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. 2022 Dec 20;8(1):473–479. doi: 10.1021/acsomega.2c05187

Microwave-Assisted Rapid and Green Synthesis of Schiff Bases Using Cashew Shell Extract as a Natural Acid Catalyst

Satish B Manjare 1,*, Rakesh K Mahadik 1, Kalpesh S Manval 1, Prajal P More 1, Siddhesh S Dalvi 1
PMCID: PMC9835518  PMID: 36643449

Abstract

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The Schiff bases were prepared with aromatic aldehyde and aromatic amine using cashew shell extract as a catalyst under microwave irradiation. This reaction is rapid, efficient, and solvent-free and involves the one-pot synthesis of Schiff bases under microwave irradiation. The synthesized Schiff bases were characterized by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, 13C NMR spectroscopy, and gas chromatography–mass spectrometry (GC–MS). The advantages of the preparation of Schiff bases under microwave irradiation are high yield, shorter reaction time, easy, elimination of side products, and quick product isolation. The synthesized Schiff base derivatives are well known for their biological activity like antibacterial and antifungal activity.

1. Introduction

Green chemistry is the global term for the development and modification of chemical processes.1 This may help chemists to initiate a revolution in the principles and practices of various industries by designing chemical products and methods for the elimination of pollution.2

The chemical products are prepared using conventional and nonconventional synthesis processes. In conventional organic synthesis processes, it takes a longer time, resulting in a higher cost. These processes require some hazardous solvents and reagents.3 To overcome these drawbacks of conventional processes, the nonconventional processes are the best alternative to perform organic transformations. In nonconventional processes, microwave-assisted synthesis has become an interesting method for researchers in the past few decades. The synthesis of organic molecules using microwaves has proven to be economical, clean, and environmentally friendly with a shorter reaction time.4,5

Schiff bases are imine compounds with a −C=N bond linkage.6 Schiff base derivatives play an important role in the field of inorganic medicinal chemistry. In this connection, Schiff base derivatives show diversified applications in antimicrobial activity2,7 and antitumor activity and have excellent chelating ability.8−12 The literature review study reveals that free Schiff base derivatives show no cytotoxic behavior compared to their metal complexes.13 The novel application of Schiff bases with metal complexes is the successive cleavage of DNA molecule bonding via a nonoxidative mechanism.14 Schiff bases are well known for their use in rubber additives15 and the pharmaceutical industry.16 Various literature reports about the synthesis of Schiff bases are available. These reports show that the transition-metal complexes of Cu(II), Co(II), Fe(II), Ni(II), and V(II) were produced from bidentate Schiff bases, which exhibit good antibacterial activity.17,18 The various organic transformations using a microwave-assisted reaction19−21 are reported. In this work, we report a microwave-assisted synthesis of Schiff bases using anacardic acid present in cashew shell extract, which acts as an acid catalyst. The cashew nut is native to Central America and India, mostly in the Konkan region of Maharashtra.22 Cashew nut shells were obtained from the cashew nut processing industry. The peeled-off shells are thrown into the environment. This biowaste is very hazardous to the environment. These cashew nut shells have an anacardic acid phenolic compound and cardanol.23 Schiff base preparation using this methodology has a faster reaction rate, shorter time, easy workup, and good yield. These beneficial points make this methodology more interesting and attractive.

2. Material and Methods

All of the chemicals were purchased from HiMedia, Ratnagiri, Maharashtra, India, and used without purification. Solvents were dried by standard methods to use for reactions. A microwave energy source (model: Panasonic microwave) was used for carrying out microwave irradiation reactions. TLC was carried out with Merck silica gel 60-F254 plates, and column chromatography was performed over silica gel (60–120 mesh) obtained from commercial suppliers. All of the yields given in this work are referred to as an isolated yield. 1H and 13C nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Advance III spectrometer (400 MHz, Switzerland) using CDCl3 as a solvent and tetramethylsilane as an internal standard. GC–MS spectra were recorded on a Shimadzu spectrometer, Singapore. The Fourier transform infrared (FTIR) spectrum was obtained using the KBr water technique on a 3000 Hyperion microscope with vertex 80 FTIR system from Bruker, Germany.

