Synthesis of acylhydrazines and, symmetrical and asymmetrical diacylhydrazines from carboxylic acid via the Vilsmeier reagent mediated process

Article abstract of DOI:10.1007/s11164-016-2738-x

(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent) has been used as an efficient and convenient reagent for the one-pot synthesis of acylhydrazines and symmetrical and asymmetrical diacylhydrazines from carboxylic acids. This reaction proceeded smoothly under mild conditions and it is quite practical, since the starting carboxylic acids can be easily handled and stored. Cleanliness, simplicity of the method and good to excellent yield of products are other advantages of this method.

Full text of DOI:10.1007/s11164-016-2738-x

Res Chem Intermed
DOI 10.1007/s11164-016-2738-x
Synthesis of acylhydrazines and, symmetrical
and asymmetrical diacylhydrazines from carboxylic
acid via the Vilsmeier reagent mediated process
Maaroof Zarei1 Maliheh Eslami Nakhli1
•
Received: 10 August 2016 / Accepted: 6 September 2016
Ó Springer Science+Business Media Dordrecht 2016
Abstract (Chloromethylene)dimethylammonium chloride (Vilsmeier reagent) has
been used as an efficient and convenient reagent for the one-pot synthesis of
acylhydrazines and symmetrical and asymmetrical diacylhydrazines from car-
boxylic acids. This reaction proceeded smoothly under mild conditions and it is
quite practical, since the starting carboxylic acids can be easily handled and stored.
Cleanliness, simplicity of the method and good to excellent yield of products are
other advantages of this method.
Keywords Acylhydrazines Á Diacylhydrazines Á Vilsmeier reagent Á One-pot Á
Hydrazine
Introduction
Acylhydrazines (RCONHNH2) and diacylhydrazines (RCONHNHCOR0) have
attracted considerable attention for decades as important organic synthons [1, 2].
Recently, many compounds containing these moieties have been reported which
exhibit extensive application in biological activities such as antibacterial, antifungal
[3], anticancer [4], herbicidal [5] and larvicidal [6] activities. N-tert-Butyl-N,N0-
diacylhydrazines discovered by Rohm and Haas Co., with their high insecticidal
activities and low toxicity to nontarget organisms such as mammalians, have
attracted considerable attention in recent years [7]. Tebufenozide, methoxyfenozide,
&
Maaroof Zarei
mzarei@hormozgan.ac.ir; maaroof1357@yahoo.com
1
Department of Chemistry, Faculty of Sciences, University of Hormozgan, Bandar Abbas 71961,
Iran
123

M. Zarei, M. E. Nakhli
Fig. 1 Commercial insecticides and pesticides contain diacylhydrazine moiety
halofenozide and chromafenozide are commercial insecticides and pesticides
(Fig. 1).
Meanwhile, some compounds bearing a diacylhydrazine unit have been reported
as polo-like kinase 1 (PLK1) [8] and malarial plasmepsin [9] inhibitors. It’s worthy
of attention that diacylhydrazines have been used as ligands to promote CuI-
catalyzed C–N cross-coupling reactions of aryl bromides with N-heterocycles [10].
Generally, acylhydrazines can be obtained by reaction of hydrazine with acyl
chlorides or esters [11, 12]. Reaction of acylhydrazines with acyl chlorides or esters
has been commonly used for synthesis of diacylhydrazines [13, 14].
Some acyl halides are not commercially available, difficult to prepare or
unstable. To promote this transformation from carboxylic acid, some acid activators
have been used, including DCC [15], polyphosphoric acid [16] and PhOPCl2 [17].
But some of these reagents are expensive, not readily available, hygroscopic and
moisture-sensitive. Low yield, unnecessary waste and painful chromatographic
separation are other disadvantages of these reagents.
(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent) 1 has been
found to be useful in formylation, dehydration, chlorination, and other reactions
[18–21]. It has also emerged as a convenient reagent in the synthesis of b-sultams
[22] and b-lactams [23–25]. Vilsmeier reagent is easily prepared as a white solid by
reaction of N,N-dimethylformamide (DMF) and chlorinating agents such as
(COCl2) or SOCl2 in dry CH2Cl2 [23]. This reagent can be kept for a long time
by storage in a well-capped bottle which is also commercially available.
In this paper, we described the use of Vilsmeier reagent as an efficient and
versatile reagent for one-pot synthesis of acylhydrazines and symmetrical and
asymmetrical diacylhydrazines from carboxylic acids.
123

