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Konjac glucomannan supported palladium complex: An efficient and recyclable catalyst for Heck reaction
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REACTIVE & FUNCTIONAL POLYMERS
Reactive & Functional Polymers 68 (2008) 384–388
www.elsevier.com/locate/react
Konjac glucomannan supported palladium complex: An efficient and recyclable catalyst for Heck reaction Pu Liu a,*, Yonghuan Yang a, Ye Liu b, Xiangyu Wang a a
b
Department of Chemistry, Zhengzhou University, Zhengzhou, Henan 450052, PR China Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, PR China Received 4 December 2006; received in revised form 17 July 2007; accepted 18 July 2007 Available online 27 July 2007
Abstract Konjac glucomannan supported palladium catalyst was prepared and applied for Heck arylation reaction of conjugate alkenes with aryl halides, to afford corresponding cross-coupling products in good to excellent yields. The catalyst was recovered by simple filtration and reused for five times without loss of activity. Ó 2007 Published by Elsevier Ltd. Keywords: Palladium catalyst; Konjac glucomannan; Biopolymer; Heck reaction
1. Introduction Soluble and insoluble polymer-supported catalysts have received much attention in organic cross-coupling reactions due to industrial interest of the resulting products and the need for research of recoverable catalysts with long-term stability [1,2]. Although homogeneous catalysts often have higher activities, heterogeneous catalysts possess significant advantages from a practical point of view as well as in terms of sustainable green chemistry for the ease of product purification and the potential for recycle. Typically, inorganic material, such as silica, zeolites and metal oxide, have been employed as * Corresponding author. Tel.: +86 371 67761927; fax: +86 371 67766076. E-mail address: [email protected] (P. Liu).
1381-5148/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.reactfunctpolym.2007.07.031
solid supports in heterogeneous catalytic systems [3–5]. Recently, a number of studies have focused on the use of biopolymer as support for catalytic application [6–10]. Biopolymers have several interesting features, for example, high sorption capacity and stability of metal anions. The physical and chemical versatility of biopolymers make them attractive to use as supports. Moreover, biopolymers can be moulded in different forms, flakes, gel beads, fibers, membranes, hollow fibers and sponge, or supported on inert materials. So biopolymers are attractive candidates to explore for supported catalysts [11,12]. Konjac glucomannan (KGM) is a natural polysaccharide isolated from the tubers of amorphophallus konjac plants. It consists of b-1,4-linked D-glucose and D-mannose units, and the molar ratio of glucose and mannose has been reported to be around 1–1.60 [13–15].
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
KGM possesses excellent biodegradability, biocompatibility and many unique pharmacological functions. It has been generally used in food, filmformation, chemical engineering, and also specifically in biomedical applications (drug delivery, cellular therapy, etc). The abundant hydroxyl groups and certain amount of acetyl groups in KGM have high activity, metal ions can chelated to these active groups [16]. However, as a support for catalytic application, it has not been reported. Herein, we report the efficient Heck arylation reaction of conjugate alkenes with aryl halides using Konjac glucomannan supported palladium complex as catalyst. 2. Experimental 2.1. Characterization and materials Melting points were taken with a XT4A(Beijing Keyi) micro melting point apparatus, the temperature are uncorrected. IR spectra were obtained using a Perkin–Elmer FT-IR 1750 spectrometer. 1 H NMR spectra were recorded on a Bruker DPX-2400 spectrometer with TMS as an internal standard in CDCl3 or DMSO-d6 as solvent. The elemental content of palladium was determined by HITACHIZ-8000 atomic absorption spectroscopy. TG–DSC measurement was carried on STA409PC (German NETZSCH) thermogravimetry and differential scanning calorimeter. Agilent 4890D gas chromatography (Shanghai Anjielun China) with hydrogen flame temperature detector was used. Xray photoelectron spectra (XPS) were recorded on a Perkin–Elmer PHI 5000C ESCA system equipped with a dual X-ray source, of which the Al Ka (1486.6 eV) anode and a hemispherical energy analyzer were used. The background pressure during data acquisition was kept below 10 6 Pa. Measurement was performed at pass energy of 93.90 eV. All the binding energies were calibrated by using contaminant carbon (C1S = 284.6 eV) as a reference. Reagents were used as received without further purification. 2.2. Catalyst preparation To a solution of PdCl2 (0.344 g) in ethanol was added Konjac glucomannan (10.0 g). The mixture was stirred for 54 h at 60 °C. After being cooled to the room temperature, the mixture was filtered, washed several times with ethanol and acetone
ArI +
Y
KGM-Pd Solvent, base
385
Ar Y
Scheme 1. The arylation reaction of olefin with aryl halide.
