1,3-Dipolar Cycloaddition of Nitrile Imine with Carbon Dioxide: Access to 1,3,4-Oxadiazole-2(3H)-ones

Article abstract of DOI:10.1021/acs.joc.7b00963

Efficient synthesis of 1,3,4-oxadiazole-2(3H)-one was achieved by CsF/18-crown-6 mediated 1,3-dipolar cycloaddition of nitrile imine and 2.0 MPa of CO₂. CsF/18-crown-6 played a key role in enhancing the reactivity of CO₂ as a 1,3-dipolarophile. The practical utility of this transition-metal-free approach to 1,3,4-oxadiazole-2(3H)-one is highlighted by the convenient synthesis of a commercial herbicide Oxadiazon and a MAO B inhibitor.

Full text of DOI:10.1021/acs.joc.7b00963

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Note
1,3-Dipolar Cycloaddition of Nitrile Imine with Carbon
Dioxide: Access to 1,3,4-Oxadiazole-2(3H)-ones
Chun-Xiao Guo, Wen-Zhen Zhang, Ning Zhang, and Xiao-Bing Lu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b00963 • Publication Date (Web): 26 Jun 2017
Downloaded from http://pubs.acs.org on June 27, 2017
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The Journal of Organic Chemistry
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1,3-Dipolar Cycloaddition of Nitrile Imine with Carbon Dioxide: Access
to 1,3,4-Oxadiazole-2(3H)-ones
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ChunꢀXiao Guo, WenꢀZhen Zhang,* Ning Zhang and XiaoꢀBing Lu
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, P. R. China
Eꢀmail: zhangwz@dlut.edu.cn
ABSTRACT: Efficient synthesis of 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀone was achieved by CsF/18ꢀcrownꢀ6 mediated 1,3ꢀdipolar cycloaddiꢀ
tion of nitrile imine and 2.0 MPa of CO2. CsF/18ꢀcrownꢀ6 played a key role in enhancing the reactivity of CO2 as a 1,3ꢀ
dipolarophile. The practical utility of this transitionꢀmetalꢀfree approach to 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀone is highlighted by the conꢀ
venient synthesis of a commercial herbicide Oxadiazon and a MAO B inhibitor.
1,3,4ꢀOxadiazoleꢀ2(3H)ꢀone core is a privileged scaffold
frequently found in diverse compounds which show many
biological and pharmaceutical activities (Figure 1). Oxadiazon
and Oxadiargyl are commercial and environmentally benign
herbicides and still used in agriculture widely. BMS 191011
has been established as an opener of the cloned largeꢀ
conductance, Ca2+ꢀactivated potassium channel.1 NSC 130852
shows promising antimycobacterial activity.2 Those comꢀ
pounds also serve as selective monoamine oxidase B (MAO B)
inhibitors,3 fungicides,4 and useful synthetic intermediate for
other fine chemicals.5 Although various methods for the conꢀ
struction of substituted 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀone have been
developed, most of these rely on laborious multiꢀstep proceꢀ
dures and use phosgene and benzotrichloride.6 Recently,
Chen7a and Jiang7b reported palladiumꢀcatalyzed oxidative
carbonylation of acylhydrazines with carbon monoxide to
synthesize 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀones. Although the use of
phosgene was abandoned, this approach showed relatively
Figure 1. Structures of biologically important substituted
limited substrate scope and employed expensive transition
1,3,4-oxadiazole-2(3H)-ones.
metal and equivalent metal oxidative reagents. Therefore, the
Carbon dioxide (CO2) as a C1 synthon for chemical syntheꢀ
sis has gained considerable attention because it is an abundant,
lowꢀcost and nonꢀtoxic feedstock.8 Except for using as an elecꢀ
trophile to react with various nucleophiles, CO2 is also utilized
as a cycloaddition partner to construct carbonylꢀcontaining
heterocycles. Although transitionꢀmetal catalyzed cycloaddiꢀ
tion of CO2 with unsaturated compounds9 and epoxides10 has
development of more efficient and feasible methods to prepare
diversely substituted 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀones is highly
desirable.
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been frequently reported in recent years, studies on 1,3ꢀdipolar CO2 pressure (Table 1). Organic bases used in Matsubara’s
cycloaddition reactions11,12 using CO2 as a 1,3ꢀdipolarophile
have rarely been depicted probably due to the linear arrangeꢀ
ment of two C=O bond in carbon dioxide and its high thermoꢀ
dynamic stability and kinetic inertness. 1,3ꢀDipolar cycloaddiꢀ
tion of nitrile imine with CO2 was firstly observed in 1980 by
Pfoertner and Foricher in the photoreaction of 3ꢀmethylꢀ4ꢀ
phenylsydnone.13 Another example involving nitrile imine and
CO2 was reported by Matsubara’s group in 1996,14 in which
just two 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀone products were syntheꢀ
sized in inapplicable yields (14%ꢀ25%) under harsh reaction
conditions. The major challenge to make this reaction efficient
and practical is the low reactivity of CO2 toward 1,3ꢀdipoles
and fast dimerization of inꢀsitu formed nitrile imines.15 Herein,
we reported an efficient CsF/18ꢀcrownꢀ6 mediated 1,3ꢀdipolar
cycloaddition reaction of nitrile imines with CO2 to give variꢀ
ous 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀones in good yield. CsF/18ꢀ
crownꢀ6 plays a key role in enhancing the reactivity of CO2 as
a 1,3ꢀdipolarophile. The practical utility of this transitionꢀ
metalꢀfree16 approach is highlighted by the convenient syntheꢀ
sis of a commercial herbicide Oxadiazon and a MAO B inhibiꢀ
tor.
