Preparation of Imidazole Derivatives via Bisfunctionalization of Alkynes Catalyzed by Ruthenium Carbonyl

Article abstract of DOI:10.1055/s-0037-1611871

A one-step, oxidative bisfunctionalization of alkynes to generate cis -enediol diacetates catalyzed by ruthenium carbonyl (triruthenium dodecacarbonyl) is presented. The reaction was performed using the alkyne, (diacetoxyiodo)benzene, Ru ₃ (CO) ₁₂ as the catalyst, and toluene as the solvent at 100 °C to give the cis -enediol diacetates in up to 82percent yields. This method overcomes the shortcomings of existing methods, such as tedious reaction steps, substrate limitations, and the use of toxic reagents. Furthermore, the reaction of module cis -enediol diacetates with ammonium carbonate [(NH ₄) ₂ CO ₃ ] in an alcohol solvent gave imidazole derivatives in 37-84percent yields, thus providing a simple and mild new method for the synthesis of imidazole compounds.

Full text of DOI:10.1055/s-0037-1611871

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2019, 51, A–I
paper
A
en
Y.-t. Ruan et al.
Paper
Synthesis
Preparation of Imidazole Derivatives via Bisfunctionalization of
Alkynes Catalyzed by Ruthenium Carbonyl
Yi-tong Ruana
R
PhI(OAc)2
Ru3(CO)12
Yue-peng Chena
Ling-hui Gua,b
Yang Luoa
OAc
N
(NH4)2CO3
RCH2OH
NH
R2
OAc
toluene
R2 = H
R1
R2
R1
R1
R2
Ze Yanga
Ling He*a
16 examples
up to 82% yield
8 examples
up to 84% yield
a Key Laboratory of Drug-Targeting and Drug Delivery System of the Edu-
cation Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug
and Sichuan Research Center for Drug Precision Industrial Technology,
Department of Medicinal Chemistry, West China School of Pharmacy,
Sichuan University, Chengdu, Sichuan, 610041, P. R. of China
heling2012@scu.edu.cn
b Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Prov-
ince, Sichuan Industrial Institute of Antibiotics, Chengdu University,
Chengdu, 610052, P. R. of China
Received: 13.12.2018
Accepted after revision: 31.05.2019
Published online: 26.06.2019
tionally, the reactions of alkynes with iodobenzene carbox-
ylates to produce halogen-, amino-, or acetoxy-substituted
olefin derivatives and o-dicarbonyl compounds have been
reported in the literature (Scheme 1). In 2011, Liu and co-
workers14 described the synthesis of tetrasubstituted (E)-
olefin derivatives, which were produced by hydroamination
of alkynes and PhI(OAc)2 mediated C–H acetoxylation
(Scheme 1, eq. 5). In 2014, Xia and co-workers15 reported
that under the catalysis of Cu(OTf)2, PhI(OAc)2 oxidized
arylalkynes to form -diketones (Scheme 1, eq. 3). In addi-
tion, they found that arylalkynes reacted with PhI(OAc)2 as
a oxidant under metal-free conditions using tetrabutylam-
monium halide (Bu4NX) to give -haloenol acetates without
any catalyst (Scheme 1, eq. 6). In 2015, Priebbenow et al.16
developed a method for the regioselective and stereoselec-
tive iodoacyloxylation of alkynes with a combination of an
iodobenzene carboxylate and iodine (Scheme 1, eq. 7).
Moreover, Deng and Luo,17 Biffis and co-workers,18 Sreed-
har and co-workers,19 and Bäckvall and co-workers.20 re-
ported that alkynes reacted with PhI(OAc)2 to afford -ace-
toxy ketones catalyzed by AgOAc, CuCl(L)(PPh3), Fe(OAc)2,
Pd(OAc)2, respectively (Scheme 1, eqs. 2 and 4).
Obviously, the aforementioned methods suffer from
limitations of the reaction scope, the use of multiple metal
catalysts, or the utilization of high-cost and toxic reagents.
Therefore, it is interesting and important to develop a more
convenient and efficient method for the synthesis of acylat-
ed cis-enediols and then to use them to construct heterocy-
clic derivatives. Herein, we have designed a new method for
the synthesis of cis-enediol diacetates by the reaction of
alkynes with (diacetoxyiodo)benzene under the catalysis of
ruthenium carbonyl, following by using the reaction mod-
ule to construct imidazole derivatives (Scheme 1).
DOI: 10.1055/s-0037-1611871; Art ID: ss-2018-h0827-op
Abstract A one-step, oxidative bisfunctionalization of alkynes to gen-
erate cis-enediol diacetates catalyzed by ruthenium carbonyl (triruthe-
nium dodecacarbonyl) is presented. The reaction was performed using
the alkyne, (diacetoxyiodo)benzene, Ru3(CO)12 as the catalyst, and tolu-
ene as the solvent at 100 °C to give the cis-enediol diacetates in up to
82% yields. This method overcomes the shortcomings of existing meth-
ods, such as tedious reaction steps, substrate limitations, and the use of
toxic reagents. Furthermore, the reaction of module cis-enediol diace-
tates with ammonium carbonate [(NH4)2CO3] in an alcohol solvent gave
imidazole derivatives in 37–84% yields, thus providing a simple and mild
new method for the synthesis of imidazole compounds.
