Simple and Efficient Amberlite 15-catalyzed Synthesis of Dihydroquinazolinones

Article abstract of DOI:10.1134/S1070428020080199

Abstract: The Amberlite 15 catalyzed synthesis of substituted 2,3-dihydroquinazolin-4(1H)-ones was reported. The reaction conditions were optimized by screening in different solvents and catalysts. The substrate scope of the reaction was also studied, and

Full text of DOI:10.1134/S1070428020080199

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2020, Vol. 56, No. 8, pp. 1468–1475. © Pleiades Publishing, Ltd., 2020.
Simple and Efficient Amberlite 15-catalyzed Synthesis
of Dihydroquinazolinones
a,
b,c
b
c
T. Krishnaji *, V. N. Murthy , A. Raghunadh , and L. V. Rao
a
Department of Chemistry, CHRIST (Deemed to be University), Hosur Road, Bangalore, 560029 India
b
Technology Development Centre, Custom Pharmaceutical Services, Dr. Reddy’s Laboratories Ltd., Hyderabad, 500049 India
c
Department of Chemistry, GIS, GITAM University, Visakhapatnam, 530045 India
*
e-mail: krishnaji.tadiparthi@christuniversity.in
Received March 11, 2020; revised March 22, 2020; accepted March 24, 2020
Abstract—The Amberlite 15 catalyzed synthesis of substituted 2,3-dihydroquinazolin-4(1H)-ones was reported.
The reaction conditions were optimized by screening in different solvents and catalysts. The substrate scope of the
reaction was also studied, and a plausible mechanism for the reaction was proposed.
Keywords: dihydroquinazolinones, Amberlite 15, one-pot synthesis, aza-Michael addition
DOI: 10.1134/S1070428020080199
INTRODUCTION
antidiabetic [10]. In addition, the dihydroquinazolinone
moiety is found in antidepressants, antihistamines,
and vasodilating agents. Because of their biological
activity, the synthesis of dihydroquinazolinones has
always been of great interest to researchers, and many
methods for synthesizing different derivatives of di-
hydroquinazolinone have been reported (Scheme 1)
[11–24]. However, each method has its own limitations,
such as harsh reaction conditions, use of expensive
metal catalysts, or low yields. As a continuation
The dihydroquinazolinone core is incorporated in
various biologically important natural and synthetic
compounds like Quinethazone, Benzouracil, Evo-
diamine, Fenquizone, NC1 substance 1D19143, and
Proquazone (Fig. 1). Such compounds proved to
be excellent pharmacores and exhibited numerous
therapeutic properties, including anticancer [1, 2],
antihypertension [3], anticonvulsant [4], antibacterial
[
5, 6], anti-inflammatory [7, 8], antianxietic [9], and
O
S
O
O
O
N
N
H N
NH
NH
2
O
N
N
H
N
H
O
H
Quinethazone
Benzouracil
Evodiamine
O
O
S
O
NH
H N
NH
N
H
2
O
N
N
N
H
O
Fenquizone
NC1 Substance 1D19143
Proquazone
Fig. 1. Some biologically important dihydroquinazolinone compounds.
1
468

SIMPLE AND EFFICIENT AMBERLITE 15-CATALYZED SYNTHESIS OF DIHYDROQUINAZOLINONES 1469
Scheme 1.
O
O
N
Previous Work
OH
OH
R'
+
R'–NH2
N
O
O
[20]
1
,4-Dioxane, HCl, 90–100°C
52–76%
O
O
O
N
O
+ R'–NH2
R'
N
N
Br
Water–PEG400, 4:1
6–92%
[
21]
22]
O
O
6
O
O
N
H
O
R
+
R–NH2
Ar
OH
N
[
I , K CO , water, 3 h,
2
2
3
reflux
0–94%
N
Ar
9
H
O
O
O +
O
N
H N
N
2
[23]
CeO (nano)
N
2
N
43–84%
H
Br
[24]
This Work
O
O
O
R
O
CHO
CHO
O
R
N
N
OH
COOEt
N
H
+
O
O
COOMe
N
H
N
Amberlite 15
,4-Dioxane
TBAF
Amberlite 15,
1,4-Dioxane
1
R NH2
59–74%
O
O
COOEt
O
of our earlier efforts [25–29] toward the synthesis
of various heterocyclic compounds, in the present
work we developed a simple and efficient Amberlite
RESULTS AND DISCUSSION
The retrosynthetic analysis of the proposed
molecule of dihyroquinazolinone is depicted in
Scheme 2. Accordingly, we developed our method
for the synthesizing these compounds, using the
1
5-catalyzed one-pot synthesis of α,β-unsaturated esters
of dihydroquinazolinone.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

