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Sonochemical synthesis of 5-substituted 1H-tetrazoles catalyzed by ZrP2O7 nanoparticles and regioselective conversion into new 2,5-disubstituted tetrazoles

  • Javad Safaei-Ghomi EMAIL logo , Soleiman Paymard-Samani , Safura Zahedi and Hossein Shahbazi-Alavi
Published/Copyright: September 24, 2015
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Zeitschrift für Naturforschung B
From the journal Zeitschrift für Naturforschung B Volume 70 Issue 11

Abstract

The ultrasound-assisted preparation of 2-(1H-tetrazol-5-yl) acrylonitrile derivatives via a one-pot multi-component method is described successfully using ZrP2O7 nanoparticles as a catalyst. Readily available tetrazoles can be transformed into the corresponding 1,5- and 2,5-disubstituted tetrazoles. 2,4′-Dibromoacetophenone gave the corresponding 2,5-disubstituted derivative as the only isomer. Synthesis of tetrazole derivatives with excellent yields in short times, a wide range of products under ultrasound irradiation, environmental benignity and a simple work-up procedure are some of the important features of this protocol.

Keywords: 2,5-disubstituted tetrazoles; one pot; sonochemical synthesis; 5-substituted 1H-tetrazoles

1 Introduction

Ultrasonically accelerated organic synthesis has received significant attention in recent years [1, 2]. The strategy of ultrasound as an energy source offers major advantages to promote organic reactions in the form of design and development [3, 4]. When an acoustic pressure wave propagates through a reaction mixture, it facilitates the breakdown of μm-sized bubbles in the solution. Sonication of multi-component reaction systems accelerates the reaction rates by confirming better contacts [5].

In recent years, developing multi-component reactions in order to produce biologically active compounds has been accelerated and thus become one of the very important areas of research in organic and medicinal chemistry [6]. Several heterocyclic compounds containing a tetrazole moiety were found to be useful intermediates for medical drugs; moreover, they have a wide range of other applications, such as in coordination chemistry as ligands, and are used in various materials science applications including propellants [7], explosives [8] and synthons [9]. For these reasons the synthesis of this heterocyclic nucleus is of much current importance. Recently, tetrazole derivatives have been synthesized by various catalysts such as Pd(OAc)2-ZnBr2 [10], Yb(OTf)3 [11], Zn(OTf)3 [12], nanocrystalline ZnO, Zn/Al hydrotalcite [13], Zn hydroxyapatite [14], Cu2O [15, 16], FeCl3-SiO2 [17], CdCl2 [18], BaWO4, γ-Fe2O3 [19], mesoporous ZnS nanospheres [20], ZnS nanoparticles [21], CuFe2O4 nanoparticles [22], copper (II) supported on Fe3O4@SiO2 nanoparticles [23] and CoY zeolite [24]. 1,5-Disubstituted tetrazoles are important in biology and medicine as NAD(P)H oxidase inhibitors [25], glucokinase activators [26], hepatitis C virus serine protease NS3 inhibitors [27], selective cyclooxygenase-2 inhibitors [28], calcitonin gene-related peptide receptor antagonists and antimigraine agents [29]. Biological activities of 2,5-disubstituted tetrazoles are also reported such as antiviral and antifungal activities [30, 31].

In recent years, heterogeneous catalysts have gained more importance due to the environmental and economic factors. They have successfully been utilized in several organic transformations to minimize undesirable waste causing environmental pollution. The use of solid acids as heterogeneous catalysts has received significant interest in different areas of organic synthesis [32]. Solid acids have many advantages such as ease of handling, decreasing reactor and environmentally safe disposal [33]. Also, wastes and byproducts can be minimized or avoided by developing cleaner synthesis routes [34]. Solid acid nanocrystalline metal oxides have been employed for decades in a wide variety of organic transformations such as epoxidation [35] and benzylation [36]. ZrP2O7 nanocrystals are environmentally benign and economically feasible solid catalyst that offers several advantages, such as ease of handling and work-up, mild reaction conditions and reusability.

Thus keeping the environmentally benign features of sonochemical assisted synthesis in mind and as part of our continuing pursuit in developing multi-component reactions for the synthesis of heterocyclic compounds [37–40], in this paper, we report a simple and expeditious method for the synthesis of tetrazoles and new disubstituted tetrazoles in a two-part study. First, we report on a convenient, high-yielding synthesis of 2-(1H-tetrazol-5-yl)acrylonitrile derivatives (5-substituted 1H-tetrazoles) through the three-component domino Knoevenagel condensation/1,3-dipolar cycloaddition reaction of aldehydes, malononitrile and sodium azide in the presence of ZrP2O7 nanoparticles (NPs) as catalyst employing ultrasound as an efficient energy source. In the second part, we report on the synthesis of a series of new disubstituted tetrazoles through treatment of tetrazolate salts with benzyl bromide and 2,4′-dibromoacetophenone (Scheme 1).