respectively, and dried under vacuum to get grey Konjac glucomannan supported palladium catalyst (KGM–Pd). The palladium content in KGM–Pd catalyst was determined to be 1.21 wt.% by atomic absorption spectroscopy. 2.3. Reaction procedures In order to evaluate the catalytic activity of KGM–Pd, the arylation reaction of olefin with aryl halide was studied (Scheme1). A mixture of aryl halide, olefin, base, solvent and KGM–Pd was stirred under nitrogen in oil bath at the proper temperature for several hours. The reaction mixture was cooled, then the catalyst was separated by filtration, washed with solvent and reused in the next run. For entries (Tables 1 and 2) and entries 4–13 (Table 3), the filtrates were poured into 2% HCl solution to pH 1, white precipitates were formed. The precipitates were filtered, washed with H2O and dried to give the crude products, then recrystallized from ethanol. The products were characterized by melting points and 1H NMR. For entries 1–3 (Table 3), the filtrates were analyzed by GC. 3. Results and discussion 3.1. The characterization of KGM–Pd catalyst 3.1.1. IR and XPS analysis The natural KGM, stretching vibration of O–H group is a broad band and occurs at about 3441.1 cm 1. The band at 1061.8 and 1012.6 cm 1 assigned to stretching vibration of –CH2–O–CH2– groups. The peak at 1734.4 cm 1 due to C@O groups in KGM. The intense peak at 1647.0 cm 1 is attributed to the in-plane deformation of the water molecule [17]. Compared to those peaks of KGM, the broad band of KGM–Pd at 3440.2 cm 1 is due to O–H stretching vibration; the stretching vibration of –CH2–O–CH2– got shift to 1065.1 and 1020.0 cm 1. In order to study the details of interaction between KGM and palladium, KGM, KGM–Pd and re-catalyst were characterized by XPS. The deconvoluted peaks are calculated by the program
386
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
Table 1 Effect of various reaction conditions on the yield of cinnamate Entry
Temperature (°C)
n(PhI):n(AA)
Catalyst (g)
Base (mmol)
Solvent
Reaction time (h)
Yield (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
70 90 100 110 120 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1 1:1.2 1:1.3 1:1.6 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.01 0.03 0.06 0.05 0.05 0.05
Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) NaOAc (25) Bu3N (25) Pyridine (25) Et3N (10) Et3N (15) Et3N (20) Et3N (30) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25)
DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF EtOH NMP 1,4-Dioxane DMF DMF DMF DMF DMF DMF
1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 0.5 2.5 3
13.6 86.4 91.9 81.9 83.4 81.3 82.7 85.4 88.4 0 90.6 15.3 73.5 88.8 88.6 85.9 1.70 88.6 67.9 79.0 82.7 91.9 64.7 81.3 74.1
PhI: 10.0 mmol, the volume of solvent: 6 mL. Table 2 Yield of reaction with catalyst recycle Recycle no.
Fresh
1
2
3
4
5
Yield (%)
91.9
88.5
88.1
91.0
87.9
89.3
Reaction conditions: 10.0 mmol PhI, n(PhI):n(AA):n(Et3N) = 1: 1.4:2.5, 6 mL DMF, 100 °C, 0.05 g cat., reaction time 1.5 h.
