Pd–<i>S</i>-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for Heck and Suzuki reactions

Arash Ghorbani-Choghamarani; Bahman Tahmasbi; Nourolah Noori; Sara Faryadi

doi:10.1016/j.crci.2016.06.010

Pd–S-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for Heck and Suzuki reactions

Arash Ghorbani-Choghamarani ¹ ; Bahman Tahmasbi ¹; Nourolah Noori ¹; Sara Faryadi ¹

¹ Department of Chemistry, Faculty of Science, Ilam University, P.O. Box 69315516, Ilam, Iran

Comptes Rendus. Chimie, Volume 20 (2017) no. 2, pp. 132-139.

Abstract

Supported Pd–S-methylisothiourea on magnetic nanoparticles (Pd–SMU-MNPs) as an efficient and magnetically reusable nanocatalyst was prepared and applied for the Heck and Suzuki cross-coupling reactions. All coupling reactions proceeded in short reaction times with good to excellent yields. After completion of reactions, the catalyst was easily separated from the reaction mixture using an external magnetic field and reused for several consecutive runs without significant loss of its catalytic efficiency and activity. This nanomagnetic catalyst was characterized by FT-IR spectroscopy, XRD, VSM, ICP-OES, TEM and SEM techniques. The leaching of the catalyst has been examined by a hot filtration test and ICP-OES analysis.

Metadata

Received: 2016-03-15
Accepted: 2016-06-28
Published online: 2016-08-08

DOI: 10.1016/j.crci.2016.06.010

Keywords: Magnetic nanoparticle, Heck reaction, Suzuki reaction, CC coupling, Palladium

Author's affiliations:

Arash Ghorbani-Choghamarani ¹; Bahman Tahmasbi ¹; Nourolah Noori ¹; Sara Faryadi ¹

¹ Department of Chemistry, Faculty of Science, Ilam University, P.O. Box 69315516, Ilam, Iran

@article{CRCHIM_2017__20_2_132_0,
     author = {Arash Ghorbani-Choghamarani and Bahman Tahmasbi and Nourolah Noori and Sara Faryadi},
     title = {Pd{\textendash}\protect\emph{S}-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for {Heck} and {Suzuki} reactions},
     journal = {Comptes Rendus. Chimie},
     pages = {132--139},
     publisher = {Elsevier},
     volume = {20},
     number = {2},
     year = {2017},
     doi = {10.1016/j.crci.2016.06.010},
     language = {en},
}

TY  - JOUR
AU  - Arash Ghorbani-Choghamarani
AU  - Bahman Tahmasbi
AU  - Nourolah Noori
AU  - Sara Faryadi
TI  - Pd–S-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for Heck and Suzuki reactions
JO  - Comptes Rendus. Chimie
PY  - 2017
SP  - 132
EP  - 139
VL  - 20
IS  - 2
PB  - Elsevier
DO  - 10.1016/j.crci.2016.06.010
LA  - en
ID  - CRCHIM_2017__20_2_132_0
ER  -

%0 Journal Article
%A Arash Ghorbani-Choghamarani
%A Bahman Tahmasbi
%A Nourolah Noori
%A Sara Faryadi
%T Pd–S-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for Heck and Suzuki reactions
%J Comptes Rendus. Chimie
%D 2017
%P 132-139
%V 20
%N 2
%I Elsevier
%R 10.1016/j.crci.2016.06.010
%G en
%F CRCHIM_2017__20_2_132_0

Arash Ghorbani-Choghamarani; Bahman Tahmasbi; Nourolah Noori; Sara Faryadi. Pd–S-methylisothiourea supported on magnetic nanoparticles as an efficient and reusable nanocatalyst for Heck and Suzuki reactions. Comptes Rendus. Chimie, Volume 20 (2017) no. 2, pp. 132-139. doi : 10.1016/j.crci.2016.06.010. https://comptes-rendus.academie-sciences.fr/chimie/articles/10.1016/j.crci.2016.06.010/

