C. H NMR (400
6
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801671
Advanced Synthesis & Catalysis
CDCl3) δ 9.54 (s, 1H), 8.93 (d, J = 7.8 Hz, 1H), 8.67
(s, 1H), 8.55 (d, J = 8.0 Hz, 1H), 8.38 (s, 1H), 8.24
(dd, J = 17.7, 8.0 Hz, 2H), 7.82 (t, J =8.0 Hz, 1H),
7.70 (t, J = 8.0 Hz, 1H). 13C NMR (101 MHz, CDCl3)
δ 175.92, 157.09, 148.75, 148.33, 141.04, 137.99,
136.31, 135.74, 131.59, 131.27, 130.24, 129.94,
128.34, 126.08, 123.75, 120.70. HRMS (ESI)
(M+H)+ Calcd. for C16H10N3O6: 340.0565, Found:
340.0563.
(3-fluorophenyl)(4-(3-fluorophenyloxazol)-2-
yl)methanone (2k)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
15:1 as the eluent. 68.7 mg, 80% yield, yellowish
o
1
white solid, melting point: 94.8-97.5 C. H NMR
(400 MHz, CDCl3) δ 8.43 (dd, J = 7.8, 1.1 Hz, 1H),
8.35-8.30 (m, 1H), 8.18 (s, 1H), 7.66-7.52 (m, 3H),
7.49-7.34 (m, 2H), 7.09 (ddd, J = 8.3, 2.5, 1.9 Hz,
1H). 13C NMR (101 MHz, CDCl3) δ 177.04 (d, J =
2.6 Hz), 163.14 (d, J = 247.3 Hz), 162.48 (d, J =
248.6 Hz), 157.18, 141.74 (d, J = 2.7 Hz), 136.94,
136.53 (d, J = 7.0 Hz), 131.85 (d, J = 8.3 Hz), 130.58
(d, J = 8.3 Hz), 130.21 (d, J = 7.7 Hz), 126.83 (d, J =
3.0 Hz), 121.42 (d, J = 3.0 Hz), 121.20 (d, J = 21.5
Hz), 117.69 (d, J = 23.4 Hz), 115.83 (d, J = 21.1 Hz),
112.86 (d, J = 23.0 Hz). HRMS (ESI) (M+H)+ Calcd.
for C16H10NO2F2: 286.0675, Found: 286.0673.
(2-methylphenyl)(4-(2-methylphenyloxazol)-2-
yl)methanone (2o)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
40:1 as the eluent. 58.8 mg, 85% yield, bright yellow
o
1
solid, melting point: 100.8-102.3 C. H NMR (400
MHz, CDCl3) δ 8.09 (d, J = 7.8 Hz, 1H), 7.97 (s,
1H), 7.79 (s, 1H), 7.45 (t, J = 7.8 Hz, 1H), 7.32 (t, J =
8.0 Hz, 5H), 2.54 (s, 3H), 2.47 (s, 3H). 13C NMR
(101 MHz, CDCl3) δ 182.16, 157.42, 142.06, 139.57,
138.05, 135.75, 134.99, 132.21, 131.61, 131.56,
130.94, 129.23, 128.89, 128.67, 126.16, 125.13,
21.63, 20.75. HRMS (ESI) (M+H)+ Calcd. for
C18H16NO2: 278.1176, Found: 278.1173.
(3-chlorophenyl)(4-(3-chlorophenyloxazol)-2-
yl)methanone (2l)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA =
25:1 as the eluent. 62.2 mg, 78% yield, pink yellow
o
1
solid, melting point: 130.7-133.5 C. H NMR (400
MHz, CDCl3) δ 8.53 (d, J = 6.8 Hz, 2H), 8.18 (s, 1H),
7.84 (s, 1H), 7.73 (d, J = 6.8 Hz, 1H), 7.66 (d, J = 7.8
Hz, 1H), 7.53 (t, J = 7.2 Hz, 1H), 7.43 – 7.36 (m, 2H).
13C NMR (101 MHz, CDCl3) δ 177.09, 157.20,
141.63, 136.98, 136.19, 135.01, 134.81, 134.06,
131.48, 130.77, 130.25, 129.88, 129.22, 129.02,
125.91, 123.92. HRMS (ESI) (M+H)+ Calcd. for
C16H10NO2Cl2: 319.0083, Found: 319.0081.