of XPS Peak 41. The results are shown in Figs. 1 and 2. The binding energies of O1s in KGM–Pd are 532.1 eV and 533.5 eV, which are 0.5 eV and 0.4 eV higher than those in KGM respectively. The fresh catalyst shows two peaks at 335.8 eV of Pd3d5/2 which is attributed to Pd(0) and 336.5 eV of Pd3d5/2 which is attributed to Pd(II) [18], Pd(0)(3d5/2) binding energy in the fresh catalyst is 0.7 eV higher than that in Pd black(3d5/2 = 335.1 eV), the Pd(II)(3d5/2) binding energy in the catalyst is 1.3 eV lower than that in PdCl2 (3d5/2 = 337.8 eV). These results show that Pd particles are immobilized on biopolymer KGM, and imply that coordination bonds are formed between O of KGM and palladium particles. The results are also in agreement with IR spectra. From Fig. 2b, we can find that Pd(0) particle is unique state in the re-catalyst, the re-catalyst is black. All
these results show that Pd(II) in the fresh catalyst was reduced to Pd(0) during the reaction process, and the Pd(0) is the centre of catalytic activity. 3.1.2. TG-DSC analysis Generally, Heck reaction was conducted under the heated condition. The thermal stability of catalyst has a great effect on the catalytic activity and the reused performance. TG-DSC curves of KGM–Pd catalyst is presented in Fig. 3. A endothermic peak near 100 °C (very weak and broad) is attributed to the lost of the adsorptive water and a exothermic peak near 289.7 °C (very strong and sharp) is attributed to the decompose of catalyst. The weight loss which was observed in the temperature range 266–380 °C. These results indicate the KGM–Pd catalyst has a good thermal stability from the room temperature to 266 °C. 3.2. The cross-coupling reaction of iodobenzene with acrylic acid catalyzed by KGM–Pd 3.2.1. Effect of reaction conditions on the crosscoupling reaction of iodobenzene with acrylic acid In order to evaluate catalytic activity of KGM– Pd, the arylation reaction of iodobenzene (PhI) with
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
387
Table 3 Heck reactions of aryl halide with olefins Entry
ArI (mmol)
Y (mmol)
Base (mmol)
Catalyst (g)
Temperature (°C)
Time (h)
Solvent (mL)
Yield (%)
1 2 3 4 5 6 7 8 9 10 11 12 13
C6H5I (2) C6H5I (2) C6H5I (2) C6H5I (10) C6H5I (10) 4-CH3C6H4I (2) 4-CH3OC6H4I (2) 4-CH3OCOC6H4I (2) 4-CH3C6H4I (2) 4-CH3OC6H4I (2) 4-CH3OCOC6H4I (2) 4-CH3C6H4I (2) 4-CH3OC6H4I (2)
COOBu-n (2.2) COOMe (2.2) COOEt (2.2) CONH2 (14) Ph (13) COOH (2.8) COOH (2.8) COOH (2.8) CONH2 (2.8) CONH2 (2.8) CONH2 (2.8) Ph (2.6) Ph (2.6)
Et3N(5) Et3N(5) Et3N(5) Et3N(25) Et3N(18) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5)
0.05 0.05 0.05 0.05 0.10 0.025 0.025 0.05 0.05 0.05 0.05 0.05 0.05
100 100 100 100 120 100 100 100 120 120 120 120 120
1.5 1 1 2 12.5 10 10 6 3.5 5.5 1.5 12 12
DMF(4) DMF(4) DMF(4) DMF(2) DMF(6) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4)
99.0 90.8 93.0 85.5 95.6 82.8 87.8 92.7 85.8 88.8 92.9 87.9 88.2
a
a.u.
O1s
as follows: PhI:10 mmol, n(PhI):n(AA):n(Et3N) = 1: 1.4:2.5, catalyst 0.05 g, solvent DMF 6 mL and 100 °C for 1.5 h. Under the above conditions, the yield of cinnamate was 91.9%. 3.2.2. Catalyst recycling For the practical application in the Heck reaction, the lifetime of heterogeneous catalysts and
528
530
532
534
536
538
Binding energy (eV)
a
b
Pd3d
O1s
a.u.
a.u.
Pd(11)
528
530
532
534
536
Pd(0)
332
538
334
acrylic acid (AA) was studied. Effect of different reaction conditions (reaction temperature (entries 1–5), molar ratio of iodobenzene to acrylic acid (entries 3, 6–9), kinds and amount of base (entries 3, 10–16), solvent (entries 3, 17–19), amount of catalyst (entries 3, 20–22), and reaction time (entries 3, 23–25)) on the yield of cinnamate was investigated, the results are summarized in Table 1. The appropriate conditions for the reaction were established
338
340
342
344
346
b
Pd3d
a.u.
Fig. 1. O1s XPS spectra of (a) KGM and (b) KGM–Pd.
336
Binding eneryg (eV)
Binding energy (eV)
332
334
336
338
340
342
344
346
Binding energy (eV) Fig. 2. Pd3d XPS spectra of (a) fresh KGM–Pd and (b) the used KGM–Pd.
388
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
4. Conclusions
Fig. 3. TG-DSC spectra of KGM–Pd catalyst.