Key words imidazoles, bisfunctionalization, alkyne, cis-enediol diace-
tate, ruthenium carbonyl
Enediol dicarboxylates, -hydroxy ketones, or -ester
ketone1–4 are potential dihydroxy compounds that play im-
portant roles in the construction of heterocyclic com-
pounds as useful organic synthetic blocks.5,6 Many natural
products and pharmacologically active molecules also have
the enediol diacetate functional group.7,8 However, synthet-
ic methods for enediol diacetates are reported rarely, espe-
cially cis-enediol diacetates. The reduction and acylation of
dicarbonyl compounds have been used to directly prepare
cis-enediol diacetates with reducing agents, such as SmI2,
R2Sn, or NaBH4 and so on (Scheme 1, eq. 1).9,10 Larock and
co-workers11 developed one-pot conversion of internal
alkynes into trans-enediol diacetates using Hg(OAc)2 cata-
lyzed by Pd(OAc)2 via -acetoxyvinylmercurials. Riek and
Wu12 and Ueda and Kise13 reported the synthesis of acylat-
ed trans-enediols from acyl halides by copper-mediated
coupling and electroreductive coupling, respectively. Addi-
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
Y.-t. Ruan et al.
Paper
Synthesis
Previous work
R2
R1
O
O
R2
R1
OAc
R2
O
O
SmI2
Ac2O
SnMe2
AcCl
Eq.1
AcO
R1
OAc
O
Eq.2
Eq.3
R2
OAc
Eq.5
Eq.6
R1
R1
RNH2, PhI(OAc)2
CH2Cl2, 0 °C
PhI(OAc)2, AgOAc
or CuCl(L)(PPh3)
or Fe(OAc)2
NHR
OAc
O
Cu(OTf)2
PhI(OAc)2
Bu4NX
R2
R2
R1
R2
R1
R1
PhI(OAc)2
X
O
PhI(OAc)2, Pd(OAc)2
BQ
DMSO, 50 °C, 18 h
PhI(OAc)2
I2, DCE, rt
O
OAc
I
R2
R1
R
R1
Eq.4
Eq.7
OAc
This work
R
PhI(OAc)2
OAc
(NH4)2CO3
RCH2OH
Ru3(CO)12
N
OAc
R1
R2
R1
NH
R2
toluene
R2
R1
Scheme 1 Various strategies for the functionalization of alkynes
At the beginning of this work, we investigated the ef-
fects of different metal catalysts such as Ru, Rh, Cu, Pd, and
Ag as well the amount of catalyst on the reaction of 4-me-
thoxyphenylacetylene (1b) and PhI(OAc)2. The reaction was
carried out under a nitrogen atmosphere, using anhydrous
toluene as the solvent, with molar ratio 4-methoxypheny-
lacetylene/PhI(OAc)2 1:1 at 65 °C for 8 hours. Of the cata-
lysts examined, only Ru3(CO)12 gave the target products in
good yields (Table 1, entries 1–16). We next investigated the
effects of solvent, temperature, and molar ratio of sub-
strates on this reaction. To our delight, the yield was higher
than 80% when 2 mol% Ru3(CO)12 was used as the catalyst
with toluene as the solvent and a molar ratio of 4-methoxy-
phenylacetylene (1b)/PhI(OAc)2 1:2.5 at 100 °C (Table 1, en-
try 25). As a consequence, the reaction conditions for the
synthesis of cis-enediol diacetates were determined.
To test the scope of this reaction system, we examined
the reactions of various substrates under the optimized
conditions (Scheme 2). The vast majority of aromatic termi-
nal alkynes gave the target products 2a–p in moderate to
good yields. Moreover, electronic effects also played a role
in the reaction as much higher yields were observed for
electron-rich benzene substrates (2b–e, 2m, 2n). Among all
the substrates, 4-methoxyphenylacetylene (1b) had the
highest reactivity and gave the target product 2b in 82%
yield.
In addition, we found that 1-phenylprop-1-yne (1q) and
3-ethynylpyridine (1r) produced (Z)-1-phenylprop-1-enyl
acetate (3) and 2-oxo-2-(3-pyridyl)ethyl acetate (4),21,22 re-
spectively, under these reaction condition (Scheme 3),
which also provided information on the production of
monoacetyl oxidation products. We also found that when
Cu(SO3CF3)2 and AgSO3CF3 were used as the reaction cata-
lysts with 4-alkoxyphenylacetylenes as substrates, the
products were 1-acetoxy-2-arylacetylenes 5a,b (Scheme 3).
Unfortunately, the reaction of diphenylacetylene is very
slow under the same conditions and gave only trace prod-
ucts. In order to further investigate the universality of the
reaction, we used ethyl 3-arylpropynoates 6 as substrates, 2
mol% Ru3(CO)12 as catalyst, and toluene as solvent and ob-
tained the monoacetoxy derivatives 7. The addition of wa-
ter to the reaction favored the formation of the monoace-
toxy derivatives 7, hence it is suggested that the hydrogen
at the  position of compound 7 is provided by water. The
optimum results show that a good yield can be obtained by
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

C
Y.-t. Ruan et al.
Paper
Synthesis
Table 1 Optimization of the Reaction Conditions for the Formation of
cis-Enediols Derivatives
temperature on the formation of imidazole derivatives were
investigated by using 1-(4-methoxyphenyl)ethene-1,2-diyl
diacetate (2b) with (NH4)2CO3 as the nitrogen source and
methanol as the solvent (Table 2). The results showed that a
reaction temperature 64 °C gave the highest yield.
O
O
catalyst
O
+
PhI(OAc)2
solvent, T °C
O
O
Table 2 Optimization of the Reaction Conditions for the Formation of
O
Imidazolesa
1b
2b
Entry Catalyst
Solventa Equiv.b T (°C) Time (h) Yield (%)c
N
O
O
(NH4)2CO3
MeOH
NH
O
1
–
toluene 1:1
toluene 1:1
toluene 1:1
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
37
65
65
65
rt
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
24
12
2
2
2
2
0
O
2
Ru(bpy)3Cl2
Grubbs II
0
O
O
3
0
2b
8b
4
[Rh(Me(CH2)6CO2)2]2 toluene 1:1
0
Entry
Temp (°C)
Time (h)
Yield (%)b
5
Rh(CO)2acac
PdCl2
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:1
trace
0
6
1
2
3
r.t.