2.1. Preparation of Cashew Shell Extract

The cashew shells were collected from the cashew nut industry, MIDC, Mirjole, Ratnagiri, Maharashtra, India. These cashew shells were sun-dried for 4 days and powdered using a grinder. Then, 10.0 g of cashew shell powder was added to a 250 mL beaker with 100 mL of double-distilled water. The mixture was warmed for 20 min. This warmed mixture was filtered and collected in a glass stoppered bottle. This filtrate was stored in a refrigerator at 4 °C and is designated as a cashew shell extract.

2.2. General Procedure for the Synthesis of Schiff Bases under Microwave Irradiation

Aromatic aldehyde (mmol), aromatic amine (1 mmol), and cashew shell extract (1 mL) were added to a 100 mL conical flask. This conical flask was covered with aluminum foil. The reaction mixture was kept in a microwave at 600 W. The time required to prepare Schiff bases under microwave irradiation varies between 80 and 120 s for all entries of Table 3. This reaction was carried out without any solvent. The reactions were monitored by TLC (Scheme 1). After the completion of reaction, the reaction mass was obtained using ethyl acetate (15 mL). This was kept for 3 min. Then, this organic layer was dried using Na2SO4. This organic layer was evaporated on a rotatory evaporator to obtain the crude product. This crude product was purified by column chromatography on silica gel (60–120 mesh) as a stationary phase and a mobile phase of 0–5% n-hexane/ethyl acetate. The purified Schiff base derivative was characterized by FTIR, 1H NMR, 13C NMR, and GC–MS. All of the prepared Schiff bases are known, and their spectral data matches with the reported literature values.19 These spectral data are provided in the Supporting Information. Figure 1 shows the flow chart for the synthesis of Schiff bases.

Table 3. Microwave-Assisted Synthesis of Schiff Bases in the Presence of Cashew Shell Extract.

2.2.

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Scheme 1. Schiff Base Derivatives Prepared under a Microwave Irradiation Mechanism.

Scheme 1

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Figure 1.

Figure 1

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Flow chart of synthesis procedure of Schiff Bases.

3. Results and Discussion

The improvement of reaction conditions served as a validation for this methodology. The optimization reaction condition was validated for the model reaction of salicylaldehyde (1 mmol) and aniline (1 mmol). Using conventional heating, the practical yield of the reaction was examined. Salicylaldehyde (1 mmol) and aniline (1 mmol) were mixed together for this reaction and agitated at room temperature for 45 min without the addition of cashew shell extract. The Schiff base derivative product was not produced by this reaction (Table 1, entry 1). After that, for 3 h at 70 °C, the same model reaction was conducted. Still, the Schiff base derivative product that was anticipated does not develop (Table 1, entry 2). After stirring for 45 min at room temperature and the addition of cashew shell extract (1 mL), the production of the Schiff base derivative product was examined, and only a trace quantity of Schiff base derivative product yield was obtained (Table 1, entry 3). If the model reaction took place at 70 °C for 45 min, trace amounts of the product were produced (Table 1, entry 4). The model reaction’s optimization was then verified in a microwave environment. This model reaction was exposed to microwave radiation at 600 W for 80 s without a solvent or cashew shell extract (Table 2, entry 1). When the model reaction (Table 2, entry 2) was performed without a solvent, without cashew shell extract, and with microwave irradiation for 80 s at 400 W, the Schiff base product yield observed was 70%. When an identical reaction (Table 2, entry 3) was conducted at 600 W for 80 s with the addition of cashew shell extract, the yield for the Schiff base products was 88.04%. By employing cashew shell extract, the percentage yield of Schiff base derivative products increased in a consistent manner. This process yields the resultant product quickly. The efficacy of this technology was tested for various aromatic amines and aromatic aldehydes. This procedure for various aromatic amines and aromatic aldehydes using microwave energy results in excellent to good yield (Table 3). As shown in Table 3, a slight reduction in the practical yield for Schiff base was observed when an electron-withdrawing group, such as −NO2, is present on the aromatic system. The table shows that microwave irradiation results in a quicker reaction time and a larger yield of Schiff base products. Figure 2 depicts a possible mechanism of this process.