Version originale du texte intégral

1 Introduction

Palladium commonly has been applied as one of the powerful metals for CC coupling reactions [1–3]. Cross-coupling reactions such as Heck and Suzuki reactions were used as significant procedures in modern synthetic organic chemistry for the preparation of natural products, pharmaceuticals, agrochemicals, herbicides, biologically active compounds, UV screens, polymers, hydrocarbons, liquid crystal materials and advanced materials [4–7]. Homogeneous Pd-catalysts have been widely reported in carbon–carbon coupling reactions because of their high catalytic activity [8], while, in the catalytic reactions, separation and reusability of the catalyst is an important factor because of stringent ecological and economical demands for sustainability [9–11]. Therefore, nanoparticles (NPs) have recently emerged as efficient alternatives for the immobilization of homogeneous catalysts [12,13]. Because, by decreasing the support size, the surface area is increased and consequently a semi-homogeneous media is obtained, which can be used as a bridge to improve the gap between homogeneous and heterogeneous catalysts [14]. However, in order to simplify catalyst recovery and reusability of the particles, magnetic nanoparticles (MNPs) have recently emerged in catalyst science, and they can be rapidly isolated from the reaction mixture using an external magnet [15]. More importantly, magnetic separation is more effective and easier than filtration or centrifugation [16]. Among the various magnetic nanoparticles, Fe₃O₄ MNPs have many advantages such as easy preparation, having a high surface-area, low toxicity, and easy availability [17,18]. Therefore, Fe₃O₄ MNPs are considered as ideal support for the heterogenization of homogeneous catalysts [10–13].

2 Result and discussion

2.1 Catalyst preparation

In continuation of our studies about the application of new catalysts in organic functional group transformations [16,19], herein we report a simple and efficient method for the carbon–carbon cross-coupling reaction in the presence of catalytic amounts of Pd–SMU-MNPs. The Pd–SMU-MNPs were prepared by the concise route that has been outlined in Scheme 1. Initially, naked Fe₃O₄ MNPs were prepared by coprecipitation of iron(II) and iron(III) ions in basic solution at 80 °C [16], followed by modification using (3-chloropropyl)trimethoxysilane (CPTES). Subsequently, S-methylisothiourea immobilized on Fe₃O₄ magnetic nanoparticles (SMU-MNPs) via the reaction of ClPrSiFe₃O₄ with a S-methylisothiourea hemisulfate salt. Finally, Pd–SMU-MNPs were prepared via coordination of palladium(II) with SMU-MNPs followed by reduction of Pd(II) to Pd(0) by NaBH₄. The catalyst has been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), inductively coupled plasma atomic emission spectroscopy (ICP-OES), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).

Scheme 1
Preparation process of Pd–SMU-MNPs.

2.2 Catalyst characterization

The morphology and particle size of Pd–SMU-MNPs were evaluated by SEM and TEM analysis. The SEM image shows that these nanoparticles are spherical in shape with an average diameter of 24 ± 3 nm (Fig. 1). Also, TEM images reveal that the diameter of the Pd–SMU-MNPs is 15 ± 3 nm (Fig. 2).

In order to determine the exact amount of palladium in Pd–SMU-MNPs, the ICP-OES technique was performed. The amount of loaded palladium on the Pd–SMU-MNPs was found to be 1.54 × 10⁻³ mol g⁻¹ based on inductively coupled plasma atomic emission spectroscopy (ICP-OES).

The XRD patterns of the Fe₃O₄ nanoparticles and catalyst showed several peaks at 2θ values of 30.5°, 35.8°, 43.6°, 54.3°, 57.5° and 63.2° related to crystal planes in the Fe₃O₄ cubic lattice (Fig. 3). Also the XRD pattern of Pd–SMU-MNPs shows a series of peaks (40.0°, 46.4° and 67.4°), and these results revealed that the surface modification of the Fe₃O₄ nanoparticles didn't destroy their cubic lattice structures [20].

Fig. 3
XRD patterns of Fe₃O₄ nanoparticles (a) and Pd–SMU-MNPs (b).

Successful functionalization of the Fe₃O₄ NPs can be inferred from the FT-IR technique. Fig. 4 shows FT-IR spectra of Fe₃O₄, Cl-MNPs, SMU-MNPs and Pd–SMU-MNPs. The FT-IR spectrum for bare Fe₃O₄ shows a stretching vibration at 3390–3440 cm⁻¹ from both symmetrical and asymmetrical modes of OH bonds, which are attached to the surface of MNPs. The presence of Fe₃O₄ was shown in FT-IR by two strong absorption bands around 582 and 443 cm⁻¹, which corresponds to the FeO bond of Fe₃O₄ [13]. The stretching vibrations at 990 cm⁻¹ (corresponding to FeOSi bonds) and 1057 and 780 cm⁻¹ (related to OSi bonds) indicate that the silica organic group was successfully coated on the surface of Fe₃O₄ nanocrystals [16,21]. Furthermore, the presence of the anchored organic groups including propyl silane is confirmed by CH stretching vibrations that appear at 2885 and 2973. Also, in the FT-IR spectrum of SMU-MNPs, the located bands around 1629 cm⁻¹ correspond to the CN stretching vibrations, indicating that Cl of Cl-MNPs has been successfully replaced by S-methylisothiourea.