1470
KRISHNAJI et al.
Scheme 2.
O
R
O
N
CHO
O
O
+
N
H
+ R NH2
COOMe
N
O
O
H
O
O
synthesis of dihyroquinazolinone 1a by the reaction of
-bromoisatoic anhydride (2a), cyclopropylamine (3a),
varying the amount of Amberlite 15 (0.05–0.5 wt %)
and good yields were obtained with Amberlite 15
(0.1 wt %) under similar conditions. The reaction was
further tried to undergo aza-Michael reaction with
tetrabutylammoniumfluoride (TBAF), but this attempt
may have failed due to the lack of electrophilicity at
the allylic carbon atom [24]. However the obtained α,β-
6
and (E)-methyl-4-(2-formylphenoxy)but-2-enoate (4)
as model substrates. During optimization we carried
out the reaction in various solvents and catalysts and
after fine tuning we found a good conversion rate with
Amberlite 15 in 1,4-dioxane under reflux conditions
1
13
(Table 1). However the yield of compound 1a was low,
unsaturated ester 1a was characterized by H and
C
when the reaction was conducted at room temperature.
In addition few more experiments were conducted by
NMR. Furthermore, the substrate scope of this reaction
has been studied by varying different types of amines and
Table 1. Solvent and catalyst screening for the synthesis of dihyroquinazolinone 1a
2
a
3a
1a
Entry
Solvent
Catalyst
Yield of 1a, %
1
2
3
4
5
6
7
8
9
DMSO
Amberlite 15
Amberlite 15
Amberlite 15
Amberlite 15
Amberlite 15
Amberlite 15
Amberlite 15
Acetic acid
BF ∙OEt
35
74
36
55
45
50
10
55
50
63
65
1,4-Dioxane
DMF
Acetonitrile
Toluene
THF
Ethanol
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
3
2
1
0
1
TiCl4
1
FeCl3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

SIMPLE AND EFFICIENT AMBERLITE 15-CATALYZED SYNTHESIS OF DIHYDROQUINAZOLINONES 1471
Тable 2. Substrate scope for the synthesis of dihydroquinazolinones
Comp. no.
Formula
Yield, % Comp. no.
Formula
Yield, %
1
a
65
1d
68
1
b
72
1e
74
1
c
59
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

1472
KRISHNAJI et al.
to our delight all the substrates have been well tolerated
under the given optimized reaction conditions in order
to get novel functionalized dihyroquinazolinones with
reasonably good yields (Table 2). In addition the single
crystal X-ray diffraction analysis of dihyroquinazoli-
none 1b was used to confirm the structure (for details of
the XRD experiment, see Supporting Information). The
ORTEP diagram of the molecule (Fig. 2) provides clear
evidence for the presence of the bromine atom, three
phenyl rings, and methyl groups attached to aromatic
ring.
Fig. 2. ORTEP diagram of compound 1b (the thermal
ellipsoids of non-hydrogen atoms are drawn at a 50% pro-
bability level).
Scheme 3.
O
O
O
Amberlite 15
,4-Dioxane
+
NH2
N
(1)
(2)
(3)
1
H
N
H
O
NH2
2b
3a
CHO
Amberlite 15
,4-Dioxane
N
+
NH2
1
COOMe
O
COOMe
O
4
3a
5
O
CHO
Amberlite 15
O
+
No reaction
1
,4-Dioxane
COOMe
O
N
O
H
2b
4
Scheme 4.
MeO C
O
N
O
2
R
O
O
N
H
R
NH2
CO2
R
O
N
O
H
–
–H O
H
2
N
H
O
NH2
O
O
CO Me
2
R
N
O
N
H
MeO2C
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

