CO2/Photoredox-Cocatalyzed Tandem Oxidative Cyclization of α-Bromo Ketones and Amines to Construct Substituted Oxazoles

Article abstract of DOI:10.1021/acs.joc.9b00283

CO₂/photoredox-cocatalyzed tandem oxidative cyclization of α-bromo ketones and amines for the preparation of substituted oxazoles has been achieved. The avoidance of using both transition-metal catalysts and peroxides makes this method more sustainable and renewable.

Full text of DOI:10.1021/acs.joc.9b00283

Subscriber access provided by ALBRIGHT COLLEGE
Note
CO2/Photoredox Cocatalyzed Tandem Oxidative Cyclization of #-
Bromo Ketones and Amines to Construct Substituted Oxazoles
Xiaowei Zhang, Yonghui He, Jing Li, Rui Wang, Lijun Gu, and Ganpeng Li
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 22 May 2019
Downloaded from http://pubs.acs.org on May 22, 2019
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 7
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
CO2/Photoredox Cocatalyzed Tandem Oxidative Cyclization of
α-Bromo Ketones and Amines to Construct Substituted
Oxazoles
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Xiaowei Zhang, ‡a Yonghui He, ‡b Jing Li, b Rui Wang, a Lijun Gu, *b,c and Ganpeng Li *b
a School of Chemistry and Environment, Yunnan Minzu University
b Key Laboratory of Chemistry in Ethnic Medicinal Resources, State Ethnic Affairs Commission & Ministry of Education,
Yunnan Minzu University, Kunming, Yunnan, 650500, China;
c Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang
550025, China
Supporting Information Placeholder
Ar
O
O
N
R
Br
R
NH2
+
Ar
DBN
CO2 as a mediator
eosin Y catalyzed photoredox reactions
19 examples
ABSTRACT: CO2/photoredox cocatalyzed tandem oxidative cyclization of α-bromo ketones and amines for the preparation of
substituted oxazoles has been achieved. The avoidance of using both transition-metal catalysts and peroxides make this method
more sustainable and renewable.
Substituted oxazoles are widely found in various molecules
with biological activities. They are of significance to the
community of pharmaceutical discovery.1 Of biologically active
natural products that contain oxazole moieties, the diazonamide
and phorboxazole families in particular, display remarkable anti-
neoplastic properties.2 Moreover, substituted oxazoles have found
industrial application as scintillator and laser dyes.3 Subsequently,
many new methods have been applied to prepare oxazoles.4,5
Although a variety of highly efficient methods have been reported
to synthesize the substituted oxazoles, the exploration for more
methods is in continuous demand. In particular, the development
of new synthetic methods toward substituted oxazoles, aiming at
affording greater levels of molecular complexity and improved
functional group compatibility in a convergent and atom-
economical fashion from cheap starting chemicals under mild
conditions is a primary research endeavors which is sought by
many in modern chemical science. Metal-free-catalyzed reactions,
which are often used to satisfy the above criteria, are among the
most magnetic synthetic methods.
photoredox reactions are effected under mild conditions without
radical initiators or stoichiometric reagents. Moreover, some
organic dyes, such as eosin Y, have recently emerged as superior
alternatives to the transition metal photoredox catalysts, which
have much lower costs7. Driven by visible light, some novel
discoveries have been reported effected in the presence of the
eosin Y.4a
On the basis of our previous experience with eosin Y catalyzed
photoredox reactions,8 we rationalized that eosin Y can act as a
promoter for the synthesis of oxazole derivatives irradiated by
visible light in the presence of CO2. Herein, we would like to
report our efforts on the transformations promoted by visible light
of α-bromo ketones and amines towards the synthesis of
substituted oxazoles induced by eosin
Y under a CO2
atmosphere.9 Mechanistically,10 we envisaged eosin Y would
undergo a single-electron transfer (SET) with α-amino carbonyl
compound A to furnish the amine radical cation and [eosin Y]•━
(Scheme 1). After deprotonation, radical cation [A]•+ will form
radical B. At the same time, the catalyst radical anion [eosin Y]•━
will reduce intermediate II, to give the corresponding radical III
and [eosin Y]. With the aid of DMSO and intermediate III, the
radical B will generate an alkyl carbonate C. Decomposition of
the alkyl carbonate C would produce an imine intermediate D.
A good number of interests in synthetic community is focusing
on the visible light photoredox catalysis recently, largely because
of the readiness of reactions conditions, sustainability,
environmental friendliness, etc..4,6 Compare to thermal reactions,
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 7
1
2
3
4
Intermediate E would be obtained via the enolization of D.5a Then
F would be obtained via the intramolecular nucleophilic addition
of E. As a result, G would collapse into the product 3aa via an
oxidative dehydrogenation reaction.
Ph
Ph
"standard reaction conditions"
eosin Y (3 mol%), 20W blue LED
NH2
O
+
O
Ph
N
DMSO (2 mL), DBN (2.5 equv)
CO2, 20 h, r.t.
Br
Ph
1a
3aa
2a
5
6
7
8
To assess the reaction platform, we started our studies by
examining the CO2/photoredox co-catalyzed tandem oxidative
cyclization of α-bromo ketones and benzylamines to prepare
substituted oxazoles. We were pleased to find that, under
optimized conditions, 2,5-diphenyloxazole 3aa was afforded in
76% yield (Table 1, The reactions in control clearly indicated that
CO2 and light are all needed for reactivity (entry 2-4). Decreasing
the amount of 1,5-diazabicyclo [4.3.0]non-5-ene (DBN) from 2.5
to 1.8 equiv reduced the yield to 64% (entry 5). It turned out that
eosin Y was much better than other photoredox catalysts (See
entries 6-8). Subsequently, an examination of the reaction solvent
revealed that dimethyl sulfoxide (DMSO) was the optimal
reaction medium for this transformation (entries 9-11),
presumably with DMSO acting as an oxidant. Other bases, such
as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 2,6-lutidine and
Et3N were less efficient than DBN (entries 12-14). We found that
the presence of H2O had a negative influence on the reaction
(entry 15). It was presumed that the presence of water disfavored
the generation of intermediate II. That the by-product of the
reaction is H2O is another plausible reason. Using (benzylamino)-
1-phenylethanone (A) as the starting material, the desired target
3aa was afforded in 86% yield under standard reaction conditions
(entry 16). Unfortunately, no product 3aa was obtained in Ar
atmosphere (entry 17). The scalability of the reaction could be
showcased by the facile preparation of 0.73 g of product 3aa
(entry 18).