reaction13 are not suitable for the present reaction system (enꢀ
tries 1ꢀ3). The use of 1,8ꢀdiazabicyclo[5.4.0]undecꢀ7ꢀene
(DBU) led to the formation of the dimer 3a, whereas no deꢀ
sired product 2a was detected (entry 1). No transformation
was observed in the presence of Et3N (entry 2). 1,4ꢀ
diazabicyclo[2.2.2]octane (DABCO) gave very low yield of
2a (entry 3). The use of Cs2CO3 and CsF bases resulted in a
slightly improved yield of 2a (entries 4 and 5). In light of preꢀ
vious reports by Moses14a and our group17, the combination
use of crown ethers and inorganic bases in some baseꢀ
mediated reaction not only enhances the solubility of the bases
in organic solvents but also promotes the formation of reaction
intermediates. Cs2CO3/18ꢀcrownꢀ6 gave almost same result as
Cs2CO3 alone (entry 6), while the combination of CsF with 18ꢀ
crownꢀ6 led to a strikingly increased yield of 2a (entry 7). The
obvious difference between Cs2CO3/18ꢀcrownꢀ6 and CsF/18ꢀ
crownꢀ6 implies that fluorine anion probably accelerated the
1,3ꢀdipolar cycloaddition with CO2. It was reported by Arnold
et al that fluorine anion could react with CO2 to form (F–CO2)ꢀ
anion and thereby significantly enhancing the reactivity of the
C=O bond.18 This phenomenon was also observed in some
reactions involving CO2.19 It is noteworthy that fluorine anion
alone was not enough to facilitate this reaction since the comꢀ
bination of KF with 18ꢀcrownꢀ6 only gave 14% yield of 2a. It
is tentatively ascribed to the relatively low basicity of KF,
difficultly promoting the formation of nitrile imine (entry 8).
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Table 1. Optimization of the reaction conditionsa
A decrease of CsF/18ꢀcrownꢀ6 amount from 2.5 to 1.2
equivalents shut down the reaction (entry 10). Interestingly,
the decrease of 18ꢀcrownꢀ6 loading alone did not affect the
yield of 2a (entry 11). Among a variety of solvents tested (see
Supporting Information), toluene was revealed to be the optiꢀ
Yield
Entry
Base/Additive (equivalent)
Solvent
2a
<1b
<1b
3b
3a
9
<1b
o
1
DBU (2.5)
THF
mal solvent (entry 13). Decreasing the temperature to 0 C
resulted in low conversion and 22% yield of 2a was obtained
2
Et3N (2.5)
THF
o
(entry 14). Whereas rising temperature up to 70 C gave 30%
3
DABCO (2.5)
THF
8
yield of 2a and other unidentified products (entry 15). Under
1.0 atm CO2 atmosphere, this reaction also proceeded but a
strikingly decreased yield of 2a was obtained (entry 16). The
gramꢀscale reaction of 1a gave 67% yield of 2a, which
demonstrated the utility of this reaction system in preparativeꢀ
scale syntheses (entry 17).
4
Cs2CO3 (2.5)
THF
25
20
27
85
14
60
3b
13
10
7
5
CsF (2.5)
THF
6
Cs2CO3/18ꢀcrownꢀ6 (2.5/2.5)
CsF/18ꢀcrownꢀ6 (2.5/2.5)
KF/18ꢀcrownꢀ6 (2.5/2.5)
CsF/18ꢀcrownꢀ6 (2.0/2.0)
CsF/18ꢀcrownꢀ6 (1.2/1.2)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
CsF/18ꢀcrownꢀ6 (2.5/0.4)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
CsF/18ꢀcrownꢀ6 (2.5/1.2)
THF
7
THF
12
<1b
9
<1b
12
10
5
<1b
19
<1b
18
8
THF
The substrate scope of 1,3ꢀdipolar cycloaddition of nitrile
imine and CO2 under the optimized reaction conditions was
investigated (Scheme 1). A series of hydrazonyl chlorides
bearing electronꢀwithdrawing (fluoro, chloro, bromo) and
electronꢀdonating (methyl, methoxyl, tertꢀbutyl) substituents
on benzoyl chloride moiety conducted the cycloaddition with
CO2 smoothly to afford the corresponding 1,3,4ꢀoxadiazoleꢀ
2(3H)ꢀones in good yields (2bꢀ2g). The structural assignment
for these products was further confirmed by a singleꢀcrystal Xꢀ
ray analysis of 2f20. βꢀNaphthyl, furanꢀ and thiopheneꢀgroups
were also found to be compatible functionalities for this reacꢀ
tion (2hꢀ2j). The methyl, ethyl, cyclopropyl, and even stericalꢀ
ly hindered tertꢀbutyl substituted hydrazonyl chloride also
provided the corresponding products (2kꢀ2n) in good yields.
Hydrazonyl chlorides containing methyl, bromo, and chloro
substituents on phenylhydrazone moiety participated in the
reaction successfully to afford the desired products (2o, 2q,
2r) in excellent yields. Except for the arylhydrazones, subꢀ
strates derived from benzylhydrazine (1s) and butylhydrazine
(1t) were also suitable substrates for this reaction.
9
THF
10
11
12
13
14c
15d
16e
THF
THF
85
70
89
22
30
11
65
THF
toluene
toluene
toluene
toluene
toluene
17f
a
Reaction conditions: 1a (0.2 mmol), CO2 (2.0 MPa), solvent
o
(2 mL), 25 C, 12 h. Isolated yield is given according to the averꢀ
age of two runs. b Yields were determined by NMR using 1,1,2,2ꢀ
tetrachloroethane as an internal standard. c 0 oC. d 70 oC. e 1.0 atm
of CO2. f 1a (4.5 mmol, 1.04g), toluene (40 mL).
Our studies began by using hydrazonyl chloride as the niꢀ
trile imine precursor and subjecting 1a to stoichiometric
amounts of various bases in THF at 25 C under a 2.0 MPa
o
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The Journal of Organic Chemistry
system could effectively produce the nitrile imine intermediate,
Scheme 1. Substrate scope a
1
2
but only CsF/18ꢀcrownꢀ6 led to the high efficiency for the 1,3ꢀ
dipolar cycloaddition reaction, suggesting that CsF/18ꢀcrownꢀ
6 played a key role in enhancing the reactivity of CO2 as a 1,3ꢀ
dipolarophile.
R2
R2
N
3
4
5
6
CsF/18-crown-6
toluene, rt, 12 h
NH
N
N
CO2
+
O
Scheme 2. 1 Synthesis of MAO B inhibitor 2u and Oxadia-
zon 2v.
R1
R1 Cl
O
2
2.0 MPa
1
7
8
9
2b, X = 4-F, 84%
Ph
2c, X = 4-Cl, 72%
2d, X = 4-Br, 90%
N
N
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O
O
2e
, X = 4-Me, 87%
X
2f, X = 4-OMe, 84%
2g, X = 4-tBu, 78%
2f
Ph
N
Ph
Ph
N
N
N
N
N
O
O
O
O
O
O
O
O
S
2h, 82%
Ph
2i, 61%
2j, 89%
Ph
N
Ph
Ph
N
N
N
N
N
N
N
O
O
O
O
O
tBu
O
O
Et
Me
a
b
PPh3/CCl4, MeCN, rt, 12 h. Standand reaction conditions, 4
mL toluene. c Standand reaction conditions, 24 h.