Scheme 1: One-pot syntheses of mono- and disubstituted tetrazoles in the presence of ZrP2O7 nanoparticles under heating and sonication conditions.
Scheme 1:

One-pot syntheses of mono- and disubstituted tetrazoles in the presence of ZrP2O7 nanoparticles under heating and sonication conditions.

2 Results and discussion

2.1 Structural analysis of ZrP2O7 nanoparticles

The morphology and particle size of ZrP2O7 NPs were investigated by scanning electron microscopy (SEM) as shown in Fig. 1. The SEM image shows particles with diameters in the range of nanometers. The X-ray diffraction (XRD) pattern of ZrP2O7 NPs is shown in Fig. 2. The average NP size was estimated from the full-width half-maximum of the peaks with the use of the Scherrer equation. The results show that ZrP2O7 NPs were obtained with an average diameter of 11 nm as confirmed by the XRD analysis. The pattern agrees well with the reported pattern for zirconium pyrophosphate (JCPDS No. 49-1079).

Fig. 1: SEM image of the ZrP2O7 nanoparticles.
Fig. 1:

SEM image of the ZrP2O7 nanoparticles.

Fig. 2: The XRD pattern of the ZrP2O7 nanoparticles (top) and from JCPDS No. 49-1079 (bottom) for comparison.
Fig. 2:

The XRD pattern of the ZrP2O7 nanoparticles (top) and from JCPDS No. 49-1079 (bottom) for comparison.

2.2 Catalytic behavior of ZrP2O7 nanoparticles

To optimize the reaction conditions such as the type of catalyst and the influence of quantity of the catalyst (Table 1), a series of experiments were conducted both under ultrasonic irradiation and conventional heating, taking the reaction of benzaldehyde (1 mmol), malononitrile (1 mmol) and sodium azide (1.2 mmol) as a model reaction. Initially, we selected commercial ZrP2O7 and ZrP2O7 nanoparticles, and then the above reaction was optimized to get a high yield of the desired product both under a sonic condition and in an oil bath. It was found that, in some cases, the yields of the products were higher under an ultrasonic condition than conventional heating (Table 1). Also it is pertinent to mention that, with ZrP2O7 NPs, the yield is excellent, which can be attributed to the present higher surface areas which are mainly responsible for their catalytic activity.

Table 1

Optimization of the model reaction using various catalysts under heating and ultrasonic conditions in DMF.a

EntryCatalyst (mol%)ConventionalSonication
Time (min)Temperature (°C)Yield (%)bTime (min)Yield (%)b
1Commercial ZrP2O7 (6)36050146040
2Nano-ZrP2O7 (4)36050355060
3Nano-ZrP2O7 (6)36050554093
4Nano-ZrP2O7 (10)36050564093
5Nano-ZrP2O7 (4)3607080––
6Nano-ZrP2O7 (6)3607090––
7Nano-ZrP2O7 (10)3607089––
8Nano-ZrP2O7 (4)36012078––
9Nano-ZrP2O7 (6)36012083––
10Nano-ZrP2O7 (10)36012083––

aBenzaldehyde (1 mmol), malononitrile (1 mmol), NaN3 (1.2 mmol).

bIsolated yield.

Bold values indicate the best results in reaction conditions.

To optimize the amount of catalyst, different amounts of ZrP2O7 were applied for the model reaction, and the results of this study are given in Table 1. As shown in Table 1, 6 mol% of catalyst is essential for the present reaction (Table 1).

2.3 Synthesis of 5-substituted 1H-tetrazoles

In order to find the generality of the use of ZrP2O7 NPs in DMF for the reaction of aldehyde with malononitrile and sodium azide under ultrasonic and heating conditions, different substituted aromatic aldehydes were selected (Table 2). As shown in Table 2, in all cases the ultrasound waves increased the rate of reaction. The cavitation effect which was produced by ultrasonication is probably the reason of this occurrence [42]. Under sonication, the reaction mixture is activated by inducing high local temperatures and pressures generated inside the cavitation bubble and its interfaces when it collapses, which can accelerate the reaction rate and shorten the reaction time [43, 44].

Table 2

Synthesis of tetrazoles under heating and sonication conditions catalyzed by ZrP2O7 nanoparticles.

EntryProductRM.p. (°C) [ref]ConventionalaSonication
Time (min)Yield (%)bTime (min)Yield (%)b
13aH168–170 [41]360914093
23bo-Me157–159 [40]360864089
33cm-Me130–132 [40]360914093
43dp-Me189–191 [40]360904091
53ep-OMe153–155 [40]360904092
63fp-iPr128–130 [40]360904090
73gp-NO2166–168 [41]360954094
83hp-Br164–166 [41]360854088
93ip-OH159–161 [41]360924093
103jm-OH168–170360904092
113ko-OMe150–152360874089
123l2,3-OMe178–180360864088

aThe temperature is 70°C in this method.

bisolated yield.

Adsorption of substrates on the nano-ZrP2O7 surface is accelerated by the effects of ultrasonic irradiation.