(2-methoxylphenyl)(4-(2-methoxylphenyl)-2-
yl)methanone (2p)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
20:1 as the eluent. 57.9 mg, 75% yield, bright yellow
1
grease. H NMR (400 MHz, CDCl3) δ 8.30, 8.17 (d,
J = 7.8 Hz, 1H) , 7.76 (d, J = 7.8 Hz, 1H) , 7.55 (d, J
= 8.0 Hz, 1H), 7.31 (d, J = 7.8 Hz, 1H), 7.09 (d, J =
7.8 Hz, 1H), 7.04 (d, J = 8.0 Hz, 2H), 6.97 (d, J = 8.0
13
Hz, 1H), 3.97 (s, 3H), 3.80 (s, 3H). C NMR (101
(3-bromophenyl)(4-(3-bromophenyloxazol)-2-
yl)methanone (2m)
It is synthesized basing on General Procedures and
MHz, CDCl3) δ 181.39, 158.99, 157.30, 156.55 ,
139.38, 138.20, 133.75, 131.08, 129.24, 128.14,
126.54, 120.80, 120.32, 119.02, 111.97, 110.46,
55.94, 55.34. HRMS (ESI) (M+H)+ Calcd. for
C18H16NO4: 310.1073, Found: 310.1071.
purified
by
column
chromatography
with
PE/EA=20:1 as the eluent. 62.9 mg, 62% yield, deep
yellow solid, melting point: 141.5-144.2 oC. 1H NMR
(400 MHz, CDCl3) δ 8.68 (s, 1H), 8.58 (d, J = 7.8 Hz,
1H), 8.18 (s, 1H), 7.99 (s, 1H), 7.79 (dd, J = 17.3, 7.9
Hz, 2H), 7.53 (d, J = 7.8 Hz, 1H), 7.46 (t, J = 8.0 Hz,
1H), 7.34 (t, J = 8.0 Hz, 1H). 13C NMR (101 MHz,
CDCl3) δ 177.11, 157.20, 141.53, 136.99, 136.41,
133.68, 131.97 , 131.74, 130.52, 130.14, 129.70,
128.83, 127.20, 124.40, 123.12, 122.77. HRMS (ESI)
(M+H)+ Calcd. for C16H10NO2Br2: 406.9020, Found:
406.9018.
7.35 – 7.29
(2-chlorophenyl)(4-(2-chlorophenyloxazol)-2-
yl)methanone (2q)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
35:1 as the eluent. 73.5 mg, 78% yield, yellowish
o
1
white solid, melting point: 113.0-115.6 C. H NMR
(400 MHz, CDCl3) δ 8.56 (s, 1H), 8.09 (d, J = 7.6 Hz,
1H), 7.78 (d, J = 7.6 Hz, 1H), 7.51 (s, 2H), 7.48 –
7.42 (m, 2H) 7.35 – 7.29 (m, 2H). 13C NMR (101
MHz, CDCl3) δ 180.26, 156.52, 140.27 , 139.50,
135.69, 132.90, 132.73, 131.77, 130.93, 130.58,
130.28, 130.18, 129.56, 128.55, 127.12, 126.57.
HRMS (ESI) (M+H)+ Calcd. for C16H10NO2Cl2:
319.0082, Found: 319.0081.
(3-nitrophenyl)(4-(3-nitrophenyloxazol)-2-
yl)methanone (2n)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA= 5:1
as the eluent. 39.8 mg, 47% yield, deep yellow solid,
o
1
melting point: 155.2-158.0 C. H NMR (400 MHz,
7
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801671
Advanced Synthesis & Catalysis
15:1 as the eluent. 24.1 mg, 46% yield, yellow liquid.
1H NMR (400 MHz, CDCl3) δ 7.41 (s, 1H), 1.43 (s,
9H), 1.29 (s, 9H). 13C NMR (101 MHz, CDCl3) δ
193.72, 155.81, 152.07, 133.69, 43.85, 31.14, 29.18 ,
26.86. HRMS (ESI) (M+H)+ Calcd. for C12H10NO2:
210.1486, Found: 210.1485.
(2-bromophenyl)(4-(2-bromophenyloxazol)-2-
yl)methanone (2r)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA
=25:1 as the eluent. 77.1 mg, 76% yield, yellow white
o
1
solid, melting point: 117.0-118.8 C. H NMR (400
MHz, CDCl3) δ 8.63 (s, 1H), 7.79 (d, J = 7.6 Hz, 1H),
7.74 (d, J = 7.6 Hz, 1H), 7.71 (s, 2H), 7.44 (dd, J =
14.2, 5.9 Hz, 2H), 7.38 – 7.27 (m, 2H). 13C NMR
(101 MHz, CDCl3) δ 180.98, 156.27, 140.71, 140.58
139.97, 137.58, 133.73, 133.67, 132.74, 130.88,
130.52, 129.85, 127.63, 127.13, 121.29, 120.88.
HRMS (ESI) (M+H)+ Calcd. for C16H10NO2Br2:
406.9019, Found: 406.9017.