2m, 74%
2n, 86%
2l,
2k, 71%
77%
Scheme 3. 1,3-Dipolar cycloaddition of nitrile imine with
carbonyl sulphide.
Bn
Bu
Y
2o, Y = 4-Me, 95%
2p, Y = 4-OMe, 57%
N
N
N
N
O
O
N
N
2q
, Y = 4-Br, 88%
O
O
Ph
Ph
O
2r
, Y = 3-Cl, 92%
O
2s, 84%
2t, 86%
Ph
a 1 (0.2 mmol), CsF (0.5 mmol), 18ꢀcrownꢀ6 (0.24 mmol), CO2
(2.0 MPa), toluene (2 mL), 25 oC, 12 h. Isolated yield.
With easy accessibility of the raw material, broad substrate
scope and high efficiency, this reaction system would provide
a concise and feasible access to valuable compounds containꢀ
ing 1,3,4ꢀoxadiazoleꢀ2(3H)ꢀone skeleton. The reversible MAO
B inhibitor 2u3, which is considered as a potential drug applied
to the clinical therapy at the early stage of Parkinson’s disease,
was obtained in 89% isolated yield via 1,3ꢀdipolar cycloaddiꢀ
tion of 1u and CO2 (Scheme 2). The commercial herbicide
Oxadiazon 2v was also successfully synthesized through this
efficient cycloaddition reaction system in 88% isolated yield
(Scheme 2).
In summary, we have developed an efficient, transitionꢀ
metalꢀfree and practical access to a broad range of substituted
1,3,4ꢀoxadiazoleꢀ2(3H)ꢀones via 1,3ꢀdipolar cycloaddition of
nitrile imine and CO2. The key to the success of this transforꢀ
mation is the use CsF as a base and 18ꢀcrownꢀ6 as a pivotal
additive to enhance the formation of nitrile imine intermediate.
CsF/18ꢀcrownꢀ6 played a key role in enhancing the reactivity
of CO2 as a 1,3ꢀdipolarophile. This approach was successfully
applied in the convenient synthesis of a commercial herbicide
Oxadiazon and a MAO B inhibitor.
Considering carbonyl sulphide (COS) is an analogue of carꢀ
bon dioxide, the 1,3ꢀdipolar cycloaddition of nitrile imine with
COS was also carried out. Under the standard reaction condiꢀ
tions for CO2, nitrile imine precursors 1a and 1k reacted with
0.5 MPa of COS smoothly to afford 1,3,4ꢀthiadiazolꢀ2(3H)ꢀ
one compounds 4a and 4k respectively (Scheme 3).
EXPERIMENTAL SECTION
General Information. Unless otherwise stated, all manipuꢀ
lations were performed using standard Schlenk techniques
under a dry nitrogen or carbon dioxide atmosphere. DMF and
DMAc were distilled under N2 atmosphere with CaH2. CH3CN
and DCE were distilled with P2O5. THF, DME, Et2O, 1, 4ꢀ
dioxane and toluene were distilled from sodiꢀ
um/benzophenone. All of the solvents were stored over 4Å
molecular sieves before used. Column chromatography was
performed on silica gel (200ꢀ300 mesh). Thin layer chromaꢀ
tography was performed on 0.20 mm GF254 plates. Visualizaꢀ
tion was accomplished with UV light (254 nm). 18ꢀcrownꢀ6
was recrystallized in CH3CN. Unless otherwise indicated, carꢀ
bon dioxide (99.999%) and carbonyl sulphide (99%) was used
without further purification.
To demonstrate the pivotal role of CsF and 18ꢀcrownꢀ6 in
promoting the 1,3ꢀdipolar cycloaddition, some control experiꢀ
ments were carried out using NMR method (see SI). When
Cs2CO3 was added to the tolueneꢀd8 solution of 1k, signal of
nitrile imine was observed and the dimer was immediately
formed. When CsF was added to the tolueneꢀd8 solution of 1k,
no obvious signals of nitrile imine and the dimer were found.
The addition of 18ꢀcrownꢀ6 to above systems evidently enꢀ
hanced the formation of nitrile imine and the dimer in the abꢀ
sence of CO2. Both Cs2CO3/18ꢀcrownꢀ6 and CsF/18ꢀcrownꢀ6
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NMR spectra were recorded on 400M or 500M (1H NMR, Rf = 0.3 (EtOAc/petroleum ether = 1:30). m.p. 123–124 oC. 1H
400 MHz or 500MHz; 13C NMR, 101 MHz or 126 MHz) specꢀ
trometer in CDCl3 at ambient temperature and chemical shifts
are expressed in parts per million (δ, ppm). Proton chemical
shifts are referenced to 7.26 ppm (CHCl3) and carbon chemiꢀ
cal shifts are referenced to 77.0 ppm (CDCl3). Data reporting
uses the following abbreviations: s, singlet; d, doublet; t, triꢀ
plet; m, multiplet; hept, heptet, and J, coupling constant in Hz.
High resolution mass spectra (HRMS) were recorded on a Qꢀ
TOF mass spectrometry equipped with Zꢀspray ionization
source. Infrared spectra (IR) were measured using a Nicolet
NEXUS FTꢀIR spectrophotometer.
NMR (400 MHz, CDCl3) δ 7.93 (d, J = 8.0 Hz, 2H), 7.82 (d, J
= 8.5 Hz, 2H), 7.66 (d, J = 8.5 Hz, 2H), 7.48 (dd, J = 8.0, 7.4
Hz, 2H), 7.29 (t, J = 7.4 Hz, 1H). 13C NMR (126 MHz,
CDCl3) δ 152.9, 150.5, 135.9, 132.5 (2C), 129.3 (2C), 127.4
(2C), 126.7, 126.3, 122.4, 118.4 (2C). IR (neat): ν 2917, 1770,
1404, 1355, 1070, 735 cmꢀ1. HRMS (ESI, m/z): calculated for
C14H10BrN2O2 [M+H]+: 316.9920, found: 316.9928.
