One-pot synthesis of 3-substituted-4H-[1,2,3] triazolo[5,1-c][1,4]oxazin-6(7H)-ones from propargyl alcohols, chloroacetyl chloride, and sodium azide

Article abstract of DOI:10.1177/1747519820948355

An efficient, one-pot synthesis of 3-substituted-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-ones is developed via sequential esterification, substitution, and 1,3-dipolar cycloaddition processes of various propargyl alcohols, chloroacetyl chloride, and so

Full text of DOI:10.1177/1747519820948355

948355CHL0010.1177/1747519820948355Journal of Chemical ResearchZhang et al.
research-article2020
Research Paper
Journal of Chemical Research
1–4
© The Author(s) 2020
Article reuse guidelines:
sagepub.com/journals-permissions
One-pot synthesis of 3-substituted-4H-[1,2,3]
triazolo[5,1-c][1,4]oxazin-6(7H)-ones from
propargyl alcohols, chloroacetyl chloride, and
sodium azide
https://doi.org/10.1177/1747519820948355
DOI: 10.1177/1747519820948355
journals.sagepub.com/home/chl
Xiao-Lan Zhang1,2, Mei-Hong Wei1, Jun-Min Chen1,
Shou-Ri Sheng1 and Xiao-Ling Liu1
Abstract
An efficient, one-pot synthesis of 3-substituted-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-ones is developed via
sequential esterification, substitution, and 1,3-dipolar cycloaddition processes of various propargyl alcohols, chloroacetyl
chloride, and sodium azide. This method provides a variety of novel 1,2,3-triazole-fused oxazinones and has several
advantages including simple operation, high efficiency, and good-to-excellent product yields (80%–95%) without the
need to isolate the ester and azide intermediates.
Keywords
3-substituted-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-ones, chloroacetyl chloride, one-pot procedure, propargyl
alcohols, sodium azide
Date received: 9 May 2020; accepted: 18 July 2020
R
CH2OH
R
N
R
O
NaN3
DMF
Et3N
DMF
O
O
+
N
N
O
ClCOCH2Cl
Cl
pharmaceuticals and agrochemicals.14,15 Thus, it is not
surprising that the incorporation of an oxazinone ring
into poly-heterocyclic structures might result in novel
and potentially biologically active compounds. To our
knowledge, several heterocyclic ring-fused oxazinones
such as pyrido[3,2-d][1,2]oxazinones,16 [3,4-d][1,2] oxa-
zin-4-ones, thieno[3,4-d][1,2]oxazin-4-ones, and pyrido [3,2-
d][1,2]oxazin-5-ones17 have been documented. However,
Introduction
1,2,3-Triazoles are a very important class of heterocyclic
compounds, which are widely applied in pharmaceuticals,
agrochemicals, dyes, corrosion inhibitors, biochemicals,
polymers, and functional materials.1–5 Up to now, many
methods based on the azide–alkyne cycloaddition have been
developed to prepare 1,2,3-triazole derivatives.6–11 Among
them, one-pot multicomponent reactions in which azides are
prepared in situ prior to the cycloaddition are an attractive
approach, as time-consuming work-up and purification pro-
tocols are minimized and they avoid the handling of poten-
tially explosive azides. Poly-heterocyclic compounds may
be used as potential drug candidates because they might
exhibit different modes of biological activities compared
with their parent ring systems.12 1,2,3-Triazoles fused with
other heterocyclic moieties have also gained significant
importance due to their diverse array of pharmaceutically
active functionalities, exhibiting antitumor, antiprolifera-
tive, antivirus, and glycosidase inhibitory activities.13
1Key Laboratory of Functional Small Organic Molecule, Ministry of
Education, Jiangxi Normal University, Nanchang, P.R. China
2College of Chemistry and Chemical Engineering, Shangrao Normal
University, Shangrao, P.R. China
Corresponding authors:
Jun-Min Chen, Key Laboratory of Functional Small Organic Molecule,
Ministry of Education, Jiangxi Normal University, Nanchang 330022,
Jiangxi, P.R. China.