55
64
24
8
35
47
54
7
Cu(OAc)2
0
8
Cu(acac)2
0
6
9
Cu(quinox)Cl2
Cu(quinox)(NO3)2
Cu(SO3CF3)2
AgSO3CF3
0
a Molar ratio 2b/(NH4)2CO3 = 1:20.
b Isolated yields.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
0
0
We further explored the scope of this optimized reac-
tion system (Table 2) by applying various enediol diacetates
as substrates; most substrates 2a–c,e–h,m gave the target
products 8a–h in good yields (Table 3). Furthermore, the re-
action of (Z)-1-(4-methoxyphenyl)ethene-1,2-diyl diace-
tate (2b) with (NH4)2CO3 and ethanol at 64 °C gave 2-meth-
yl-substituted imidazole 9 in 48% yield. Thus it was also
shown that the carbon at the 2-position of the imidazole
ring was provided by the alcohol. The yield of product using
ethanol (48%) was slightly lower than that of the corre-
sponding reaction using methanol (54%) (Scheme 4). Subse-
quently, we performed further experiments in order to
prove the origin of the carbon at the 2-position of the imid-
azole ring. Thus the reaction of 2b, (NH4)2CO3, and formal-
dehyde or acetaldehyde with acetonitrile as solvent at 64 °C
also gave 8b and 9. Similarly, the reaction of 2b, (NH4)2CO3
and benzyl alcohol (solvent) at 64 °C gave 5-(4-methoxy-
phenyl)-2-phenyl-1H-imidazole.
The reaction mechanism for the formation of enediol di-
acetates and imidazole derivatives (Scheme 5) is proposed
on the basis of the literature.15,19 First, Ru3(CO)12 is oxidized
into Ru2(CO)12Ru(OAc)2, followed by complexation with the
alkyne to form intermediate A. Due to steric hindrance, OAc
adds to the alkyne from the opposite face to the complexed
metal catalyst to give B, Ru3(CO)12 is released from B to pro-
duce the target product C. Imidazole derivative G is synthe-
sized from C by aminolysis, accompanied by oxidation of
the alcohol into an aldehyde, and further condensation, de-
hydration, and deprotonation.
0
Ru3(CO)12 (10 mol%) toluene 1:1
54
53
53
46
0
Ru3(CO)12 (5 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (1 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
Ru3(CO)12 (2 mol%)
toluene 1:1
toluene 1:1
toluene 1:1
DCM
MeCN
THF
1:1
1:1
1:1
1:1
32
0
MeOH
0
toluene 1:1
toluene 1:1
toluene 1:1
toluene 1:2
toluene 1:2.5
toluene 1:3
0
45
100
100
100
100
13
62
76
82
83
a The solvent was dried.
b Ratio 1b/PbI(OAc)2.
c Isolated yields.
using the molar ratio of alkyne/PhI(OAc)2/H2O 1:1:1, at
100 °C for 2 hours (Scheme 3), but the reactivity of acetyl-
ene ketones and acetylenecarboxamides was poor.
After assembling various enediol diacetates, these reac-
tion modules were used to construct imidazoles with a sim-
ple nitrogen source, (NH4)2CO3.23–27 The effects of reaction
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

D
Y.-t. Ruan et al.
Paper
Synthesis
OAc
2.5 equiv PhI(OAc)2
2 mol% Ru3(CO)12
OAc
OAc
R1
R2
R1
anhyd toluene
N2, 100 °C, 2 h
R2
1
2
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
O
O
2d 64%
2c 77%
OAc
2b 82%
2a 58%
OAc
OAc
OAc
OAc
OAc
OAc
F
Cl
Br
2f 46%
2g 54%
2h 63%
OAc
2e 68%
OAc
OAc
OAc
OAc
OAc
OAc
O2N
Cl
2l 63%
2k 22%
2j 37%
2i 35%
OAc
OAc
O
OAc
OAc
OAc
OAc
AcO
OAc
S
N
OAc
O
O
2m 58%
2n 51%
2o 45%
2p 34%
Scheme 2 Synthesis of enediol diacetates. Reagents and conditions: 1, PhI(OAc)2 (2.5 equiv), Ru3(CO)12 (2 mol%), toluene, N2, 100 °C, 2 h.
OAc
2.5 equiv PhI(OAc)2
2 mol% Ru3(CO)12
toluene
OAc
N
NH
OAc
(NH4)2CO3
100 °C, 2 h
EtOH, 64 °C, 6 h
1q
1r
3 78%
O
O
O
9
48%
2.5 equiv PhI(OAc)2
2 mol% Ru3(CO)12
O
Scheme 4 Effect of alcohol
O
O
toluene
100 °C, 2 h
N
N
In summary, we have developed a new method for the
synthesis of cis-enediol diacetates by the reaction of
alkynes with (diacetoxyiodo)benzene in a transition-metal-
catalyzed reaction, then using the reaction module with a
simple nitrogen source (NH4)2CO3 to construct imidazole
derivatives easily in one-pot. The approach assembled a se-
rial of products in moderate to good yields, and it made up
the shortcomings of existing methods by using a wide vari-
ety of substrates, simple and inexpensive reagents, and
moderate conditions. This reaction leads a new path for the
synthesis of imidazole derivatives and also lays the founda-
tions for bioactivity screening.