Fig. 4
FT-IR spectra of Fe₃O₄ (a), Cl-MNPs (b), SMU-MNPs (c) and Pd–SMU-MNPs (d).

The superparamagnetic properties of particles were measured using the VSM technique. The magnetization curves of Fe₃O₄ MNPs and Pd–SMU-MNPs are shown in Fig. 5. The magnetic measurements show that Pd–SMU-MNPs have a saturated magnetization value of 42 emu g⁻¹ and Fe₃O₄ MNPs have a saturated magnetization value of 74 emu g⁻¹. Decreasing the magnetic properties of the Pd–SMU-MNPs (74 → 42 emu g⁻¹), compared with the Fe₃O₄ MNPs is due to the coating of the Fe₃O₄ MNPs by organic layers and a palladium complex.

Fig. 5
Magnetization curves of Fe₃O₄ (a) and Pd–SMU-MNPs (b) at room temperature.

2.3 Catalytic study

In order to study the catalytic activity of Pd–SMU-MNPs, Suzuki reaction has been performed using sodium tetraphenyl borate (NaBPh₄) and phenylboronic acid (PhB(OH)₂) in the presence of this nanostructural compound (Scheme 2).

Scheme 2
Pd–SMU-MNPs catalyzed the Suzuki reaction.

In order to optimize the reaction conditions, the effect of various parameters such as temperature, solvent (DMF, DMSO, toluene, water or PEG), bases (Et₃N, KOH, NaOEt or K₂CO₃) and amount of catalyst were examined for the cross-coupling of iodobenzene with PhB(OH)₂ (Table 1). We found that the reaction did not proceed in the absence of Pd–SMU-MNPs (Table 1, entry 9). As shown in Table 1, the best results were observed in the presence of 0.006 gr, 0.92 mol % of Pd–SMU-MNPs (Table 1, entry 4). Also, different bases and various solvents have been examined and the best results were obtained in H₂O as solvent using 3 mmol of K₂CO₃ at 50 °C.

Table 1

Entry	Solvent (2 mL)	Base (3 mmol)	Catalyst (g)	Temperature (°C)	Time (min)	Yield %^a
1	DMSO	K₂CO₃	0.006 (0.92 mol %)	50	25	91
2	DMF	K₂CO₃	0.006 (0.92 mol %)	50	25	95
3	Toluene	K₂CO₃	0.006 (0.92 mol %)	50	30	43
4	H₂O	K₂CO₃	0.006 (0.92 mol %)	50	30	96
5	PEG	K₂CO₃	0.006 (0.92 mol %)	50	30	97
6	H₂O	(Et)₃N	0.006 (0.92 mol %)	50	30	56
7	H₂O	KOH	0.006 (0.92 mol %)	50	30	61
8	H₂O	NaOEt	0.006 (0.92 mol %)	50	30	18
9	H₂O	K₂CO₃	–	50	600	–^b
10	H₂O	K₂CO₃	0.002 (0.31 mol %)	50	30	37
11	H₂O	K₂CO₃	0.003 (0.46 mol %)	50	30	49
12	H₂O	K₂CO₃	0.005 (0.75 mol %)	50	30	68
13	H₂O	K₂CO₃	0.006 (0.92 mol %)	40	30	55
14	H₂O	K₂CO₃	0.006 (0.92 mol %)	r.t.	100	34

^a Isolated yields.

^b No reaction.

After optimization conditions, we examined the catalytic activity of Pd–SMU-MNPs for various aryl halides and the results are summarized in Table 2. In this study, various aryl iodides (Table 2, entries 1–3), bromides (Table 2, entries 4–10) and chlorides (Table 2, entries 11–13) were reacted with phenylboronic acid efficiently. All products were obtained in good yields. Therefore, this methodology is an efficient protocol for the cross-coupling a wide range of aryl halide including Cl, Br and I.