Email: jxnuchenjm@163.com
Xiao-Ling Liu, Key Laboratory of Functional Small Organic Molecule,
Ministry of Education, Jiangxi Normal University, Nanchang 330022,
Jiangxi, P.R. China.
The 1,4-oxazinone framework is a well-known hetero-
cyclic moiety, which is widely present in numerous bio-
logically active compounds with potential applications in Email: liuxiaoling@jxnu.edu.cn
Creative Commons Non Commercial CC BY-NC: This article is distributed under the terms of the Creative Commons
Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use,
reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and
Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).

2
Journal of Chemical Research 00(0)
Table 1. Preparation of compounds 3a–l via one-pot three-
Et3N
Ph
O
step reactions.a
O
Ph
CH2OH
+
O
Cl
O
Cl
DMF, rt
95%
Cl
Entry
R
Product (3)
Yield (%)b
1a
2a
1
2
3
4
5
6
7
8
C6H5 (1a)
3a
3b
3c
3d
3e
3f
3g
3h
3i
91
93
88
91
86
90
86
82
84
85
83
95
Ph
N
NaN3, DMF
100oC, 6 h
4-MeOC6H4 (1b)
2-MeOC6H4 (1c)
4-MeC6H4 (1d)
2-MeC6H4 (1e)
3-MeC6H4 (1f)
4-BrC6H4 (1g)
2-BrC6H4 (1h)
3-BrC6H4 (1i)
4-ClC6H4 (1j)
2-ClC6H4 (1k)
Me (1l)
Ph
O
O
N3
N
N
O
2a'
3a
Scheme 1. Synthesis of bicyclic triazole 3a from 3-phenyl-2-
propyn-1-ol (1a).
9
10
11
12
3j
3k
3l
little work relating to the synthesis or bioactivities of the
triazolo-fused oxazinones has been reported.18–20 Thus,
the development of simple and efficient methods for the
construction of the triazolo-fused oxazinones that avoid
the isolation of organic azide intermediates are highly
desirable. Herein, we report a facile, one-pot, three-step
protocol for the synthesis of 3-substituted-4H-[1,2,3]
triazolo[5,1-c][1,4]oxazin-6(7H)-ones involving in situ
generation and intramolecular 1,3-dipolar cycloaddition
of propargylic azidoacetates. The latter were obtained
sequential esterification of propargylic alcohols with
chloroacetyl chloride followed by nucleophilic displace-
ment with sodium azide.
aReaction conditions: 1 (1.0mmol), chloroacetyl chloride (1.2mmol),
Et3N (3.0mmol), NaN3 (2.0mmol), and solvent (10mL).
bIsolated yield.
Second, encouraged by the above results, we attempted
the preparation of 3a through a one-pot, three-step proce-
dure starting from 1a. To our delight, the one-pot synthesis
of 3a could be also realized by treating 1a with chloroacetyl
chloride in DMF at room temperature using triethylamine
as the base for 1 h, followed by the addition of sodium
azide. After stirring for 5 h at 100 °C, the desired triazolo-
fused oxazinone 3a was isolated in 91% yield (Table 1,
entry 1) as the exclusive product in three-steps.
Results and discussion
Finally, to explore the generality and scope of the reac-
tion (Scheme 2), the reaction was carried out with various
propargyl alcohols under the optimized reaction conditions
and the results are summarized in Table 1.
As observed in Table 1, for all substrates, the reaction
proceeded smoothly and the corresponding products 3a–l
were obtained in good-to-excellent yields. In addition, no
significant difference in the reactivity was found for the
examined aromatic propargyl alcohols, including those
containing chloro, bromo, methyl, or methoxy substituents
on the phenyl ring (Table 1, entries 2–11). It is noteworthy
that a higher yield was obtained when R was a methyl
group rather than an aryl group (Table 1, entry 12).