For the first time, the palladium supported on KGM catalyst was developed which was successfully employed in the carbon–carbon bond formation to give good yields and selectivities only to the trans-products. Effect of different reaction conditions on the reaction of iodobenzene with acrylic acid was investigated. The catalyst was recycled up to five times without significant loss in the catalytic activity. For the arylation of conjugated alkenes with aryl halides, it offers practical advantages such as easy preparation, separation from the reaction mixture and reuse. References
their reusability are very important factors. After the completion of reaction, the catalyst was recovered by simple filtration and washed with solvent (DMF), and reused in next reaction of iodobenzene with acrylic acid. From Table 2, it can be seen that the catalyst was recycled up to five times without significant loss in the catalytic activity, and the yield of 89.3% in the 5th recycle was still achieved. Under the appropriate reaction conditions, when using PdCl2 (0.0010 g, the Pd amount is as same as 0.05 g of KGM–Pd) instead of KGM–Pd catalyst, the yield of cinnamate was only 79.1%, and the homogeneous PdCl2 catalysts cannot be recovered and reused.
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
3.3. The cross-coupling reaction of aryl halide with diverse olefins The cross-coupling reactions of various aryl iodides with diverse olefins were also investigated. The progresses of reaction were monitored by TLC. The results are summarized in Table 3. It shows that all of aryl iodides employed could be cross-coupled with olefins to give the desired trans-products in good yields, the trans-selectivity was always near quantitative and no cis-products were observed.
[12] [13] [14] [15] [16] [17] [18]
J.A. Gladysz, Chem. Rev. 102 (2002) 3215. D.C. Sherrington, Chem. Commun. 21 (1998) 2275. A.G.S. Prado, C. Airoldi, J. Mater. Chem. 12 (2002) 3823. V. Sage, J.H. Clark, D.J. Macquarrie, J. Catal. 227 (2004) 502. R. Bouarab, O. Cherif, A. Auroux, Green Chem. 5 (2003) 209. W.L. Wei, H.Y. Zhu, C.L. Zhao, M.Y. Huang, Y.Y. Jang, React. Funct. Polym. 59 (2004) 33. K.R. Reddy, N.S. Kumar, P.S. Reddy, B. Sreedhar, M.L. Kantam, J. Mol. Catal. A: Chem. 252 (2006) 12. K. Huang, L. Xue, Y.C. Hu, M.Y. Huang, Y.Y. Jiang, React. Funct. Polym. 50 (2002) 199. P. Liu, L. Wang, X.Y. Wang, Chinese Chem. Lett. 15 (2004) 475. X. Xu, P. Liu, S.H. Li, P. Zhang, X.Y. Wang, React. Kinet. Catal. Lett. 88 (2006) 217. J.H. Clark, D.J. Macquarrie (Eds.), Green Chemistry and Technology, Blackwell, Abingdon, 2002. E. Guibal, Prog. Polym. Sci. 30 (2005) 71. K. Kato, K. Matsuda, Agr. Biol. Chem. 33 (1969) 1446. M. Maeda, H. Shimahara, N. Sugiyama, Agr. Biol. Chem. 44 (1980) 245. F. Smith, H.C. Srivastava, J. Am. Chem. Soc. 81 (1959) 1715. F.Y. Zhang, Y.M. Zhou, Y. Cao, J. Chen, Mater. Lett. (2007), doi:10.1016/j.matlet.2007.03.108. H. Zhang, M. Yoshimura, K. Nishinari, M.A.K. Williams, T.J. Foster, I.T. Norton, Biopolymer 59 (2001) 38. M. Faticanti, N. Cioffi, S. De Rossi, N. Ditaranto, P. Porta, L. Sabbatini, T.B. Zacheo, Appl. Catal. B: Environ. 60 (2005) 73.