4 26%
1 equiv PhI(OAc)2
10 mol% Cu(SO3CF3)2
or 10 mol% AgSO3CF3
O
anhyd toluene, N2
100 °C, 2 h
R1
R1
5a,5b
1b,1c
R1 = 4-OMe, yield = 80%
R1 = 4-OEt, yield = 68%
O
O
O
O
1 equiv PhI(OAc)2
2 mol% Ru3(CO)12
OEt
OEt
R2
R2
toluene, 1 equiv H2O
100 °C, 2 h
6a, 6b, 6c, 6d
7a, 7b, 7c, 7d
R2 = H, yield = 43%
R2 = 4-Me, yield = 57%
Silica gel F254 plates were used for TLC; the spots were examined un-
der UV light (254 nm) and then developed by I2 vapor. Flash chroma-
tography was performed on silica gel H. Anhyd solvents were purified
according to standard procedures. All other commercial reagents
were purchased from commercial sources and used without purifica-
tion. NMR spectra were recorded on a Varian Mercury spectrometer
R
2 = 4-OMe, yield = 71%
R2 = 4-OEt, yield = 62%
Scheme 3 Specific cases with some substrates under different condi-
tions
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

E
Y.-t. Ruan et al.
Paper
Synthesis
Table 3 Synthesis of Imidazole Derivativesa
was heated to 100 °C for 2 h. Then the mixture was allowed to cool
and the solvent was removed in vacuo and the residue was purified
by flash chromatography (silica gel, petroleum ether) to afford the
product. Alternatively toluene was removed by flash chromatography
and the appropriate fractions concentrated in vacuo to give the crude
residue, which was used directly for the next step reaction.
OAc
N
(NH4)2CO3
OAc
NH
R1
R1
MeOH, 64 °C, 6 h
2
8
En- Substrate
try
Product
Yield (%)b
Arylethynyl Acetates 5; General Procedure
To a mixture of PhI(OAc)2 (122.4 mg, 0.38 mmol) and Ag(SO3CF3) (9.8
mg, 0.04 mmol) or Cu(SO3CF3)2 in a dried round-bottomed flask un-
der a N2 atmosphere was added 1 (0.40 mmol) in dry toluene (3 mL);
the mixture was heated to 100 °C for 2 h. Then the mixture was al-
lowed to cool and the solvent was removed in vacuo; the residue was
purified by flash chromatography (silica gel, petroleum ether/EtOAc
20:1) to afford product 5.
OAc
N
1
8a 84
NH
OAc
OAc
2
8b 54
8c 51
N
NH
OAc
Ethyl (Z)-3-Acetoxy-3-arylacrylates 7; General Procedure
O
O
To a mixture of PhI(OAc)2 (93.4 mg, 0.29 mmol) and Ru3(CO)12 (3.7
mg, 0.006 mmol) was added 5 (0.29 mmol) in toluene (6 mL) and H2O
(5.2 mg, 0.29 mmol) and the mixture was heated to 100 °C for 2 h.
Then the mixture was allowed to cool and the solvent was removed in
vacuo; the residue was purified by flash chromatography (silica gel,
petroleum ether/EtOAc 20:1) to afford product 7.
3
OAc
N
NH
OAc
O
O
4
8d 67
8e 37
OAc
N
NH
OAc
4-Aryl-1H-imidazoles 8 and 9; General Procedure
A mixture of (NH4)2CO3 (864 mg, 9 mmol) and 2 (0.45 mmol) in
MeOH (5 mL) were stirred at 64 °C for 6 h. Then the solvent was re-
moved in vacuo and the residue was purified by flash chromatogra-
phy (silica gel, petroleum ether/EtOAc 2:1) to afford product 8.
5
N
OAc
NH
OAc
Cl
F
Cl
(Z)-1-Phenylethene-1,2-diyl Diacetate (2a)
6
8f 64
8g 41
8h 64
OAc
N
NH
Yellow liquid; yield: 64 mg (58%).
1H NMR (400 MHz, CDCl3):  = 7.74 (s, 1 H), 7.42 (s, 2 H), 7.37–7.31
(m, 3 H), 2.34 (s, 3 H), 2.21 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.7, 166.9, 135.0, 132.1, 128.7,
124.8, 124.3, 20.6, 20.5.
HRMS (ESI): m/z [M + NH4]+ calcd for C12H16NO4: 238.1074; found:
238.1072.
OAc
F
7
OAc
N
NH
OAc
Br
Br
8
OAc
N
NH
(Z)-1-(4-Methoxyphenyl)ethene-1,2-diyl Diacetate (2b)
OAc
Yellow liquid; yield: 102 mg (82%).
1H NMR (400 MHz, CDCl3):  = 7.61 (s, 1 H), 7.33 (d, J = 8.8 Hz, 2 H),
6.87 (d, J = 8.8 Hz, 2 H), 3.80 (s, 3 H), 2.31 (s, 3 H), 2.19 (s, 3 H).
O
O
13C NMR (100 MHz, CDCl3):  = 167.8, 167.0, 160.1, 135.1, 125.9,
124.6, 123.6, 114.2, 55.3, 20.6, 20.6.
a Reaction conditions: 2, (NH4)2CO3 (20 equiv), MeOH, 64 °C, 6 h.
b Isolated yields.
HRMS (ESI): m/z [M + NH4]+ calcd for C13H18NO5: 268.1179; found:
268.1176.
(400 MHz) and are referenced to TMS. LCMS/HRMS were recorded on
a Bruker Daltonics Data analysis 3.2 mass spectrometer. X-ray data
were collected on a Bruker APEX-II equipped with a CCD area detector
using Mo/K radiation. The structures were solved by direct method
using SHELXL-97.
(Z)-1-(4-Ethoxyphenyl)ethene-1,2-diyl Diacetate (2c)
Yellow liquid; yield: 100 mg (77%).
1H NMR (400 MHz, CDCl3):  = 7.61 (s, 1 H), 7.32 (d, J = 8.8 Hz, 2 H),
6.86 (d, J = 8.8 Hz, 2 H), 4.02 (q, J = 7.0 Hz, 2 H), 2.31 (s, 3 H), 2.19 (s, 3
H), 1.40 (t, J = 7.0 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.8, 167.0, 159.4, 135.1, 125.8,
124.3, 123.5, 114.7, 63.5, 20.6, 20.5, 14.7.