As outlined in Scheme 1, our initial exploratory efforts
were devoted to the synthesis of 3-phenyl-4H-[1,2,3]
triazolo[5,1-c][1,4]oxazin-6(7H)-one (3a) from 3-phenyl-
2-propyn-1-ol (1a), which was treated with chloroacetyl
chloride (1.2 equiv.) in the presence of triethylamine to give
3-phenyl-propargyl chloroacetate (2a) in 95% yield. Next,
the reaction of 2a with an excess amount of sodium azide (2
equiv.) in N,N-dimethylformamide (DMF) at 100°C for 1h
formed the intermediate (2a’). Without isolation of the
azide 2a’, the reaction mixture was further heated for 4 h,
where upon the latter underwent a constrained intramolecu-
lar 1,3-dipolar cycloaddition with the alkyne moiety to fur-
nish regioselectively the desired bicyclic compound 3a in
95% yield as the only product. The formation of compound
3a was confirmed by nuclear magnetic resonance (NMR)
spectroscopy. The 1H NMR spectrum of 3a has two charac-
teristic singlets corresponding to the methylene protons at
3.90 (–OCH2–) and 4.99 (–COCH2–) ppm, respectively. In
the 13C NMR spectrum, the ester carbonyl carbon appeared
at 167.8 ppm, and the aromatic carbon signals appeared in
the range of 131.9–121.9 ppm.
In summary, an efficient, one-pot, three-step protocol
has been developed for the preparation of 3-substituted-
4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-ones
with
good-to-excellent yields via sequential esterification, sub-
stitution and 1,3-dipolar cycloaddition reactions. This pro-
cedure should make it possible to rapidly prepare compound
libraries for drug discovery programs as it avoids time-con-
suming and costly isolation and purification protocols
involving synthetic intermediates.
Not surprisingly, when 1a was reacted with chloroacetyl
chloride, other solvents such as toluene, dichloromethane,
tetrahydrofuran (THF), DMF, dimethyl sulfoxide (DMSO),
or 1,4-dioxane were also applicable for this transformation,
Experimental
and all gave excellent results. However, among the various Propargyl alcohols 1a–k were prepared in good yields by
solvents screened, non-polar or weak polar solvents were the reactions of aryl bromides with propargyl alcohol in the
not suitable for the subsequent substitution and 1,3-dipolar presence of dichlorobis(triphenylphosphine)palladium
cycloaddition reactions, while the aprotic, highly polar sol- according to a reported method.21 Other reagents and sol-
vent DMF provided the best results.
vents were purchased from commercial suppliers and were

Zhang et al.
3
3-(4-Methoxyphenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3b): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.38 (d, J = 8.4Hz, 2 H), 6.82 (d, J = 8.4Hz, 2
H), 4.98 (s, 2 H), 3.91 (s, 2 H), 3.75 (s, 3 H); 13C NMR
(100MHz, CDCl3): δ 167.9, 160.1, 133.5, 114.0, 113.7,
87.2, 80.9, 55.2, 54.0, 50.0; IR (film): 3053, 2944, 2543,
2113, 1749, 1608, 1505, 1160, 1038, 832cm−1; Anal. calcd
for C12H11N3O3: C, 58.77; H, 4.52; N, 17.13; found: C,
58.94; H, 4.63; N, 17.20%.
R
N
1. Et3N, DMF, rt
2. NaN3, 100oC
O
O
R
CH2OH
+
Cl
Cl
N
O
N
O
1
3
Acylation
Cycloaddition
R
O
R
O
Substitution
O
N3
Cl
2
2'
3-(2-Methoxyphenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3c): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.42 (dd, J = 7.5, 1.4Hz, 1 H), 7.34–7.30 (m, 1
H), 6.93–6.87 (m, 2 H), 5.08 (s, 2 H), 3.95 (s, 2 H), 3.87 (s,
3 H); 13C NMR (100MHz, CDCl3): δ 1678, 160.3, 134.0,
130.6, 128.9, 120.5, 110.7, 85.8, 83.8, 55.8, 54.3, 50.2; IR
(film): 3042, 2970, 1730, 1605, 1463, 1370, 1262, 1130,
1068, 755cm−1; Anal. calcd for C12H11N3O3: C, 58.77; H,
4.52; N, 17.13; found: C, 58.96; H, 4.71; N, 17.23%.