Entry
Yiel
Variation from the “ standard
reaction conditions”
d (%)b
1
none
76
0
9
2
without DBN
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3
in Ar atmosphere
in the darkness
0
4
trace
64
trace
trace
8
5
DBN (1.8 equiv)
6
fac-Ir(ppy)3 as catalyst
Ru(bpy)3(PF6)2 as catalyst
Rose Bengal as catalyst
MeCN as solvent for 30 h
DMF as solvent for 30 h
THF as solvent for 30 h
DBU as the base
7
8
9
0
10
11
12
13
14
15
16c
0
0
19
23
14
7
2,6-lutidine as the base
Et3N
0.1 mL H2O was added
Scheme 1. Proposed Mechanism for CO2/photoredox
Catalyzed Tandem Oxidative Cyclization of α-bromo
Ketones and Amines.
(benzylamino)-1-phenylethanone
(0.3 mmol) as the starting material
86
17d
18e
(benzylamino)-1-phenylethanone
(0.3 mmol) as the starting material
0
O
O
H+
N
N
N
N
+
N
CO2
OH
O
N
large-scale reaction
55
II
I
O
a
O
Ph
Reaction conditions: 1a (0.3 mmol), 2a (0.3 mmol),
eosin Y (3 mol%), DMSO (2.0 mL), DBN (2.5 equiv),
Br
Ph
NH2
+
Ph
NH
Ph
+
HBr
2a
A
1a
room temperature, 20 W blue LED light (λmax = 450 nm)
Ph
in CO2 atmosphere for 20 h. b Isolated yield. c Reaction
O
MeSMe
GC-MS
analysis
DBN
NH
d
conditions: standard reaction conditions.
conditions: standard reaction conditions, without CO2, in
Ar atmosphere. Reaction conditions: 1a (1.19 g, 6.0
mmol), 2a (0.64 g, 6.0 mmol), eosin Y (0.117 g, 0.18
mmol), DMSO (8.0 mL), DBN (1.86 g, 15 mmol), room
temperature, 20 W blue LED light (λmax = 450 nm) in
CO2 atmosphere for 22 h.
Reaction
Ph
O
N
O
O
SET
N
II
C
III
OH
e
OH
[eosin Y]
[eosin Y]
H2O
+
DMSO
CO2
[eosin Y]
O
Ph
*
N
Ph
D
With the conditions optimized, we next explored the reaction
scope. A series of ketones 1 were investigated as shown in Table
2. The data indicate that reactions of 2-bromoketones 1 with
electron-abundant groups (methyl, methoxy) and electron-
deficient groups (halogen, cyano) on the benzene ring proceeded
well with yields from moderate to good (See Table 2, entries 1-5).
In addition, the substitution patterns of the arene ring (para, and
ortho position) did not influence the efficiency obviously (See
Table 2, entries 3 and 4). Interestingly, the polysubstituted
substrate 1g gave the desired target 3ag with a good yield. We
also performed the transformation of 2a with 1h bearing a
heterocycle moiety and obtained the substituted oxazole 3ah in
64% yield (See Table 2, entry 7). Furthermore, unsaturated α-
bromoketones also gave the corresponding products in 51% yield
(See Table 2, entry 8). Unfortunately, aliphatic 1-bromopropan-2-
O
-H+
SET
Ph
[A]
A
NH
Ph
B
Ph
HO
+
H+
H
O
Ph
Ph
NH
O
-H+
N
Ph
Ph
Ph
NH
F
E
G
photoredox
cycle
dehydrogenation
cycle
3aa
Table 1. Optimization of the Reaction Conditions a
ACS Paragon Plus Environment

Page 3 of 7
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
one did not work under these reaction conditions (See Table 2,
Ph
3ak
O
O
N
entry 9). Interestingly, reaction of 2-bromo-1-phenylpropan-1-one
1k with benzylamine 2a could give the desired product 4-methyl-
2,5-diphenyloxazole 3ak in 75% yield (See Table 2, entry 10).
Ph
Br
Ph
10
75
1k
Table 2. Scope of Substrate 1a
a Reaction conditions: 1 (0.3 mmol), 2a (0.3 mmol), eosin Y (3
mol%), DMSO (2.0 mL), DBN (2.5 equiv), room temperature,
20 W blue LED light (λmax = 450 nm) in CO2 atmosphere for 20
h. b Isolated yield.
20W blue LED
eosin Y (3 mol%)
R
O
O
Ph
NH2
Ph
Br
+
DMSO (2 mL), DBN
CO2, 20 h, r.t.
N
R
9
2a
3
1
Next, we investigated the general applicability of this visible-
light promoted tandem oxidative cyclization reaction with respect
to an array of amines 2. The substituents at the phenyl ring of
benzylamines had no obvious influence on the efficiency of this
reaction, and the expected oxazole products were produced in
yields from moderate to good. It was discovered that the halo-
substituted benzylamine gave good yield for these transformations
(Table 3, entries 2, 3 and 5). The heteroaryl amine was
subsequently used in this reaction, affording the desired product
in good yield (Table 3, entry 4). It is noteworthy that alkyl-,
alkenyl-, alkynyl-substituted amines were also tolerated in this
reaction (Table 3, entries 6-8). For example, prop-2-yn-1-amine
furnished the products in moderate yield (Table 3, entry 8).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Entry Substrates 1
Products 3
Yield
(%)b
O
Br
O
1
77
71
Ph
N
3ab
1b
O
OMe
Br
O
2
3
Ph
Ph
Ph
Ph
MeO
N
1c
3ac
Some control experiments were performed to explore the
mechanistic details of this reaction. It has been reported that 2-
bromo-1-phenylethanones can be oxidized to 2-oxo-2-
phenylacetaldehydes, which might react with benzylamines to
synthetize benzoxazoles. To explore this possibility, we checked
the possibilities of the aldehyde formations by the reactions in
Tables 1-3. No aldehydes were found, which suggested that the
transformation does not proceed via a aldehyde intermediate.