(Z)-1-(Het)arylethene-1,2-diyl Diacetates 2a–p, (Z)-1-Phenylprop-
1-enyl Acetate (3), and 2-Oxo-2-(3-pyridyl)ethyl Acetate (4); Gen-
eral Procedure
HRMS (ESI): m/z [M + NH4]+ calcd for C14H20NO5: 282.1336; found:
282.1336.
To a mixture of PhI(OAc)2 (394.6 mg, 1.225 mmol) and Ru3(CO)12 (6.3
mg, 0.01 mmol) in a dried round-bottomed flask under a N2 atmo-
sphere was added 1 (0.50 mmol) in dry toluene (3 mL); the mixture
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

F
Y.-t. Ruan et al.
Paper
Synthesis
Ru3(CO)12
PhI(OAc)2
R
H
2
H
N
– PhI
NH
R
R1
N
R1
R2
Ru2(CO)12Ru(OAc)2
R2
H2O
NH
R1
F
R2
G
R
HO
NH
PhI(OAc)2
Ru3(CO)12
H
R1
R2
OAc
Ru2(CO)12Ru
OAc
N
R1
H
R2
E
A
OAc
R2
Ru2(CO)12Ru
NH
AcO
NH3
R1
R2
RCHO
O2
NH2
R1
R1
R2
C
AcO
OAc
RCH2OH
D
B
(NH4)2CO3
Scheme 5 Proposed mechanism for enediol diacetates and imidazole derivatives
(Z)-1-(p-Tolyl)ethene-1,2-diyl Diacetate (2d)
HRMS (ESI): m/z [M + H]+ calcd for C12H12FO4: 239.0714; found:
239.0714.
Yellow liquid; yield: 74 mg (64%).
1H NMR (400 MHz, CDCl3):  = 7.69 (s, 1 H), 7.29 (d, J = 8.2 Hz, 2 H),
7.15 (d, J = 8.0 Hz, 2 H), 2.34 (s, 3 H), 2.32 (s, 3 H), 2.20 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.6, 166.8, 138.6, 135.0, 129.3,
124.1, 124.1, 29.6, 21.1, 20.4.
HRMS (ESI): m/z [M + H]+ calcd for C13H15O4: 235.0965; found:
(Z)-1-(4-Bromophenyl)ethene-1,2-diyl Diacetate (2h)
Yellow liquid; yield: 93 mg (63%).
1H NMR (400 MHz, CDCl3):  = 7.72 (s, 1 H), 7.48 (d, J = 8.3 Hz, 2 H),
7.27 (d, J = 7.4 Hz, 2 H), 2.33 (s, 3 H), 2.21 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.6, 166.8, 163.7, 162.0, 134.3,
235.0965.
128.3, 126.3, 126.2, 124.6, 115.8, 115.7, 20.5, 20.4.
(Z)-1-(4-Ethylphenyl)ethene-1,2-diyl Diacetate (2e)
HRMS (ESI): m/z [M + H]+ calcd for C12H12BrO4: 298.9913; found:
298.9914.
Yellow liquid; yield: 84 mg (68%).
1H NMR (400 MHz, CDCl3):  = 7.70 (s, 1 H), 7.32 (d, J = 8.2 Hz, 2 H),
7.18 (d, J = 8.2 Hz, 2 H), 2.64 (q, J = 7.6 Hz, 2 H), 2.33 (s, 3 H), 2.20 (s, 3
H), 1.22 (t, J = 7.6 Hz, 3 H).
(Z)-1-(4-Nitrophenyl)ethene-1,2-diyl Diacetate (2i)
Yellow liquid; yield: 46 mg (35%).
1H NMR (400 MHz, CDCl3):  = 7.49–7.34 (m, 4 H), 7.16–7.12 (m, 1 H),
13C NMR (100 MHz, CDCl3):  = 167.7, 166.9, 145.0, 129.4, 129.1,
3.85 (s, 3 H), 2.23 (s, 3 H).
128.4, 128.2, 124.3, 28.6, 20.6, 20.5, 15.4.
13C NMR (100 MHz, CDCl3):  = 167.4, 166.5, 147.4, 138.8, 133.1,
HRMS (ESI): m/z [M + H]+ calcd for C14H17O4: 249.1121; found:
127.5, 124.6, 124.0, 20.5, 20.4.
249.1122.
HRMS (ESI): m/z [M + H]+ calcd for C12H12NO6: 266.0659; found:
(Z)-1-(4-Chlorophenyl)ethene-1,2-diyl Diacetate (2f)
266.0661.
Yellow liquid; yield: 58 mg (46%).
(Z)-1-(3-Chlorophenyl)ethene-1,2-diyl Diacetate (2j)
1H NMR (400 MHz, CDCl3):  = 7.71 (s, 1 H), 7.33 (m, 4 H), 2.33 (s, 3 H),
Yellow liquid; yield: 47 mg (37%).
2.21 (s, 3 H).
1H NMR (400 MHz, CDCl3):  = 7.74 (s, 1 H), 7.37 (s, 1 H), 7.28 (s, 3 H),
13C NMR (100 MHz, CDCl3):  = 167.6, 166.8, 134.5, 134.1, 130.7,
2.34 (s, 3 H), 2.22 (s, 3 H).
128.9, 125.6, 125.0, 20.5, 20.5.
13C NMR (100 MHz, CDCl3):  = 167.5, 166.7, 134.8, 134.1, 133.8,
HRMS (ESI): m/z [M + H]+ calcd for C12H12ClO4: 255.0419; found:
123.0, 128.7, 125.6, 124.4, 122.3, 20.6, 20.5.
255.0420.
HRMS (ESI): m/z [M + NH4]+ calcd for C12H15ClNO4: 272.0684; found:
(Z)-1-(4-Fluorophenyl)ethene-1,2-diyl Diacetate (2g)
272.0684.
Yellow liquid; yield: 64 mg (54%).