Table 2

Entry	Aryl halide	Phenylating reagent	Time (min)	Yield (%)^a	Melting point (ºC) [Ref.]
1	Iodobenzene	Phenylboronic acid	30	96	62–65 [22]
2	4-Iodotoluene	Phenylboronic acid	60	94	42–44 [22]
3	2-Iodotoluene	Phenylboronic acid	300	90	Oil [23]
4	4-Bromonitrobenzene	Phenylboronic acid	20	99	115–117 [24]
5	4-Bromochlorobenzene	Phenylboronic acid	90	95	70–72 [23]
6	4-Bromobenzonitrile	Phenylboronic acid	60	96	82–84 [23]
7	Bromobenzene	Phenylboronic acid	40	91^b	64–66 [22]
8	4-Bromotoluene	Phenylboronic acid	40	92^b	42–44 [22]
9	4-Bromophenol	Phenylboronic acid	40	92^b	161–163 [23]
10	4-Bromobenzaldehyde	Phenylboronic acid	70	88	55–57 [25]
11	4-Chloronitrobenzene	Phenylboronic acid	100	90^b^,^c	115–116 [24]
12	Chlorobenzene	Phenylboronic acid	125	89^b^,^c	63–66 [22]
13	4-Chlorobenzonitrile	Phenylboronic acid	140	92^b^,^c	82–84 [23]
14	Iodobenzene	Sodium tetraphenyl borate	30	97	64–66 [22]
15	4-Iodotoluene	Sodium tetraphenyl borate	45	94	43–44 [22]
16	2-Iodotoluene	Sodium tetraphenyl borate	280	91	Oil [23]
17	4-Bromonitrobenzene	Sodium tetraphenyl borate	40	98	116–117 [24]
18	4-Bromochlorobenzene	Sodium tetraphenyl borate	20	99	70–72 [23]
19	4-Bromobenzonitrile	Sodium tetraphenyl borate	60	90	82–85 [23]
20	4-Bromophenol	Sodium tetraphenyl borate	60	90	161–163 [23]
21	4-Bromobenzaldehyde	Sodium tetraphenyl borate	100	89	56–58 [25]
22	4-Chloronitrobenzene	Sodium tetraphenyl borate	90	93^b^,^c	115–117 [24]
23	Chlorobenzene	Sodium tetraphenyl borate	140	90^b^,^c	62–65 [22]
24	4-Chlorobenzonitrile	Sodium tetraphenyl borate	170	93^b^,^c	82–85 [23]

^a Isolated yield.

^b PEG used as the solvent.

^c Pd–SMU-MNPs was 8 mg, 1.2 mol %.

Also, the same reaction conditions have been applied for the cross-coupling of aryl halides with NaBPh₄ in the presence of Pd–SMU-MNPs (Table 2, entries 14–24). Aryl halides including electron-neutral, electron-rich and electron-poor substituents reacted with NaBPh₄ to produce the corresponding biphenyl in good to excellent yields (88–99% yield of products).

Also, we examined the catalytic activity of Pd–SMU-MNPs in the Heck reaction (Scheme 3). In order to find out the best reaction conditions, the coupling reaction of iodobenzene with butyl acrylate was selected as the model reaction (Table 3). The reaction conditions, such as the solvent (Table 3, entries 1–5), base (Table 3, entries 6–9), and amount of catalyst (Table 3, entries 9–13), were optimized in this model reaction (Table 3). Also, the effect of temperature (Table 3, entries 12–15) was examined. As shown in Table 3, the best conditions were obtained in the presence of Pd–SMU-MNPs (8 mg, 1.2 mol %) in DMF using K₂CO₃ at 120 °C (Table 3, entry 2).

Scheme 3
Pd–SMU-MNPs catalyzed the Heck reaction.

Table 3

Entry	Solvent (2 mL)	Base (3 mmol)	Catalyst (g)	Temperature (°C)	Time (min)	Yield %^a
1	DMSO	K₂CO₃	0.008 (1.2 mol %)	120	90	30
2	DMF	K₂CO₃	0.008 (1.2 mol %)	120	90	95
3	Toluene	K₂CO₃	0.008 (1.2 mol %)	120	90	15
4	DMSO:H₂O	K₂CO₃	0.008 (1.2 mol %)	120	90	45
5	PEG	K₂CO₃	0.008 (1.2 mol %)	120	90	60
6	DMF	(Et)₃N	0.008 (1.2 mol %)	120	90	65
7	DMF	KOH	0.008 (1.2 mol %)	120	90	30
8	DMF	NaOEt	0.008 (1.2 mol %)	120	90	Trace
9	DMF	K₂CO₃	–	120	1200	–^b
10	DMF	K₂CO₃	0.004 (0.6 mol %)	120	90	35
11	DMF	K₂CO₃	0.005 (0.75 mol %)	120	90	60
12	DMF	K₂CO₃	0.007 (1.05 mol %)	120	90	70
13	DMF	K₂CO₃	0.008 (1.2 mol %)	60	90	25
14	DMF	K₂CO₃	0.008 (1.2 mol %)	80	90	55
15	DMF	K₂CO₃	0.008 (1.2 mol %)	100	90	70

^a Isolated yield.