When the transformation of 1a with 2a was conducted in the
presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl, a
radical-capturing agent), the reaction was then totally quenched.
These results implied that a radical pathway may have been
presented in this transformation. The reaction failed to show any
activity in the absence of CO2 which clearly suggested the unique
role of CO2 in this reaction. Moreover, the yield of desired
product dropped significantly without photocatalyst in the
reaction and/or under dark conditions. It was noteworthy that
there were no reduced products from CO2 such as CO HCO2H, or
Br
O
Br
Br
O
70
53
1d
N
3ad
O
F
Br
O
N
4
5
F
1e
3ae
3af
O
CN
Br
O
N
66
69
64
NC
1f
O
OMe
OMe
−
HCO2 were found either by gas-phase GC analysis (Confer the
MeO
MeO
Br
O
N
Supporting Information). To find the oxidant in facto and to
determine the reduced product in this reaction, dibutyl sulfoxide
was selected as solvent in place of DMSO. The corresponding
product 3aa was thus obtained in 61% yield. The GC-MS analysis
of the reaction mixture clearly revealed the evidence of the
solvent being the oxidant in facto and generating the expected
dibutyl sulfide.
Ph
6
7
3ag
1g
O
Br
Br
S
O
S
Ph
Ph
To explore the detailed mechanistic information of the catalyst
with substrates, a series of experiments were performed (seen in
the Supporting Information). Our first attempt at assessing the
oxidative quenching ability of the DBN-CO2 adduct to [eosin Y]
catalyst showed no quenching effect. In contrast, the addition of
2-(benzylamino)-1-phenylethanone to the excited [eosin Y]
catalyst resulted in a strongly enhanced quenching effect. These
results implied that a reductive quenching of [eosin Y]* by 2-
(benzylamino)-1-phenylethanone was involved in the mechanism.
1h
Br
N
3ah
O
Ph
O
Br
Ph
8
9
51
0
N
3ai
3aj
1i
O
O
Ph
Br
Table 3. Scope of Substrates 2a
N
1j
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 7
1
2
3
4
associated with deprotonation of radical cation [A]•+ forming
radical H demands a much higher energy barrier of 5.4 kcal/mol
(Scheme 2). On the basis of these observations, a proposed
mechanistic pathway has been obtained (Scheme 1).
Ph
20W blue LED
eosin Y (3 mol%)
O
R
O
N
NH2
Br
+
R
Ph
DMSO (2 mL), DBN
CO2, 20 h, r.t.
1a
2
3
5
6
7
8
Yield (%)b
79
Scheme 2. Alternative Reaction Pathway
Entry Substrates 2
Products 3
O
Ph
Ph
NH2
O
N
O
NH
MeO
Ph
Ph
DMSO
-H+
Ph
NH
MeO
O
2b
1
[A]
Ph
I
9
O
III
H
3ba
OH
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
Ph
N
Ph
O
N
NH2
J
Cl
F
Cl
F
2
3
68
70
In summary, we have afforded a novel CO2/photoredox
cocatalyzed tandem oxidative cyclization of α-bromo ketones and
amines for the synthesis of substituted oxazoles. Notably, this
methodology has been achieved without using metal salts and
tolerated various functional groups such as halide, ether, alkenyl,
nitrile, alkynyl, and so on. This method is characterization of the
mild reaction conditions and operational simplicity.
2c
3ca
Ph
O
N
NH2
2d
3da
Ph
S
O
EXPERIMENTAL SECTION
NH2
Material and Methods. Reagents and solvents were
purchased and used without further treatments. IR spectra were
recorded on an EQUINOX-55 spectrometer with a KBr matrix. 1H
NMR and 13C NMR spectra were recorded on an Bruker-400
spectrometer with TMS as an internal standard. Chemical shift
values (δ) are given in ppm. Coupling constants (J) were
measured in Hz. High resolution mass spectrometer (HRMS)
spectra were obtained from a Bruker micrOTOF-Q II analyzer.
200-300 mesh silica gel was used for column chromatography.
Photocatalytic reactor (HY-CL016) was obtained from Shenzhen
Hongye Photoelectric Technology, Co. Ltd (China).
4
73
S
N
2e
3ea
Cl
Cl
NH2
Ph
O
F
5
6
7
8
60
49
44
56
F
N
2f
3fa
Ph
NH2
O
2g
N
3ga
Typical experimental procedure for the synthesis of
compounds 3. To a Schlenk tube were added 2-bromoketones 1
(0.3 mmol), amines 2 (0.3 mmol), DBN (0.75 mmol), eosin Y (3
mol%), DMSO (2.0 mL). Then the tube was filled with CO2, and
stirred at room temperature with the irradiation of a 20 W blue
LED at ir = 450nm ± 10 nm (at a distance of approximately 10
cm so that the reaction mixture did not heat up during the course
of the reaction) for about 16 h-20 h. Upon the completion of the
reaction, the mixture was diluted in 50 mL ethyl acetate, washed
with a saturated solution of brine (2 × 10 mL), 1 M HCl (1 × 8
mL), a saturated solution of brine (10 mL), dried (Na2SO4) and
concentrated in vacuum, and the resulting residue was purified
with silica gel column chromatography (eluent: hexane/ethyl
acetate) to furnish the products 3.
Ph
O
N
NH2
2h
2i
3ha
Ph
O
NH2
N
3ia
a Reaction conditions: 1a (0.3 mmol), 2 (0.3 mmol), eosin Y (3
mol%), DMSO (2.0 mL), DBN (2.5 equiv), room temperature,
20 W blue LED light (λmax = 450 nm) in CO2 atmosphere for 20
h. b Isolated yield.