Synthesis of acylhydrazines and, symmetrical and asymmetrical…
Experimental
Materials and methods
All required chemicals were purchased from Merck, Aldrich and Acros chemical
companies. The melting points were determined on a silicone oil bath and are
uncorrected. IR spectra were measured on a galaxy series FT-IR 5000 spectrometer.
NMR spectra were recorded in DMSO-d6 using a Bruker spectrophotometer (1H
NMR 300 MHz, 13C NMR 75 MHz) using tetramethylsilane as an internal standard,
and coupling constants were given in cycles per second (Hz). Elemental analyses
were run on a Vario EL III elemental analyzer. Thin-layer chromatography (TLC)
was carried out on silica gel 254 analytical sheets obtained from Fluka.
General procedure for synthesis of acylhydrazines 2–5
A solution of carboxylic acid (1.0 mmol), Vilsmeier reagent (1.0 mmol) and Et3N
(3.0 mmol) in dry CH2Cl2 (10 mL) at room temperature was added to a solution of
hydrazine hydrate (4.0 mmol) in dry CH2Cl2 (5 mL) and the mixture was stirred
7 h. The mixture was washed successively with saturated NaHCO3 (15 mL) and
brine (15 mL). The organic layer was dried (Na2SO4), filtered and the solvent was
removed under reduced pressure to give the crude products. The crude residues were
purified by crystallization from ethanol 95 %. Spectral data for 2–5 have been
previously reported [26–29].
General procedure for synthesis of symmetrical diacylhydrazines 6–16
Hydrazine hydrate (0.2 mmol) was added to a solution of carboxylic acid
(1.0 mmol), Vilsmeier reagent (1.0 mmol) and Et3N (4.0 mmol) in dry CH3CN
(15 mL) at room temperature and the mixture was stirred 7 h. Saturated NaHCO3
(15 mL) was added and the mixture was extracted with EtOAc (3 9 15 mL). The
organic layer was washed with brine (20 mL), dried (Na2SO4), filtered and the
solvent was removed under reduced pressure to give the crude products. The crude
residues were purified by crystallization from ethanol 95 %. Spectral data for 6–7,
10, 13 and 15 have been previously reported [30–34].
2-(4-Chlorophenoxy)-N0-(2-(4-chlorophenoxy)acetyl)acetohydrazide
(8) White
solid. mp: 130–132 °C. IR (KBr) cm-1: 1633 (CO), 3294 (NH); H NMR d 4.70
(2CH2, s, 4H), 6.78–7.28 (ArH, m, 8H), 9.86 (2NH, s, 2H); 13C NMR d 65.4 (CH2),
115.9, 127.1, 129.3, 157.2 (aromatic carbons), 168.7 (CO). Anal. Calcd for
C16H14Cl2N2O4: C, 52.05; H, 3.82; N, 7.59. Found: C, 52.18; H, 3.93; N, 7.67.
1
2-(1,3-Dioxoisoindolin-2-yl)-N0-(2-(1,3-dioxoisoindolin-2-yl)acetyl)acetohydrazide
(9) Off-white solid. mp [210 °C. IR (KBr) cm-1: 1640 (CO), 1735, 1776 (CO,
1
Phth), 3330 (NH); H NMR d 4.22 (2CH2, s, 4H), 7.47–7.70 (ArH, m, 8H), 9.55
(2NH, s, 2H); 13C NMR d 46.1 (CH2), 125.0, 132.0, 132.4 (aromatic carbons),
123