1
2
3
4
5
6
7
8
5ꢀ(4ꢀMethylphenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2e)7 [CAS: 73634ꢀ97ꢀ6]. white solid (43.8 mg, 87% yield). Rf
9
o
1
= 0.2 (EtOAc/petroleum ether = 1:30). m.p. 155–156 C. H
NMR (500 MHz, CDCl3) δ 7.95 (d, J = 8.0 Hz, 2H), 7.84 (d, J
= 8.0 Hz, 2H), 7.47 (dd, J = 8.0, 7.4 Hz, 2H), 7.31 (d, J = 8.0
Hz, 2H), 7.27 (t, J = 7.4 Hz, 1H), 2.43 (s, 3H). 13C NMR (126
MHz, CDCl3) δ 153.8, 150.8, 142.6, 136.2, 129.8 (2C), 129.2
(2C), 126.1, 126.0 (2C), 120.7, 118.3 (2C), 21.7. IR (neat): ν
3290, 1725, 1658, 1339, 742 cmꢀ1. HRMS (ESI, m/z): calculatꢀ
ed for C15H13N2O2 [M+H]+: 253.0972, found: 253.0974.
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Substrates 1 were prepared according to the reported proceꢀ
dures.21
General procedure for the reaction of hydrazonyl chlo-
ride with CO2 or COS. A 20 mL oven dried autoclave conꢀ
taining a stir bar was charged with hydrazonyl chloride 1 (0.20
mmol), 18ꢀcrownꢀ6 (63.4 mg, 1.2 equiv.), CsF (76.0 mg, 2.5
equiv.) and 2.0 mL toluene in a glove box. After removal from
the glove box, the autoclave was purged with CO2 (or COS)
three times and then pressurized to 2.0 MPa CO2 (or 0.5 MPa
COS). The reaction mixture was stirred in room temperature at
5ꢀ(4ꢀMethoxyphenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2f)7 [CAS: 1643432ꢀ84ꢀ1]. white solid (45.0 mg, 84% yield).
Rf = 0.2 (EtOAc/petroleum ether = 1:30). m.p. 131–133 oC. 1H
NMR (500 MHz, CDCl3) δ 7.95 (d, J = 8.0 Hz, 2H), 7.89 (d, J
= 8.7 Hz, 2H), 7.47 (dd, J = 8.0, 7.4 Hz, 2H), 7.27 (t, J = 7.4
Hz, 1H), 7.01 (d, J = 8.7 Hz, 2H), 3.89 (s, 3H). 13C NMR (126
MHz, CDCl3) δ 162.5, 153.6, 150.8, 136.2, 129.2 (2C), 127.8
(2C), 126.0, 118.3 (2C), 115.9, 114.5 (2C), 55.5. IR (neat): ν
2919, 1769, 1356, 829, 741 cmꢀ1. HRMS (ESI, m/z): calculated
for C15H13N2O3 [M+H]+: 269.0921, found: 269.0920.
o
25 C for 12 h. Then the remaining gas was vented slowly.
The reaction mixture was diluted with water (15 mL) and exꢀ
tracted with ethyl acetate (3 × 10 mL). The combined organic
layers were washed with water and brine, dried over anhyꢀ
drous Na2SO4 and evaporated under vacuum. The product was
isolated by column chromatography on silica gel (petroleum
etherꢀethyl acetate = 40:1 to 1:1).
5ꢀ(4ꢀtertꢀButylphenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
3,5ꢀDiphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2a)7
[CAS:
(2g). brown oil (45.9 mg, 78% yield). Rf
=
0.4
1
19226ꢀ10ꢀ9]. white solid (42.5 mg, 89% yield). Rf = 0.4
(EtOAc/petroleum ether = 1:40). H NMR (400 MHz, CDCl3)
δ 7.96 (d, J = 8.2 Hz, 2H), 7.88 (d, J = 8.4 Hz, 2H), 7.53 (d, J
= 8.4 Hz, 2H), 7.47 (dd, J = 8.2, 7.6 Hz, 2H), 7.28 (t, J = 7.6
Hz, 1H), 1.36 (s, 9H). 13C NMR (126 MHz, CDCl3) δ 155.7,
153.8, 150.8, 136.2, 129.2 (2C), 126.1 (2C), 126.0, 125.9
(2C), 120.6, 118.4 (2C), 35.1, 31.1 (3C). IR (neat): ν 3429,
2964, 1784, 1592, 1371, 966, 751 cmꢀ1. HRMS (ESI, m/z):
calculated for C18H19N2O2 [M+H]+: 295.1441, found:
295.1439.
o
1
(EtOAc/petroleum ether = 1:30). m.p. 109–110 C. H NMR
(400 MHz, CDCl3) δ 7.97 – 7.95 (m, 4H), 7.56 – 7.46 (m, 5H),
7.29 (t, J = 7.4 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 153.6,
150.7, 136.1, 131.9, 129.2 (2C), 129.1 (2C), 126.2, 126.0
(2C), 123.5, 118.4 (2C). 19F NMR (377 MHz, CDCl3) δ ꢀ106.6
(s). IR (neat): ν 3422, 2912, 1779, 1355, 732, 679 cmꢀ1. HRMS
(ESI, m/z): calculated for C14H10N2O2Na [M+Na]+: 261.0634,
found: 261.0627.
5ꢀ(4ꢀFluorophenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2b)7 [CAS: 1643432ꢀ85ꢀ2]. white solid (43.0 mg, 84%). Rf =
0.3 (EtOAc/petroleum ether = 1:40). m.p. 139–140 oC. 1H
NMR (400 MHz, CDCl3) δ 7.98 – 7.93 (m, 4H), 7.48 (dd, J =
8.0, 7.4 Hz, 2H), 7.29 (t, J = 7.4 Hz, 1H), 7.24 – 7.19 (m, 2H).
13C NMR (126 MHz, CDCl3) δ 165.9, 163.9, 151.7 (d, J =
284.5 Hz), 136.0, 129.2 (2C), 128.3 (d, J = 8.9 Hz) (2C),
126.2, 119.8 (d, J = 3.3 Hz), 118.3 (2C), 116.5 (d, J = 22.4
Hz) (2C). IR (neat): ν 2921, 1783, 1357, 842, 741 cmꢀ1. HRMS
(ESI, m/z): calculated for C14H10FN2O2 [M+H]+: 257.0721,
found: 257.0726.