(5-methyl-4-phenyloxazol-2-yl)(phenyl)methanone
(4a)
It is synthesized from 1-phenylpropanone (0.25 mmol)
and acetophenone (0.25 mmol) basing on General
Procedures and purified by column chromatography
with PE/EA = 20:1 as the eluent. 36.2 mg, 55% yield,
yellow liquid. 1H NMR (400 MHz, CDCl3) δ 8.58 (d,
J = 7.7 Hz, 2H), 7.76 (d, J = 7.6 Hz, 2H), 7.65 (t, J =
7.1 Hz, 1H), 7.54 (t, J = 7.7 Hz, 2H), 7.48 (t, J = 7.2
(naphthyl)(4-naphthyl-2-yl)methanone (2s)
13
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
25:1 as the eluent. 65.4 mg, 75% yield, yellow solid,
Hz, 2H), 7.38 (t, J = 7.4 Hz, 1H), 2.70 (s, 3H). C
NMR (101 MHz, CDCl3) δ 178.65, 155.59, 147.99,
137.27, 135.21, 133.75, 130.99, 128.75, 128.41,
128.06, 126.95, 125.86, 12.35. HRMS (ESI) (M+H)+
Calcd. for C17H14NO2: 264.1021, Found: 264.1017.
o
1
melting point: 138.7-141.2 C. H NMR (400 MHz,
CDCl3) δ 9.37 (s, 1H), 8.50 (d, J = 7.6 Hz, 1H), 8.41
(s, 1H), 8.28 (s, 1H), 8.10 (d, J = 3.6 Hz, 1H), 8.03 –
13
7.83 (m, 6H), 7.74 – 7.58 (m, 2H), 7.54 (s, 2H). C
(5-ethyl-4-phenyloxazol-2-yl)(phenyl)methanone
(4b)
NMR (101 MHz, CDCl3) δ 178.61, 157.81, 142.78,
136.53, 136.01, 134.16, 133.44, 132.39, 132.27,
130.25, 130.25, 129.14, 128.72, 128.38, 128.30,
127.80, 127.27, 126.83, 126.66, 126.55, 125.51,
125.01, 123.43, 119.07. HRMS (ESI) (M+H)+ Calcd.
for C24H16NO2: 350.1176, Found: 350.1175.
It is synthesized from butyrophenone (0.25 mmol)
and acetophenone (0.25 mmol) basing on General
Procedure and purified by column chromatography
with PE/EA=20:1 as the eluent. 35.9 mg, 52% yield,
yellow liquid. 1H NMR (400 MHz, CDCl3) δ 8.57 (d,
J = 7.8 Hz, 2H), 7.74 (d, J = 7.6 Hz, 2H), 7.65 (t, J =
7.3 Hz, 1H), 7.54 (t, J = 7.4 Hz, 2H), 7.48 (t, J = 7.3
Hz, 2H), 7.38 (t, J = 7.4 Hz, 1H), 3.06 (q, J = 7.4 Hz,
(furan)(4-furan-2-yl)methanone (2t)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
20:1 as the eluent. 58% yield, brown black grease. 1H
NMR (400 MHz, CDCl3) δ 8.20 (s, 1H), 8.06 (s, 1H),
7.81 (s, 1H), 7.48 (s, 1H), 6.85 (s, 1H), 6.68 (s, 1H),
13
2H), 1.43 (t, J = 7.5 Hz, 3H). C NMR (101 MHz,
CDCl3) δ 178.70, 155.62, 152.94 , 136.60, 135.28,
133.70, 131.31, 130.97, 128.74, 128.39, 128.09,
127.11, 19.79, 12.35. HRMS (ESI) (M+H)+ Calcd.
for C18H16NO2: 278.1176, Found: 278.1173
13
6.52 (s, 1H). C NMR (101 MHz, CDCl3) δ 165.50,
156.71, 150.03, 149.10, 145.62, 142.89, 135.85,
135.15, 124.64, 112.91, 111.52, 108.33. HRMS (ESI)
(M+H)+ Calcd. for C12H8NO4: 230.0445, Found:
230.0444.
(5-propyl-4-phenyloxazol-2-yl)(phenyl)methanone
(4c)
It is synthesized from valerophenone (0.25 mmol)
and acetophenone (0.25 mmol) basing on General
Procedures and purified by column chromatography
with PE/EA=20:1 as the eluent. 44.3 mg, 61% yield,
yellow liquid. 1H NMR (400 MHz, CDCl3) δ 8.58 (d,
J = 7.7 Hz, 2H), 7.75 (d, J = 7.6 Hz, 2H), 7.64 (t, J =
7.3 Hz, 1H), 7.51 (dt, J = 22.8, 7.4 Hz, 4H), 7.38 (t, J
= 7.1 Hz, 1H), 3.00 (t, J = 7.6 Hz, 2H), 1.94-1.79 (m,
(thiophene)(4-thiophene-2-yl)methanone (2u)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
1
15:1 as the eluent. 52% yield, brown grease. H
NMR (400 MHz, CDCl3) δ 8.72 (s, 1H), 8.04 (s, 1H),
7.83 (d, J = 4.5 Hz, 1H), 7.48 (s, 1H), 7.37 (d, J = 4.7
Hz, 1H), 7.26 (s, 1H), 7.12 (s, 1H).13C NMR (101
MHz, CDCl3) δ 170.41, 156.78, 140.48, 137.82,
137.41, 136.69, 135.39, 132.33, 128.64, 127.85,
126.03, 125.24. HRMS (ESI) (M+H)+ Calcd. for
C12H8NO2S2: 261.9992, Found: 261.9992.