M. Zarei, M. E. Nakhli
168.7 (CO, phth), 170.4 (CO). Anal. Calcd for C20H14N4O6: C, 59.12; H, 3.47; N,
13.79. Found: C, 59.28; H, 3.60; N, 13.86.
3-Hydroxy-N0-(3-hydroxy-2-naphthoyl)-2-naphthohydrazide (11) White solid. mp:
153–155 °C IR (KBr) cm-1: 1639 (CO), 3050–3397 (OH), 3415 (NH); 1H NMR d
7.34–7.91 (ArH, m, 12H), 9.93 (2NH, s, 2H), 11.33 (2OH, s, 2H); 13C NMR d
113.1, 121.6, 123.4, 126.7, 128.8, 130.2, 130.4, 132.5, 136.6, 155.4 (aromatic
carbons), 165.3 (CO). Anal. Calcd for C22H16N2O4: C, 70.96; H, 4.33; N, 7.52.
Found: C, 71.06; H, 4.43; N, 7.47.
3-Hydroxy-N0-(3-hydroxybenzoyl)benzohydrazide (12) White solid. mp: 99–101 °C.
IR (KBr) cm-1: 1632 (CO), 3154–3659 (NH, OH); 1H NMR d 6.93–7.47 (ArH, m, 8H),
10.43 (2NH, s, 2H), 11.59 (2OH, s, 2H); 13C NMR d 114.3, 120.7, 122.1, 130.5, 133.8,
157.2 (aromatic carbons), 166.7 (CO). Anal. Calcd for C14H12N2O4: C, 61.76; H, 4.44; N,
10.29. Found: C, 61.68; H, 4.50; N, 10.22.
N0-(2,6-Dimethoxybenzoyl)-2,6-dimethoxybenzohydrazide (14) Off-white solid.
1
mp: 158–160 °C. IR (KBr) cm-1: 1637 (CO), 3441 (NH); H NMR d 3.71 (4
OMe, s, 12H), 6.77–7.45 (ArH, m, 6H), 9.72 (2NH, s, 2H); 13C NMR d 55.4 (CH3),
123.4, 128.5, 133.9, 148.5 (aromatic carbons), 166.9 (CO). Anal. Calcd for
C18H20N2O6: C, 59.99; H, 5.59; N, 7.77. Found: C, 60.11; H, 5.74; N, 7.70.
2-Methoxy-N0-(2-methoxyacetyl)acetohydrazide (16) White solid. mp: 52–54 °C.
1
IR (KBr) cm-1: 1644 (CO), 3227 (NH); H NMR d 3.29 (2OMe, s, 6H), 4.14
(2CH2, s, 4H), 9.35 (2NH, s, 2H); 13C NMR d 58.7 (OMe), 70.0 (CH2), 171.8 (CO).
Anal. Calcd for C6H12N2O4: C, 40.91; H, 6.87; N, 15.90. Found: C, 41.04; H, 6.99;
N, 15.96.
General procedure for synthesis of asymmetrical diacylhydrazines 17–26
Acylhydrazines 2–5 (1.0 mmol) was added to a solution of carboxylic acid
(1.5 mmol), Vilsmeier reagent (1.5 mmol) and Et3N (5.0 mmol) in dry CH3CN
(15 mL) at room temperature and the mixture was stirred 6 h. Saturated NaHCO3
(20 mL) was added and the mixture was extracted with EtOAc (3 9 15 mL). The
organic layer was washed with brine (20 mL), dried (Na2SO4), filtered and the
solvent was removed under reduced pressure to give the crude products. The crude
residues were purified by crystallization from ethanol 95 %. The data for 19 has
been previously reported [35].
2-(4-Chlorophenoxy)-N0-(2-phenoxyacetyl)acetohydrazide (17) White solid. mp:
130–132 °C. IR (KBr) cm-1: 1635 (CO), 3199 (NH); 1H NMR d 4.61, 4.64 (2 CH2,
2 s, 4H), 6.84–7.32 (ArH, m, 9H), 9.72, 9.87 (2 NH, 2 s, 2H); 13C NMR d 60.3,
65.9 (CH2) 115.9, 116.0, 122.3, 126.9, 129.0, 129.5, 157.1, 159.4 (aromatic carbons)
168.9, 176.4 (CO). Anal. Calcd for C16H15ClN2O4: C, 57.41; H, 4.52; N, 8.37.
Found: C, 57.55; H, 4.69; N, 8.44.
2-Methoxy-N0-(2-phenoxyacetyl)acetohydrazide (18) White solid. mp: 81–83 °C.
IR (KBr) cm-1: 1639 (CO), 3214 (NH); 1H NMR d 3.32 (OMe, s, 3H), 4.19, 4.73 (2
123