(Z)-3-Phenylprop-1-ene-1,2-diyl Diacetate (2k)
1H NMR (400 MHz, CDCl3):  = 7.65 (s, 1 H), 7.44–7.30 (m, 2 H), 7.03
(t, J = 8.6 Hz, 2 H), 2.32 (s, 3 H), 2.20 (s, 3 H).
Yellow liquid; yield: 25 mg (22%).
1H NMR (400 MHz, CDCl3):  = 7.32–7.27 (m, 2 H), 7.25–7.18 (m, 3 H),
7.01 (s, 1 H), 3.48 (s, 2 H), 2.10 (d, J = 4.1 Hz, 6 H).
13C NMR (100 MHz, CDCl3):  = 167.5, 166.7, 134.2, 131.8, 131.2,
125.8, 125.1, 122.6, 20.5, 20.5.
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Synthesis
13C NMR (101 MHz, CDCl3):  = 168.0, 167.3, 136.3, 136.0, 129.3,
(Z)-1-Phenylprop-1-enyl Acetate (3)
128.9, 127.3, 125.1, 36.9, 20.9, 20.9.
HRMS (ESI): m/z [M + H]+ calcd for C13H15O4: 235.0965; found:
235.0966.
Yellow liquid; yield: 68 mg (78%).
1H NMR (400 MHz, CDCl3):  = 7.35 (ddd, J = 24.4, 15.2, 7.5 Hz, 5 H),
5.53 (q, J = 7.4 Hz, 1 H), 2.13 (s, 3 H), 1.80 (d, J = 7.4 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 169.7, 146.7, 134.4, 128.2, 128.2,
128.1, 114.6, 21.0, 12.8.
(Z)-1-(Naphthalen-2-yl)ethene-1,2-diyl Diacetate (2l)
Yellow liquid; yield: 85 mg (63%).
1H NMR (400 MHz, CDCl3):  = 7.88 (s, 1 H), 7.80 (d, J = 8.8 Hz, 4 H),
HRMS (ESI): m/z [M + H]+ calcd for C11H13O2: 177.0910; found:
177.0910.
7.54–7.50 (m, 1 H), 7.49–7.45 (m, 2 H), 2.39 (s, 3 H), 2.23 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.8, 166.9, 135.2, 133.3, 133.2,
2-Oxo-2-(3-pyridyl)ethyl Acetate (4)
129.4, 128.6, 128.2, 127.7, 126.7, 126.5, 125.2, 123.5, 121.7, 20.7, 20.6.
HRMS (ESI): m/z [M + H]+ calcd for C16H15O4: 271.0965; found:
271.0966.
Yellow liquid; yield: 23 mg (26%).
1H NMR (400 MHz, CDCl3):  = 9.14 (s, 1 H), 8.84 (s, 1 H), 8.22 (d, J =
8.0 Hz, 1 H), 7.47 (dd, J = 7.8, 4.8 Hz, 1 H), 5.33 (s, 2 H), 2.24 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 191.4, 170.3, 154.2, 149.0, 135.2,
129.8, 123.9, 65.9, 20.4.
(Z)-1-(3-Methoxyphenyl)ethene-1,2-diyl Diacetate (2m)
Yellow liquid; yield: 72 mg (58%).
HRMS (ESI): m/z [M + H]+ calcd for C9H10NO3: 180.0655; found:
180.0655.
1H NMR (400 MHz, CDCl3):  = 7.73 (s, 1 H), 7.26 (d, J = 8.0 Hz, 1 H),
7.00 (d, J = 7.7 Hz, 1 H), 6.91 (s, 1 H), 6.85 (dd, J = 8.2, 2.3 Hz, 1 H), 3.81
(s, 3 H), 2.32 (s, 3 H), 2.20 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.6, 166.9, 159.9, 135.0, 133.6,
129.8, 125.0, 116.8, 114.1, 110.2, 55.3, 20.6, 20.5.
(4-Methoxyphenyl)ethynyl Acetate (5a)
Yellow liquid; yield: 60 mg (80%).
1H NMR (400 MHz, CDCl3):  = 7.95 (d, J = 8.8 Hz, 2 H), 6.95 (d, J = 8.4
Hz, 2 H), 3.87 (s, 3 H), 2.56 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 196.8, 163.4, 130.5, 130.3, 129.0,
HRMS (ESI): m/z [M + H]+ calcd for C13H15O5: 251.0914; found:
251.0913.
128.2, 125.2, 113.6, 55.4, 26.3.
HRMS (ESI): m/z [M + H]+ calcd for C11H11O3: 191.0703; found:
191.0702.
(Z)-1-(2,5-Dimethoxyphenyl)ethene-1,2-diyl Diacetate (2n)
Yellow liquid; yield: 71 mg (51%).
1H NMR (400 MHz, CDCl3):  = 8.09 (s, 1 H), 6.90–6.83 (m, 2 H), 6.80
(dd, J = 8.9, 2.8 Hz, 1 H), 3.85 (s, 3 H), 3.77 (s, 3 H), 2.31 (s, 3 H), 2.20 (s,
3 H).
13C NMR (100 MHz, CDCl3):  = 167.7, 166.7, 153.4, 150.7, 131.9,
129.3, 121.4, 113.5, 113.4, 112.1, 56.0, 55.7, 20.6, 20.5.
(4-Ethoxyphenyl)ethynyl Acetate (5b)
Yellow liquid; yield: 55 mg (68%).
1H NMR (400 MHz, CDCl3):  = 7.93 (d, J = 8.8 Hz, 2 H), 6.92 (d, J = 8.8
Hz, 2 H), 4.10 (q, J = 7.0 Hz, 2 H), 2.55 (s, 3 H), 1.44 (t, J = 7.0 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 175.1, 162.9, 134.0, 130.6, 130.1,
114.6, 114.1, 63.7, 26.3, 14.6.