Scheme 2. One-pot, three-step synthesis of triazolo-fused
oxazinone derivatives 3.
used without further purification. The reaction progress
was monitored by thin-layer chromatography (TLC) on
GF254 silica gel analytical aluminum plates, and the prod-
ucts were visualized under UV spectrophotometer. Column
chromatography was performed using silica gel 60 (250–
004 mesh) with petroleum ether (bp. 60–90 °C)/ethyl ace-
tate as eluent. Melting points were measured using a
3-(4-Methylphenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3d): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.33 (d, J = 8.0Hz, 2 H), 7.09 (d, J = 7.8Hz, 2
H), 4.98 (s, 2 H), 3.89 (s, 2 H), 2.30 (s, 3 H); 13C NMR
(100MHz, CDCl3): δ 167.8, 139.3, 131.9, 129.2, 118.8,
87.5, 81.5, 54.0, 50.1, 21.4; IR (film): 3035, 2978, 1741,
1610, 1508, 1375, 1164, 1041, 828cm−1; Anal. calcd for
C12H11N3O2: C, 62.87; H, 4.84; N, 18.33; found: C, 62.99;
H, 4.98; N, 18.47%.
1
Beijing-Taike X-4 apparatus without correction. H NMR
and 13C NMR spectra were recorded in deuterated CDCl3
on a Bruker Avance 400 MHz NMR spectrometer, operat-
ing at 400 and 100MHz, respectively. Fourier-transform
infrared spectroscopy (FTIR) analyses were performed
with a Perkin-Elmer SP One FTIR spectrophotometer.
Microanalyses were performed with a Carlo Erba 1106
Elemental Analyzer.
3-(2-Methylphenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3e): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.41 (d, J = 7.6Hz, 1 H), 7.23–7.17 (m, 2 H),
7.11 (t, J = 7.4Hz, 1 H), 5.02 (s, 2 H), 3.89 (s, 2 H), 2.41
(s, 3 H); 13C NMR (100MHz, CDCl3): δ 167.8, 140.7,
132.3, 129.6, 129.1, 125.6, 121.7, 86.3, 85.9, 54.1, 50.2,
20.6; IR (film): 3037, 2984, 1740, 1612, 1510, 1165, 1042,
742cm−1; Anal. calcd for C12H11N3O2: C, 62.87; H, 4.84; N,
18.33; found: C, 62.94; H, 4.96; N, 18.45%.
General procedure for the preparation of
3-substituted-4H-[1,2,3]triazolo[5,1-c][1,4]
oxazin-6(7H)-ones
Propargyl alcohol 1a–l (1.0mmol) was dissolved in dry
DMF (10mL) and then cooled to 0°C. Anhydrous Et3N
(0.3g, 3 equiv.) and chloroacetyl chloride (0.14g; 1.2
mmol) were added, and the reaction mixture was allowed
to stir at room temperature. After the disappearance of the
starting materials (monitored by TLC), sodium azide
(0.13g, 2.0 mmol) was added to the reaction mixture. The
reaction was heated to 100°C, stirred for 5h and then
cooled to room temperature. The reaction mixture was
treated with water (10mL) and extracted with ethyl ace-
tate (3×10mL). The combined organic extract was
washed with brine, dried over anhydrous sodium sulfate,
filtered and concentrated in vacuo. The residue was sub-
jected to flash column chromatography with petroleum
ether/ethyl acetate (5/1) as eluent to afford the desired
product 3a–l.
3-(3-Methylphenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3f): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.31 (s, 1 H), 7.24 (d, J = 7.2Hz, 1 H), 7.17 (t, J
= 8.0Hz, 1 H), 7.11 (d, J = 7.6Hz, 1 H), 4.97 (s, 2 H), 3.88
(s, 2 H), 2.28 (s, 3 H); 13C NMR (100MHz, CDCl3): δ
167.8, 138.1, 132.5, 129.9, 129.0, 128.3, 121.7, 87.5, 81.8,
53.9, 50.1, 21.1; IR (film): 3033, 2987, 1737, 1610, 1508,
1168, 1040, 865, 780, 728cm−1. Anal. calcd for C12H11N3O2:
C, 62.87; H, 4.84; N, 18.33; found: C, 62.96; H, 4.97; N,
18.48%.