Synthesis of acylhydrazines and, symmetrical and asymmetrical…
CH2, 2 s, 4H), 6.79–7.25 (ArH, m, 5H), 9.59, 9.63 (2 NH, 2 s, 2H); 13C NMR d
57.7 (OMe), 66.2, 69.7 (CH2), 115.9, 122.5, 129.6, 159.3 (aromatic carbons), 169.1,
172.2 (CO). Anal. Calcd for C11H14N2O4: C, 55.46; H, 5.92; N, 11.76. Found: C,
55.41; H, 6.03; N, 11.70.
2-(4-Chlorophenoxy)-N0-(2-(2,4-dichlorophenoxy)acetyl)acetohydrazide (20) White
1
solid. mp: 146–148 °C. IR (KBr) cm-1: 1636 (CO), 3217 (NH); H NMR d 4.69,
4.80 (2 CH2, 2 s, 4H), 6.90–7.45 (ArH, m, 7H), 9.50, 10.10 (2 NH, 2 s, 2H); 13C
NMR d 65.6, 65.9 (CH2), 115.5, 117.2, 125.7, 127.1, 128.4, 128.7, 129.2, 130.8,
153.5, 157.4 (aromatic carbons), 169.0, 174.1 (CO). Anal. Calcd for C16H13Cl3-
N2O4: C, 47.61; H, 3.25; N, 6.94. Found: C, 47.55; H, 3.13; N, 6.86.
2-(2,4-Dichlorophenoxy)-N0-(2-methoxyacetyl)acetohydrazide (21) White solid.
1
mp: 77–79 °C. IR (KBr) cm-1: 1637 (CO), 3225 (NH); H NMR d 3.44 (OMe,
s, 3H), 4.14, 4.75 (2 CH2, 2 s, 4H), 6.71–7.34 (ArH, m, 3H), 9.15, 9.37 (2 NH, 2 s,
2H); 13C NMR d 58.8 (OMe), 65.9, 69.0 (CH2), 117.3, 125.3, 128.5, 128.8, 130.8,
153.3 (aromatic carbons), 168.0, 171.0 (CO). Anal. Calcd for C11H12Cl2N2O4: C,
43.02; H, 3.94; N, 9.12. Found: C, 43.15; H, 4.11; N, 9.20.
2-(Naphthalen-2-yloxy)-N0-(2-phenoxyacetyl)acetohydrazide (22) White solid.
1
mp: 142–144 °C. IR (KBr) cm-1: 1650 (CO), 3216 (NH); H NMR d 4.60, 4.72
(2 CH2, 2 s, 4H), 6.96–7.87 (ArH, m, 12H), 9.65, 9.74 (2 NH, 2 s, 2H); 13C NMR d
64.0, 65.3 (CH2), 109.9, 115.7, 117.6, 121.5, 124.0, 127.2, 127.3, 128.7, 129.4,
129.5, 131.1, 135.2, 156.1, 159.2 (aromatic carbons), 168.7, 175.6 (CO). Anal.
Calcd for C20H18N2O4: C, 68.56; H, 5.18; N, 8.00. Found: C, 68.64; H, 5.31; N,
7.92.
2-(4-Chlorophenoxy)-N0-(2-(naphthalen-2-yloxy)acetyl)acetohydrazide (23) White
solid. mp: 146–148 °C. IR (KBr) cm-1: 1638 (CO), 3246 (NH); 1H NMR
d
4.63, 4.80 (2 CH2, 2 s, 4H), 6.85–7.56 (ArH, m, 11H), 9.49, 9.63 (2 NH, 2 s, 2H);
13C NMR d 60.4, 65.4 (CH2), 110.0, 116.0, 117.6, 124.0, 127.1, 127.2, 127.3,
128.8, 129.3, 129.4, 131.1, 135.2, 156.0, 157.2 (aromatic carbons), 168.7, 174.3
(CO). Anal. Calcd for C20H17ClN2O4: C, 62.42; H, 4.45; N, 7.28. Found: C, 62.51;
H, 4.58; N, 7.23.
2-(2,4-Dichlorophenoxy)-N0-(2-(naphthalen-2-yloxy)acetyl)acetohydrazide (24) White
1
solid. mp: 170–172 °C. IR (KBr) cm-1: 1643 (CO), 3225 (NH); H NMR d 4.72,
4.81 (2 CH2, 2 s, 4H), 6.79–8.00 (ArH, m, 10H), 9.96, 9.97 (2 NH, 2 s, 2H); 13C
NMR d 65.6, 65.9 (CH2), 117.2, 117.7, 123.9, 125.6, 127.1, 127.2, 127.3, 127.4,
128.5, 128.6, 128.7, 129.3, 130.8, 131.0, 135.0, 156.0 (aromatic carbons), 168.6,
175.5 (CO). Anal. Calcd for C20H16Cl2N2O4: C, 57.30; H, 3.85; N, 6.68. Found: C,
57.25; H, 3.94; N, 6.71.
2-Methoxy-N0-(2-(naphthalen-2-yloxy)acetyl)acetohydrazide (25) White solid.
mp: 158–160 °C. IR (KBr) cm-1: 1649 (CO), 3254 (NH); 1H NMR d 3.36
(OMe, s, 3H), 4.16, 4.80 (2 CH2, 2 s, 4H), 7.05–7.75 (ArH, m, 7H), 9.35, 9.94 (2
NH, 2 s, 2H); 13C NMR d 58.8 (OMe), 65.3, 69.7 (CH2), 109.7, 117.8, 124.4,
127.0, 127.3, 128.8, 129.4, 131.1, 135.1, 156.3 (aromatic carbons), 168.8, 171.7
123

