Fast highly efficient 'on-solvent' non-catalytic cascade transformation of benz-aldehydes and 4-hydroxycoumarin into bis(4-hydroxycoumarinyl)arylmethanes

Article abstract of DOI:10.24820/ark.5550190.p010.023

Non-catalytic cascade reaction of benzaldehydes and two equivalents of 4-hydroxycoumarin initiated by reflux in propanol results in the fast (15 min) and efficient formation of substituted tetrahydro-1H-xanthen-1-ones in 93-98% yields. The developed fast

Full text of DOI:10.24820/ark.5550190.p010.023

The Free Internet Journal
for Organic Chemistry
Paper
Archive for
Organic Chemistry
Arkivoc 2017, part iii, 121-129
Fast highly efficient ‘on-solvent’ non-catalytic cascade transformation of benz-
aldehydes and 4-hydroxycoumarin into bis(4-hydroxycoumarinyl)arylmethanes
Michail N. Elinson,* Anatoly N. Vereshchagin, and Olga O. Sokolova
Department of Organic Chemistry, N. D. Zelinsky Institute of Organic Chemistry,
Leninsky prospect 47, 119991 Moscow, Russia
E-mail: elinson@ioc.ac.ru
Dedicated to Prof. Oleg A. Rakitin on the occasion of his 65th birthday
Received 01-17-2017
Accepted 03-04-2017
Published on line 05-10-2017
Abstract
Non-catalytic cascade reaction of benzaldehydes and two equivalents of 4-hydroxycoumarin initiated by reflux
in propanol results in the fast (15 min) and efficient formation of substituted tetrahydro-1H-xanthen-1-ones in
93–98%
yields.
The
developed
fast
cascade
approach
to
the
substituted
bis(4-
hydroxycoumarinyl)arylmethanes, which are known as medicinally relevant substances with anti-HIV,
antibiotic, anti-inflammatory and anti-cancer activity, is beneficial from the viewpoint of diversity-oriented
large-scale processes and represents fast, efficient and environmentally benign synthetic concept for cascade
reactions strategy.
Keywords: Non-catalytic, carbanions, 4-hydroxycoumarin, bis(4-hydroxycoumarinyl)aryl-methanes, green
chemistry
DOI: https://doi.org/10.24820/ark.5550190.p010.023
Page 121
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
Introduction
Cascade reactions are known as powerful method to construct molecular complexity from readily available
1,2
starting materials by combining two or more reactions into a single transformation. Cascade reactions
forming a number of bonds by one operation are useful for the creation of polycyclic and spirocyclic
3
compounds. Thus, cascade reactions are of increasing importance in modern organic chemistry. This is not
only due to the need for the more efficient and less labour-intense methodologies for the synthesis of
pharmaceuticals and other fine chemicals, but also because of the increasing importance of the environmental
4,5
considerations.
Coumarins or benzopyran-2-ones, are one of the most known oxygen heterocyclic compounds which are
6
efficiently studied from their discovery up to our days. The great interest to these compounds is due to their
7
,8
9
10
11
12
known anti-cancer,
antidiabetic and antidepressant activities.
-Hydroxycoumarins are important class of biologically active substances in nature and in medicine. They
exhibit sufficient anticoagulant activity and among them, there are some drugs – Warfarin and
anti-inflammatory, antihyperlipidemic
anticholinesterase,
antinociceptive,
13
4
14
Acenocoumarol. Many of them display important pharmacological effects, as anti-inflammatory , anti-
cancer, anti-HIV and antiviral agents.
15
16
Dicoumarol (a coumarin anticoagulant, 3,3′-methylenebis[4-hydroxycoumarin]) is a competitive NADH
quinone oxidoreductase (NQO1) inhibitor, and used as an anticoagulant by interfering with the metabolism of
1
7
vitamin K. Dicoumarol is known as microtubule stabilizing natural product that is synergistic with Taxol.
18
Dicoumarol also potentiates cisplatin-induced apoptosis urogenital cancer cell lines. Dicoumarol and its
19,20
21
derivatives display wide range of pharmacological activity such as anti-HIV,
antibiotic, antitumor and
22
anti-inflammatory.