Experimental procedure for large-scale reaction for the
synthesis of compounds 3aa. To a Schlenk tube were added 2-
bromoketones 1a (1.19 g, 6.0 mmol), amines 2a (0.64 g, 6.0
mmol), eosin Y (0.117 g, 0.18 mmol), DMSO (8.0 mL), DBN
(1.86 g, 15 mmol). Then the tube was filled with CO2, and stirred
at room temperature with the irradiation of a 20 W blue LED at ir
= 450nm ± 10 nm (at a distance of approximately 10 cm so that
the reaction mixture did not heat up during the course of the
reaction) for 22 h. Upon the completion of the reaction, the
mixture was diluted in 150 mL ethyl acetate, washed with a
saturated solution of brine (2 × 30 mL), 1 M HCl (2 × 20 mL), a
saturated solution of brine (20 mL), dried (Na2SO4) and
concentrated in vacuum, and the resulting residue was purified
with silica gel column chromatography (eluent: hexane/ethyl
acetate = 50:1) to furnish the products 3aa (0.73g, 55% yield).
To understand CO2/eosin Y cocatalyzed tandem oxidative
cyclization of α-bromo ketones and amines, we carried out a DFT
study using the package Gaussian 16 with the theory level of
M06-2X / 6-31G(d) // M06-2X / 6-311++G(d, p) / SMD11.
Unsurprisingly, a amine radical cation [A]•+ is formed by a SET
from α-amino carbonyl compound A to the excited state [Eosin
Y*], which is an energetically downhill process. The amine
radical cation [A]•+ readily undergoes almost barrierless base-
mediated deprotonation to afford the radical B at -19 kcal/mol.
With the aid of DMSO and intermediate III, the radical B would
yield an alkyl carbonate C in a highly exothermic reaction (ΔG =
-61.9 kcal/mol). Then imine D would be formed by the
decompose of C at -82.9 kcal/mol. Thus the energy demand of the
formation of [A]•+ is easily compensated from the radical B to the
dehydrogenation product D. The alternative reaction pathway
ACS Paragon Plus Environment

Page 5 of 7
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
2H), 7.70 (d, J = 7.2 Hz, 2H), 7.47-7.43 (m, 5H), 7.35 (t, J = 7.6 Hz, 1H), 2.51
Characterization Data for the Products. 2,5-Diphenyloxazole (3aa):
Purified by column chromatography (petroleum ether/ethyl acetate = 50:1), 50
mg, 76% yield, known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3)
δ: 8.13 (d, J = 8.4 Hz, 2H), 7.72 (d, J = 7.2 Hz, 2H), 7.49-7.42 (m, 6H), 7.36 (t,
J = 7.6 Hz, 1H); 13C{H} NMR (100 MHz, CDCl3) δ: 161.0, 151.1, 130.2,
128.8, 128.7, 128.3, 127.9, 127.3, 126.1, 124.1, 123.3; IR (neat cm-1) 3063,
1602, 1566, 1485, 1129, 947; LRMS (EI 70 ev) m/z: 221 (M+); HRMS m/z
(ESI) calcd for C15H12NO (M+H)+ 222.0913, found 222.0921.
(s, 3H); 13C{H} NMR (100 MHz, CDCl3) δ: 159.2, 145.3, 133.3, 130.1, 129.0,
128.7, 128.7, 128.4, 127.5, 127.3, 126.1, 125.2, 13.4; IR (neat cm-1) 3413,
2931, 1604, 1511, 1454, 869; LRMS (EI 70 ev) m/z: 235 (M+); HRMS m/z
(ESI) calcd for C16H14NO (M+H)+ 236.1070, found 236.1081.
2-(4-Methoxyphenyl)-5-phenyloxazole (3ba): Purified by column
chromatography (petroleum ether/ethyl acetate = 30:1), 59 mg, 79% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.04 (d, J =
9.2 Hz, 2H), 7.70 (d, J = 8.4 Hz, 2H), 7.44-7.39 (m, 3H), 7.31 (t, J = 7.2 Hz,
1H), 6.99 (d, J = 9.2 Hz, 2H), 3.85 (s, 3H); 13C{H} NMR (100 MHz, CDCl3) δ:
161.2, 161.1, 150.6, 128.8, 128.1, 128.0, 127.8, 123.9, 123.1, 120.1, 114.1,
55.3; IR (neat cm-1) 3393, 2934, 1607, 1486, 1134, 723; LRMS (EI 70 ev) m/z:
251 (M+); HRMS m/z (ESI) calcd for C16H14NO2 (M+H)+ 252.1019, found
252.1027.
2-Phenyl-5-(p-tolyl)oxazole (3ab): Purified by column chromatography
(petroleum ether/ethyl acetate = 50:1), 54 mg, 77% yield, known compound,[4e]
white solid; 1H NMR (400 MHz, CDCl3) δ: 8.00 (d, J = 8.0 Hz, 2H), 7.52 (d, J
= 8.0 Hz, 2H), 7.39-7.34 (m, 3H), 7.29 (s, 1H), 7.15 (d, J = 9.2 Hz, 2H), 2.28
(s, 3H); 13C{H} NMR (100 MHz, CDCl3) δ: 160.7, 151.4, 138.4, 130.1, 129.5,
129.1, 128.7, 126.1, 125.2, 124.0, 122.7, 21.3; IR (neat cm-1) 3403, 2927, 1611,
1543, 1445, 1304, 953, 726; LRMS (EI 70 ev) m/z: 235 (M+); HRMS m/z (ESI)
calcd for C16H14NO (M+H)+ 236.1070, found 236.1072.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2-(4-Chlorophenyl)-5-phenyloxazole
(3ca):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 40:1), 52 mg, 68% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.06 (d, J =
8.8 Hz, 2H), 7.78 (d, J = 7.2 Hz, 2H), 7.48-7.44 (m, 5H), 7.39 (t, J = 7.2 Hz,
1H); 13C{H} NMR (100 MHz, CDCl3) δ: 160.2, 151.3, 136.4, 129.1, 128.8,
127.8, 127.6, 127.5, 126.9, 124.6, 123.6; IR (neat cm-1) 3429, 1602, 1554,
1433, 1341, 836; LRMS (EI 70 ev) m/z: 255 (M+); HRMS m/z (ESI) calcd for
C15H11ClNO (M+H)+ 256.0524, found 256.0532.