It can be seen that the reaction is influenced by the presence of electron-donating and electron-withdrawing substituents on the aromatic ring of aldehydes. It is of interest to note that aromatic aldehydes containing electron-withdrawing substituents afford the desired products in good to excellent yields. Details of the stereochemical structure determination have been earlier described by Bazgir and co-workers [41].

2.4 Synthesis of 1,5- and 2,5-disubstituted tetrazoles

It has been shown previously that the reaction of tetrazolate salts with alkylhalides gave the corresponding 1,5-disubstituted and 2,5-disubstituted derivatives as mixtures [45]. Herein we report the treatment of tetrazolate salts prepared in situ, as shown in Scheme 1, with benzyl bromide under heating and sonication conditions to obtain the corresponding 1,5-disubstituted (isomers 6) and 2,5-disubstituted (isomers 5) derivatives as mixtures in which 5 isomers were the major products (Table 3). Separation of the isomers was achieved by column chromatography on silica gel using chloroform methanol as eluent. In their mass spectra, both the slowly (6j, 6i) and the faster (5j, 5i) moving compound showed the same molecular ion peak. In the 13C NMR spectra, the signals for the carbon CH2 atom attached to the tetrazole ring are very distinct, appearing at δ = 51.67 ppm in 6i and at δ = 56.80 ppm in 5i; the vinylic carbon atom attached to the nitrile group showed up at δ = 88.87 (6i) and δ = 93.32 (5i) ppm. In the 1H NMR spectra, the signal for CH2 attached to the tetrazole ring is observed at δ = 5.96 for 5i and δ = 5.85 ppm for 6i. The ratio of isolated yields of the above two isomers (5i:6i = 10.8 and 5j:6j = 8.6) was determined by 1H NMR. Steric factors have a vital role in the ratio for formation of isomers 5/6 [46–48].

Table 3

Synthesis of disubstituted tetrazoles from treatment of tetrazolate salts with benzyl bromide and 2,4′-dibromoacetophenone under heating and sonication conditions catalyzed by ZrP2O7 NPs.

EntryProductRR1M.p. (°C)ConventionalaSonication
Time (min)Yield (%)bTime (min)Yield (%)b
14aH
188–1901590292
24bo-Me
173–1741586289
34cm-Me
189–1901590291
44dp-Me
216–2181588291
54ep-Ome
202–2031589290
64fp-iPr
177–1791587288
74ip-OH
249–2511591291
84jm-OH
201–2021589292
96i

5i		p-OHBenzyl230–231

162–163		3090c1091c
106j

5j		m-OHBenzyl236–238

149–151		4588c1090c

aThe temperature is 70°C in this method.

bIsolated yields.

cYield of mixture of products and ratio of isolated yields of the two isomers (ratio of 5i to 6i is 10.8 and ratio of 5j to 6j is 8.6) as determined by 1H NMR.

2.5 Regioselective synthesis of 2,5-disubstituted tetrazoles

The reaction of tetrazolate salts prepared in situ, as shown in Scheme 2, with 2,4′-dibromoacetophenone under heating and sonication conditions gave the corresponding 2,5-disubstituted derivatives as the only isomers (Table 3). The best evidence for the formation of the 2,5-disubstituted derivative is its less steric hindrance and the appearance of a deshielded singlet for CH2 (6–7 ppm) in the 1H NMR spectra of 4a–4j.

Scheme 2: Possible mechanism for the regioselective synthesis of mono- and disubstituted tetrazoles in the presence of nano-ZrP2O7.
Scheme 2:

Possible mechanism for the regioselective synthesis of mono- and disubstituted tetrazoles in the presence of nano-ZrP2O7.

We postulate that when tetrazolate salts are treated with 2,4′-dibromoacetophenone, coordination of the carbonyl oxygen atom with ZrP2O7 NPs in intermediate B forms organometallated complex C. It is tentatively proposed that steric control of organometallated complex C is responsible for selective attack of the N-2 position of tetrazolate salts onto the C–Br bond form (Scheme 2). According to this mechanism, adsorption of aldehyde and 2,4′-dibromoacetophenone is improved on the nano-ZrP2O7 surface at the first step of the reaction and intermediate B, respectively, by the effects of ultrasonic irradiation.

Subsequently, the same reaction was carried out several times to check the reusability of the catalyst. It could be reused three times with a minimal loss of activity. It was found that product yields decreased to a small extent on each reuse (run 1, 92 %; run 2, 91 %; run 3, 89 %).

When the reaction was carried out under heating conditions, the reaction preceded slowly, while under ultrasonic irradiation, it gave excellent yields of products in short reaction time.

3 Conclusions

In conclusion, we have developed a new and highly efficient protocol for the synthesis of tetrazoles and also synthesis of highly regioselective disubstituted tetrazoles in the presence of ZrP2O7 NPs under ultrasonic irradiation. This method is operationally simple; the catalyst can be easily recycled, and reused at least three times without a significant loss of catalytic activity.