3-(4-Bromophenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
3-Phenyl-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-one 6(7H)-one (3g): Yellow liquid; 1H NMR (400MHz,
(3a): Yellow liquid; 1H NMR (400MHz, CDCl3): δ 7.46– CDCl3): δ 7.45 (d, J = 8.4Hz, 2 H), 7.30 (d, J = 8.4Hz, 2
7.44 (m, 2 H), 7.34–7.27 (m, 3 H), 4.99 (s, 2 H), 3.90 (s, 2 H), 5.00 (s, 2 H), 3.95 (s, 2 H); 13C NMR (100MHz,
H); 13C NMR (100MHz, CDCl3): δ 167.8, 131.9, 129.0, CDCl3): δ 167.7, 133.4, 131.7, 123.4, 120.8, 86.2, 83.2,
128.4, 121.9, 87.3, 82.1, 53.9, 50.1; IR (film): 3025, 2965, 53.8, 50.2; IR (film): 3068, 2968, 1760, 1568, 1285, 1173,
1727, 1607, 1466, 1368, 1269, 1136, 1065, 742cm−1. Anal. 1035, 820, 690, 558cm−1; Anal. calcd for C11H8N3O2Br: C,
calcd for C11H9N3O2: C, 61.39; H, 4.22; N, 19.53; found: C, 44.92; H, 2.74; N, 14.29; found: C, 45.13; H, 2.92; N,
61.50; H, 4.35; N, 19.42%.
14.48%.

4
Journal of Chemical Research 00(0)
3-(2-Bromophenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3h): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.48 (dd, J = 8.0, 0.8Hz, 1 H), 7.38 (dd, J = 7.6,
1.6Hz, 1 H), 7.17 (dd, J = 7.4, 1.0Hz, 1 H), 7.10 (dd, J =
7.8, 1.8Hz, 1 H), 4.97 (s, 2 H), 3.87 (s, 2 H); 13C NMR
(100MHz, CDCl3): δ 167.7, 133.8, 132.5, 130.2, 127.1,
125.7, 124.0, 86.5, 85.7, 53.9, 50.2; IR (film): 3066, 2965,
Funding
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: This
work was supported by the National Natural Science Foundation
of China (No. 21762022), the Research Program of Jiangxi
Province Department of Education (Nos GJJ160289 and
GJJ11380), the Opening Foundation of Key Laboratory of
1756, 1565, 1284, 1175, 1032, 780, 675, 555cm−1; Anal. Functional Small Organic Molecules of Ministry of Education
(Nos KLFS-KF-201912 and KLFS-KF-201928), and the Opening
Foundation of National Research Center for Carbohydrate
Synthesis (No. GJDTZX-KF-201414).
calcd for C11H8N3O2Br: C, 44.92; H, 2.74; N, 14.29; found:
C, 45.19; H, 2.90; N, 14.45%.
3-(3-Bromophenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3i): Yellow liquid; 1H NMR (400MHz, ORCID iD
CDCl3): δ 7.58 (s, 1 H), 7.45 (d, J = 8.0Hz, 1 H), 7.37–
7.35 (m, 1 H), 7.16 (t, J = 8.0Hz, 1 H), 5.00 (s, 2 H), 3.95
(s, 2 H); 13C NMR (100MHz, CDCl3): δ 167.7, 134.6,
132.2, 130.5, 129.9, 123.8, 122.1, 85.6, 83.5, 53.7, 50.1; IR
(film): 3065, 2963, 1758, 1562, 1281, 1178, 1029, 786,
674, 553cm−1; Anal. calcd for C11H8N3O2Br: C, 44.92; H,
2.74; N, 14.29; found: C, 45.14; H, 2.92; N, 14.41%.
Xiao-Ling Liu
https://orcid.org/0000-0002-1733-9946
Supplemental material
Supplemental material for this article is available online.
References
1. Moses JE and Moorhouse AD. Chem Soc Rev 2007; 36:
1249.
2. Mamidyala SK and Finn MG. Chem Soc Rev 2010; 39:
1252.
3. Thirumurugan P, Matosiuk D and Jozwiak K. Chem Rev
2013; 113: 4905.