13
2H), 1.05 (t, J = 7.3 Hz, 3H). C NMR (101 MHz,
CDCl3) δ 178.62, 155.67, 151.95, 137.12, 135.29,
133.66, 131.35, 130.95, 128.71, 128.36, 128.06,
127.12, 28.13, 21.39, 13.87. HRMS (ESI) (M+H)+
Calcd. for C19H17NO2: 292.1333, Found: 292.1331.
(tert-butyl)(4-tert-butyl-2-yl)methanone (2v)
It is synthesized basing on General Procedures and
purified by column chromatography with PE/EA=
(4,5-diphenyloxazol-2-yl)(phenyl)methanone
(4d)[9c]
8
This article is protected by copyright. All rights reserved.

10.1002/adsc.201801671
Advanced Synthesis & Catalysis
[5] a) S. Samanta, R. R. Donthiri, M. Dinda, S. Adimurthy,
RSC Adv. 2015, 5, 66718-66722; b) S. R. Bathula, M. P.
Reddy, K. K. D. R. Viswanadham, P. Sathyanarayana,
M. S. Reddy, Eur. J. Org. Chem. 2013, 4552–4557.
It is synthesized from valerophenone (0.25 mmol)
and acetophenone (0.25 mmol) basing on General
Procedures and purified by column chromatography
with PE/EA=20:1 as the eluent. 43.1 mg, 53% yield,
yellow solid, melting point: 119.7-122.2 oC. 1H NMR
(400 MHz, CDCl3) δ 8.62 (d, J = 7.5 Hz, 2H), 7.78
(m, 4H), 7.68 (t, J = 7.4 Hz, 1H), 7.57 (t, J = 7.7 Hz,
2H), 7.46 (m, 6H). 13C NMR (101 MHz, CDCl3) δ
178.63, 155.92, 148.61, 137.31, 135.27, 133.77,
131.55, 130.93, 129.81, 128.80, 128.75, 128.69,
128.43, 128.20, 127.68, 127.35. HRMS (ESI)
(M+H)+ Calcd. for C22H15NO2: 326.1176, Found:
326.1173.
[6] a) S. Y. Mai, C. W. R, M. Chen, J. H. Su, J. F. Du, Q. L.
Song, Chem. Commun. 2017, 53, 10366-10369; b) H. H.
Peng, N. G. Akhmedov, Y.-F. Liang, N. Jiao, X. D. Shi,
J. Am. Chem. Soc. 2015, 137, 8912-8915.
[7] a) Q.-H. Gao, Z. Fei, Y.-P. Zhu, M. Lian, F.-C. Jia, M.-
C. Liu, N.-F. She, A.-X. Wu, Tetrahedron 2013, 69,
22-28; b) T. Chatterjee, J. Y. Cho, E. J. Cho, J. Org.
Chem. 2016, 81, 6995-7000; c) T. Hu, H. Yan, X. X.
Liu, C. Y. Wu, Y. X. Fan, J. Huang, G. S. Huang,
Synlett 2015, 26, 2866-2869; d) W. Xu, U. Kloeckner,
B. J. Nachtsheim, J. Org. Chem. 2013, 78, 6065–6074.
Acknowledgements
[8] a) M. F. Zheng, L. B. Huang, H. W. Huang, X. W. Li,
W. Q. Wu, H. F. Jiang, Org. Lett. 2014, 16, 5906-5909;
b) S. Imai, H. Hikui, K. Moriyama, H. Togo,
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P. Zhao, J. J. Zhang, Y.-D. Wu, H.-Z. A.-X. Wu, Chem.
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Krishna, Y. L. Prapurna, Synth. Commun. 2018, 48,
1986–1993.
We gratefully acknowledge the National Natural Science
Foundation of China (21572049) for financial support.
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10.1002/adsc.201801671
Advanced Synthesis & Catalysis
FULL PAPER
Dimethyl Sulfoxide Oxygen Donor-Based
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Regioselective Synthesis of 2,4-disubstituted
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Adv. Synth. Catal. Year, Volume, Page – Page
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10
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