SIMPLE AND EFFICIENT AMBERLITE 15-CATALYZED SYNTHESIS OF DIHYDROQUINAZOLINONES 1473
1
3
To gain insight to the mechanism of the reaction, we
performed few control experiments (Scheme 3). First we
treated isatoic anhydride (2b) with cyclopropylamine
7.73 s (1H). C NMR spectrum (100 MHz, DMSO-d ),
6
δ, ppm: 5.3, 9.1, 27.9, 51.5, 66.5 (2C), 107.5, 112.6,
115.8, 116.7, 120.7, 120.9, 125.9, 128.2, 129.1, 129.8,
135.6, 143.8, 144.8, 154.5, 163.2, 165.7. Mass spectrum,
m/z: 457.10 [M + 1].
(3a), the reaction involved ring opening to form an
amide [Scheme 3, reaction (1)]. Cyclopropylamine (3a)
was further treated with aldehyde 4 to form imine 5
Methyl-(Z)-4-{2-[3-(3,4-dimethylbenzyl)-6-
bromo-4-oxo-1,2,3,4-tetrahydroquinazolin-2-yl]-
phenoxy}but-2-enoate (1b). Yellow solid, yield
2%, mp 199–201°C. H NMR spectrum (400 MHz,
DMSO-d ), δ, ppm: 2.15 s (3H), 2.17 s (3H), 3.52 d
1H, J 14.8 Hz), 3.67 s (3H), 4.73–4.86 m (2H), 5.31 d
1H, J 17.6 Hz), 5.97 d (J 13.6 Hz, 1H), 6.01 d (1H, J
.8 Hz), 6.63 d (1H, J 8.8 Hz), 6.91–6.95 m (2H), 6.99–
.01 m (2H), 7.02–7.06 m (2H), 7.11–7.14 d.d (1H, J1
.6, J 4.0 Hz), 7.22 d (1H, J 2.0 Hz), 7.29–7.35 m (2H),
.79 d (1H, J 2.4 Hz). C NMR spectrum (100 MHz,
DMSO-d ), δ, ppm: 19.0 (2C), 26.8, 46.1, 51.5, 63.8,
6.5, 107.7, 112.6, 115.6, 116.7, 120.6, 127.6, 128.9,
29.6, 130.0, 133.9, 135.3, 135.7, 136.3, 143.5, 145.3,
54.7, 161.2, 165.7. Mass spectrum, m/z: 537.20
[Scheme 3, reaction (2)]. However, no product formation
was observed, when isatoic anhydride (2b) was reacted
with aldehyde 4 [Scheme 3, reaction (3)]. The results of
the control experiments clear evidence to suggest initial
amide formation followed by imine formation and,
finally, aza-Michael addition and allowed us to propose
the reaction mechanism which is depicted in Scheme 4.
1
7
6
(
(
2
7
7
7
EXPERIMENTAL
All reactions were carried out in oven or flame-
dried glassware under an argon atmosphere, employing
standard techniques for handling air-sensitive materials.
All solvents were reagent grade. All other reagents were
used as received. Unless otherwise noted, reactions
were magnetically stirred and monitored by TLC on
Merck-Kiesegel 60 F plates. Flash chromatography
was performed on silica gel (230–400 mesh) using
distilled hexane and ethyl acetate. The yields refer to
chromatographically and spectroscopically pure com-
2
1
3
6
6
1
1
[M + 1].
Methyl-(Z)-4-(2-{4-oxo-3-[(tetrahydrofuran-2-
yl)methyl]-1,2,3,4-tetrahydroquinazolin-2-yl}-