4 Experimental section

4.1 Materials and apparatus

4.1.1 General

All organic materials were purchased commercially from Sigma-Aldrich and Merck and were used without further purification. ZrP2O7 nanoparticles were prepared according to the procedure reported by Javidan et al. under ultrasonic irradiations [49]. A multiwave ultrasonic generator (Sonicator 3200; Bandelin, MS 73, Germany), equipped with a converter/transducer and titanium oscillator (horn), 12.5 mm in diameter, operating at 20 kHz with a maximum power output of 200 W, was used for the ultrasonic irradiation. The ultrasonic generator automatically adjusted the power level. All melting points are uncorrected and were determined in capillary tubes on a Boetius melting point microscope. FT-IR spectra were recorded with KBr pellets using a Magna-IR spectrometer 550 Nicolet. NMR spectra were recorded on a Bruker 400 MHz spectrometer with [D6]DMSO as solvent and TMS as internal standard. CHN compositions were measured by a Carlo ERBA Model EA 1108 analyzer. Powder XRD was carried out on a Philips diffractometer of X’pert Company with monochromatized CuKα radiation (λ = 1.5406 Å). The microscopic morphology of the catalyst was visualized by SEM (LEO 1455VP). The mass spectra were recorded on a Joel D-30 instrument at an ionization potential of 70 eV.

4.2 Preparation of zirconium pyrophosphate nanoparticles

The catalyst was prepared via the sonochemical method (worked at 20 kHz frequency and 80 W power). ZrOCl2 was used as the zirconium source. First, the stoichiometric amount of ZrOCl2·8H2O was added in 20 mL of distilled water and sonicated to complete dissolution. Afterward H3PO4 (85 %) was added dropwise in 20 min and the mixture was sonicated. When the reaction was completed, a disperse white precipitate was obtained. The solid was filtered and washed with distilled water and ethanol several times. Subsequently the catalyst was dried at 100 °C for 8 h and calcined at 500 °C for 1 h to obtain pure nano zirconium pyrophosphate.

4.3 Reusability of catalyst

To evaluate the high performance of the catalyst, reusability of ZrP2O7 NPs was studied in a model reaction. The catalyst was recovered after each run, washed with chloroform and hot ethanol (three times) and dried at 100 °C for 12 h prior to use, and tested for its activity in the subsequent run and fresh catalyst was not added. The catalyst was tested for three runs. It was found that the catalyst displayed very good reusability.

4.4 General procedure for the synthesis of 2-(1H-tetrazol-5-yl)acrylonitrile derivatives

4.4.1 Heating method (method A)

Nano-ZrP2O7 (6 mol%) was added to a mixture of aldehyde (1 mmol), malononitrile (0.066 g, 1 mmol) and sodium azide (0.78 g, 1.2 mmol) in DMF (5 mL) and stirred at 70 °C for 6 h. After completion of the reaction, as indicated by TLC, the reaction mixture was filtered. To the filtrate 30 mL of 2 n aq. HCl was added with vigorous stirring causing the tetrazole to precipitate. The precipitate was filtered and dried in a drying oven to furnish the tetrazoles. All of the products were identified with m.p., 1H NMR, 13C NMR, CHN and FT-IR spectroscopy techniques.

4.4.2 Ultrasound irradiation method (method B)

In a two-necked flask, a solution of aldehyde (1 mmol), malononitrile (1 mmol), sodium azide (1.2 mmol) and nano-ZrP2O7 (6 mol%) in DMF (5 mL) was sonicated at 20 kHz frequency and 40 W power at room temperature. After completed reaction, as indicated by TLC, the reaction mixture was filtered. To the filtrate 30 mL of 2 n aq. HCl was added with vigorous stirring causing the tetrazoles to precipitate. The precipitate was filtered and dried in an oven to furnish the tetrazoles.

4.5 General procedure for the synthesis of disubstituted tetrazoles

4.5.1 Heating method (method A)

Nano-ZrP2O7 (6 mol%) was added to a mixture of aldehyde (1 mmol), malononitrile (1 mmol) and sodium azide (1.0 mmol) in DMF (5 mL) and stirred at 70 °C until the TLC confirmed complete conversion of the aldehyde. At that point the reaction mixture was allowed to cool to room temperature and then benzyl bromide (1 mmol) or 2,4′-dibromoacetophenone (1 mmol) was added. The mixture was further stirred at 70 °C until completion (monitoring by TLC; see Table 3). After completion, the catalyst was separated by centrifugation and washed with chloroform and hot ethanol (three times). Water was added to the centrifugation with vigorous stirring causing the disubstituted tetrazole to precipitate. The precipitate was filtered and dried in an oven to furnish the corresponding N-alkylated tetrazole. Most of the compounds were obtained in pure form after simple trituration with hexane and ethyl acetate, whereas a few others were purified by column chromatography (CHCl3–MeOH 9.5:0.5).