Dicoumarols are generally synthesized by cascade reaction of two equivalents of 4-hydroxycoumarin and
different aldehydes. In the recent years, several methods have been reported to accomplish this reaction. In
2
3
24
25
26
most of them, different catalysts are used, such as molecular iodine, DBU, piperidine, MnCl , propane-
2
27
28
1
,2,3-triyltris(hydrogen sulfate),
tetrabutylammonium bromide (TBAB),
hexatungstate, dodecylbenzene sulfonic acid (DBSA), silica chloride nanoparticles (nano SiO
tetrabutylammonium
29
30
31
2
Cl). Refluxing
32
33
for long time (5-6 hours) in ethanol or acetic acid are also known.
Although all this procedures for the synthesis of corresponding dicoumarols have their merits, but all of
them suffer from some drawbacks, such as unsufficient yields, prolonged reaction times, the use of costly
reagents or catalysts. The recovery of the catalyst and the procedure of isolation pure dicoumarols may also
be complicated in many cases.
Recently we have accomplished some non catalytic cascade and multicomponent reactions of carbonyl
3
4-38
compounds and C-H acids.
Considering our results on the non-catalytic multicomponent and cascade
34-38
transformation of C-H acids and carbonylcompounds
as well as the certain biomedical application of bis(4-
hydroxycoumarinyl)arylmethanes mentioned above, we were prompted to design a convenient fast and facile
non-catalytic methodology for the fast efficient cascade synthesis of substituted bis(4-
hydroxycoumarinyl)arylmethanes based on cascade reaction of of benzaldehydes and 4-hydroxycoumarin.
Results and Discussion
As it follows from introduction, we were interested in designing a fast convenient and facile non-catalytic
methodology for the efficient synthesis of functionalized bis(4-hydroxycoumarinyl)arylmethane system based
©
Page 122
ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
on multicomponent reaction of benzaldehydes 1a-g, and 4-hydroxycoumarine (2) (Scheme 1, Tables 1 and 2).
Scheme 1. Cascade transformation of benzaldehydes 1a-g and 4-hydroxycoumarin (2) into
3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) (3a-g).
On the first step of this investigation the transformation of benzalaldehyde 1a and two molecules of 4-
hydroxycoumarine (2) was studied (Table 1).
Table 1. Cascade transformation of benzaldehyde (1a) and 4-hydroxycoumarin (2) into 3,3'-(phenyl-
a
methylene)bis(4-hydroxy-2H-chromen-2-one) (3a)
b
Entry
Solvent (mL) Catalyst (mol%)
T (°C)
78
Time (min)
Yield (%)
1
2
3
EtOH, 10
EtOH, 10
EtOH, 10
NaOAc, 10%
KF, 10%
—
30
30
30
76
74
75
78
78
4
5
6
7
8
9
EtOH, 10
n-PrOH, 10
n-PrOH, 5
n-PrOH, 3
n-PrOH, 1
n-PrOH, 1
n-PrOH, 1
n-PrOH, 1
—
—
—
—
—
—
—
—
—
—
78
97
15
30
30
30
30
20
15
10
30
70
85
88
93
96
95
95
93
85
97
97
97
97
10
11
12
97
97
95-100
aReaction conditions: 4-hydroxycoumarin (1.62 g, 10 mmol); benzaldehyde (0.53 g, 5 mmol).
bIsolated yield.
Page 123
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
In ethanol as a solvent under reflux (78 °C) in the presence of NaOAc or KF as catalyst in 30 min. reaction
time 3,3'-(phenylmethylene)bis(4-hydroxy-2H-chromen-2-one) (3a) was obtained in 76 and 74% yield (entries
1,2; Table 1).
The most interesting was the fact that just the same yield (75%) was obtained in ethanol without any
catalyst (entry 3, Table 1). Somewhat lower yields 70% were found when reaction time was shortened to 15
min.
The yield of 3,3'-(phenyl-methylene)bis(4-hydroxy-2H-chromen-2-one) (3a) was increased to 85%, when
reaction was carried out in boiling propanol (97° C) without any catalyst (entry 5, Table 1).
In the last years the concept of ‘on-water’ and ‘on-solvent’ reactions with using minimum quantities of
39-43
the solvents to carry out reactions in suspensions or emulsions has been developed.
Thus, further
minimization of the quantity of solvent and reaction time have been investigated showing improved yields
(entries 5-8, Table 1) while no-solvent conditions result in some yield’s decrease (entry 12, Table 1).
Under optimal non-catalytic conditions (1 mL of PrOH, 97 °C, 15 min) 3,3'-(phenyl-methylene)bis(4-
hydroxy-2H-chromen-2-one) (3a) was obtained in 95% yield.