Table 1. Optimization Studies Using Salicylaldehyde and Aniline under Conventional Heating.

entry catalyst (cashew shell extract in mL) temp (°C) time (min) % yield
1 0 RT 45  
2 0 70 180  
3 1 RT 45 trace
4 1 70 45 trace
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Table 2. Optimization Studies Using Salicylaldehyde and Aniline under a Microwave Energy Source.

entry catalyst (cashew shell extract in mL) microwave energy (W) time (s) % yield
1 0 600 80  
2 1 400 80 65.00
3 1 600 80 88.04
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Figure 2.

Figure 2

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Possible mechanism of preparation of Schiff base derivative in the presence of cashew shell extract.

3.1. 2-[(E)-(Phenylimino)methyl]phenol (Table 3, Entry 1)

Salicylaldehyde (2.44 gm), aniline (1.825 mL), and cashew shell extract (3 mL) were used. 2-[(E)-(Phenylimino)methyl]phenol is obtained as a pale yellow solid. MP = 52 °C (Rf = 0.65, n-hexane/ethyl acetate). FTIR: 3064.42 cm–1 for aromatic −OH stretching, 2886.47 cm–1 for aromatic −C–H stretching, 1682.11 and 1616.42 cm–1 for −N=CH– stretching, 1484.53 cm–1 for Ar–C=C– stretching. 1H NMR δ 7.35 (m, 5H), δ 8.65 (s, 1H), δ 6.76 (d, 1H), δ 7.12 (dd, 1H), δ 6.85 (dd, 1H), δ 7.45 (d, 1H). 13C NMR δ 119.07, δ 153.2, δ 130.1, δ 127.3, δ 160.1, δ 118.5, δ 132.28, δ 161.13, δ 162.68, δ 116.0, δ 132.5, δ 121.5, δ 130.6. GC–MS molecular formula: C13H11NO, molecular weight: 197, mass fragment (m/z): 197, 180, 167, 151, 139, 120, 104, 91, 78, 77, 65, 51, 50, 39.

3.2. (E)-N-(4-Nitrobenzylidene)benzenamine (Table 3, Entry 2)

4-Nitrobenzaldehyde (3.02 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(4-Nitrobenzylidene)benzenamine was obtained as a yellow solid. MP = 70 °C (Rf = 0.55, n-hexane/ethyl acetate). FTIR: 3077.78 cm–1 for aromatic −C–H stretching, 2879.78 cm–1 for aliphatic −C–H stretching, 1682.17 and 1626.54 cm–1 for −N=CH– stretching, 1517.76 cm–1 for Ar–C=C– stretching, 1347.01 and 1315.83 cm–1 for −NO2 stretching. 1H NMR δ 7.3 (m, 5H), δ 8.39 (s, 1H), δ 7.56 (d, 1H), δ 8.40 (d, 1H). 13C NMR δ 127.3, δ 130.1, δ 120.96, δ 150.91, δ 157.37, δ 130.1, δ 141.56, δ 121.2, δ 150.91. GC–MS molecular formula: C13H10N2O2, molecular weight: 226, mass fragment (m/z): 226, 195, 179, 167, 152, 140, 127, 115, 104, 90, 77, 76, 63, 51, 39, 28.

3.3. (E)-N-(4-Chlorobenzylidene)benzenamine (Table 3, Entry 3)

4-Chlorobenzaldehyde (2.81 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(4-Chlorobenzylidene)benzenamine was obtained as a white solid. MP = 53 °C (Rf = 0.52, n-hexane/ethyl acetate). FTIR: 3081.43 cm–1 for aromatic −C–H stretching, 2983.48 cm–1 for aliphatic −C–H stretching, 1654.06 and 1621.27 cm–1 for −N=CH– stretching, 1584.48 cm–1 for Ar–C=C– stretching, 828.23 cm–1 for Ar–Cl stretching. 1H NMR δ 7.3 (m, 5H), δ 8.45 (s, 1H), δ 7.56 (d, 2H), δ 7.50 (d, 2H). 13C NMR δ 122.3, δ 153.2, δ 130.1, δ 127.3, δ 131.9, δ 130.6, δ 129.0, δ 136.6. GC–MS molecular formula: C13H10NCl, molecular weight: 214, mass fragment (m/z): 214, 200, 180, 152, 126, 112, 104, 89, 77, 63, 51.