M. Zarei, M. E. Nakhli
(CO). Anal. Calcd for C15H16N2O4: C, 62.49; H, 5.59; N, 9.72. Found: C, 62.62; H,
5.75; N, 9.80.
2-(4-Chlorophenoxy)-N0-(2-methoxyacetyl)acetohydrazide (26) White solid. mp:
1
114–116 °C. IR (KBr) cm-1: 1631 (CO), 3228 (NH); H NMR d 3.32 (OMe, s,
3H), 4.17, 4.79 (2 CH2, 2 s, 4H), 6.74–7.27 (ArH, m, 4H), 8.58, 8.62 (2 NH, 2 s,
2H); 13C NMR d 57.4 (OMe), 66.1, 68.2 (CH2), 115.9, 127.2, 129.4, 157.3
(aromatic carbons), 168.7, 171.7 (CO). Anal. Calcd for C11H13ClN2O4: C, 48.45; H,
4.81; N, 10.27. Found: C, 48.58; H, 4.97; N, 10.21.
Results and discussion
Reaction of carboxylic acids with Vilsmeier reagent in the absence of any nucleophile
gives acyl chlorides [36]. Initially, we set up a model reaction with phenoxyacetic acid
(1 mmol), triethylamine (3 mmol), Vilsmeier reagent 1 (1 mmol), and hydrazine
hydrate (4 mmol) in dry dichloromethane at room temperature. After workup and
crystallization from ethyl acetate, 2-phenoxyacetohydrazide 2 was obtained at a 91 %
yield. According to this result, acylhydrazines 2–5 were prepared in one stage from
carboxylic acids with excellent yields (Scheme 1).
In this method acylhydrazines are formed not from the acyl halides or esters but
directly from the carboxylic acids. The by-products are DMF and triethylamine
hydrochloride salt which both are easily removed by aqueous workup.
Preparation of diacylhydrazines from acylhydrazines by the general procedure
and successful results obtained from one-pot synthesis of acylhydrazines promoted
us to undertake one-pot synthesis of symmetrical diacylhydrazines directly from the
carboxylic acids. Treatment of phenoxyacetic acid, triethylamine and Vilsmeier
reagent 1 with hydrazine hydrate in dry dichloromethane at room temperature gave
2-phenoxy-N0-(2-phenoxyacetyl)-acetohydrazide 6 at a low yield. This reaction was
Scheme 1 Synthesis of acylhydrazines 2–5
123