5-(4-Methoxyphenyl)-2-phenyloxazole
(3ac):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 30:1), 53 mg, 71% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.00 (d, J =
8.4 Hz, 2H), 7.54 (d, J = 8.8 Hz, 2H), 7.39-7.33 (m, 3H), 7.21 (s, 1H), 6.86 (d,
J = 8.8 Hz, 2H), 3.72 (s, 3H); 13C{H} NMR (100 MHz, CDCl3) δ: 160.4, 159.6,
151.1, 130.0, 128.6, 127.4, 126.0, 125.6, 121.8, 120.7, 114.2, 55.2; IR (neat
cm-1) 3387, 2912, 1567, 1421, 1238, 823; LRMS (EI 70 ev) m/z: 251 (M+);
HRMS m/z (ESI) calcd for C16H14NO2 (M+H)+ 252.1019, found 252.1027.
2-(4-Fluorophenyl)-5-phenyloxazole
(3da):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 40:1), 50 mg, 70% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.11 (dd, J =
6.8 Hz, J = 5.2 Hz, 2H), 7.71 (d, J = 7.2 Hz, 2H), 7.49-7.42 (m, 3H), 7.36 (t, J
= 7.2 Hz, 1H), 7.19 (t, J = 8.0 Hz, 2H); 13C{H} NMR (100 MHz, CDCl3) δ:
165.2 (d, J = 249.5 Hz), 160.2, 151.2, 129.0, 128.9, 128.4 (d, J = 2.2 Hz),
128.3, 128.2, 127.8, 124.1, 123.7 (d, J = 2.9 Hz), 116.0 (d, J = 22.0 Hz); IR
(neat cm-1) 3411, 3033, 1612, 1476, 1273, 903; LRMS (EI 70 ev) m/z: 239
(M+); HRMS m/z (ESI) calcd for C15H11FNO (M+H)+ 240.0819, found
240.0819.
5-(2-Bromophenyl)-2-phenyloxazole
(3ad):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 40:1), 63 mg, 70% yield,
known compound,[4e] pale yellow solid; 1H NMR (400 MHz, CDCl3) δ: 8.01-
7.99 (m, 2H), 7.84 (s, 1H), 7.72 (dd, J = 2.0 Hz, J = 1.6 Hz, 1H), 7.57 (dd, J =
0.8 Hz, J = 1.2 Hz, 1H), 7.37-7.34 (m, 3H), 7.30-7.26 (m, 1H), 7.07-7.03 (ddd,
J = 2.0 Hz, J = 1.2 Hz, J = 1.6 Hz, 1H); 13C{H} NMR (100 MHz, CDCl3) δ:
160.9, 148.6, 134.0, 130.4, 129.1, 128.7, 128.6, 128.3, 128.0, 127.4, 127.0,
126.3, 119.7; LRMS (EI 70 ev) m/z: 299 (M+); HRMS m/z (ESI) calcd for
C15H11BrNO (M+H)+ 300.0019, found 300.0034.
5-Phenyl-2-(thiophen-2-yl)oxazole
(3ea):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 50:1), 50 mg, 73% yield,
known compound,[4e] light yellow solid; 1H NMR (400 MHz, CDCl3) δ: 7.74
(d, J = 4.0 Hz, 1H), 7.70 (d, J = 7.2 Hz, 2H), 7.45-7.43 (m, 3H), 7.39 (s, 1H),
7.35 (t, J = 7.6 Hz, 1H), 7.14 (t, J = 7.2 Hz, 1H); 13C{H} NMR (100 MHz,
CDCl3) δ: 157.3, 150.7, 129.9, 128.8, 128.4, 128.2, 127.9, 127.6, 127.5, 124.0,
123.2; IR (neat cm-1) 3403, 3021, 1601, 1424, 1203, 876; LRMS (EI 70 ev)
m/z: 227 (M+); HRMS m/z (ESI) calcd for C13H10NOS (M+H)+ 228.0478,
found 228.0483.
5-Phenyl-2-(4-fluoro-3-chlorophenyl)oxazole (3fa): Purified by column
chromatography (petroleum ether/ethyl acetate = 30:1), 49 mg, 60% yield, new
compound, white solid; 1H NMR (400 MHz, CDCl3) δ: 7.89 (d, J = 8.0 Hz,
1H), 7.90-7.87 (dt, J = 2.4 Hz, J = 1.6 Hz, 1H), 7.62 (d, J = 7.2 Hz, 2H), 7.45-
7.40 (m, 3H), 7.36 (t, J = 7.6 Hz, 1H), 7.16 (td, J = 2.4 Hz, J = 2.4 Hz, J = 2.4
Hz, 1H); 13C{H} NMR (100 MHz, CDCl3) δ: 164.0, 161.6, 159.83, 159.80,
151.5, 130.48, 130.40, 129.3, 129.2, 128.8, 128.5, 127.6, 124.1, 123.4, 121.88,
121.85, 117.2, 117.0, 113.2, 112.9; IR (neat cm-1) 3411, 1575, 1412, 1128, 916,
709; LRMS (EI 70 ev) m/z: 273 (M+); HRMS m/z (ESI) calcd for
C15H10ClFNO (M+H)+ 274.0429, found 274.0439.
5-Phenyl-2-propyloxazole (3ga): Purified by column chromatography
(petroleum ether/ethyl acetate = 40:1), 27 mg, 49% yield, known compound,[4e]
yellow oil; 1H NMR (500 MHz, CDCl3) δ: 7.65 (d, J = 7.5 Hz, 2H), 7.44 (t, J =
7.5 Hz, 2H), 7.34 (t, J = 7.5 Hz, 1H), 7.30 (s, 1H), 2.84 (t, J = 7.5 Hz, 2H), 1.89
(m, 2H), 1.06 (t, J = 7.5 Hz, 3H); 13C{H} NMR (100 MHz, CDCl3) δ: 164.5,
150.8, 128.8, 128.2, 128.0, 123.9, 121.6, 30.1, 21.5, 13.6; IR (neat cm-1) 3455,
2927, 1559, 1451, 1239, 774; LRMS (EI 70 ev) m/z: 187 (M+); HRMS m/z
(ESI) calcd for C12H14NO (M+H)+ 188.1070, found 188.1061.