Under these optimal conditions 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) 3a-g were
obtained in 93-98% yield (Table 2).
Table 2. Synthesis of biscoumarin derivatives 3a-ga
a
Entry
R
H
Yield (%)
1
2
3
4
5
6
7
95
98
96
93
97
95
96
4-Me
2-OMe
4-tBu
4-Cl
4-F
3-Br
aReaction conditions: 4-hydroxycoumarin (1.62 g, 10 mmol); substituted benzaldehyde (5 mmol); n-PrOH, 1
mL; 97 °C, 15 min.
b
Isolated yield.
With the above results taken into consideration and the mechanistic data on non-catalytic ‘domino’
36-38
transformations
the following mechanism for the non-catalytic cascade transformation of benzaldehydes 1
and 4-hydroxycoumarin (2) into 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) 3 was suggested. The
initiation step of the catalytic cycle is the thermal deprotonation of a molecule of 4-hydroxycoumarin 2 with
the 4-hydroxycoumarin anion A formation (Scheme 2).
Page 124
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
Scheme 2. Cascade transformation of benzaldehydes
1
and 4-hydroxycoumarin (2) into
3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones) 3.
Knoevenagel condensation of the anion A with benzaldehydes 1 leads to formation of Knoevenagel
44
adduct 4 with the elimination of a hydroxide anion. The subsequent hydroxide-promoted Michael addition of
-hydroxycoumarin (2) to electron-deficient Knoevenagel adduct 4 results in subsequent anions B and C
formation. Protonation of anion C with the next molecule of 4-hydroxycoumarin 2 leads to the corresponding
,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-one) 3 formation with the regeneration of anion A at the last
4
3
step of the catalytic cycle (Scheme 2).
Conclusions
The very simple and fast (15 min.) non-catalytic procedure can produce an efficient and selective
transformation of benzaldehyde, and 4-hydroxycoumarin into substituted 3,3'-(arylmethylene)bis(4-hydroxy-
2H-chromen-2-ones) in excellent 93-98% yields. This new non-catalytic cascade process opens an efficient and
convenient way to substituted 3,3'-(arylmethylene)bis(4-hydroxy-2H-chromen-2-ones), the pharmacologically
active substances with known anti-HIV, antibiotic, anti-inflammatory, anti-cancer activity and promising
compounds for different biomedical applications. This non-catalytic cascade procedure utilizes simple
equipment; it is easily carried out and is valuable from the viewpoint of environmentally benign diversity-
oriented large-scale processes.
Page 125
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
Experimental Section
General. All melting points were measured with a Gallenkamp melting-point apparatus and are uncorrected.
1
H spectra were recorded in CDCl
3
with a Bruker Avance II 300 spectrometer at ambient temperature.
Si. All chemicals used in this study were commercially available.
Chemical shift values are relative to Me
4
General procedure. A mixture of 4-hydroxycoumarin (1.62 g, 10 mmol) and benzaldehyde (5 mmol) in 1 mL of
n-PrOH was heated under stirring at 97 °C for 15 min. Then the precipitated product was filtered off, rinsed
with an ice-cold ethanol (1 mL) and dried under reduced pressure.
3
,3'-(Phenylmethylene)bis(4-hydroxy-2H-chromen-2-one) (3a). White solid; 1.98 g (95%); mp 230-231 ºC (Lit.
45
mp 228-230 ºC); δ
H
(300 MHz, CDCl
3
): δ 6.13 (s, 1H, CH), 7.10–8.17 (m, 13H, Ar), 11.33 (br s, 1H, OH), 11.55
(br s, 1H, OH).
3
2
1
3
,3'-((2-Methoxyphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3b). White solid; 2.17 g (98%); mp
46
25-226 ºC (Lit. mp 225-226 °C); δ
H
(300 MHz, CDCl
3
): δ 3.60 (s, 3H, OCH ), 6.11 (s, 1H, CH), 6.80–8.09 (m,
3
2H, Ar), 11.23 (br s, 2H, 2×OH).
,3'-(p-Tolylmethylene)bis(4-hydroxy-2H-chromen-2-one) (3c). White solid; 2.06 g (96%); mp 267-268 ºC (Lit.
45
mp 266-268 ºC); δ
H
(300 MHz, CDCl
H, OH), 11.53 (br s, 1H, OH).
,3'-((4-(tert-Butyl)phenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3d). White solid; 2.18 g (93%); mp
50-251 ºC (Lit. mp 247-248 °C); δ
2H, Ar), 11.28 (br s, 1H, OH), 11.51 (br s, 1H, OH).