4.5.2 Ultrasound irradiation method (method B)

In a two-necked flask, a solution of aldehyde (1 mmol), malononitrile (1 mmol), sodium azide (1 mmol) and nano-ZrP2O7 (6 mol%) in DMF (5 mL) was sonicated at 20 kHz frequency and 40 W power, until the TLC confirmed complete conversion of the aldehyde (Table 2). Then benzyl bromide (1 mmol) or 2,4′- dibromoacetophenone (1 mmol) was added and the contents were further sonicated (20 kHz frequency and 40 W) until completion (see Table 3). After completed reaction, as indicated by TLC, the catalyst was separated off by centrifugation. To the centrifugate was added water with vigorous stirring causing the disubstituted tetrazole to precipitate. The precipitate was filtered and dried in a drying oven to furnish the tetrazoles. Most of the compounds were obtained in pure form after simple trituration with hexane and ethyl acetate, whereas a few others were purified by column chromatography (CHCl3–MeOH 9.5:0.5).

4.6 Representative spectral data

4.6.1 (E)-3-(3-Hydroxyphenyl)-2-(1H-tetrazol-5-yl)acrylonitrile (3j)

Yellow powder. – FT-IR (KBr): v = 3217, 3056, 2908, 2236, 1708, 1605, 1542, 1284, 1238, 786 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 4.68 (brs, NH), 6,98 (d, J = 7.2, 1H, ArH), 7.38 (m, 2H, ArH), 7.44 (s, 1H, ArH), 8.25 (s, 1H, CH), 10.04 (s, brs, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 96.8, 115.8, 116.1, 120.1, 121.7, 130.7, 133.6, 148.9, 155.7, 158.2. – Analysis for C10H7N5O: calcd. C 56.34, H 3.31, N 32.85; found C 56.20; H 3.35, N 32.95.

4.6.2 (E)-3-(2-Methoxyphenyl)-2-(1H-tetrazol-5-yl)acrylonitrile (3k)

Yellow powder. – FT-IR (KBr): v = 3046, 2952, 2223, 1597, 1261, 1017, 757 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 3.90 (s, 3H, CH3), 3.59 (brs, NH, overlap with solvent), 7.12 (t, J = 7.2 Hz, 1H, ArH), 7.19 (d, J = 7.2 Hz, 1H, ArH), 7.56 (t, J = 7.6 Hz, 1H, ArH), 8.08 (d, J = 7.6 Hz, 1H, ArH), 8.54 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 56.4, 97.4, 112.4, 116.0, 121.1, 121.2, 128.6, 134.7, 143.3, 158.6, 170.1. – Analysis for C11H9N5O: calcd. C 58.14, H 3.99, N 30.82; found C 58.10, H 4.00, N 30.87.

4.6.3 (E)-3-(2,3-Dimethoxyphenyl)-2-(1H-tetrazol-5-yl)acrylonitrile (3l)

Shiny yellow powder. – FT-IR (KBr): v = 3040, 2937, 2218, 1611, 1577, 1279, 1080, 990, 741 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 3.66 (brs, NH, overlap with solvent), 3.81 (s, 3H, OCH3), 3.84 (s, 3H, OCH3), 7.27 (m, 2H, ArH), 7.72 (d, J = 7.6 Hz, 1H, ArH), 8.48 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 56.4, 61.8, 98.4, 115.7, 117.3, 119.6, 125.0, 126.4, 143.2, 148.9, 153.0, 155.6. – Analysis for C12H11N5O2: calcd. C 56.03, H 4.31, N 27.22; found C 55.99, H 4.25, N 27.41.

4.6.4 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-phenyl-acrylonitrile (4a)

White powder. – FT-IR (KBr): v = 3090, 2987, 2223, 1702, 1581, 1221, 990 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 6.76 (s, 2H, CH2), 7.59 (m, 3H, ArH), 7.85 (dd, J = 8.4, 1.6 Hz, 2H, ArH), 7.99 (dd, J = 8.4,1.6 Hz, 2H, ArH), 8.05 (m, 2H, ArH), 8.50 (d, J = 1.6 Hz, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 59.8, 98.3, 116.1, 129.4, 129.7, 130.4, 130.8, 132.6, 132.7, 132.8, 133.0, 148.3, 161.5, 190.9. – MS (EI, 70 eV): m/z (%) = 394 (0.4) [M]+, 396 (0.4) [M+2]+, 393 (0.8) [M–H]+, 395 (0.8) [M+2–H]+, 311 (3), 309 (4), 185 (93), 183 (100), 157 (42), 155 (84), 127 (23), 103 (18), 76 (30). – Analysis for C18H12BrN5O: calcd. C 54.84, H 3.07, N 17.76; found C 54.54, H 3.17, N 17.86.