^b No reaction.

This optimized reaction conditions was then applied for the cross-coupling of different aryl halides including iodides (Table 4, entries 1–5), bromides (Table 4, entries 6–9) and chlorides (Table 4, entries 10–12) in the presence of Pd–SMU-MNPs and all products were obtained in good yield (91–97%). The reaction of various aryl halides (including electron-donating and electron-withdrawing groups) with butyl acrylate was investigated to confirm the generality of the present methodology.

Table 4

Entry	Aryl halide	Time (min)	Yield (%)^a	Melting point (°C) [Ref.]
1	Iodobenzene	90	96	Oil [23]
2	4-Iodotoluene	120	95	Oil [23]
3	2-Iodotoluene	350	91	Oil [23]
4	4-Iodoanisole	90	93	Oil [23]
5	2-Iodoanisole	450	92	Oil [26]
6	4-Bromonitrobenzene	90	97	60–62 [23]
7	4-Bromochlorobenzene	720	91	Oil [27]
8	4-Bromobenzonitrile	75	95	40–42 [27]
9	Bromobenzene	80	95	Oil [23]
10	Chlorobenzene	300	93	Oil [23]
11	4-Chlorobenzonitrile	420	90	39–42 [27]
12	4-Chloronitrobenzene	330	91	60–63 [23]

^a Isolated yields.

2.4 Recyclability of the catalyst

The reusability of catalysts is an important advantage from an industrial point of view. Therefore, the recovery and recyclability of Pd–SMU-MNPs were examined in the coupling reaction of iodobenzene with phenylboronic acid. After completion of the reaction, the catalyst was rapidly isolated from the reaction mixture by magnetic decantation and washed with diethyl ether to remove residual organic materials. Then, the reaction vessel was charged with fresh substrates and subjected to the next run. As shown in Fig. 6, the catalyst can be reused over eight times without any significant loss of its catalytic activity or palladium leaching. The average isolated yield for eight runs was 94.5%, which clearly proved the practical recyclability of this catalyst.

Fig. 6
Recyclability of Pd–SMU-MNPs in the coupling of iodobenzene with phenylboronic acid.

In order to show that Pd–SMU-MNPs act heterogeneously in the reaction media, a hot filtration test was performed in the coupling reaction of iodobenzene with butyl acrylate. In this study, we obtained the yield of product in the half time of the reaction that was 63%. Then the reaction was repeated and in half time of the reaction, the catalyst separated and allowed the filtrate to react further. The yield of reaction in this stage was 64% confirming that the Pd–SMU-MNPs act heterogeneously in the reaction media.

Also, to determine the exact leaching of palladium in the catalyst, the amount of Pd in Pd–SMU-MNPs was determined by ICP-OES after six times recycling. The amount of Pd in the recovered catalyst was found to be 1.49 × 10⁻³ mol g⁻¹ based on ICP-OES. Therefore the amount of Pd in the catalyst after six times recovery is comparable with the fresh catalyst (1.54 × 10⁻³ mol g⁻¹ for fresh Pd–SMU-MNPs). Therefore, only 3% leaching of palladium from the catalyst was observed after six runs. The results from the hot filtration test and ICP-OES technique showed that leaching of palladium during the reaction is negligible.

Also, in order to determine leaching of palladium in the reaction mixture, the Suzuki reaction through the coupling of iodobenzene with phenylboronic acid was performed and the obtained biphenyl has been characterized by ICP-OES to detect amounts of palladium in products. Interestingly, in this analysis even trace amounts of palladium weren't observed in the biphenyl product.

2.5 Comparison of the catalyst with previously reported ones

In order to examine the efficiency of the described procedure, we compared the results of the coupling of iodobenzene with phenylboronic acid with those of the previously reported procedures in the literature (Table 5). This catalyst showed a shorter reaction time and higher reaction yield than the other catalysts. Also Pd–SMU-MNPs are superior in terms of price, bio-compatibility, stability and easy separation than the previously reported works. In addition, the recoverability and recyclability of Pd–SMU-MNPs is more rapid and easier than the other catalysts. As is evident Pd–SMU-MNPs (in this work) have many advantages such as a low reaction time, high number of TNO and TOF, high yield of products, reacting at low temperature and use of water as the solvent.