5ꢀ(2ꢀNaphthyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2h).
white solid (47.3 mg, 82% yield). Rf = 0.2 (EtOAc/petroleum
ether = 1:40). m.p. 140ꢀ142 oC. 1H NMR (500 MHz, CDCl3) δ
8.35 (s, 1H), 7.97 – 7.84 (m, 6H), 7.57 – 7.54 (m, 2H), 7.47
(dd, J = 7.8, 7.4 Hz, 2H), 7.28 (t, J = 7.4 Hz, 1H). 13C NMR
(126 MHz, CDCl3) δ 153.7, 150.7, 136.1, 134.7, 132.7, 129.2
(2C), 129.0, 128.9, 128.1, 128.0, 127.2, 126.8, 126.1, 121.8,
120.6, 118.3 (2C). IR (neat): ν 2922, 1775, 1498, 1263, 747
cmꢀ1. HRMS (ESI, m/z): calculated for C18H13N2O2 [M+H]+:
289.0972, found: 289.0971.
5ꢀ(2ꢀFuryl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2i) [CAS:
1628570ꢀ35ꢀ3]. brown solid (27.8 mg, 61% yield). Rf = 0.3
(EtOAc/petroleum ether = 1:40). m.p. 96–98 oC. 1H NMR
(500 MHz, CDCl3) δ 7.85 (d, J = 8.0 Hz, 2H), 7.58 (s, 1H),
7.39 (dd, J = 8.0, 7.6 Hz, 2H), 7.21 (t, J = 7.6 Hz, 1H), 7.02 (d,
J = 3.4 Hz, 1H), 6.54 – 6.53 (m, 1H). 13C NMR (126 MHz,
CDCl3) δ 149.8, 147.0, 146.0, 138.7, 135.9, 129.2 (2C), 126.3,
118.4 (2C), 114.5, 112.1. IR (neat): ν 2922, 1773, 1497, 1368,
955, 763, 688 cmꢀ1. HRMS (ESI, m/z): calculated for
C12H9N2O3 [M+H]+: 229.0608, found: 229.0603.
5ꢀ(4ꢀChlorophenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2c)7a [CAS: 1643432ꢀ87ꢀ4]. white solid (39.2 mg, 72% yield).
Rf = 0.3 (EtOAc/petroleum ether = 1:40). m.p. 118–119 oC. 1H
NMR (500 MHz, CDCl3) δ 7.93 (d, J = 8.0 Hz, 2H), 7.88 (d, J
= 8.0 Hz, 2H), 7.50 – 7.47 (m, 4H), 7.29 (t, J = 7.3 Hz, 1H).
13C NMR (126 MHz, CDCl3) δ 152.8, 150.5, 138.3, 136.0,
129.5 (2C), 129.2 (2C), 127.2 (2C), 126.3, 122.0, 118.3 (2C).
IR (neat): ν 2922, 1779, 1354, 830, 748 cmꢀ1. HRMS (ESI,
m/z): calculated for C14H9ClN2O2Na [M+Na]+: 295.0245,
found: 295.0239.
3ꢀPhenylꢀ5ꢀ(2ꢀthienyl)ꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2j)7a
5ꢀ(4ꢀBromophenyl)ꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
[CAS: 1628570ꢀ34ꢀ2]. brown solid (43.5 mg, 89% yield). Rf =
(2d)7a [CAS: 1643432ꢀ89ꢀ6]. white solid (57.0 mg, 90% yield).
0.2 (EtOAc/petroleum ether = 1:40). m.p. 135–137 oC. 1H
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NMR (500 MHz, CDCl3) δ 7.92 (d, J = 8.0 Hz, 2H), 7.69 (d, J
131.8, 129.4, 129.0 (2C), 125.9 (2C), 123.6, 120.3 (2C), 114.4
(2C), 55.6. IR (neat): ν 3420, 2919, 1768, 1513, 818 cmꢀ1.
HRMS (ESI, m/z): calculated for C15H13N2O3 [M+H]+:
269.0921, found: 269.0915.
1
2
3
4
5
6
7
8
= 3.6 Hz, 1H), 7.56 (d, J = 5.0 Hz, 1H), 7.46 (dd, J = 8.0, 7.6
Hz, 2H), 7.27 (t, J = 7.6 Hz, 1H), 7.16 (dd, J = 5.0, 3.6 Hz,
1H). 13C NMR (126 MHz, CDCl3) δ 150.4, 150.1, 135.9,
130.2, 129.8, 129.2 (2C), 128.1, 126.2, 125.0, 118.3 (2C). IR
(neat): ν 2922, 1789, 1471, 1090, 946, 752, 684 cmꢀ1. HRMS
(ESI, m/z): calculated for C12H9N2O2S [M+H]+: 245.0379,
found: 245.0371.
3ꢀ(4ꢀBromophenyl)ꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2q)7b [CAS: 1778703ꢀ73ꢀ3]. brown solid (55.8 mg, 88%
yield). Rf = 0.4 (EtOAc/petroleum ether = 1:40). m.p. 140–142
1
oC. H NMR (400 MHz, CDCl3) δ 7.93 (d, J = 7.8 Hz, 2H),
5ꢀMethylꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2k) [CAS:
28740ꢀ63ꢀ8]. colorless solid (27.1 mg, 77% yield). Rf = 0.2
(EtOAc/petroleum ether = 1:40). m.p. 73–75 oC. 1H NMR
(500 MHz, CDCl3) δ 7.83 (d, J = 8.0 Hz, 2H), 7.43 (dd, J =
8.0, 7.6 Hz, 2H), 7.24 (t, J = 7.6 Hz, 1H), 2.35 (s, 3H). 13C
NMR (126 MHz, CDCl3) δ 153.8, 151.1, 136.0, 129.1 (2C),
125.9, 118.1 (2C), 12.1. IR (neat): ν 2923, 1766, 1500, 1376,
1134, 954, 757, 686 cmꢀ1. HRMS (ESI, m/z): calculated for
C9H9N2O2 [M+H]+: 177.0659, found: 177.0656.
7.87 – 7.85 (m, 2H), 7.60 – 7.49 (m, 5H). 13C NMR (126
MHz, CDCl3) δ 153.8, 150.4, 135.2, 132.3 (2C), 132.2, 129.1
(2C), 126.0 (2C), 123.3, 119.7 (2C), 119.3. IR (neat): ν 2922,
1782, 1489, 1353, 733 cmꢀ1. HRMS (ESI, m/z): calculated for
C14H10N2O2Br [M+H]+: 316.9920, found: 316.9913.