REACTIVE & FUNCTIONAL POLYMERS
Reactive & Functional Polymers 68 (2008) 384–388
www.elsevier.com/locate/react
Konjac glucomannan supported palladium complex: An efficient and recyclable catalyst for Heck reaction Pu Liu a,*, Yonghuan Yang a, Ye Liu b, Xiangyu Wang a a
b
Department of Chemistry, Zhengzhou University, Zhengzhou, Henan 450052, PR China Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, Shanghai 200062, PR China Received 4 December 2006; received in revised form 17 July 2007; accepted 18 July 2007 Available online 27 July 2007
Abstract Konjac glucomannan supported palladium catalyst was prepared and applied for Heck arylation reaction of conjugate alkenes with aryl halides, to afford corresponding cross-coupling products in good to excellent yields. The catalyst was recovered by simple filtration and reused for five times without loss of activity. Ó 2007 Published by Elsevier Ltd. Keywords: Palladium catalyst; Konjac glucomannan; Biopolymer; Heck reaction
1. Introduction Soluble and insoluble polymer-supported catalysts have received much attention in organic cross-coupling reactions due to industrial interest of the resulting products and the need for research of recoverable catalysts with long-term stability [1,2]. Although homogeneous catalysts often have higher activities, heterogeneous catalysts possess significant advantages from a practical point of view as well as in terms of sustainable green chemistry for the ease of product purification and the potential for recycle. Typically, inorganic material, such as silica, zeolites and metal oxide, have been employed as * Corresponding author. Tel.: +86 371 67761927; fax: +86 371 67766076. E-mail address: [email protected] (P. Liu).
1381-5148/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.reactfunctpolym.2007.07.031
solid supports in heterogeneous catalytic systems [3–5]. Recently, a number of studies have focused on the use of biopolymer as support for catalytic application [6–10]. Biopolymers have several interesting features, for example, high sorption capacity and stability of metal anions. The physical and chemical versatility of biopolymers make them attractive to use as supports. Moreover, biopolymers can be moulded in different forms, flakes, gel beads, fibers, membranes, hollow fibers and sponge, or supported on inert materials. So biopolymers are attractive candidates to explore for supported catalysts [11,12]. Konjac glucomannan (KGM) is a natural polysaccharide isolated from the tubers of amorphophallus konjac plants. It consists of b-1,4-linked D-glucose and D-mannose units, and the molar ratio of glucose and mannose has been reported to be around 1–1.60 [13–15].
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
KGM possesses excellent biodegradability, biocompatibility and many unique pharmacological functions. It has been generally used in food, filmformation, chemical engineering, and also specifically in biomedical applications (drug delivery, cellular therapy, etc). The abundant hydroxyl groups and certain amount of acetyl groups in KGM have high activity, metal ions can chelated to these active groups [16]. However, as a support for catalytic application, it has not been reported. Herein, we report the efficient Heck arylation reaction of conjugate alkenes with aryl halides using Konjac glucomannan supported palladium complex as catalyst. 2. Experimental 2.1. Characterization and materials Melting points were taken with a XT4A(Beijing Keyi) micro melting point apparatus, the temperature are uncorrected. IR spectra were obtained using a Perkin–Elmer FT-IR 1750 spectrometer. 1 H NMR spectra were recorded on a Bruker DPX-2400 spectrometer with TMS as an internal standard in CDCl3 or DMSO-d6 as solvent. The elemental content of palladium was determined by HITACHIZ-8000 atomic absorption spectroscopy. TG–DSC measurement was carried on STA409PC (German NETZSCH) thermogravimetry and differential scanning calorimeter. Agilent 4890D gas chromatography (Shanghai Anjielun China) with hydrogen flame temperature detector was used. Xray photoelectron spectra (XPS) were recorded on a Perkin–Elmer PHI 5000C ESCA system equipped with a dual X-ray source, of which the Al Ka (1486.6 eV) anode and a hemispherical energy analyzer were used. The background pressure during data acquisition was kept below 10 6 Pa. Measurement was performed at pass energy of 93.90 eV. All the binding energies were calibrated by using contaminant carbon (C1S = 284.6 eV) as a reference. Reagents were used as received without further purification. 2.2. Catalyst preparation To a solution of PdCl2 (0.344 g) in ethanol was added Konjac glucomannan (10.0 g). The mixture was stirred for 54 h at 60 °C. After being cooled to the room temperature, the mixture was filtered, washed several times with ethanol and acetone
ArI +
Y
KGM-Pd Solvent, base
385
Ar Y
Scheme 1. The arylation reaction of olefin with aryl halide.