,3'-((4-Chlorophenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3e). White solid; 2.17 g (97%); mp 260-
3
): δ 2.36 (s, 3H, CH
3
), 6.09 (s, 1H, CH), 7.05–8.13 (m, 12H, Ar), 11.31 (br s,
1
3
2
1
3
2
47
H
(300 MHz, CDCl
3
): δ 1.33 (s, 9H, 3×CH
3
), 6.09 (s, 1H, CH), 7.11–8.12 (m,
48
61 ºC (Lit. mp 256-258 °C); δ
H
(300 MHz, CDCl
3
): δ 6.06 (s, 1H, CH), 7.11–8.15 (m, 12H, Ar), 11.33 (br s, 1H,
OH), 11.55 (br s, 1H, OH).
3
,3'-((4-Fluorophenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3f). White solid; 2.04 g (95%); mp 213-
48
214 ºC (Lit. mp 211-212 °C); δ
H
(300 MHz, CDCl
3
): δ 6.07 (s, 1H, CH), 6.95–8.16 (m, 12H, Ar), 11.33 (br s, 1H,
OH), 11.56 (br s, 1H, OH).
3
,3'-((3-Bromophenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3g). White solid; 2.36 g (96%); mp 275-
45
276 ºC (Lit. mp 280-282 °C); δ
H
(300 MHz, CDCl ): δ 6.09 (s, 1H, CH), 7.08–8.13 (m, 12H, Ar), 11.31 (br s, 1H,
3
OH), 11.53 (br s, 1H, OH).
Acknowledgements
The research was supported by the Council at President of the Russian Federation (Project MD-380.2017.3)
References
1
.
.
Thompson, L. A. Curr. Opin. Chem. Biol. 2002, 4, 324.
https://doi.org/10.1016/S1367-5931(00)00096-X
Nefzi, A.; Ostresh, J. M.; Houghten, R. A. Chem. Rev. 1997, 97, 449.
2
Page 126
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
https://doi.org/10.1021/cr960010b
3.
4.
5.
Nicolaou, K. C.; Edmonds, D. J.; Bulger, P. G. Angew. Chem. 2006, 45, 7134.
https://doi.org/10.1002/anie.200601872
Padwa, A. Pure Appl. Chem. 2003, 75, 47.
https://doi.org/10.1351/pac200375010047
Grondal, C.; Jeanty, M.; Enders, D. Nat. Chem. 2010, 2, 167.
https://doi.org/10.1038/nchem.539
6
.
Hepworth, J. D.; Gabbutt, C. D.; Heron, B. M. In Comprehensive Heterocyclic Chemistry-II; Katritzky,
A. R., Rees, C. W., Scriven, E. F. V., Eds.; Pergamon: NewYork, 1996; Vol. 5, pp 417-434.
Sashidhara, K. V.; Kumar, A.; Kumar, M.; Sarkar, J.; Sinha, S. Bioorg. Med. Chem. Let. 2010, 20, 7205.
https://doi.org/10.1016/j.bmcl.2010.10.116
Huang, X. Y.; Shan, Z. J.; Zhai, H. L.; Su, L.; Zhang, X. Y. Chem. Biol. Drug Des. 2011, 78, 651.
https://doi.org/10.1111/j.1747-0285.2011.01195.x
7
8
9
1
1
1
.
.
.
Kontogiorgis, C. A.; Hadjipavlou-Litina, D. J. J. Med. Chem. 2005, 48, 6400.
https://doi.org/10.1021/jm0580149
0. Sashidhara, K. V.; Kumar, A.; Kumar, M.; Srivastava, A.; Puri, A. Bioorg. Med. Chem. Lett. 2010, 20, 6504.
https://doi.org/10.1016/j.bmcl.2010.09.055
1. Kurt, B. Z.; Gazioglu, I.; Sonmez, F.; Kucukislamoglu, M. Bioorg. Chem. 2015, 59, 80.
https://doi.org/10.1016/j.bioorg.2015.02.002
2. Barros, T. A. A.; Freitas, L. A. R.; Filho, J. M. B.; Nunes, X. P.; Giulietti, A. M.; Souza, G. E.; Santos, R. R.;
Soares, M. B.; Villarreal, C. F. J. Pharm. Pharmacol. 2010, 62, 205.
https://doi.org/10.1211/jpp.62.02.0008
1
1
1
1
3. 13.Sashidhara, K. V.; Kumar, A.; Chatterjee, M.; Rao, K. B.; Singh, S.; Verma, A. K.; Palit, G. Bioorg. Med.