4. Schulze B and Schubert US. Chem Soc Rev 2014; 43:
2522.
3-(4-Chlorophenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3j): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.36 (dd, J = 6.8, 2.0Hz, 2 H), 7.28 (dd, J = 6.8,
2.0Hz, 2 H), 5.00 (s, 2 H), 3.94 (s, 2 H); 13C NMR
(100MHz, CDCl3): δ 167.8, 135.1, 133.2, 128.7, 120.3,
86.1, 83.1, 53.8, 50.1; IR (film): 3056, 2975, 1760, 1568,
1170, 1042, 825, 780, 674cm−1; Anal. calcd for
C11H8N3O2Cl: C, 52.92; H, 3.23; N, 16.83; found: C, 53.12;
H, 3.52; N, 16.94%.
5. Kantheti S, Narayan R and Raju KVSN. RSC Adv 2015; 5:
3687.
6. Meldal M and Tomøe CW. Chem Rev 2008; 108: 2952.
7. Meldal M and Tomøe CW. Chem Soc Rev 2010; 39: 1280.
8. Hein JE and Fokin VV. Chem Soc Rev 2010; 39: 1302.
9. Sokolova NV and Nenajdenko VG. RSC Adv 2013; 3: 16212.
10. Hassan S and Müller TJJ. Adv Synth Catal 2015; 357: 617.
3-(2-Chlorophenyl)-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-
6(7H)-one (3k): Yellow liquid; 1H NMR (400MHz,
CDCl3): δ 7.47 (dd, J = 7.6, 1.6Hz, 1 H), 7.38 (d, J =
8.0Hz, 1 H), 7.28–7.20 (m, 2 H), 5.06 (s, 2 H), 3.95 (s, 2 11. Chen Z, Cao G, Song J, et al. Chin J Chem 2017; 35: 1797.
H); 13C NMR (100MHz, CDCl3): δ 167.7, 136.1, 133.7,
12. Horton DA, Bourne GT and Smythe ML. Chem Rev 2003;
103: 893.
130.1, 129.3, 126.5, 121.8, 87.2, 83.9, 53.8, 50.2; IR (film):
3061, 2982, 1755, 1600, 1558, 1165, 1040, 739cm−1; Anal.
13. Tron GC, Pirali T, Billington RA, et al. Med Res Rev 2008;
28: 278.
calcd for C11H8N3O2Cl: C, 52.92; H, 3.23; N, 16.83; found:
C, 53.18; H, 3.54; N, 16.92%.
14. Shukla A, Nycholat C, Subramanian MV, et al. J Agric Food
Chem 2004; 52: 5144.
15. Isshiki Y, Kohchi Y, Iikura H, et al. Bioorg Med Chem Lett
3-Methyl-4H-[1,2,3]triazolo[5,1-c][1,4]oxazin-6(7H)-
1
one (3l): Yellow liquid; H NMR (400MHz, CDCl3): δ
2011; 21: 1795.
4.98 (s, 2 H), 3.87 (s, 2 H), 2.38 (3 H); 13C NMR (100MHz,
16. Frackenpohl J, Adelt I, Antonicek H, et al. Bioorg Med Chem
2009; 17: 4160.
17. Qu J and Cheng Y. Tetrahedron 2013; 69: 888.
CDCl3): δ 167.5, 85.7, 83.0, 53.9, 49.9, 12.2; IR (film):
3035, 2968, 1742, 1602, 1550, 1385, 1166, 1042cm−1;
Anal. calcd for C6H7N3O2: C, 47.06; H, 4.61; N, 27.44; 18. Balducci E, Bellucci L, Petricci E, et al. J Org Chem 2009;
74: 1314.
found: C, 47.28; H, 4.85; N, 27.62%.
19. Moliner FD, Crosignani S, Galatini A, et al. ACS Comb Sci
2011; 13: 453.
20. Wu FS, Tong W, Liang Y, et al. RSC Adv 2016; 6: 63855.
21. Guan JT, Weng TQ, Yu G-A, et al. Tetrahedron Lett 2007;
48: 7129.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.