4.6.5 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(o-tolyl)acrylonitrile (4b)

White powder. – FT-IR (KBr): v = 3091, 2989, 2949, 2228, 1699, 1584, 1227 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 2.49 (s, 3H, CH3), 6.78 (s, 2H, CH2), 7.39 (t, 2H, ArH), 7.46 (t, 1H, ArH), 7.85 (d, J = 8 Hz, 2H, ArH), 7.94–8.00 (m, 3H, ArH), 8.63 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 19.8, 59.8, 100.6, 115.8, 126.8, 128.3, 129.4, 130.8, 131.2, 132.0 (2C), 132.6, 133.0, 139.1, 147.3, 161.3, 190.9. – MS (EI, 70 eV): m/z (%) = 408 (0.8) [M]+, 410 (0.8) [M+2]+, 407 (1.6) [M–H]+, 409 (1.7) [M+2–H]+, 394 (7), 392 (8), 196 (50), 185 (79), 183 (100), 169 (31), 157 (35), 155 (38), 141 (52), 76 (26). – Analysis for C19H14BrN5O: calcd. C 55.90, H 3.46, N 17.15; found C 55.86, H 3.2, N 17.18.

4.6.6 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(m-tolyl)acrylonitrile (4c)

Cream powder. – FT-IR (KBr): v = 3001, 2954, 2220, 1698, 1583, 1222, 992 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 2.44 (s, 3H, CH3), 6.62 (s, 2H, CH2), 7.45 (s, 1H, ArH), 7.49 (t, 1H, ArH), 7.86 (s, 2H, ArH), 7.92 (d, J = 6.4 Hz, 2H, ArH), 8.11 (d, J = 6.4 Hz, 2H, ArH), 8.40 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 20.9, 59.3, 97.6, 115.6, 127.0, 128.9, 129.2, 130.4, 130.5, 132.2, 132.3, 132.7, 133, 138,6, 147.8, 161.1, 190.4. – Analysis for C19H14BrN5O: calcd. C 55.90, H 3.46, N 17.15; found C 55.87, H 3.2, N 17.17.

4.6.7 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(p-tolyl)acrylonitrile (4d)

White powder. – FT-IR (KBr): v = 3289, 2987, 2231, 1722, 1585, 1518, 1290, 837 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 2.39 (s, 3H, CH3), 6.75 (s, 2H, CH2), 7.40 (d, J = 8.4 Hz, 2H, ArH), 7.85 (d, J = 8.4 Hz, 2H, ArH), 7.98 (t, 4H, ArH), 8.44 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 21.3, 59.3, 96.5, 115.8, 128.9, 129.6, 129.8, 130.0, 130.4, 132.2, 132.7, 142.9, 147.7, 161.2, 190.5; MS (EI, 70 eV): m/z (%) = 408 (0.8) [M]+, 410 (0.8) [M+2]+, 407 (13) [M–H]+, 409 (13) [M+2–H]+, 325 (2), 323 (2), 196 (72), 185 (86), 183 (100), 168 (74), 157 (31), 155 (32), 140 (20), 76 (13). – Analysis for C19H14BrN5O: calcd. C 55.90, H 3.46, N 17.15; found C 55.95, H 3.41, N 17.10.

4.6.8 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(4-methoxyphenyl)acrylonitrile (4e)

Yellowish powder. – FT-IR (KBr): v = 3003, 2215, 1698, 1586, 1514, 1266, 1178, 834 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 3.85 (s, 3H, OCH3), 6.72 (s, 2H, CH2), 7.14 (d, J = 8 Hz, 2H, ArH), 7.84 (d, J = 8.4 Hz, 2H, ArH), 7.98 (d, J = 8 Hz, 2H, ArH), 8.07 (d, J = 8.4 Hz, 2H, ArH), 8.38 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 56.1, 59.7, 94.6, 115.3, 116.6, 125.3, 129.4, 130.8, 132.6, 132.8, 133.1, 147.7, 162.0, 163.0, 190.9. – MS (EI, 70 eV): m/z (%) = 424 (1.7) [M]+, 426 (0.8) [M+2]+, 423 (4) [M–H]+, 425 (4) [M+2–H]+, 212 (38), 186 (71), 184 (100), 157 (19), 155 (21), 141 (12), 114 (13), 76 (7). – Analysis for C19H14BrN5O2: calcd. C 53.79, H 3.33, N 16.51; found C 53.65, H 3.30, N 16.64.

4.6.9 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(4-isopropylphenyl)acrylonitrile (4f)

Cream powder. – FT-IR (KBr): v = 3100, 2959, 2222, 1700, 1598, 1396, 1342, 1223, 992, 820 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 1.23 (d, 6H, 2CH3), 2.97 (m, 1H, CH), 6.75 (s, 2H, CH2), 7.47 (d, J = 8 Hz, 2H, ArH), 7.86 (d, J = 8.4 Hz, 2H, ArH), 7.99 (m, 4H, ArH), 8.40 (s, 1H, CH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 23.5, 33.6, 59.3, 96.6, 115.8, 127.3, 128.9, 130.0, 130.2, 130.4, 132.2, 132.7, 147.7, 153.5, 161.2, 190.5. – MS (EI, 70 eV): m/z (%) = 436 (1.7) [M]+, 438 (0.8) [M+2]+, 435 (3) [M–H]+, 437 (3) [M+2–H]+, 366 (3), 364 (3), 338 (4), 336 (4), 224 (38), 198 (18), 183 (100), 181 (100), 155 (51), 140 (8), 127 (13), 76 (15). – Analysis for C21H18BrN5O: calcd. C 57.81, H 4.16, N 16.05; found C 57.88, H 4.16, N 16.05.