3.4. (E)-N-(4-Chlorobenzylidene)-4-nitrobenzenamine (Table 3, Entry 4)

4-Chlorobenzaldehyde (2.81 g), 4-nitroaniline (2.76 g), and cashew shell extract (3 mL) were used. (E)-N-(4-Chlorobenzylidene)-4-nitrobenzenamine was obtained as a yellow solid. MP = 136 °C (Rf = 0.52, n-hexane/ethyl acetate). FTIR: 3477.92–3361.09 cm–1 for −NH2 stretching, 3093.43 cm–1 for aromatic −C–H stretching, 2919.74 cm–1 for aliphatic −C–H stretching, 1686.87 cm–1 for −N=CH– stretching, 1582.21 and 1506.57 cm–1 for Ar–C=C– stretching, 1334.50 cm–1 for aromatic −NO2 stretching, 1169.15 cm–1 aliphatic −C–C– stretching, 850.43 cm–1 for Ar–Cl stretching. 1H NMR δ 8.2 (d, 2H), δ 7.5 (d, 2H), δ 8.39 (s, 1H), δ 7.56 (d, 2H), δ 7.30 (d, 2H). 13C NMR δ 151.65, δ 120.85, δ 126.2, δ 158.84, δ 137.38, δ 131.9, δ 130.6, δ 129.0, 136.6. GC–MS molecular formula: C13H9ClN2O2, molecular weight: 260, mass fragment (m/z): 260, 244, 230, 213, 201, 178, 167, 152, 139, 103, 89, 76, 63, 50.

3.5. (E)-N-[4-(Dimethylamino)benzylidene]benzenamine (Table 3, Entry 5)

4-(Dimethylamino)benzaldehyde (2.98 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-[4-(Dimethylamino)benzylidene]benzenamine was obtained as a blackish-brown solid. MP = 62 °C (Rf = 0.50, n-hexane/ethyl acetate). FTIR: 2950 cm–1 for aromatic −C–H stretching, 2819.95 cm–1 for aromatic −C–H stretching, 1661.59 and 1600.89 cm–1 for −N=CH– stretching, 1550.83 and 1527.93 cm–1 for Ar–C=C– stretching. 1H NMR δ 7.35 (m, 5H), δ 8.33 (s, 1H), δ 7.39 (d, 2H), δ 6.70 (d, 2H), δ 3.091 (s, 6H). 13C NMR δ 127.3, δ 130.49, δ 125, δ 154.33, δ 160.2, δ 120.94, δ 130.1, 110.98, δ 152.5, δ 40.18. GC–MS molecular formula: C15H16N2, molecular weight: 224, mass fragment (m/z): 223, 207, 179, 145, 120, 102, 91, 77, 63, 51, 42.

3.6. (E)-N-(4-Methoxybenzylidene)benzenamine (Table 3, Entry 6)

4-Methoxybenzaldehyde (2.72 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(4-Methoxybenzylidene)benzenamine is obtained as a red solid. MP = 50 °C (Rf = 0.52, n-hexane/ethyl acetate). FTIR: 3050.49 and 2962.28 cm–1 for aromatic −C–H stretching, 2880.32 cm–1 for aliphatic −C–H stretching, 1684.32 and 1621.28 cm–1 for −N=CH– stretching, 1573.88 and 1507.88 cm–1 for Ar–C=C– stretching, 1073.49 and 1030.43 cm–1 for −C–O–C ether linkage. 1H NMR δ 7.37 (m, 5H), δ 8.39 (s, 1H), δ 7.42 (d, 2H), δ 6.98 (d, 2H), δ 3.87 (s, 3H). 13C NMR δ 120.9, δ 130.5, δ 125.5, δ 152.3, δ 159.7, δ 126.1, δ 130.2, 114.2, δ 162.2, δ 55.43. GC–MS molecular formula: C14H13NO, molecular weight: 211, mass fragment (m/z): 211, 195, 179, 167, 151, 134, 115, 104, 90, 77, 63, 51, 39, 27, 15.