Table 5

Entry	Catalyst (mol % of Pd)	Size of catalyst (nm)	Condition	Temperature (°C)	Time (min)	Yield (%)^a	TON	TOF (h⁻¹)	Ref.
1	NHC–Pd(II) complex (1.0 mol %)	–	THF, Cs₂CO₃	80 °C	12 h	88	88	7.33	[28]
2	Pd NP (1.0 mol %)	2.5–14	H₂O, KOH	100 °C	12 h	95	95	7.92	[29]
3	CA/Pd(0) (0.5–2.0 mol %)	3.2 ± 0.4	H₂O, K₂CO₃	100 °C	120	94	188	47	[30]
4	Pd/Au NPs (4.0 mol %)	80	EtOH/H₂O, K₂CO₃	80 °C	24 h	88	22	0.92	[31]
5	Pd(II)–NHC complex (1 mol %)	–	DMF, Cs₂CO₃	100 °C	24 h	99	99	4.12	[32]
6	N,N′-Bis(2-pyridinecarboxamide)-1,2-benzene palladium complex (1 mol %)	10–20	H₂O, K₂CO₃	100 °C	180	97	97	32.33	[33]
7	Pd-MPTAT-1 (0.02 g)	50	NaOH, DMF: H₂O (1:5)	85 °C	8 h	95	–	–	[34]
8	LDH-Pd(0) (0.3 g)	6–10	K₂CO₃, 1,4-dioxane: H₂O (5:1)	80 °C	10 h	96	–	–	[35]
9	PANI-Pd (2.2 mol %)	150–300	K₂CO₃, 1,4-dioxane: H₂O (1:1)	95 °C	240	91	41.36	10.34	[36]
10	Pd–SMU-MNPs (0.006 mg, 0.92 mol %)	15 ± 3	H₂O, K₂CO₃	50 °C	30	96	104	208	This work

^a Isolated yield.

3 Experimental

3.1 Preparation of the catalyst

The Fe₃O₄ MNPs were synthesized according to our recently reported procedure via a chemical coprecipitation technique using FeCl₃·6H₂O and FeCl₂·6H₂O in basic solution at 80 °C [23]. The obtained Fe₃O₄ nanoparticles (1.5 g) was dispersed in 50 mL toluene by sonication for 30 min, then 2.5 mL of (3-choloropropyl)triethoxysilane (CPTES) was added to the mixture. The reaction mixture was stirred under a N₂ atmosphere at 40 °C for 8 h. Then, the prepared nanoparticles (Cl–MNPs) were washed with ethanol, separated by magnetic decantation and dried at room temperature. In the next step, the obtained Cl-MNPs (1 g) were dispersed in 50 mL ethanol for 20 min, then S-methylisothiourea hemisulfate salt (2.5 mmol) and potassium carbonate (2.5 mmol) were added to the reaction mixture and stirred for 24 h at 80 °C under a N₂ atmosphere. Then, the resulting nanoparticles (SMU-MNPs) were washed with ethanol and separated using magnetic decantation and dried at room temperature. The obtained SMU-MNPs (1 g) were dispersed in 25 mL ethanol by sonication for 20 min; subsequently, palladium acetate (0.5 g, 1.95 × 10⁻³ mol) was added to the reaction mixture. The reaction mixture was stirred at 80 °C for 20 h. Then, NaBH₄ (0.5 mmol) was added to the reaction mixture and it was continued for two more hours. The final product (Pd–SMU-MNPs) was separated by magnetic decantation, washed with ethanol and dried at room temperature.

3.2 General procedure for the Suzuki reaction

A mixture of aryl halide (1 mmol), phenylboronic acid (1 mmol) or sodium tetraphenyl borate (0.5 mmol), K₂CO₃ (3 mmol), and Pd–SMU-MNPs (0.006 g, 0.92 mol %) was added to a reaction vessel. The resulting mixture was stirred in H₂O or PEG-400 at 50 °C and the progress of the reaction was monitored by TLC. After completion of the reaction, the catalyst was separated by an external magnet and washed with ethylacetate. The reaction mixture was extracted with H₂O and ethylacetate and the organic layer was dried over anhydrous Na₂SO₄ (1.5 g). Then the solvent was evaporated and pure biphenyl derivatives were obtained in good to excellent yields.