phenoxy)but-2-enoate (1c). Yellow solid, yield
9%, mp 215–217°C. H NMR spectrum (400 MHz,
DMSO-d ), δ, ppm: 0.82–0.85 m (0.5H), 1.10–1.14 m
(1H), 1.39–1.47 m (0.5H), 1.59–1.61 m (0.5H), 1.76–
.93 m (4H), 2.75 d.d (0.5H, J 10.4, J 3.2 Hz), 3.60–
.83 m (5H), 4.01–4.10 m (2H), 4.88 s (2H), 6.17 d.d
1
13
pounds.The Hand CNMRspectrawererecordedusing
a Bruker instrument at 400 and 100 MHz, respectively,
1
5
6
from solutions in DMSO-d with tetramethylsilane as
6
internal standard.
1
3
1 2
Synthesis of dihydroquinazolin-4(1H)-ones 1a–1e
(
1H, J 9.2, J 2.6 Hz), 6.42 d (1H, J 19.6 Hz), 6.67 t
(
2
(
general procedure). To a solution of isatoic anhydride
a or 2b (1 mmol) in 1,4-dioxane (5 mL), amine 3a–3e
1 mmol) was added and stirred for 1 h at 70°C. (E)-
1 2
(
7
1H, J 9.2 Hz), 6.91 t (1H, J 7.2 Hz), 7.00–7.13 m (3H),
.23–7.33 m (3H), 7.72 s (1H). C NMR spectrum
100 MHz, DMSO-d ), δ, ppm: 15.1 (2C), 25.4, 28.8,
7.9, 59.0, 65.6, 67.2 (2C), 67.3, 77.8, 107.6, 112.6,
15.9, 116.8, 120.7, 125.9, 129.4, 129.8, 135.6, 145.2,
154.6, 162.0, 165.7. Mass spectrum, m/z: 423.10
[M + 1].
1
3
(
Methyl-4-(2-formylphenoxy)but-2-enoate 4 (1 mmol)
and Amberlite 15 (0.1 wt %) were added to the reaction
mixture at room temperature and the was stirred for 4 h
at 70°C. After completion of the reaction, the solvent in
the reaction mass was evaporated under vacuum and the
crude residue was purified by column chromatography
6
4
1
Methyl-(Z)-4-{2-[3-(4-methoxybenzyl)-6-bro-
mo-4-oxo-1,2,3,4-tetrahydroquinazolin-2-yl]-
cyclohexyloxy}but-2-enoate (1d). White solid, yield
(ethylacetate–hexane, 3 : 7) to get pure product 1a–1e.
Methyl-(Z)-4-[2-(6-bromo-3-cyclopropyl-4-oxo-
1
1
,2,3,4-tetrahydroquinazolin-2-yl)phenoxy]but-2-
59%, mp 215–217°C. H NMR spectrum (400 MHz,
enoate (1a). White solid, yield 65%, mp 221–223°C.
DMSO-d ), δ, ppm: 3.56–3.66 m (2H), 3.69 s (3H),
6
1
H NMR spectrum (400 MHz, DMSO-d ), δ, ppm:
3.72 s (3H), 4.76–4.88 m (2H), 5.28 d (1H, J 14.8 Hz),
5.97–6.03 m (2H), 6.64 d (1H, J 8.8 Hz), 6.85–6.87 m
(2H), 6.89–6.94 m (1H), 6.94–7.00 m (2H), 7.04–
7.13 m (2H), 7.22 m (1H), 7.28–7.35 m (2H), 7.79 d (J
6
0
.59–0.66 m (2H), 0.85–0.90 m (1H), 1.10–1.23 m
(1H), 2.33–2.39 m (1H), 3.69 s (3H), 4.89 s (2H), 6.08 s
(1H), 6.16 d (1H, J 16.0 Hz), 6.66 d (1H, J 8.4 Hz),
1
3
6
.89–6.93 m (1H), 7.04–7.12 m (3H), 7.29–7.31 m (3H),
2.4 Hz, 1H). C NMR spectrum (100 MHz, DMSO-d ),
6
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