3.7. (E)-N-Benzylidenebenzenamine (Table 3, Entry 7)

Benzaldehyde (2.03 mL), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(E)-N-Benzylidenebenzenamine was obtained as a brownish solid. MP = 50 °C (Rf = 0.54, n-hexane/ethyl acetate). FTIR: 3060 and 2886 cm–1 for aromatic −C–H stretching, 1624 and 1583 cm–1 for −N=CH– stretching, 1734 cm–1 for Ar–C=C– stretching. 1H NMR δ 7.27 (m, 5H), δ 8.50 (s, 1H), δ 7.94 (d, 2H), δ 7.40 (dd, 3H). 13C NMR δ 115.1, δ 153.2, δ 130.1, δ 128.7, δ 160.45, δ 131.4, δ 129.3, δ 128.8, δ 131.4. GC–MS molecular formula: C13H11N, molecular weight: 181, mass fragment (m/z): 181, 152, 140, 127, 115, 104, 89, 77, 74, 63, 51, 38, 27.

3.8. (E)-N-(3-Bromobenzylidene)benzenamine (Table 3, Entry 8)

3-Bromobenzaldehyde (2.34 mL), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(3-Bromobenzylidene)benzenamine was obtained as a brownish liquid. BP = 256 °C (Rf = 0.54, n-hexane/ethyl acetate). FTIR: 3060.99 and 3029.58 cm–1 for aromatic −C–H stretching, 2873.81 cm–1 for aliphatic −C–H stretching, 1700 and 1627 cm–1 for −N=CH– stretching, 1563.40–1591.70 cm–1 for Ar–C=C– stretching, 784.17–694.25 cm–1 for Ar–Br stretching. 1H NMR δ 7.29 (m, 5H), δ 8.39 (s, 1H), δ 7.59 (d, 1H), δ 7.22 (dd, 1H), δ 7.44 (d, 1H), δ 7.79 (d, 1H). 13C NMR δ 120.9, δ 151.4, δ 130.1, δ 127.6, δ 158.5, δ 138.1, δ 130.3, δ 129.2, 131.1, δ 134.0, δ 123.0, δ 131.2. GC–MS molecular formula: C13H10NBr, molecular weight: 259, mass fragment (m/z): 259, 182, 155, 152, 127, 102, 90, 76, 63, 50, 39.

3.9. (E)-N-(3-Chlorobenzylidene)benzenamine (Table 3, Entry 9)

3-Chlorobenzaldehyde (2.26 mL), aniline (1.825 mL), and cashew shell extract (3 mL) were used. (E)-N-(3-Chlorobenzylidene)benzenamine was obtained as a brownish-red liquid. BP = 278 °C (Rf = 0.53, n-hexane/ethyl acetate). FTIR: 3062.84 and 3028.98 cm–1 for aromatic −C–H stretching, 2874 cm–1 for aliphatic −C–H stretching, 1701.51 and 1627.99 cm–1 for −N=CH– stretching, 1592.55 and 1568.59 cm–1 for Ar–C=C– stretching, 1096.83 and 1074.34 cm–1 for −C–O–C– stretching, 838.59 cm–1 for Ar–Cl stretching. 1H NMR δ 7.3 (m, 5H), δ 8.40 (s, 1H), δ 7.48 (d, 1H), δ 7.23 (dd, 1H), δ 7.30 (d, 1H), δ 7.75 (s, 1H). 13C NMR δ 120.9, δ 151.4, δ 130.1, δ 127.2, δ 126.4, δ 158.6, δ 135.2, δ 130, 131.2, δ 138, δ 129.3. GC–MS molecular formula: C13H10NCl, molecular weight: 215, mass fragment (m/z): 215, 200, 180, 151, 126, 112, 104, 89, 77, 63, 51, 40.

3.10. 3-[(E)-(Phenylimino)methyl]phenol (Table 3, Entry 10)

3-Hydroxybenzaldehyde (2.44 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. 3-[(E)-(Phenylimino)methyl]phenol was obtained as a red solid. MP = 66 °C (Rf = 0.52, n-hexane/ethyl acetate). FTIR: 3052.39 cm–1 for aromatic −OH stretching, 2916.25 cm–1 for aromatic −C–H stretching, 1622.12 cm–1 for −N=CH– stretching, 1586.41 cm–1 for Ar–C=C– stretching. 1H NMR δ 7.33 (m, 5H), δ 8.37 (s, 1H), δ 7.22 (d, 1H), δ 7.20 (dd, 1H), δ 6.95 (d, 1H), δ 7.09 (s, 1H), δ 5.41 (s, 1H). 13C NMR δ 122.3, δ 151.4, δ 130.1, δ 127.3, δ 161, δ 137.2, δ 122.2, δ 130.1, 119.3, δ 156.3, δ 114.3. GC–MS molecular formula: C13H11NO, molecular weight: 197, mass fragment (m/z): 197, 180, 167, 151, 139, 120, 104, 91, 78, 77, 65, 51, 50, 39.