4.6.10 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(4-hydroxyphenyl)acrylonitrile (4i)

Yellowish powder. – FT-IR (KBr): v = 3224, 3010, 2988, 2950, 2219, 1700, 1594, 1571, 1289, 1225, 1173, 833 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 6.60 (d, 2H, CH2), 7.05 (d, J = 8.4 Hz, 2H, ArH), 7.85 (d, J = 8.4 Hz, 2H, ArH), 8.06 (d, J = 8.4 Hz, 2H, ArH), 8.10 (d, J = 8.4 Hz, 2H, ArH), 8.31 (s, 1H, CH), 9.42 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 59.7, 93.2, 116.0, 116.7, 116.8 (2C), 123.9, 129.3, 130.8, 132.6, 133.1, 147.9, 162,1, 190.9. – MS (EI, 70 eV): m/z (%) = 410 (1.1) [M]+, 412 (1.1) [M+2]+, 409 (4) [M–H]+, 411 (4) [M+2–H]+, 198 (62), 185 (56), 183 (68), 170 (100), 157 (22), 155 (21), 76 (7). – Analysis for C18H12BrN5O2: calcd. C 52.70, H 2.95, N 17.07; found C 52.57, H 3.01, N 17.14.

4.6.11 (E)-2-(2-(2-(4-Bromophenyl)-2-oxoethyl)- 2H-tetrazol-5-yl)-3-(3-hydroxyphenyl)acrylonitrile (4j)

Cream powder. – FT-IR (KBr): v = 3148, 2937, 2226, 1701, 1615, 1584, 1268, 1231, 995 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 6.75 (s, 2H, CH2), 6.98 (s, 1H, ArH), 7.37 (d, J = 7.4 Hz, 1H, ArH), 7.44 (d, J = 7.4 Hz, 1H, ArH), 7.48 (s, 1H, ArH), 7.84 (d, J = 8 Hz, 2H, ArH), 7.97 (d, J = 8 Hz, 2H, ArH), 8.37 (s, 1H, CH), 9.96 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 59.8, 97.9, 116.0, 116.2, 120.1, 121.9, 129.4, 130.8, 132.6, 133.1, 133.8, 148.4, 158.2, 161.6, 190.9, 238.7. – Analysis for C18H12BrN5O2: calcd. C 52.70, H 2.95, N 17.07; found C 52.59, H 2.99, N 17.14.

4.6.12 (E)-2-(2-Benzyl-2H-tetrazol-5-yl)-3- (3-hydroxyphenyl)acrylonitrile (5j)

Cream powder. – FT-IR (KBr): v = 3320, 3034, 2925, 2224, 1733, 1595, 1449, 1232, 720 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 6.01, (s, 2H, CH2), 6.97 (dd, J = 8,1.2 Hz, 1H, ArH), 7.33–7.46 (m, 8H, ArH), 8.31 (s, 1H, CH), 9.96 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 56.8, 97.9, 116.0, 116.1, 120.0, 121.9, 128.8, 129.2, 129.4, 130.7, 133.8, 134.2, 148.2, 158.2, 161.6. – MS (EI, 70 eV): m/z (%) = 303 (13) [M]+, 274 (12), 258 (4), 247 (17), 246 (19), 232 (33), 156 (18), 91 (100), 77 (12). – Analysis for C17H13N5O: calcd. C 67.32, H 4.32, N 23.09; found C 67.29, H 4.34, N 23.10.

4.6.13 (E)-2-(2-Benzyl-2H-tetrazol-5-yl)-3- (4-hydroxyphenyl)acrylonitrile (5i)

Cream powder. – FT-IR (KBr): v = 3380, 2924, 2223, 1592, 1287, 1217, 731 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 5.96 (s, 2H, CH2), 6.92 (d, J = 8.4 Hz, 2H, ArH), 7.38 (s, 5H, ArH), 7.93 (d, J = 8.4 Hz, 2H, ArH), 8.23 (s, 1H, CH), 10.75 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 56.8, 93.3, 116.6, 116.8, 123.8, 128.8, 128.9. 129.2, 129.4, 133.0, 134.2, 147.8, 161.9. – MS (EI, 70 eV): m/z (%) = 303 (33) [M]+, 274 (36), 258 (11), 247 (42), 246 (40), 232 (43), 156 (45), 91 (100), 77 (12). – Analysis for C17H13N5O: calcd. C 67.32, H 4.32, N 23.09; found C 67.35, H 4.32, N 23.00.