Chem. Lett. 2011, 21, 1937.
https://doi.org/10.1016/j.bmcl.2011.02.040
4. Luchini, A.C.; Rodrigues-Orsi, P.; Cestari, S.H.; Seito, L.N.; Witaicenis, A.; Pellizzon, C.H.; Stasi, L.C.D. Biol.
Pharm. Bull. 2008, 31, 1343.
https://doi.org/10.1248/bpb.31.1343
5. Velasco-Velázquez, M.A.; Agramonte-Hevia, J.; Barrera, D.; Jiménez-Orozco, A.; García-Mondragón, M.J.;
Mendoza-Patiño, N.; Landa, A.; Mandoki, J. Cancer Lett. 2003, 198, 179.
https://doi.org/10.1016/S0304-3835(03)00333-1
6. Kirkiacharian, B.S.; Clercq, E.; Kurkjian, R.; Pannecouque, C. J. Pharm. Chem. 2008, 42, 265.
https://doi.org/10.1007/s11094-008-0103-0
1
1
7. Madari, H.; Panda, D.; Wilson, L.; Jacobs, R. S. Cancer Res. 2003, 63, 1214.
8. Watanabe, J.; Nishiyama, H.; Matsui, Y.; Ito, M.; Kawanishi, H.; Kamoto, T.; Ogawa, O. Oncogene 2006,
25, 2500.
https://doi.org/10.1038/sj.onc.1209162
1
2
2
9. Yu, D. L.; Suzuki M.; Xie, L.; Morris-Natschke, S. L.; Lee, K. H. Med. Res. Rev. 2003, 23, 322.
https://doi.org/10.1002/med.10034
0. Su, C. X.; Mouscadet, J. F.; Chiang, C. C.; Tsai, H. J.; Hsu, L. Y. Chem. Pharm. Bull. 2006, 54, 682.
https://doi.org/10.1248/cpb.54.682
1. Fylaktakidou, K. C.; Hadjipavlou-Litina, D. J.; Litines, K. E.; Nicolaides, D. N. Curr. Pharm. Des. 2004, 10,
3813.
https://doi.org/10.2174/1381612043382710
Page 127
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
22. Borges, F.; Roleira, F.; Mihazes, N.; Santana, L.; Uriarte, E. Curr. Med. Chem. 2005, 12, 887.
https://doi.org/10.2174/0929867053507315
23. Kidwai, M.; Bansal, V.; Mothsra, P.; Saxena, S.; Somvanshi, R. K.; Dey, S.; Singh, T. P. J. Mol. Catal. A:
Chem. 2007, 268, 76.
https://doi.org/10.1016/j.molcata.2006.11.054
24. Hagiwara, H.; Fujimoto, N.; Suzuki, T.; Ando, M. Heterocycles 2000, 3, 549.
https://doi.org/10.3987/COM-99-8817
25. Li, J.; Hou, Z.; Chen, G. H.; Li, F.; Zhou, Y.; Xue, X. Y.; Li, Z. P.; Jia, M.; Zhang, Z. D.; Li, M. K.; Luo, X. X. Org.
Biomol. Chem. 2014, 12, 5528.
https://doi.org/10.1039/c4ob00772g
2
2
2
2
3
3
3
6. Sangshetti, J. N.; Kokare, N. D.; Shinde, D. B. Green Chem. Lett. Rev. 2009, 2, 233.
https://doi.org/10.1080/17518250903393874
7. Rezaei, R.; Moezzi, F.; Doroodmand. M. M. Chin. Chem. Lett. 2014, 25, 183.
https://doi.org/10.1016/j.cclet.2013.10.033
8. Khurana, J. M.; Kumar, S. Tetrahedron Lett. 2009, 50, 4125.
https://doi.org/10.1016/j.tetlet.2009.04.125
9. Davoodnia, A. Bull. Korean Chem. Soc. 2011, 32, 4286.
https://doi.org/10.5012/bkcs.2011.32.12.4286
0. Pawar, B.; Shinde, V.; Chaskar, A. Green Sustainable Chem. 2013, 3, 56.
https://doi.org/10.4236/gsc.2013.32010
1. Karimian, R.; Piri, F.; Safari, A. A.; Davarpanah, S. J. J. Nanostructure Chem. 2013, 3, 52.
https://doi.org/10.1186/2193-8865-3-52
2. Manolov, I.; Maichle-Moessmer, C.; Nicolova, I.; Danchev, N. Arch. Pharm. Chem. Life Sci. 2006, 339,
319.