3.11. 4-[(E)-(Phenylimino)methyl]phenol (Table 3, Entry 11)

4-Hydroxybenzaldehyde (2.44 g), aniline (1.825 mL), and cashew shell extract (3 mL) were used. 4-[(E)-(Phenylimino)methyl]phenol was obtained as a brownish solid. MP = 210 °C (Rf = 0.51, n-hexane/ethyl acetate). FTIR: 3169.89 cm–1 for aromatic −OH stretching, 2921.74 and 2858.83 cm–1 for aromatic −C–H stretching, 1671.60 cm–1 for −N=CH– stretching, 1578.04 and 1512.93 cm–1 for Ar–C=C– stretching. 1H NMR δ 7.26 (m, 5H), δ 8.39 (s, 1H), δ 7.41 (d, 1H), δ 6.96 (d, 1H), δ 6.9 (s, 1H). 13C NMR δ 120.9, δ 153.2, δ 129.2, δ 127.3, δ 126.4, δ 132.3, δ 115.9, δ 161.3. GC–MS molecular formula: C13H11NO, molecular weight: 197, mass fragment (m/z): 197, 178, 167, 141, 120, 104, 89, 77, 65, 51, 39, 28.

This Schiff base derivative is all documented. Using the agar well-diffusion method, the 2-[(E)-(phenylimino)methyl]phenol antibacterial activity was evaluated against bacillus Gram-positive bacteria, which demonstrates a successful zone of inhibition.

4. Conclusions

In this work, we have developed a green methodology for the synthesis of Schiff base derivatives. The reaction was carried out without solvent in a conical flask. The anacardic acid present in the cashew shell extracts acts as a catalyst. It is observed that Schiff base derivative product yield is excellent to good (88.27–80.00%). The reaction shows a higher percent yield of Schiff base derivatives in a shorter period of time. The reactions were completed in a shorter period of time, i.e., 80–120 s, under microwave irradiation. The spectral data (FTIR, 1H NMR, 13C NMR, and GC–MS) of Schiff base derivative in the presence of cashew shell extract as a natural acid catalyst is provided in the Supporting Information. Compared with the traditional pathway, this pathway is solvent-free, easy, cleaner, and safe. This pathway does not employ any toxic side product, and it is simple to workup with maximum efficiency for the formation of Schiff base derivatives. This cashew shell will help to prepare those Schiff bases that have a core bioactive nucleus of drug molecules.

Acknowledgments

The authors are grateful to Priyanka D. Pendhari, Ratnagiri Sub-Campus, University of Mumbai, Ratnagiri, India, for her kind help. The authors are grateful to Dr. Kishor V. Sukhatankar [Director (I/c)] and Abhinandan A. Boragave, Assistant Registrar, Ratnagiri Sub-Campus, University of Mumbai, Ratnagiri, for his constant encouragement and providing laboratory facility. The authors acknowledge SAIF IIT, Powai, Mumbai, for FTIR analysis and Punyashlok Ahilyadevi Holkar Solapur University, Solapur, for 1H NMR, 13C NMR, and GC–MS analyses.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c05187.

  • Flow chart of the synthesis procedure of Schiff bases; possible mechanism of preparation of Schiff bases; zone of inhibition of 2-[(E)-(phenylimino)methyl]phenol; scheme of Schiff base derivatives prepared under microwave irradiation; table of optimization studies using salicylaldehyde and aniline under conventional heating; table of optimization studies using salicylaldehyde and aniline under a microwave energy source; table of microwave-assisted synthesis of Schiff bases in the presence of cashew shell extract; 1H NMR and 13C NMR spectra and GC–MS analysis of the Schiff bases. (PDF)

Author Contributions

S.B.M. and R.K.M. designed the research; R.K.M., K.S.M., P.P.M., and S.S.D. performed the experiments; K.S.M. and R.K.M. wrote the manuscript; S.B.M. and S.S.D. corrected and edited the manuscript; and S.B.M. created the TOC graphic, and it is original. All authors have read and agreed that the present version of the manuscript is suitable for publication. All authors have seen and approved the manuscript for submission.