HRMS (ESI): m/z [M + H]+ calcd for C14H17O6: 281.1020; found:
281.1019.
HRMS (ESI): m/z [M + H]+ calcd for C12H13O3: 205.0859; found:
205.0859.
(Z)-1-(2-Thienyl)ethene-1,2-diyl Diacetate (2o)
Yellow liquid; yield: 50 mg (45%).
1H NMR (400 MHz, CDCl3):  = 7.66 (s, 1 H), 7.23 (d, J = 4.9 Hz, 1 H),
7.08 (d, J = 2.8 Hz, 1 H), 6.99–6.95 (m, 1 H), 2.31 (s, 3 H), 2.19 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.4, 166.6, 135.2, 130.8, 127.5,
125.3, 124.4, 124.2, 20.5, 20.4.
HRMS (ESI): m/z [M + H]+ calcd for C10H11O4S: 227.0373; found:
Ethyl (Z)-3-Acetoxy-3-phenylacrylate (7a)28
Yellow liquid; yield: 29 mg (43%).
1H NMR (400 MHz, CDCl3):  = 7.54–7.46 (m, 2 H), 7.41–7.35 (m, 3 H),
5.91 (s, 1 H), 4.12–4.07 (m, 2 H), 2.18 (s, 3 H), 1.17 (t, J = 7.1 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 168.2, 164.9, 160.4, 133.3, 130.1,
128.7, 127.8, 111.1, 60.4, 21.1, 14.0.
227.0372.
HRMS (ESI): m/z [M + H]+ calcd for C13H15O4: 235.0965; found:
235.0965.
(Z)-1-(3-Acetoxy-1-methyl-1H-indol-5-yl)ethene-1,2-diyl Diace-
tate (2p)
Yellow liquid; yield: 56 mg (34%).
Ethyl (Z)-3-Acetoxy-3-(p-tolyl)acrylate (7b)
1H NMR (400 MHz, CDCl3):  = 7.70 (s, 1 H), 7.59 (s, 1 H), 7.29 (d, J =
7.8 Hz, 2 H), 7.24 (s, 1 H), 3.75 (s, 3 H), 2.36 (d, J = 7.0 Hz, 6 H), 2.21 (s,
3 H).
13C NMR (100 MHz, CDCl3):  = 168.5, 167.9, 167.1, 136.3, 133.7,
129.4, 123.6, 120.1, 119.4, 118.9, 114.2, 109.7, 33.0, 21.1, 20.7.
Yellow liquid; yield: 42 mg (57%).
1H NMR (400 MHz, CDCl3):  = 7.41 (d, J = 8.1 Hz, 2 H), 7.18 (d, J = 8.0
Hz, 2 H), 5.86 (s, 1 H), 4.11 (d, J = 7.1 Hz, 2 H), 2.36 (s, 3 H), 2.18 (s, 3
H), 1.19 (t, J = 7.1 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 168.2, 165.0, 160.7, 140.4, 130.4,
128.6, 128.5, 110.4, 60.4, 21.5, 21.1, 14.0.
HRMS (ESI): m/z [M + H]+ calcd for C17H18NO6: 332.1129; found:
332.1129.
HRMS (ESI): m/z [M + H]+ calcd for C14H17O4: 249.1121; found:
249.1120.
© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

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Synthesis
Ethyl (Z)-3-Acetoxy-3-(4-methoxyphenyl)acrylate (7c)
13C NMR (100 MHz, CD3OD):  = 141.2, 135.1, 133.2, 126.9, 125.7,
122.5, 113.0, 26.0, 12.6.
Yellow liquid; yield: 56 mg (71%).
HRMS (ESI): m/z [M + H]+ calcd for C11H13N2: 173.1073; found:
173.1073.
1H NMR (400 MHz, CDCl3):  = 7.50 (d, J = 8.8 Hz, 2 H), 6.89 (d, J = 8.8
Hz, 2 H), 5.82 (s, 1 H), 4.12 (q, J = 7.1 Hz, 2 H), 3.82 (s, 3 H), 2.18 (s, 3
H), 1.21 (t, J = 7.1 Hz, 3 H).
4-(4-Chlorophenyl)-1H-imidazole (8e)29
13C NMR (100 MHz, CDCl3):  = 168.3, 165.2, 161.0, 160.4, 130.5,
Yellow solid; yield: 29 mg (37%); mp 138–139 °C.
113.2, 109.7, 60.3, 55.2, 21.1, 14.1.
1H NMR (400 MHz, DMSO-d6):  = 8.05 (s, 1 H), 7.88 (s, 2 H), 7.62–
HRMS (ESI): m/z [M + H]+ calcd for C14H17O5: 265.1071; found:
7.37 (m, 3 H).
265.1069.
13C NMR (100 MHz, DMSO-d6):  = 167.2, 136.5, 133.5, 129.9, 128.8.
Ethyl (Z)-3-Acetoxy-3-(4-ethoxyphenyl)acrylate (7d)
HRMS (ESI): m/z [M + H]+ calcd for C9H8ClN2: 179.0371; found:
Yellow liquid; yield: 51 mg (62%).
179.0370.
1H NMR (400 MHz, CDCl3):  = 7.49 (d, J = 8.8 Hz, 2 H), 6.87 (d, J = 8.8
Hz, 2 H), 5.81 (s, 1 H), 4.12 (q, J = 7.1 Hz, 2 H), 4.05 (d, J = 7.0 Hz, 2 H),
2.19 (s, 3 H), 1.41 (t, J = 7.0 Hz, 3 H), 1.21 (t, J = 7.1 Hz, 3 H).
4-(4-Fluorophenyl)-1H-imidazole (8f)32
Yellow solid; yield: 46 mg (64%); mp 127–129 °C.
13C NMR (100 MHz, CDCl3):  = 167.32, 164.23, 159.50, 159.44,
129.89, 129.47, 124.19, 113.33, 112.69, 108.67, 62.47, 59.32, 20.11,
13.73, 13.08.