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
3ꢀ(3ꢀChlorophenyl)ꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2r). white solid (50.2 mg, 92% yield). Rf1
= 0.3
o
(EtOAc/petroleum ether = 1:40). m.p. 119–120 C, H NMR
(400 MHz, CDCl3) δ 7.99 (t, J = 2.0 Hz, 1H), 7.96 – 7.94 (m,
2H), 7.91 – 7.89 (m, 1H), 7.57 – 7.50 (m, 3H), 7.40 (t, J = 8.2
Hz, 1H), 7.27 – 7.24 (m, 1H). 13C NMR (126 MHz, CDCl3) δ
153.8, 150.4, 137.0, 135.1, 132.2, 130.3, 129.1 (2C), 126.13,
126.06 (2C), 123.2, 118.3, 116.0. IR (neat): ν 2921, 1779,
1353, 983, 731 cmꢀ1. HRMS (ESI, m/z): calculated for
C14H9N2O2ClNa [M+Na]+: 295.0245, found: 295.0244.
5ꢀEthylꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2l) [CAS:
28669ꢀ40ꢀ1]. white solid (27.0 mg, 71% yield). Rf = 0.4
(EtOAc/petroleum ether = 1:40). m.p. 56–58 oC. 1H NMR
(500 MHz, CDCl3) δ 7.84 (d, J = 8.0 Hz, 2H), 7.43 (dd, J =
8.0, 7.6 Hz, 2H), 7.24 (t, J = 7.6 Hz, 1H), 2.68 (q, J = 7.4 Hz,
2H), 1.34 (t, J = 7.4 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ
157.7, 151.2, 136.1, 129.1 (2C), 125.9, 118.1 (2C), 20.0, 9.6.
IR (neat): ν 2960, 1783, 1501, 1015, 932, 748 cmꢀ1. HRMS
(ESI, m/z): calculated for C10H11N2O2 [M+H]+: 191.0815,
found: 191.0812.
3ꢀBenzylꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2s)22 [CAS:
27643ꢀ12ꢀ5]. white solid (43.3 mg, 86% yield). Rf = 0.4
o
1
(EtOAc/petroleum ether = 1:10). m.p. 118–119 C. H NMR
(400 MHz, CDCl3) δ 7.83 – 7.81 (m, 2H), 7.50 – 7.31 (m, 8H),
4.95 (s, 2H). 13C NMR (126 MHz, CDCl3) δ 153.5, 153.3,
134.9, 131.5, 128.9 (2C), 128.8 (2C), 128.34, 128.28 (2C),
125.7 (2C), 123.8, 49.7. IR (neat): ν 3309, 1766, 1355, 1018,
775, 731 cmꢀ1. HRMS (ESI, m/z): calculated for C15H13N2O2
[M+H]+: 253.0972, found: 253.0971.
5ꢀCyclopropylꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2m).
o
m.p. 78–79 C, white solid (29.9 mg, 74% yield). Rf = 0.4
(EtOAc/petroleum ether = 1:40). m.p. 78–79 oC. 1H NMR
(400 MHz, CDCl3) δ 7.83 (d, J = 8.0 Hz, 2H), 7.42 (dd, J =
8.0, 7.4 Hz, 2H), 7.23 (t, J = 7.4 Hz, 1H), 1.96 – 1.90 (m, 1H),
1.12 – 1.09 (m, 4H). 13C NMR (126 MHz, CDCl3) δ 157.9,
150.8, 136.1, 129.1 (2C), 125.8, 118.1 (2C), 7.1, 7.0 (2C). IR
(neat): ν 2922, 1783, 1495, 1017, 729 cmꢀ1. HRMS (ESI, m/z):
calculated for C11H11N2O2 [M+H]+: 203.0815, found:
203.0815.
3ꢀButylꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2t)23 [CAS:
41125ꢀ98ꢀ8]. colorless solid (36.6 mg, 84% yield). Rf = 0.4
(EtOAc/petroleum ether = 1:10). m.p. 41–43 oC. 1H NMR
(400 MHz, CDCl3) δ 7.84 (d, J = 6.4 Hz, 2H), 7.52 – 7.44 (m,
3H), 3.80 (t, J = 7.2 Hz, 2H), 1.83 – 1.76 (m, 2H), 1.46 – 1.37
(m, 2H), 0.97 (t, J = 7.4 Hz, 3H). 13C NMR (126 MHz, CDCl3)
δ 153.6, 153.1, 131.4, 128.9 (2C), 125.5 (2C), 123.9, 45.7,
30.2, 19.6, 13.5. IR (neat): ν 2957, 2357, 1780, 1358, 1018,
739 cmꢀ1. HRMS (ESI, m/z): calculated for C12H15N2O2
[M+H]+: 219.1128, found: 219.1123.
5ꢀtertꢀButylꢀ3ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
(2n)14
[CAS: 1739ꢀ74ꢀ8]. colorless oil (37.1 mg, 85% yield). Rf = 0.3
1
(EtOAc/petroleum ether = 1:30). H NMR (400 MHz, CDCl3)
δ 7.86 (d, J = 7.8 Hz, 2H), 7.43 (dd, J = 7.8, 7.4 Hz, 2H), 7.24
(t, J = 7.4 Hz, 1H), 1.38 (s, 9H). 13C NMR (126 MHz, CDCl3)
δ 162.8, 151.3, 136.1, 129.1 (2C), 125.8, 118.1 (2C), 32.8,
27.0 (3C). IR (neat): ν 2922, 1781, 1499, 1370, 1130, 966, 754
cmꢀ1. HRMS (ESI, m/z): calculated for C12H15N2O2 [M+H]+:
219.1128, found: 219.1124.