5-(4-Fluorophenyl)-2-phenyloxazole
(3ae):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 40:1), 38 mg, 53% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 7.98 (dd, 1J =
2.4 Hz, 2J = 1.6 Hz, 2H), 7.58 (dd, 1J = 5.2 Hz, 2J = 5.2 Hz, 2H), 7.37-7.33 (m,
3H), 7.26 (s, 1H), 7.03 (t, J = 8.8 Hz, 2H); 13C{H} NMR (100 MHz, CDCl3) δ:
163.8 (d, J = 225.1 Hz), 161.0, 150.3, 130.3, 128.7, 127.2, 126.1 (d, J = 15.3
Hz), 124.3, 124.2, 123.0 (d, J = 1.2 Hz), 116.1 (d, J = 22.0 Hz); IR (neat cm-1)
3433, 1619, 1449, 1127, 813; LRMS (EI 70 ev) m/z: 239 (M+); HRMS m/z
(ESI) calcd for C15H11FNO (M+H)+ 240.0819, found 240.0829.
4-(2-Phenyloxazol-5-yl)benzonitrile
(3af):
Purified
by
column
chromatography (petroleum ether/ethyl acetate = 30:1), 49 mg, 66% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.12 (dd, J =
3.6 Hz, J = 2.8 Hz, 2H), 7.81 (d, J = 8.4 Hz, 2H), 7.73 (d, J = 8.4 Hz, 2H), 7.58
(s, 1H), 7.49 (t, J = 3.6 Hz, 3H); 13C{H} NMR (100 MHz, CDCl3) δ: 162.3,
149.2, 132.7, 131.8, 130.9, 128.8, 126.7, 126.4, 126.2, 124.2, 118.5, 111.4; IR
(neat cm-1) 3380, 2221, 1601, 1414, 910; LRMS (EI 70 ev) m/z: 246 (M+);
HRMS m/z (ESI) calcd for C16H11N2O (M+H)+ 247.0866, found 247.0877.
5-(3,4-Dimethoxyphenyl)-2-phenyloxazole (3ag): Purified by column
chromatography (petroleum ether/ethyl acetate = 20:1), 58 mg, 69% yield,
known compound,[4e] white solid; 1H NMR (400 MHz, CDCl3) δ: 8.10 (d, J =
8.0 Hz, 2H), 7.50-7.44 (m, 3H), 7.33-7.19 (m, 2H), 7.18 (s, 1H), 6.93 (d, J =
8.4 Hz, 1H), 3.97 (s, 3H), 3.92 (s, 3H); 13C{H} NMR (100 MHz, CDCl3) δ:
160.5, 151.2, 149.3, 149.2, 130.1, 128.7, 127.4, 126.0, 122.1, 120.9, 117.1,
111.3, 107.2, 55.95, 55.91; IR (neat cm-1) 3423, 2931, 1606, 1448, 1119, 937,
705; LRMS (EI 70 ev) m/z: 281 (M+); HRMS m/z (ESI) calcd for C17H16NO3
(M+H)+ 282.1125, found 282.1117.
5-(5-Bromothiophen-2-yl)-2-phenyloxazole (3ah): Purified by column
chromatography (petroleum ether/ethyl acetate = 50:1), 58 mg, 64% yield, new
compound, yellow solid; 1H NMR (400 MHz, CDCl3) δ: 7.98 (dd, J = 4.4 Hz, J
= 2.4 Hz, 2H), 7.39 (dd, J = 1.2 Hz, J = 2.0 Hz, 3H), 7.17 (s, 1H), 7.01 (d, J =
3.6 Hz, 1H), 6.96 (d, J = 3.6 Hz, 1H); 13C{H} NMR (100 MHz, CDCl3) δ:
159.7, 144.5, 129.6, 129.5, 127.8, 126.8, 125.8, 125.2, 123.2, 122.3, 111.7; IR
(neat cm-1) 3369, 1620, 1469, 1340, 729; LRMS (EI 70 ev) m/z: 306 (M+);
HRMS m/z (ESI) calcd for C13H9BrNOS (M+H)+ 305.9583, found 305.9594.
(E)-2-Phenyl-5-styryloxazole (3ai): Purified by column chromatography
(petroleum ether/ethyl acetate = 50:1), 38 mg, 51% yield, known compound,[4e]
white solid; 1H NMR (400 MHz, CDCl3) δ: 8.12 (d, J = 8.0 Hz, 2H), 7.52-7.46
(m, 5H), 7.40 (t, J = 7.2 Hz, 2H), 7.31 (t, J = 7.6 Hz, 1H), 7.16 (t, J = 6.8 Hz,
2H), 6.96 (d, J = 16.4 Hz, 1H); 13C{H} NMR (100 MHz, CDCl3) δ: 161.0,
150.3, 136.3, 130.4, 129.4, 128.7, 128.2, 127.2, 126.5, 126.4, 126.3, 113.0; IR
(neat cm-1) 3393, 1603, 1463, 1336, 1139, 710; LRMS (EI 70 ev) m/z: 247
(M+); HRMS m/z (ESI) calcd for C17H14NO (M+H)+ 248.1070, found 248.1074.