Synthesis of acylhydrazines and, symmetrical and asymmetrical…
123

M. Zarei, M. E. Nakhli
Table 2 Synthesis of asymmetrical diacylhydrazines 17–26
Entry Acylhydrazine Compound no. Diacylhydrazine
Yield (%)
1
2
17
84
2
3
2
3
18
19
81
84
4
3
20
85
88
5
6
3
4
21
22
87
91
7
8
4
4
23
24
93
9
4
5
25
26
82
87
10
performed in dry acetonitrile and the mixture was washed with saturated sodium
hydrogen carbonate. Extraction by ethyl acetate and crystallization from ethanol
gave diacylhydrazine 6 with an 89 % yield.
Symmetrical diacylhydrazine 6–16 were synthesized by this method from
corresponding carboxylic acids and hydrazine (Table 1). Progress of reactions was
checked by TLC monitoring. All products were confirmed by spectral data.
123

Synthesis of acylhydrazines and, symmetrical and asymmetrical…
Scheme 2 Proposed mechanism
Acylhydrazines 2–5 were reacted with a solution of corresponding carboxylic
acids, triethylamine and reagent 1 in dry acetonitrile. Asymmetrical diacylhydrazi-
nes 17–26 were obtained with good to excellent yields after usual work up and
crystallization from ethanol 95 % (Table 2). In this method, Vilsmeier reagent is a
versatile and convenient reagent because of reducing by-product formation and a
simplifying work-up.
According to the reported mechanism in the literature for [22], the mechanism
below is proposed (Scheme 2).
Conclusion
In summary, Vilsmeier reagent serves as a convenient and effective reagent for
synthesis of acylhydrazines. In addition, one-pot synthesis provides easy and
versatile methods for obtaining pure symmetrical and asymmetrical diacylhydrazi-
nes in good to excellent yields under simple and mild conditions. The use of
Vilsmeier reagent eliminates the need to handle and prepare acyl halides. This
method is very efficient particularly for larger-scale applications because the side-
products (DMF and triethylamine hydrochloride salt) are easily removed by
aqueous work-up.
Acknowledgments The authors thank the University of Hormozgan Research Council for financial
support of this work.
References
1. A. Kudelko, M. Wroblowska, Tetrahedron Lett. 55, 3252 (2014)
2. K. Jasiak, A. Kudelko, Tetrahedron Lett. 56, 5878 (2015)
3. M. Zareef, R. Iqbal, B. Mirza, K.M. Khan, A. Manan, F. Asim, S.W. Khan, Arkivoc (ii), 141 (2008)
4. C. Zi-Ning, H. Juan, L. Ying, L. Yun, Y. Xin-Ling, C. Fu-Heng, Chin. J. Chem. 26, 916 (2008)
5. X.-H. Liu, L. Pan, Y. Ma, J.-Q. Weng, C.-X. Tan, Y.-H. Li, Y.-X. Shi, B.-J. Li, Z.-M. Li, Y.-G.
Zhang, Chem. Biol. Drug Des. 78, 689 (2011)
6. H. Runqiu, W. Qingmin, J. Organomet. Chem. 637–639, 94 (2001)
7. H. Wang, Z. Yang, Z. Fan, Q. Wu, Y. Zhang, N. Mi, S. Wang, Z. Zhang, H. Song, F. Liuj, J. Agric.
Food Chem. 59, 628 (2001)
8. J. Sun, P.-C. Lv, F.-J. Guo, X.-Y. Wang, X. Han, Y. Zhang, G.-H. Sheng, S.-S. Qian, H.-L. Zhu, Eur.
J. Med. Chem. 81, 420 (2014)
9. K. Ersmark, M. Nervall, E. Hamelink, L.K. Janka, J.C. Clemente, B.M. Dunn, M.J. Blackman, B.
Samuelsson, J. Aqvist, A. Hallberg, J. Med. Chem. 48, 6090 (2005)
10. L. Li, L. Zhu, D. Chen, X. Hu, R. Wang, Eur. J. Org. Chem. 2011, 2692 (2011)
11. X. Yu, L. Shi, S. Ke, Bioorg. Med. Chem. Lett. 25, 5772 (2015)
12. P.R. Kamath, D. Sunil, A.A. Ajees, Res. Chem. Intermed. 42, 5899 (2016)
13. A.-F. Li, Y.-B. Ruan, Q.-Q. Jiang, W.-B. He, Y.-B. Jiang, Chem. Eur. J. 16, 5794 (2010)
14. D. Wang, W. Chena, Y. Zheng, C. Dai, L. Wang, B. Wang, Heterocycl. Commun. 19, 171 (2013)
123