5ꢀ(4ꢀBenzoxylphenyl)ꢀ3ꢀ(2ꢀcyanoethyl)ꢀ1,3,4ꢀoxadiazolꢀ
2(3H)ꢀone (2u)3a [CAS: 147807ꢀ20ꢀ3]. white solid (57.1 mg,
89% yield). Rf = 0.5 (EtOAc/petroleum ether = 1:1). m.p. 151–
o
1
153 C. H NMR (500 MHz, CDCl3) δ 7.77 (d, J = 8.9 Hz,
2H), 7.44 – 7.39 (m, 4H), 7.37 – 7.34 (m, 1H), 7.05 (d, J = 8.9
Hz, 2H), 5.13 (s, 2H), 4.09 (t, J = 6.9 Hz, 2H), 2.88 (t, J = 6.9
Hz, 2H). 13C NMR (126 MHz, CDCl3) δ 161.7, 154.1, 153.0,
136.0, 128.7 (2C), 128.3 (2C), 127.7, 127.5 (2C), 116.2,
116.0, 115.4 (2C), 70.2, 41.5, 17.1. IR (neat): ν 3362, 2912,
2244, 1769, 1609, 1242, 998, 838, 743 cmꢀ1. HRMS (ESI,
m/z): calculated for C18H16N3O3 [M+H]+: 322.1186, found:
322.1184.
3ꢀ(4ꢀMethylphenyl)ꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone (2o)
[CAS: 528585ꢀ43ꢀ5]. white solid (28.7 mg, 57% yield). Rf =
0.2 (EtOAc/petroleum ether = 1:30). m.p. 147–149 oC. 1H
NMR (400 MHz, CDCl3) δ 7.94 – 7.92 (m, 2H), 7.81 (d, J =
8.2 Hz 2H), 7.54 – 7.47 (m, 3H), 7.26 (d, J = 8.2 Hz, 2H), 2.37
(s, 3H). 13C NMR (126 MHz, CDCl3) δ 153.4, 150.8, 136.0,
133.7, 131.8, 129.7 (2C), 129.0 (2C), 125.9 (2C), 123.6, 118.4
(2C), 21.0. IR (neat): ν 2921, 1782, 1515, 1356, 813, 683 cmꢀ1.
HRMS (ESI, m/z): calculated for C15H13N2O2 [M+H]+:
253.0972, found: 253.0970.
5ꢀtertꢀButylꢀ3ꢀ(2,4ꢀdichloroꢀ5ꢀisopropoxyphenyl)ꢀ1,3,4ꢀ
oxadiazolꢀ2(3H)ꢀone (2v) [CAS: 19666ꢀ30ꢀ9]. white solid
(60.9 mg, 88% yield). Rf = 0.3 (EtOAc/petroleum ether =
3ꢀ(4ꢀMethoxyphenyl)ꢀ5ꢀphenylꢀ1,3,4ꢀoxadiazolꢀ2(3H)ꢀone
o
1
(2p). white solid (50.9 mg, 95% yield). Rf1
=
0.2
1:40). m.p. 87–89 C. H NMR (500 MHz, CDCl3) δ 7.52 (s,
1H), 7.03 (s, 1H), 4.59 – 4.52 (m, 1H), 1.39 (d, J = 6.1 Hz,
6H), 1.37 (s, 9H). 13C NMR (126 MHz, CDCl3) δ 163.5,
153.0, 152.2, 131.4, 131.3, 126.1, 123.1, 114.9, 73.0, 32.9,
27.0 (3C), 21.8 (2C). IR (neat): ν 2964, 1788, 1488, 1249,
o
(EtOAc/petroleum ether = 1:30). m.p. 142–144 C. H NMR
(500 MHz, CDCl3) δ 7.94 (d, J = 7.6 Hz, 2H), 7.83 (d, J = 9.0
Hz, 2H), 7.56 – 7.49 (m, 3H), 6.99 (d, J = 9.0 Hz, 2H), 3.85 (s,
3H). 13C NMR (126 MHz, CDCl3) δ 157.9, 153.4, 150.9,
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1123, 1037, 748 cmꢀ1. HRMS (ESI, m/z): calculated for
Weaver, D. G.; Mathis, W. D. Synthesis 2001, 13, 1965. (d) Bancerz,
C15H19Cl2N2O3 [M+H]+: 345.0767, found: 345.0773.
M.; Georges, M. K. J. Org. Chem. 2011, 76, 6377. (e) Batanero, B.;
Barba, F. J. Org. Chem. 2013, 78, 9477. (f) Patel, S. S.; Chandna, N.;
Kumar, S.; Jain, N. Org. Biomol. Chem. 2016, 14, 5683. (g) Brahꢀ
mayya, M.; Dai, S. A.; Suen, S.ꢀY. RSC Adv. 2015, 5, 65351.
(7) (a) Wang, Y.; Meng, X.; Yang, Y.; Zhang, L.; Guo, S.; Tang,
D.; Li, Y.; Chen, B. Chem. Commun. 2015, 51, 1905. (b) Ji, F.; Li, X.;
Guo, W.; Wu, W.; Jiang, H. J. Org. Chem. 2015, 80, 5713.
(8) For recent reviews on transformation of CO2, see: (a) Huang, K.;
Sun, C.ꢀL.; Shi, Z.ꢀJ. Chem. Soc. Rev. 2011, 40, 2435. (b) Zhang, W.ꢀ
Z.; Lu, X.ꢀB. Chin. J. Catal. 2012, 33, 745. (c) Liu, Q.; Wu, L.; Jackꢀ
stell, R.; Beller, M. Nat. Commun. 2015, 6, 5933, and references cited
therein.
(9) (a) Mori, M. Eur. J. Org. Chem. 2007, 4981. (b) Louie, J.; Gibꢀ
by, J. E.; Farnworth, M. V.; Tekavec, T. N. J. Am. Chem. Soc. 2002,
124, 15188.
(10) (a) Lu, X.ꢀB.; Darensbourg, D. J. Chem. Soc. Rev. 2012, 41,
1462; (b) Martin, C.; Fiorani, G.; Kleij, A. W. ACS Catal. 2015, 5,
1353.
(11) (a) Huisgen, R. Angew. Chem. Int. Ed. Engl. 1963, 2, 565. (b)
Huisgen, R. Angew. Chem. Int. Ed. Engl. 1963, 2, 633.
(12) (a) Gothelf, K. V.; Jorgensen, K. A. Chem. Rev. 1998, 98, 863.
(b) Kissane, M.; Maguire, A. R. Chem. Soc. Rev. 2010, 39, 845. (c)
Hashimoto, T.; Maruoka, K. Chem. Rev. 2015, 115, 5366.
(13) Pfoertner, K.ꢀH.; Foricher, J. Helv. Chim. Acta. 1980, 63, 653.