4-Methyl-2,5-diphenyloxazole (3ak): Purified by column chromatography
(petroleum ether/ethyl acetate = 50:1), 53 mg, 75% yield, known compound,[4e]
white solid; 1H NMR (400 MHz, CDCl3) δ: 8.10 (dd, J = 2.0 Hz, J = 1.6 Hz,
5-Phenyl-2-vinyloxazole (3ha): Purified by column chromatography
(petroleum ether/ethyl acetate = 30:1), 23 mg, 44% yield, known compound,[4e]
1
yellow oil; H NMR (500 MHz, CDCl3) δ: 7.67 (d, J = 7.2 Hz, 2H), 7.44-7.40
(m, 2H), 7.36 (s, 1H), 7.35 (t, J = 7.6 Hz, 1H), 6.67 (dd, J = 11.2 Hz, J = 11.2
Hz, 1H), 6.27 (dd, J = 1.2 Hz, J = 0.8 Hz, 1H), 5.67 (dd, J = 0.8 Hz, J = 0.8 Hz,
1H); 13C{H} NMR (100 MHz, CDCl3) δ: 160.4, 150.8, 131.2, 128.8, 128.5,
127.7, 124.1, 123.3, 121.5; IR (neat cm-1) 3093, 1631, 1557, 1443, 992, 761;
LRMS (EI 70 ev) m/z: 171 (M+); HRMS m/z (ESI) calcd for C11H10NO
(M+H)+ 172.0757, found 172.0747.
2-Ethynyl-5-phenyloxazole (3ia): Purified by column chromatography
(petroleum ether/ethyl acetate = 30:1), 28 mg, 56% yield, new compound,
yellow solid; 1H NMR (400 MHz, CDCl3) δ: 7.58 (d, J = 7.2 Hz, 2H), 7.36 (t, J
= 8.0 Hz, 2H), 7.29-7.25 (m, 1H), 7.17 (s, 1H), 3.24 (s, 1H); 13C{H} NMR
(100 MHz, CDCl3) δ: 156.9, 152.3, 129.1, 128.9, 128.4, 125.3, 122.8, 80.4,
71.5; IR (neat cm-1) 3312, 2209, 1571, 1422, 1129, 720; LRMS (EI 70 ev) m/z:
169 (M+); HRMS m/z (ESI) calcd for C11H8NO (M+H)+ 170.0600, found
170.0593.
ASSOCIATED CONTENT
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 7
1
2
3
4
5
6
7
8
Ketones and Benzoins. Chem. Commun. 2012, 48, 3485-3487; (d) Xie, J.;
Supporting Information
Jiang, H.; Cheng, Y.; Zhu, C. Metal-Free, Organocatalytic Cascade
Formation of C-N and C-O Bonds Through Dual sp3 C-H Activation:
Oxidative Synthesis of Oxazole Derivatives. Chem. Commun. 2012, 48,
979-981; (e) Wan, C.; Zhang, J.; Wang, S.; Fan, J.; Wang, Z. Facile
Synthesis of Polysubstituted Oxazoles via A Copper-Catalyzed Tandem
Oxidative Cyclization. Org. Lett. 2010, 12, 2338-2341; (f) Wan, C.; Gao,
L.; Wang, Q.; Zhang, J.; Wang, Z. Simple and Efficient Preparation of
The Supporting Information is available free of charge on the
ACS Publications website.
Emission quenching and gas chromatography analysis
1
experimental; Density functional calculation procedures; H and
13C NMR spectra of all the products (PDF)
2,5-Disubstituted Oxazoles via
a
Metal-Free-Catalyzed Cascade
Cyclization. Org. Lett. 2010, 12, 3902-3905; (g) Jiang, H.; Huang, H.;
Cao, H.; Qi, C. TBHP/I2-Mediated Domino Oxidative Cyclization for
One-Pot Synthesis of Polysubstituted Oxazoles. Org. Lett. 2010, 12, 5561-
5563.
(6) (a) Srivastava, V.; Singh, P. P. Eosin Y catalysed photoredox
synthesis: a review. RSC Advances 2017, 7, 31377-31392; (b) Shaw, M.
H.; Twilton, J.; MacMillan, D. W. C. Photoredox Catalysis in Organic
Chemistry. J. Org. Chem. 2016, 81, 6898-6926; (c) Shi, L.; Xia, W.
Photoredox functionalization of C-H bonds adjacent to a nitrogen atom.
Chem. Soc. Rev. 2012, 41, 7687-7697.
(7) (a) Yang, X.-J.; Chen, B.; Zheng, L.-Q.; Wu, L.-Z.; Tung, C.-H.
Highly efficient and selective photocatalytic hydrogenation of
functionalized nitrobenzenes. Green Chem. 2014, 16, 1082-1086; (b)
Fidaly, K.; Ceballos, C.; Falguières, A.; Veitia, M. S.-I.; Guy, A.; Ferroud,
C. Visible light photoredox organocatalysis: a fully transition metal-free
direct asymmetric α-alkylation of aldehydes. Green Chem. 2012, 14,
1293-1297; (c) Teo, Y. C.; Pan, Y.; Tan, C. H. Organic Dye-
Photocatalyzed Acylnitroso Ene Reaction. ChemCatChem 2013, 5, 235-
240.
AUTHOR INFORMATION
Corresponding Author
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
* E-mail: gulijun2005@126.com;.
* E-mail: ganpeng_li@sina.com.cn.
Author Contributions
‡These authors contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We are grateful for the financial support from the National
Natural Science Foundation of China (21662045) and the Applied
Basic Research Project of Yunnan (2016FB019, 2016FB149); the
Opening Foundation of the Key Laboratory of Green Pesticide
and Agricultural Bioengineering, Ministry of Education, Guizhou
University (2018GDGP0103); Scientific Research Fund Project of
Education Department of Hunan Province (17C1385).
(8) (a) Gu, L.; Jin, C.; Wang, W.; He, Y.; Yang, G.; Li, G. Transition-
metal-free, visible-light induced cyclization of arylsulfonyl chlorides with
o-azidoarylalkynes:
a
regiospecific route to unsymmetrical 2,3-
disubstituted indoles. Chem. Commun. 2017, 53, 4203-4206; (b) Gu, L.;
Jin, C.; Liu, J. Metal-free, visible-light-mediated transformation of aryl
diazonium salts and (hetero)arenes: an efficient route to aryl ketones.
Green Chem. 2015, 17, 3733-3736; (c) Gu, L.; Jin, C.; Liu, J.; Ding, H.;
Fan, B. Transition-metal-free, visible-light induced cyclization of
arylsulfonyl chlorides with 2-isocyanobiphenyls to produce
phenanthridines. Chem. Commun. 2014, 50, 4643-4645.