https://doi.org/10.1002/ardp.200500149
3
3
3
3. Manolov, I.; Maichle-Moessmer, I.; Danchev, N. Eur. J. Med. Chem. 2006, 41, 882.
https://doi.org/10.1016/j.ejmech.2006.03.007
4. Elinson, M. N.; Ryzhkov, F. V.; Zaimovskaya, T. A.; Egorov, M. P. Mendeleev Commun. 2015, 25, 185.
https://doi.org/10.1016/j.mencom.2015.05.008
5. Elinson, M. N.; Sokolova, O. O.; Nasybullin, R. F.; Zaimovskaya, T. A.; Egorov, M. P. Mendeleev Commun.
2015, 25, 19.
https://doi.org/10.1016/j.mencom.2015.01.006
3
3
3
3
6. Elinson, M. N.; Nasybullin, R. F.; Sokolova, O. O.; Zaimovskaya, T. A.; Egorov, M. P. Monatsh. Chem. 2015,
146, 1689.
https://doi.org/10.1007/s00706-015-1512-x
7. Elinson, M. N.; Ilovaisky, A. I.; Merkulova, V. M.; Belyakov, P. A.; Barba, F.; Batanero, B. Tetrahedron
2012, 68, 5833.
https://doi.org/10.1016/j.tet.2012.05.005
8. Elinson, M. N.; Ilovaisky, A. I.; Merkulova, V. M.; Zaimovskaya, T. A.; Nikishin, G. I. Mendeleev Commun.
2012, 22, 143.
https://doi.org/10.1016/j.mencom.2012.05.010
9. Guo, D.; Zhu, D.; Zhou, X.; Zheng, B. Langmuir 2015, 31, 13759.
https://doi.org/10.1021/acs.langmuir.5b04031
Page 128
©ARKAT USA, Inc

Arkivoc 2017, iii, 121-129
Elinson, M. N. et al.
40. Sarkar, A.; Santra, S.; Kundu, S. K.; Hajra, A.; Zyryanov, G. V.; Chupakhin, O. N.; Charushin, V. N.; Majee,
A. Green Chem. 2016, 18, 4475.
https://doi.org/10.1039/C6GC01279E
41. Demchuk, D. V.; Elinson, M. N.; Nikishin, G. I. Mendeleev Commun. 2011, 21, 224.
https://doi.org/10.1016/j.mencom.2011.07.018
42. Vereshchagin, A. N.; Elinson, M. N.; Nasybullin, R. F.; Ryzhkov, F. V.; Bobrovsky, S. I.; Bushmarinov, I. S.
Egorov, M. P. Helv. Chim. Acta 2015, 98, 1104.
https://doi.org/10.1002/hlca.201500026
43. Elinson, M. N.; Feducovich, S. K.; Stepanov, N. O.; Vereshchagin, A. N.; Nikishin, G. I. Tetrahedron 2008,
64, 708.
https://doi.org/10.1016/j.tet.2007.11.027
44. Patai S.; Israeli Y. J. Chem. Soc. 1960, 2025.
https://doi.org/10.1039/JR9600002025
45. Rezaei, R.; Sheikhi, M. R. Res. Chem. Intermed. 2015, 41, 1283.
https://doi.org/10.1007/s11164-013-1272-3
4
4
6. Mitra, A. K.; De, A.; Karchaudhuri, N.; Misra, S. K.; Mukhopadhyay, A. K. J. Ind. Chem. Soc. 1998, 75, 666.
7. Li, J.; Sui, Y.-P.; Xin, J.-J.; Du, X.-L.; Li, J.-T.; Huo, H.-R.; Ma, H.; Wang, W.-H.; Zhou, H.-Yu; Zhan, H.-D.;
Wang, Zh.-J.; Li, C.; Sui, F.; Li, X. Bioorg. Med. Chem. Lett. 2015, 25, 5520.
https://doi.org/10.1016/j.bmcl.2015.10.063
48. Karimi-Jaberi, Z.; Nazarifar, M. R.; Pooladian, B. Chin. Chem. Lett. 2012, 23, 781.
https://doi.org/10.1016/j.cclet.2012.05.003
Page 129
©ARKAT USA, Inc