The authors declare no competing financial interest.

Supplementary Material

ao2c05187_si_001.pdf (20.1MB, pdf)

References

  1. Grewal A. S.; Kumar K.; Redhu S.; Bhardwaj S. Microwave assisted synthesis: a green chemistry approach. Int. Res. J. Pharm. Appl. Sci. 2016, 3, 278–285. [Google Scholar]
  2. Bhusnure O. G.; Vibhute Y. B.; Giram P. S.; Vibhute A. Y. Innovative Green synthesis of Schiff bases and their Antimicrobial Activity. J. Pharm. Res. 2015, 9, 670–677. [Google Scholar]
  3. Shinde A.; Zangade S.; Chavan S.; Vibhute Y. Microwave induced synthesis of bis-Schiff bases from propane-1, 3-diamine as promising antimicrobial analogs. Org. Commun. 2014, 7, 60–67. [Google Scholar]
  4. Chakraborty M.; Baweja S.; Bhagat S.; Chundawat T. S. Microwave assisted synthesis of Schiff bases: A green approach. Int. J. Chem. Reactor Eng. 2012, 10, 1–14. 10.1515/1542-6580.2973. [DOI] [Google Scholar]
  5. Rao V. K.; Reddy S. S.; Krishna B. S.; Naidu K. R. M.; Raju C. N.; Ghosh S. K. Synthesis of schiff’s bases in aqueous medium: A green alternative approach with effective mass yield and high reaction rates. Green Chem. Lett. Rev. 2010, 3, 217–223. 10.1080/17518251003716550. [DOI] [Google Scholar]
  6. Gungor T. Preparation of novel imidazo[1,2-a]pirimidine derived schiff bases at coventional and microwave heating conditions. Balikesir Univ. Bilimleri Enst. Derg. 2020, 22, 35–45. 10.25092/baunfbed.707673. [DOI] [Google Scholar]
  7. Naganagowda G.; Meijboom R.; Petsom A. Synthesis and Antimicrobial Activity of New Schiff Base Compounds Containing 2-Hydroxy-4-pentadecylbenzaldehyde Moiety. Adv. Chem. 2014, 2014, 921857. 10.1155/2014/921857. [DOI] [Google Scholar]
  8. Adsule S.; Barve V.; Chen D.; Ahmed F.; Dou Q. P.; Padhye S.; Sarkar F. H. Novel Schiff base copper complexes of quinoline-2 carboxaldehyde as proteasome inhibitors in human prostate cancer cells. J. Med. Chem. 2006, 49, 7242–7246. 10.1021/jm060712l. [DOI] [PubMed] [Google Scholar]
  9. Del Campo R.; Criado J. J.; García E.; Hermosa M. R.; Jiménez-Sánchez A.; Manzano J. L.; Monte E.; Rodríguez-Fernández E.; Sanz F. Thiourea derivatives and their nickel(II) and platinum(II) complexes: Antifungal activity. J. Inorg. Biochem. 2002, 89, 74–82. 10.1016/S0162-0134(01)00408-1. [DOI] [PubMed] [Google Scholar]
  10. Karthikeyan M. S.; Prasad D. J.; Poojary B.; Subrahmanya Bhat K.; Holla B. S.; Kumari N. S. Synthesis and biological activity of Schiff and Mannich bases bearing 2,4-dichloro-5-fluorophenyl moiety. Bioorg. Med. Chem. 2006, 14, 7482–7489. 10.1016/j.bmc.2006.07.015. [DOI] [PubMed] [Google Scholar]
  11. Romerosa A.; Campos-malpartida T.; Lidrissi C.; Saoud M.; Serrano-ruiz M.; Peruzzini M.; Garrido-cardenas J. A.; Garcia-Maroto F. Synthesis, Characterization, and DNA Binding of New Water-Soluble Cyclopentadienyl Ruthenium(II) Complexes Incorporating Phosphines. Inorg. Chem. 2006, 45, 1289–1298. 10.1021/ic051053q. [DOI] [PubMed] [Google Scholar]