(9) Riemer, D.; Schilling, W.; Goetz, A.; Zhang, Y.; Gehrke, S.; Tkach, I.;
Hollóczki, O.; Das, S. CO2-Catalyzed Efficient Dehydrogenation of
Amines with Detailed Mechanistic and Kinetic Studies. ACS Catalysis
2018, 8, 11679-11687.
REFERENCES
(1) (a) Jin, Z. Muscarine, imidazole, oxazole, and thiazole alkaloids. Nat.
Prod. Rep. 2011, 28, 1143-1191; (b) Riego, E.; Hernández, D.; Albericio,
F.; Álvarez, M. Directly Linked Polyazoles: Important Moieties in Natural
Products. Synthesis 2005, 2005, 1907-1922; (c) Yeh, V. S. C. Recent
advances in the total syntheses of oxazole-containing natural products.
Tetrahedron 2004, 60, 11995-12042; (d) Wipf, P. Synthetic Studies of
Biologically Active Marine Cyclopeptides. Chem. Rev. 1995, 95, 2115-
2134.
(2) (a) Turchi, I. J. Oxazole chemistry. A review of recent advances. Ind.
Eng. Chem. Pro. Res. Dev. 1981, 20, 32-76; (b) Turchi, I. J.; Dewar, M. J.
S. Chemistry of Oxazoles. Chem. Rev. 1975, 75, 389-437.
(3) Iddon, B. Synthesis and Reactions of Lithiated Monocyclic Azoles
Containing Two or More Hetero-Atoms. Part II: Oxazoles. Heterocycles
1994, 37, 1321-1357.
(4) (a) Qi, C.; Peng, Y.; Wang, L.; Ren, Y.; Jiang, H. Copper-catalyzed [2
+ 3] cyclization of α -hydroxyl ketones and arylacetonitriles: access to
multisubstituted butenolides and oxazoles. J. Org. Chem. 2018, 83, 11926-
11935; (b) Reddy, R. J.; Ball-Jones, M. P.; Davies, P. W. Alkynyl
Thioethers in Gold-Catalyzed Annulations to Form Oxazoles. Angew.
Chem., Int. Ed. 2017, 56, 13310-13313; (c) Chatterjee, T.; Cho, J. Y.;
Cho, E. J. Synthesis of substituted oxazoles by visible-light photocatalysis.
J. Org. Chem. 2016, 81, 6995-7000; (d) Zeng, T.-T.; Xuan, J.; Ding, W.;
Wang, K.; Lu, L.-Q.; Xiao, W.-J. [3 + 2] cycloaddition/oxidative
aromatization sequence via photoredox catalysis: one-pot synthesis of
oxazoles from 2H-azirines and aldehydes. Org. Lett. 2015, 17, 4070-4073;
(e) Gao, W.-C.; Hu, F.; Huo, Y.-M.; Chang, H.-H.; Li, X.; Wei, W.-L. I2-
catalyzed C-O bond formation and dehydrogenation: facile synthesis of
oxazolines and oxazoles controlled by bases. Org. Lett. 2015, 17, 3914-
3917.
(5) (a) Gao, Q.-H.; Fei, Z.; Zhu, Y.-P.; Lian, M.; Jia, F.-C.; Liu, M.-C.;
She, N.-F.; Wu, A.-X. Metal-free dual sp3 C-H functionalization: I2-
promoted domino oxidative cyclization to construct 2,5-disubstituted
oxazoles. Tetrahedron 2013, 69, 22-28; (b) Zhou, W.; Xie, C.; Han, J.;
Pan, Y. Catalyst-Free Intramolecular Oxidative Cyclization of N-
Allylbenzamides: A New Route to 2,5-Substituted Oxazoles. Org. Lett.
2012, 14, 4766-4769; (c) Xue, W.-J.; Li, Q.; Zhu, Y.-P.; Wang, J.-G.; Wu,
A.-X. Convergent Integration of Two Self-Labor Domino Sequences: A
Novel Method for the Synthesis of Oxazole Derivatives from Methyl
(10) (a) Riemer, D.; Mandaviya, B.; Schilling, W.; Götz, A. C.; Kühl, T.;
Finger, M.; Das, S. CO2-Catalyzed Oxidation of Benzylic and Allylic
Alcohols with DMSO. ACS Catalysis 2018, 8, 3030-3034; (b) Pérez, E.
R.; Santos, R. H. A.; Gambardella, M. T. P.; de Macedo, L. G. M.;
Rodrigues-Filho, U. P.; Launay, J.-C.; Franco, D. W. Activation of Carbon
Dioxide by Bicyclic Amidines. J. Org. Chem. 2004, 69, 8005-8011.
(11) (a) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; V. Barone; Petersson, G. A.;
Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko,
B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.;
Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.;
Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.;
Ranasinghe, D.; Zakrzewski, V. G.; J. Gao, N. R.; Zheng, G.; Liang, W.;
Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.;
Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.;
Montgomery, J. A.; Jr., J. E. P.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.;
Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi,
R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar,
S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi,
R.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman,
J. B.; Fox, D. J. In Secondary; Gaussian 16, Revision B. 01 ed. Gaussian,
Inc.: Wallingford CT, 2016; (b) Marenich, A. V.; Cramer, C. J.; Truhlar,
D. G. Universal Solvation Model Based on Solute Electron Density and on
a Continuum Model of the Solvent Defined by the Bulk Dielectric
Constant and Atomic Surface Tensions. J. Phys. Chem. B 2009, 113,
6378-6396; (c) Zhao, Y.; Truhlar, D. G. The M06 suite of density
functionals for main group thermochemistry, thermochemical kinetics,
noncovalent interactions, excited states, and transition elements: two new
functionals and systematic testing of four M06-class functionals and 12
other functionals. Theor. Chem. Acc. 2008, 120, 215-241.
ACS Paragon Plus Environment

Page 7 of 7
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7
ACS Paragon Plus Environment