1474
KRISHNAJI et al.
δ, ppm: 29.6, 45.9, 51.5, 54.9, 64.0, 66.5, 107.8, 112.6,
13.9 (2C), 115.6, 116.7, 120.9, 126.2, 127.6, 128.6
2C), 129.6, 130.3, 135.3, 135.7, 143.5, 145.3, 154.7,
58.6, 161.2, 165.7. Mass spectrum, m/z: 537.20
M + 1].
2. Cao, S.L., Feng, Y.P., Jiang, Y.Y., Liu, S.Y., Ding, G.Y.,
and Li, R.T., Bioorg. Med. Chem. Lett., 2005, vol. 15,
p. 1915.
1
(
1
[
https://doi.org/10.1016/j.bmcl.2005.01.083
3
. Chern, J.W., Tao, P.L., Wang, K.C., Gutcait, A.,
Liu, S.W., Yen, M.H., Chien, S.L., and Rong, J.K.,
J. Med. Chem., 1993, vol. 15, p. 2196.
Methyl-(Z)-4-{2-[6-bromo-3-(3-methoxypropyl)-
-oxo-1,2,3,4-tetrahydroquinazolin-2-yl]phenoxy}-
but-2-enoate (1e). White solid, yield 74%, mp 232–
4
https://doi.org/10.1021/jm00067a017
4
. Wolfe, J.F., Rathman, T.L., Sleevi, M.C., Campbell, J.A.,
and Greenwood, T.D., J. Med. Chem., 1990, vol. 33,
p. 161.
1
2
34°C. H NMR spectrum (400 MHz, DMSO-d ),
6
δ, ppm: 1.61–1.71 m (1H), 3.34–3.37 m (1H), 3.70 s
3H), 3.77–3.85 m (1H), 4.82–4.91 m (2H), 6.14–
https://doi.org/10.1021/jm00163a027
(
6
6
.17 m (2H), 6.67 d (1H, J 8.8 Hz, 1H), 6.91 d (1H, J
.8 Hz), 7.03–7.08 m (2H), 7.11 t (1H, J 4.4 Hz), 7.20 d
5. Pendergast, W., Johnson, J.V., Dickerson, S.H., Dev, I.K.,
Duch, D.S., and Smith, G.K., J. Med. Chem., 1994,
vol. 37, p. 838.
(
1H, J 2.4 Hz), 7.30–7.33 m (2H), 7.71 d (1H, J 2.0 Hz).
1
3
https://doi.org/10.1021/jm00032a019
C NMR spectrum (100 MHz, DMSO-d ), δ, ppm: 27.5,
6
6
. Kung, P.P., Casper, M.D., Cook, K.L., Wilson, L.L., Ri-
sen, L.M., Vickers, T.A., Ranken, R., Blyn, L.B.,
Wyatt, J.R., Cook, P.D., and Ecker, D.J., J. Med. Chem.,
4
1.9, 51.5, 57.8, 65.7, 66.6, 69.3, 107.7, 112.6, 116.0,
116.7, 120.8, 120.9, 126.2, 128.1, 129.2, 129.9, 135.5,
1
4
43.7, 145.3, 154.8, 161.3, 165.8. Mass spectrum, m/z:
89.20 [M + 1].
1
999, vol. 42, p. 4705.
https://doi.org/10.1021/jm9903500
CONCLUSIONS
7. Rorsch, F., Buscato, E., Deckmann, K., Schneider, G.,
Zsilavecz, M.S., Geisslinger, G., Proschak, E., and
Grosch, S., J. Med. Chem., 2012, vol. 55, p. 3792.
https://doi.org/10.1021/jm201687d
In conclusion, we have developed a simple procedure
for the preparation of different dihyroquinazolinones by
employing Amberlite 15 as a catalyst. The scope of the
reaction has been demonstrated with various amines,
and the plausible mechanism of the reaction has been
proposed based on control experiments.
8
. De Laszlo, S.E., Quagliato, C.S., Greenlee, W.J.,
Patchett, A.A., Chang, R.S.L., Lotti, V.J., Chen, T.B.,
Scheck, S.A., and Faust, K.A., J. Med. Chem., 1993,
vol. 36, p. 3207.
https://doi.org/10.1021/jm00073a024
ACKNOWLEDGMENTS
9
. Mustazza, C., Borioni, A., Sestili, I., Sbraccia, M., Ro-
domonte, A., Ferretti, R., and Giudice, M.R.D., Chem.
Pharm. Bull., 2006, vol. 54, p. 611.
The authors would like to express their gratitude to Dr.
Reddy’s Laboratory, Hyderabad, for providing facilities to
carry out this work.
https://doi.org/10.1248/cpb.54.611
FUNDING
10. Malamas, M.S. and Millen, J., J. Med. Chem., 1991,
vol. 34, p. 1492.
Dr. Krishnaji acknowledges CHRIST (Deemed to be
University), Bangalore for funding the Major Research
Project (MRP no. MRPDSC-1723).
https://doi.org/10.1021/jm00108a038
11. Comprehensive Heterocyclic Chemistry III, Katritz-
ky, A.R., Ramsden, C.A., Scriven, E.F.V., and Tay-
lor, R.J.K., Eds., Oxford: Elsevier, 2008.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
SUPPLEMENTARY MATERIALS
12. Horton, D.A., Bourne, G.T., and Smyth, M.L., Chem. Rev.,
2
003, vol. 103, p. 893.
https://doi.org/10.1021/cr020033s
Supplementary materials are available for this article at
https://doi.org/10.1134/S1070428020080199 and are acces-
sible for authorized users.
1
1
3. Mhaske, S.B. and Argade, N.P., Tetrahedron, 2006,
vol. 62, p. 9787.
https://doi.org/10.1016/j.tet.2006.07.098
4. Lee, S.H., Son, J.-K., Jeong, B.S., Jeong, T.-C.,
Chang, H.W., Lee, E.-S., and Jahng, Y., Molecules,
2008, vol. 13, p. 272.
REFERENCES
1
. Jiang,J.B.,Hesson,D.,Dusak,B.,Dexter,D.,Kang,G.,and
Hamel, E., J. Med. Chem., 1990, vol. 33, p. 1721.
https://doi.org/10.1021/jm00168a029
https://doi.org/10.3390/molecules13020272
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020