(14) Matsubara, Y.; Adachi, K.; Tada, H.; Kitano, K. Yakugaku
Zasshi 1996, 116, 255.
(15) (a) Spiteri, C.; Keeling, S.; Moses, J. E. Org. Lett. 2010, 15,
3368. (b) Zou, H.; Zhu, H.; Shao, J.; Wu, J.; Chen, W.; Giulianotti,
M. A.; Yu, Y. Tetrahedron 2011, 67, 4887. (c) Kiwai, H.; Yuan, Z.;
Tokunaga, E.; Shibata, N. Org. Lett. 2012, 14, 5330. (d) Begue, D.;
Qiao, G. G.; Wentrup, C. J. Am. Chem. Soc. 2012, 134, 5339. (e)
Giustiniano, M.; Meneghetti, F.; Mercalli, V.; Varese, M.; Giustiniꢀ
ano, F.; Novellino, E. G.; Tron, C. Org. Lett. 2014, 16, 5332. (f)
Wang, X. S.; Lee, Y. J.; Liu, W. R. Chem. Commun. 2014, 50, 3176.
(g) Garve, L. K.; Petzold, M.; Jones, P. G.; Werz, D. B. Org. Lett.
2016, 18, 564. (h) Tron, G.; Giustiniano, M.; Novellino, E. Synthesis
2016, 48, 2721.
1
2
3
4
5
6
7
8
3,5ꢀDiphenylꢀ1,3,4ꢀthiadiazolꢀ2(3H)ꢀone (4a) [CAS: 62353ꢀ
94ꢀ0]. white solid (46.2 mg, 91% yield). Rf
= 0.4
(EtOAc/petroleum ether = 1:40). m.p. 90–92 oC. 1H NMR
(500 MHz, CDCl3) δ 7.89 (d, J = 8.4 Hz, 2H), 7.77 – 7.75 (m,
2H), 7.49 – 7.46 (m, 5H), 7.33 (t, J = 7.8 Hz, 1H). 13C NMR
(126 MHz, CDCl3) δ 168.4, 150.5, 138.0, 131.1, 130.5, 129.03
(2C), 129.00 (2C), 127.0, 126.1 (2C), 121.8 (2C). IR (neat): ν
3360, 2921, 1685, 1487, 1261, 750, 685 cmꢀ1. HRMS (ESI,
m/z): calculated for C14H11N2OS [M+H]+: 255.0587, found:
255.0586.
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5ꢀMethylꢀ3ꢀphenylꢀ1,3,4ꢀthiadiazolꢀ2(3H)ꢀone (4k). colorꢀ
less oil (16.1 mg, 42% yield). Rf = 0.4 (EtOAc/petroleum ether
1
= 1:30). H NMR (500 MHz, CDCl3) δ 7.78 (d, J = 7.6 Hz,
2H), 7.43 (dd, J = 7.6, 7.4 Hz, 2H), 7.29 (t, J = 7.4 Hz, 1H),
2.48 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 169.1, 149.0,
137.9, 129.0 (2C), 126.9, 121.7 (2C), 18.3. IR (neat): ν 3360,
2924, 1696, 1492, 1261, 801, 691 cmꢀ1. HRMS (ESI, m/z):
calculated for C9H9N2OS [M+H]+: 193.0430, found: 193.0431.
ASSOCIATED CONTENT
Supporting Information.
The Supporting Information is available free of charge via the
Internet at http://pubs.acs.org.
Xꢀray crystallographic data for compound 2f (CIF)
1
Control experiments using 1H NMR; Copies of H and 13C NMR
spectra of all products
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: zhangwz@dlut.edu.cn
Notes
The authors declare no competing financial interest.
(16) For the recent examples of transitionꢀmetal free transformation
of CO2, see: (a) Zhang, Z.; Liao, L.ꢀL.; Yan, S.ꢀS.; Wang, L.; He, Y.ꢀ
Q.; Ye, J.ꢀH.; Li, J.; Zhi, Y.ꢀG.; Yu, D.ꢀG. Angew. Chem. Int. Ed.
2016, 55, 7068. (b) Zhang, W.ꢀZ.; Yang, M.ꢀW.; Lu, X.ꢀB. Green
Chem. 2016, 18, 4181. (c) Peng, Y.; Liu, J.; Qi, C.; Yuan, G.; Li, J.;
Jiang, H. Chem. Commun. 2017, 53, 2665.
(17) Guo, C.ꢀX.; Zhang, W.ꢀZ.; Zhou, H.; Zhang, N.; Lu, X.ꢀB.
Chem. Eur. J. 2016, 22, 17156.
(18) (a) Arnold, D. W.; Bradforth, S. E.; Kim, E. H.; Neumark, D.
M. J. Chem. Phys. 1995, 102, 3493. (b) Zhang, X.; Gross, U.; Seppelt,
K. Angew. Chem. Int. Ed. Engl. 1995, 34, 1858.
ACKNOWLEDGMENT
This work was supported by the Natural Science Foundation of
Liaoning Province (20170540156), and the Program for
Changjiang Scholars and Innovative Research Team in University
(IRT13008). X.ꢀB. Lu gratefully acknowledges the Chang Jiang
Scholars Program (T2011056) from the Ministry of Education of
the People's Republic of China.
(19) (a) Ukai, K.; Aoki, M.; Takaya, J.; Iwasawa, N. J. Am. Chem.
Soc. 2006, 128, 8706. (b) Takaya, J.; Tadami, S.; Ukai, K.; Iwasawa,
N. Org. Lett. 2008, 10, 2697. (c) Li, S.; Ma, S. Org. Lett. 2011, 13,
6046. (d) Li, S.; Yuan, W.; Ma, S. Angew. Chem. Int. Ed. 2011, 50,
2578. (e) Li, S.; Ma, S. Adv. Synth. Catal. 2012, 354, 2387.
(20) CCDC 1527631.
(21) (a) Zhang, C.; Liu, X.; Wang, B.; Wang, S.; Li, Z. Chem. Biol.
Drug Des. 2010, 75, 489. (b) Garve, K. B.; Petzold, M.; Jones, P. G.;
Werz, D. B. Org. Lett. 2016, 18, 564.
(22) Padwa, A.; Caruso, T.; Nahm, S.; Rodriguez, A. J. Am. Chem.
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(23) Yan, X.; Zhou, S.; Wang, Y.; Ge, Z.; Cheng, T.; Li, R. Tetraꢀ
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