HRMS (ESI): m/z [M + H]+ calcd for C15H19O5: 279.1227; found:
279.1226.
1H NMR (400 MHz, CDCl3):  = 8.95 (s, 2 H), 7.84 (s, 1 H), 7.65 (s, 2 H),
7.05 (s, 2 H).
13C NMR (100 MHz, CDCl3):  = 163.5, 161.0, 137.6, 135.5, 128.1,
128.1, 126.9, 126.8, 115.9, 115.7, 114.4.
HRMS (ESI): m/z [M + H]+ calcd for C9H8FN2: 163.0666; found:
163.0666.
4-Phenyl-1H-imidazole (8a)22
Yellow solid; yield: 65 mg (84%); mp 131–133 °C.
1H NMR (400 MHz, CDCl3):  = 7.72 (d, J = 6.3 Hz, 2 H), 7.48–7.36 (q,
J = 7.8 Hz, 3 H), 7.29–7.26 (d, J = 6.6 Hz, 2 H), 4.83 (s, 1 H).
13C NMR (100 MHz, CDCl3):  = 137.8, 135.7, 132.4, 128.7, 126.9,
124.9, 115.8.
4-(4-Bromophenyl)-1H-imidazole (8g)33
Yellow solid; yield: 40 mg (41%); mp 142–143 °C.
1H NMR (400 MHz, CDCl3):  = 7.70 (s, 1 H), 7.60 (d, J = 8.4 Hz, 2 H),
7.49 (d, J = 8.4 Hz, 2 H), 7.33 (s, 1 H).
13C NMR (100 MHz, CDCl3):  = 138.8, 135.7, 132.2, 131.8, 126.5,
120.7, 114.2.
HRMS (ESI): m/z [M + H]+ calcd for C9H9N2: 145.0760; found:
145.0761.
HRMS (ESI): m/z [M + H]+ calcd for C9H8BrN2: 222.9865; found:
222.9865.
4-(4-Methoxyphenyl)-1H-imidazole (8b)29
Yellow solid; yield: 42 mg (54%); mp 136–138 °C.
1H NMR (400 MHz, CDCl3):  = 7.76 (s, 1 H), 7.29 (dd, J = 15.2, 8.5 Hz,
4 H), 6.81 (s, 1 H), 3.82 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 159.3, 129.3, 127.3, 126.6, 125.7,
123.6, 114.6, 55.7.
HRMS (ESI): m/z [M + H]+ calcd for C10H11N2O: 175.0866; found:
175.0867.
4-(3-Methoxyphenyl)-1H-imidazole (8h)29
Yellow solid; yield: 50 mg (64%); mp 138–140 °C.
1H NMR (400 MHz, CDCl3):  = 7.65 (d, 3 H), 7.53–7.37 (m, 1 H), 6.99–
6.87 (m, 2 H), 3.83 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 160.0, 138.3, 135.4, 133.7, 129.8,
117.4, 115.2, 113.1, 110.2, 55.2.
HRMS (ESI): m/z [M + H]+ calcd for C10H11N2O: 175.0866; found:
175.0865.
4-(4-Ethoxyphenyl)-1H-imidazole (8c)30
Yellow solid; yield: 43 mg (51%); mp 139–140 °C.
4-(4-Methoxyphenyl)-2-methyl-1H-imidazole (9)
1H NMR (400 MHz, CDCl3):  = 7.66 (s, 1 H), 7.58 (d, J = 8.4 Hz, 2 H),
7.19 (s, 1 H), 6.85 (d, J = 8.5 Hz, 2 H), 3.99 (q, J = 6.9 Hz, 2 H), 1.38 (t, J =
6.9 Hz, 3 H).
13C NMR (100 MHz, CDCl3):  = 158.1, 137.8, 135.3, 126.2, 125.2,
125.1, 114.7, 63.4, 14.8.
Yellow liquid; yield: 40 mg (48%).
1H NMR (400 MHz, CDCl3):  = 7.89 (d, J = 8.8 Hz, 2 H), 6.95 (d, J = 8.7
Hz, 3 H), 3.87 (s, 3 H), 2.22 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 190.6, 170.5, 164.0, 130.8, 130.0,
127.2, 114.0, 55.5, 20.6.
HRMS (ESI): m/z [M + H]+ calcd for C11H13N2O: 189.1022; found:
189.1022.
HRMS (ESI): m/z [M + H]+ calcd for C11H13N2O: 189.1022; found:
189.1022.
4-(4-Ethylphenyl)-1H-imidazole (8d)31
Yellow solid; yield: 51 mg (67%); mp 135–137 °C.
Funding Information
1H NMR (400 MHz, DMSO-d6):  = 7.81 (s, 1 H), 7.66 (d, J = 8.0 Hz, 2
H), 7.55 (s, 1 H), 7.20 (d, J = 8.0 Hz, 2 H), 2.59 (q, J = 7.5 Hz, 2 H), 1.18
(t, J = 7.6 Hz, 3 H).
We gratefully acknowledge the financial support from the National
Natural Science Foundation of China (No. 21072131) and Sichuan
University–Lu Zhou Strategic Cooperation Projects (No. 2017 CDLZ-
S34)
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© 2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–I

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Y.-t. Ruan et al.
Paper
Synthesis
Supporting Information
(15) Xia, X.; Gu, Z.; Liu, W.; Wang, N.; Wang, H.; Xia, Y.; Gao, H.; Liu,
X. Org. Biomol. Chem. 2014, 12, 9909.
(16) Priebbenow, D. L.; Gable, R. W.; Baell, J. J. Org. Chem. 2015, 80,
4412.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1611871.
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(18) Abedi, Y.; Biffis, A.; Gava, R.; Tubaro, C.; Chelucci, G. Appl.
Organomet. Chem. 2014, 28, 512.
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