SIMPLE AND EFFICIENT AMBERLITE 15-CATALYZED SYNTHESIS OF DIHYDROQUINAZOLINONES 1475
1
1
1
1
1
2
2
5. Rueping, M., Antonchick, A.P., Sugiono, E., and Grena-
der, K., Angew. Chem., Int. Ed., 2009, vol. 48, p. 908.
https://doi.org/10.1002/anie.200804770
6. Abdel-Jalil, R.J., Voelter, W., and Saeed, M., Tetrahedron
Lett., 2004, vol. 45, p. 3475.
https://doi.org/10.1016/j.tetlet.2004.03.003
7. Davoodnia, A., Allameh, S., Fakhari, A.R., and Tavakoli-
Hoseini, N., Chin. Chem. Lett., 2010, vol. 21, p. 550.
https://doi.org/10.1016/j.cclet.2010.01.032
8. Jianguang, Z. and Jie, F., J. Org. Chem., 2011, vol. 76,
p. 7730.
24. Murthy, V.N., Satish, N.P., Krishnaji, T., Madhubabu, M.V.,
Subba Rao, J., Rao, L.V., and Raghunadh, A., RSC Adv.,
2
018, vol. 8, p. 22331.
https://doi.org/10.1039/C8RA03308K
5. Kumar, S.P., Murthy, V.N., Ganesh, K.R., Rao, G.S.,
Krishnaji, T., and Raghunadh, A., ChemistrySelect, 2018,
vol. 3, p. 6836.
2
https://doi.org/10.1002/slct.201800695
26. Jaganmohan, C., Kumar, K.P.V., Reddy, G.S., Mo-
hanty, S., Kumar, J., Rao, B.V., Krishnaji, T., and Rag-
hunadh, A., Syn. Comm., 2018, vol. 2, p. 168.
https://doi.org/10.1021/jo201054k
9. Cheng, X., Vellalath, S.K., Goddard, R., and List, B.,
J. Am. Chem. Soc., 2008, vol. 130, p. 15786.
https://doi.org/10.1021/ja8071034
0. Murthy, V.N., Nikumbh, S.P., Kumar, S.P., Chiranjeevi, Y.,
Rao, L.V., Raghunadh, A., Synlett, 2016, vol. 27, p. 2362.
https://doi.org/10.1055/s-0035-1562465
1. Madhubabu, M.V., Shankar, R., Rajeshwar Reddy,
G., Srinivasa Rao, T., Basaveswara Rao, M.V., and
Raghunadh, A., Tetrahedron Lett., 2016, vol. 57, p. 5033.
https://doi.org/10.1016/j.tetlet.2016.09.094
2. Seyedeh, B.A. and Javad, A., Tetrahedron Lett., 2016,
vol. 57, p. 181.
https://doi.org/10.1016/j.tetlet.2015.11.090
3. Zhang, J., Zhao, J., Wang, L., Liu, J., Ren, D., and
Ma, Y., Tetrahedron, 2016, vol. 72, p. 936.
https://doi.org/10.1080/00397911.2017.1391291
2
7. Venkateshwarlu, R., Murthy, V.N., Krishnaji, T., Sa-
tish, P.N., Rajesh, J., Vidavalur, S., Madhu babu, M.V.,
Rama Mohana, H., and Raghunadh, A., RSC Adv., 2020,
vol. 10, p. 9486.
https://doi.org/10.1039/C9RA09567E
2
2
8. Jaganmohan, C., Vinay, K.P., Venkateshwarlu, R., Mohan-
ty, S., Kumar, J., Venkateswara Rao, B., Raghunadh, A.,
and Krishnaji, T., Syn. Comm., 2020, vol. 50, p. 2163.
https://doi.org/10.1080/00397911.2020.1768406
9. Akula, R., Krishnaji, T., Suresh Babu, M., Murthy, V.N.,
Rao, L.V., and Kumar, U.K.S., SynOpen, 2020, vol. 4,
p. 55.
2
2
https://doi.org/10.1016/j.tet.2015.12.055
https://doi.org/10.1055/s-0040-1707203
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 8 2020