M. Zarei, M. E. Nakhli
15. Y. Qian, Z. Lu, C. Lu, Z. Chen, Y. Cui, Dyes Pigments 75, 641 (2007)
16. R.F.M. Elshaarawy, C. Janiak, Z. Naturforsch. 66, 1202 (2011)
17. C.I. Chiriac, Rev. Roum. Chim. 27, 411 (1982)
18. A. Jarrahpour, M. Zarei, Tetrahedron Lett. 48, 8712 (2007)
19. W.-B. Huang, C.-Y. Du, J.-A. Jiang, Y.-F. Ji, Res. Chem. Intermed. 39, 2849 (2013)
20. L. Pellegatti, S.L. Buchwald, Org. Process Res. Dev. 16, 1442 (2012)
21. H. Yu, Y. Zhang, T. Li, P. Liao, Q. Diao, G. Xin, Q. Meng, D. Hou, RSC Adv. 5, 11293 (2015)
22. M. Zarei, A. Jarrahpour, J. Heterocycl. Chem. 50, 438 (2013)
23. A. Jarrahpour, M. Zarei, Tetrahedron 65, 2927 (2009)
24. A. Jarrahpour, A. Fadavi, M. Zarei, Bull. Chem. Soc. Jpn 84, 320 (2011)
25. M. Zarei, M. Mohamadzadeh, Tetrahedron 67, 5832 (2011)
26. D. Kaushik, S.A. Khan, G. Chawla, S. Kumar, Eur. J. Med. Chem. 45, 3943 (2010)
27. W. Shi, X. Qian, R. Zhang, G. Song, J. Agric. Food Chem. 49, 124 (2001)
28. A. Husain, A. Ahmad, M.M. Alam, M. Ajmal, P. Ahuja, Eur. J. Med. Chem. 44, 3798 (2009)
29. H.M. Abdel Hamid, E.S. Ramadan, M. Hagar, E.S. El Ashry, Synth. Commun. 34, 377 (2004)
30. M.J. Fray, K. Cooper, M.J. Parry, R. Kenneth, J. Steele, J. Med. Chem. 38, 3514 (1995)
31. Z.Q. Yuan, H. Ishikawa, D.L. Boger, Org. Lett. 7, 741 (2005)
32. R. Palit, N. Saraswat, J. Saraswat, Int. Res. J. Pharm. 7, 1 (2016)
33. V.K. Tandon, R.B. Chhor, Synth. Commun. 31, 1727 (2001)
34. Salahuddin, M. Shaharyar, A. Mazumder, M.J. Ahsan, Arabi. J. Chem. 7, 418 (2014)
35. D. Dovlatyan, Izv. Akad. Nauk Arm. SSR Khim. Nauki. 15, 151 (1962)
36. H. Eilingsfeld, M. Seefelder, H. Weidinger, Angew. Chem. 72, 836 (1960)
123