3.3 General procedure for the Heck reaction

A mixture of aryl halide (1 mmol), n-butyl acrylate (1.2 mmol), K₂CO₃ (3 mmol), and Pd–SMU-MNPs (0.008 g, 1.2 mol %) was stirred in DMF at 120 °C (the progress of the reaction was monitored by TLC). After completion of the reaction, the mixture was cooled down to room temperature and the catalyst was separated by an external magnet, washed with diethyl ether and the reaction mixture was extracted with H₂O and diethyl ether. The organic layer was dried over Na₂SO₄ (1.5 g); the solvent evaporated and pure products were obtained in 81–98% yields.

3.4 Selected spectral data

3.4.1 1,1′-Biphenyl

¹H NMR (400 MHz, CDCl₃): δ_H = 7.66–7.64 (m, 4H), 7.52–7.41 (m, 4H), 7.42–7.38 (tt, J = 7.6, 1.2 Hz, 2H) ppm.

3.4.2 [1,1′-Biphenyl]-4-carbonitrile

¹H NMR (400 MHz, CDCl₃): δ_H = 7.79–7.76 (m, 2H), 7.74–7.71 (m, 2H), 7.65–7.62 (m, 2H), 7.55–7.51 (m, 2H), 7.49–7.45 (m, 1H) ppm.

3.4.3 4-Chloro-1,1′-biphenyl

¹H NMR (400 MHz, CDCl₃): δ_H = 7.61–7.59 (m, 2H), 7.58–7.55 (m, 2H), 7.51–7.44 (m, 4H), 7.43–7.39 (tt, J = 6, 1.6 Hz, 1H) ppm.

3.4.4 Butyl cinnamate

¹H NMR (400 MHz, CDCl₃): δ_H = 7.75–7.71 (d, J = 16 Hz, 1H), 7.58–7.56 (m, 2H), 7.44–7.41 (m, 3H), 6.55–6.47 (d, J = 16 Hz, 1H), 4.27–4.24 (t, J = 6.4 Hz, 2H), 1.77–1.71 (m, 2H), 1.51–1.46 (m, 2H), 1.03–0.99 (t, J = 7.6 Hz, 3H) ppm.

3.4.5 Butyl 3-(p-tolyl)acrylate

¹H NMR (400 MHz, CDCl₃): δ_H = 7.72–7.68 (d, J = 16 Hz, 1H), 7.48–7.46 (d, J = 8 Hz, 2H), 7.24–7.22 (d, J = 8 Hz, 2H), 6.46–6.42 (d, J = 16 Hz, 1H), 4.26–4.23 (t, J = 13.2 Hz, 2H), 2.42 (s, 3H), 1.77–1.70 (quint, J = 6.4 Hz, 2H), 1.51–1.45 (sixt, J = 7.6 Hz, 2H), 1.03–0.99 (t, J = 7.6 Hz, 3H) ppm.

3.4.6 Butyl 3-(4-methoxyphenyl)acrylate

¹H NMR (400 MHz, CDCl₃): δ_H = 7.69–7.65 (d, J = 15.6 Hz, 1H), 7.52–7.50 (d, J = 6.8 Hz, 2H), 6.94–6.93 (d, J = 7.2 Hz, 2H), 6.37–6.33 (d, J = 16 Hz, 1H), 4.25–4.22 (t, J = 6.4 Hz, 2H), 3.86 (s, 3H), 1.74–1.68 (quint, J = 6.8 Hz, 2H), 1.52–1.43 (sixt, J = 8 Hz, 2H), 1.02–0.98 (t, J = 7.6 Hz, 3H) ppm.

4 Conclusion

In conclusion, an efficient heterogeneous nanocatalyst (Pd–SMU-MNPs) was synthesized by immobilization of palladium on modified Fe₃O₄ nanoparticles. This catalyst was characterized by FT-IR, SEM, TEM, XRD, VSM and ICP-OES techniques. The Pd–SMU-MNPs exhibit an excellent catalytic activity, high reusability and air or moisture stability for the Suzuki and Heck reactions. This methodology is effective for a wide range of aryl halide including Cl, Br and I. Also, the catalyst can be recovered and recycled over eight times and used without any significant loss of its activity or palladium leaching.

Acknowledgements

This work was supported by the research facilities of Ilam University, Ilam, Iran.