4.6.14 (E)-2-(1-Benzyl-1H-tetrazol-5-yl)-3- (3-hydroxyphenyl)acrylonitrile (6j)

Yellowish powder. – FT-IR (KBr): v = 3467, 3035, 2923, 2219, 1642, 1597, 1098, 709 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 5.90 (s, 2H, CH2), 7.00 (d, J = 8 Hz 1H, ArH), 7.23 (d, J = 4 Hz, 2H, ArH), 7.31–7.38 (m, 6H, ArH), 8.06 (s, 1H, CH), 10.02 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 51.8, 95.0, 116.2, 120.8, 121.9, 128.2, 129.0, 129.4, 130.8, 133.5, 140.6, 150.3, 153.4, 153.6, 158.2. – MS (EI, 70 eV): m/z (%) = 303 (34) [M]+, 274 (36), 258 (11), 247 (42), 246 (40), 232 (54), 156 (45), 91 (100), 77 (12). – Analysis for C17H13N5O: calcd. C 67.32, H 4.32, N 23.09; found C 67.33, H 4.12, N 23.23.11.

4.6.15 (E)-2-(1-Benzyl-1H-tetrazol-5-yl)-3- (4-hydroxyphenyl)acrylonitrile (6i)

Yellow powder. – FT-IR (KBr): v = 3411, 3125, 2925, 2212, 1732, 1582, 1286, 1178, 721 cm–1. – 1H NMR (400 MHz, [D6]DMSO): δ (ppm) = 5.85 (s, 2H, CH2), 6.91 (d, J = 8.8 Hz, 2H, ArH), 7.20 (d, J = 7.6 Hz, 1H, ArH), 7.35 (m, 4H, ArH), 7.85 (d, J = 8.8 Hz, 2H, ArH), 7.99 (s, 1H, CH), 10.70 (s, 1H, OH). – 13C NMR (100 MHz, [D6]DMSO): δ (ppm) = 51.6, 88.8, 116.4, 116.7, 117.0, 123.5, 128.1, 133.5, 134.5, 150.6. 152.9, 162.0, 162.7. – MS (EI, 70 eV): m/z (%) = 303 (13) [M]+, 274 (12), 258 (4), 247 (17), 246 (19), 232 (21), 156 (30), 91 (100), 77 (13). – Analysis for C17H13N5O: calcd. C 67.32, H 4.32, N 23.09; found C 67.32, H 4.22, N 23.20.

Corresponding author: Javad Safaei-Ghomi, Faculty of Chemistry, Department of Organic Chemistry, University of Kashan, Kashan, P.O. Box 87317-51167, Iran, e-mail:

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Received: 2015-4-10
Accepted: 2015-6-17
Published Online: 2015-9-24
Published in Print: 2015-11-1

©2015 by De Gruyter

Articles in the same Issue

  1. Frontmatter
  2. In this Issue
  3. Gd4(BO2)O5F – a gadolinium borate fluoride oxide comprising a linear BO2 moiety
  4. Hydrolysis of 8-(pinacolboranyl)quinoline: where is the 8-quinolylboronic acid?
  5. Synthesis of some novel 6′-(4-chlorophenyl)-3,4′-bipyridine-3′-carbonitriles: assessment of their antimicrobial and cytotoxic activity
  6. Synthesis of some 6-alkylureido-4-aryl-2(1H)-pyridones: further transformations and pharmacological activity
  7. Multicomponent green synthesis, spectroscopic and structural investigation of multi-substituted imidazoles. Part 1
  8. Sonochemical synthesis of 5-substituted 1H-tetrazoles catalyzed by ZrP2O7 nanoparticles and regioselective conversion into new 2,5-disubstituted tetrazoles
  9. Two new taxane-glycosides from the needles of Taxus canadensis
  10. Cytotoxic 24-nor-ursane-type triterpenoids from the twigs of Mostuea hirsuta
  11. 4,15-Diamino[2.2]paracyclophane as a useful precursor for the synthesis of novel pseudo-geminal [2.2]paracyclophane compounds
https://doi.org/10.1515/znb-2015-0070
Keywords for this article
2,5-disubstituted tetrazoles; one pot; sonochemical synthesis; 5-substituted 1H-tetrazoles

Articles in the same Issue

  1. Frontmatter
  2. In this Issue
  3. Gd4(BO2)O5F – a gadolinium borate fluoride oxide comprising a linear BO2 moiety
  4. Hydrolysis of 8-(pinacolboranyl)quinoline: where is the 8-quinolylboronic acid?
  5. Synthesis of some novel 6′-(4-chlorophenyl)-3,4′-bipyridine-3′-carbonitriles: assessment of their antimicrobial and cytotoxic activity
  6. Synthesis of some 6-alkylureido-4-aryl-2(1H)-pyridones: further transformations and pharmacological activity
  7. Multicomponent green synthesis, spectroscopic and structural investigation of multi-substituted imidazoles. Part 1
  8. Sonochemical synthesis of 5-substituted 1H-tetrazoles catalyzed by ZrP2O7 nanoparticles and regioselective conversion into new 2,5-disubstituted tetrazoles
  9. Two new taxane-glycosides from the needles of Taxus canadensis
  10. Cytotoxic 24-nor-ursane-type triterpenoids from the twigs of Mostuea hirsuta
  11. 4,15-Diamino[2.2]paracyclophane as a useful precursor for the synthesis of novel pseudo-geminal [2.2]paracyclophane compounds
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