  12. More M. S.; Joshi P. G.; Mishra Y. K.; Khanna P. K. Metal complexes driven from Schiff bases and semicarbazones for biomedical and allied applications: a review. Mater. Today Chem. 2019, 14, 100195 10.1016/j.mtchem.2019.100195. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Sinha D.; Tiwari A. K.; Singh S.; Shukla G.; Mishra P.; Chandra H.; Mishra A. K. Synthesis, characterization and biological activity of Schiff base analogues of indole-3-carboxaldehyde. Eur. J. Med. Chem. 2008, 43, 160–165. 10.1016/j.ejmech.2007.03.022. [DOI] [PubMed] [Google Scholar]
  14. Vidyavathi G. T.; Vinay Kumar B.; Aravinda T.; Hani U. Cashew nutshell liquid catalyzed green chemistry approach for synthesis of a Schiff base and its divalent metal complexes: molecular docking and DNA reactivity. Nucleosides, Nucleotides Nucleic Acids 2021, 40, 264–287. 10.1080/15257770.2020.1868502. [DOI] [PubMed] [Google Scholar]
  15. Bertow N. A.; Aowda S. A.; Almaamori M. H. Synthesis of vulcanization retarder by using Schiff base with maleic anhydride. Asian J. Chem. 2014, 26, S176–S178. 10.14233/ajchem.2014.19042. [DOI] [Google Scholar]
  16. Abdul Karem L. K.; Waddai F. Y.; Karam N. H. Schiff base complexes of some drug substances (Review). J. Pharm. Sci. Res. 2018, 10, 1912–1917. [Google Scholar]
  17. Kuddushi M. M. Y.; Malek M. A. H.; Patidar V. L.; Patel M. S.; Patel R. K.; Dave R. H. Synthesis and Characterization of Schiff Base Aniline with 5-Bromo-2-Hydroxyl Benzaldehyde and Their Metal Complexes. Int. J. Recent Sci. Res. 2018, 9, 26026–26030. [Google Scholar]
  18. Sani U.; Iliyasu S. M. Synthesis, characterization and antimicrobial studies on Schiff base derived from 2-aminopyridine and 2-methoxybenzaldehyde and its cobalt (II) and nickel (II) complexes. Bayero J. Pure Appl. Sci. 2019, 11, 214–219. 10.4314/bajopas.v11i1.35s. [DOI] [Google Scholar]
  19. Pooja B.; Lalit M.; Richa G.; Pramanik T. Microwave assisted green synthesis of Schiff bases in lemon juice medium. Res. J. Chem. Environ. 2018, 22, 19–23. [Google Scholar]
  20. Kassim K.; Hamali M. A.; Yamin B. A New Alternative Synthesis of Salicylaldazine via Microwave Irradiation Method. J. Chem. 2019, 2019, 9546373. 10.1155/2019/9546373. [DOI] [Google Scholar]
  21. Hu J.; Sun J.; Zhou T.; Xu Y. Microwave-assisted synthesis of 1,3,4-thiadiazole Schiff base derivatives. J. Chem. Res. 2011, 35, 442–443. 10.3184/174751911X13128202305728. [DOI] [Google Scholar]
  22. Desai D.; Raorane C.; Patil S.; Gadgil R.; Patkar D. Anacardium Occidentale: Fountain of Phytochemicals; the Qualitative Profiling. World J. Pharm. Res. 2017, 6, 585–592. 10.20959/wjpr20175-7822. [DOI] [Google Scholar]
  23. de Sousa Leite A.; Islam Md. T.; Junior A. L. G.; Sousa M. C. S.; Alencar M. V. O. B.; Paz M. F. C. J.; Rolim H. M. L.; Medeiros M. G. F. M.; Melo-Cavalcante A. A. C.; Lopes J. A. D. Pharmacological properties of cashew (Anacardium occidentale). Afr. J. Biotechnol. 2016, 15, 1855–1863. 10.5897/ajb2015.15051. [DOI] [Google Scholar]

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