References

[1] J.T. Guan; X.M. Song; Z.Y. Zhang; B.M. Wei; Z.Q. Dai Appl. Organometal. Chem., 29 (2015), p. 87

[2] C. Xu; H.-M. Li; Z.-Q. Wang; W.-J. Fu Inorg. Chim. Acta, 423 (2014), p. 11

[3] A.-R. Hajipour; F. Raiee J. Iran. Chem. Soc., 12 (2015), p. 1177

[4] A.R. Hajipour; F. Raiee J. Iran. Chem. Soc., 12 (2015), p. 1177

[5] S.M. Islam; A.S. Roy; P. Mondal; N. Salam Appl. Organometal. Chem., 26 (2012), p. 625

[6] S. Pasa; Y.S. Ocak; H. Temel; T. Kilicoglu Inorg. Chim. Acta, 405 (2013), p. 493

[7] S. Nadri; M. Joshaghani; E. Rafiee Appl. Catal. A Gen., 362 (2009), p. 163

[8] G. Herve; G. Sartori; G. Enderlin; G. Mackenzie; C. Len RSC Adv., 4 (2014), p. 18558

[9] A. Ghorbani-Choghamarani; B. Tahmasbi; F. Arghand; S. Faryadi RSC Adv., 5 (2015), p. 92174

[10] C. Woo Lim; I.S. Lee Nano Today, 5 (2010), p. 412

[11] J. Govan; Y.K. Gun'ko Nanomaterials, 4 (2014), p. 222

[12] V. Polshettiwar; R.S. Varma Green Chem., 12 (2010), p. 743

[13] M. Hajjami; B. Tahmasbi RSC Adv., 5 (2015), p. 59194

[14] M. Hajjami; A. Ghorbani-Choghamarani; R. Ghafouri-Nejad; B. Tahmasbi New J. Chem., 40 (2016), p. 3066

[15] S. Shylesh; V. Schunemann; W.R. Thiel Angew. Chem. Int. Ed., 49 (2010), p. 3428

[16] A. Ghorbani-Choghamarani; Z. Darvishnejad; B. Tahmasbi Inorg. Chim. Acta., 435 (2015), p. 223

[17] V. Polshettiwar; R. Luque; A. Fihri; H. Zhu; M. Bouhrara; J.M. Basset Chem. Rev., 111 (2011), p. 3036

[18] A. Rostami; B. Tahmasbi; A. Yari Bull. Korean Chem. Soc., 34 (2013), p. 1521

[19] A. Ghorbani-Choghamarani; B. Tahmasbi New J. Chem., 40 (2016), p. 1205

[20] W. Zhang; X. Chen; T. Tang; E. Mijowska Nanoscale, 6 (2014), p. 12884

[21] M. Nikoorazm; A. Ghorbani-Choghamarani; N. Noori Appl. Organometal. Chem., 29 (2015), p. 328

[22] Y.Y. Peng; J. Liu; X. Lei; Z. Yin Green. Chem., 12 (2010), p. 1072

[23] A. Ghorbani-Choghamarani; B. Tahmasbi; P. Moradi Appl. Organometal. Chem., 30 (2016), p. 422

[24] A. Ghorbani-Choghamarani; F. Nikpour; F. Ghorbani; F. Havasi RSC Adv., 5 (2015), p. 33212

[25] M. Samarasimhars eddy; G. Prabhu; T.M. Vishwanatha; V.V. Sureshbabu Synthesis, 45 (2013), p. 1206

[26] Y.P. Wang; H.M. Lee J. Organomet. Chem., 791 (2015), p. 90

[27] N. Iranpoor; H. Firouzabadi; A. Tarassoli; M. Fereidoonnezhad Tetrahedron, 66 (2010), p. 2415

[28] T. Chen; J. Gao; M. Shi Tetrahedron, 62 (2006), p. 6289

[29] M. Nasrollahzadeh; S.M. Sajadi; M. Maham J. Mol. Catal. A Chem., 396 (2015), p. 297

[30] V.W. Faria; D.G.M. Oliveira; M.H.S. Kurz; F.F. Goncalves; C.W. Scheeren; G.R. Rosa RSC Adv., 4 (2014), p. 13446

[31] M. Nasrollahzadeh; A. Azarian; M. Maham; A. Ehsani J. Ind. Eng. Chem., 21 (2015), p. 746

[32] Q. Xu; W.L. Duan; Z.Y. Lei; Z.B. Zhu; M. Shi Tetrahedron, 61 (2005), p. 11225

[33] Q. Du; W. Zhang; H. Ma; J. Zheng; B. Zhou; Y. Li Tetrahedron, 68 (2012), p. 3577

[34] A. Modak; J. Mondal; M. Sasidharan; A. Bhaumik Green Chem., 13 (2011), p. 1317

[35] S. Singha; M. Sahoo; K.M. Parida Dalton Trans., 40 (2011), p. 7130

[36] H.A. Patel; A.L. Patel; A.V. Bedekar Appl. Organometal. Chem., 29 (2015), p. 1

Comments - Policy