respectively, and dried under vacuum to get grey Konjac glucomannan supported palladium catalyst (KGM–Pd). The palladium content in KGM–Pd catalyst was determined to be 1.21 wt.% by atomic absorption spectroscopy. 2.3. Reaction procedures In order to evaluate the catalytic activity of KGM–Pd, the arylation reaction of olefin with aryl halide was studied (Scheme1). A mixture of aryl halide, olefin, base, solvent and KGM–Pd was stirred under nitrogen in oil bath at the proper temperature for several hours. The reaction mixture was cooled, then the catalyst was separated by filtration, washed with solvent and reused in the next run. For entries (Tables 1 and 2) and entries 4–13 (Table 3), the filtrates were poured into 2% HCl solution to pH 1, white precipitates were formed. The precipitates were filtered, washed with H2O and dried to give the crude products, then recrystallized from ethanol. The products were characterized by melting points and 1H NMR. For entries 1–3 (Table 3), the filtrates were analyzed by GC. 3. Results and discussion 3.1. The characterization of KGM–Pd catalyst 3.1.1. IR and XPS analysis The natural KGM, stretching vibration of O–H group is a broad band and occurs at about 3441.1 cm 1. The band at 1061.8 and 1012.6 cm 1 assigned to stretching vibration of –CH2–O–CH2– groups. The peak at 1734.4 cm 1 due to C@O groups in KGM. The intense peak at 1647.0 cm 1 is attributed to the in-plane deformation of the water molecule [17]. Compared to those peaks of KGM, the broad band of KGM–Pd at 3440.2 cm 1 is due to O–H stretching vibration; the stretching vibration of –CH2–O–CH2– got shift to 1065.1 and 1020.0 cm 1. In order to study the details of interaction between KGM and palladium, KGM, KGM–Pd and re-catalyst were characterized by XPS. The deconvoluted peaks are calculated by the program
386
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
Table 1 Effect of various reaction conditions on the yield of cinnamate Entry
Temperature (°C)
n(PhI):n(AA)
Catalyst (g)
Base (mmol)
Solvent
Reaction time (h)
Yield (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
70 90 100 110 120 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1 1:1.2 1:1.3 1:1.6 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4 1:1.4
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.01 0.03 0.06 0.05 0.05 0.05
Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) NaOAc (25) Bu3N (25) Pyridine (25) Et3N (10) Et3N (15) Et3N (20) Et3N (30) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25) Et3N (25)
DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF DMF EtOH NMP 1,4-Dioxane DMF DMF DMF DMF DMF DMF
1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 0.5 2.5 3
13.6 86.4 91.9 81.9 83.4 81.3 82.7 85.4 88.4 0 90.6 15.3 73.5 88.8 88.6 85.9 1.70 88.6 67.9 79.0 82.7 91.9 64.7 81.3 74.1
PhI: 10.0 mmol, the volume of solvent: 6 mL. Table 2 Yield of reaction with catalyst recycle Recycle no.
Fresh
1
2
3
4
5
Yield (%)
91.9
88.5
88.1
91.0
87.9
89.3
Reaction conditions: 10.0 mmol PhI, n(PhI):n(AA):n(Et3N) = 1: 1.4:2.5, 6 mL DMF, 100 °C, 0.05 g cat., reaction time 1.5 h.
of XPS Peak 41. The results are shown in Figs. 1 and 2. The binding energies of O1s in KGM–Pd are 532.1 eV and 533.5 eV, which are 0.5 eV and 0.4 eV higher than those in KGM respectively. The fresh catalyst shows two peaks at 335.8 eV of Pd3d5/2 which is attributed to Pd(0) and 336.5 eV of Pd3d5/2 which is attributed to Pd(II) [18], Pd(0)(3d5/2) binding energy in the fresh catalyst is 0.7 eV higher than that in Pd black(3d5/2 = 335.1 eV), the Pd(II)(3d5/2) binding energy in the catalyst is 1.3 eV lower than that in PdCl2 (3d5/2 = 337.8 eV). These results show that Pd particles are immobilized on biopolymer KGM, and imply that coordination bonds are formed between O of KGM and palladium particles. The results are also in agreement with IR spectra. From Fig. 2b, we can find that Pd(0) particle is unique state in the re-catalyst, the re-catalyst is black. All
these results show that Pd(II) in the fresh catalyst was reduced to Pd(0) during the reaction process, and the Pd(0) is the centre of catalytic activity. 3.1.2. TG-DSC analysis Generally, Heck reaction was conducted under the heated condition. The thermal stability of catalyst has a great effect on the catalytic activity and the reused performance. TG-DSC curves of KGM–Pd catalyst is presented in Fig. 3. A endothermic peak near 100 °C (very weak and broad) is attributed to the lost of the adsorptive water and a exothermic peak near 289.7 °C (very strong and sharp) is attributed to the decompose of catalyst. The weight loss which was observed in the temperature range 266–380 °C. These results indicate the KGM–Pd catalyst has a good thermal stability from the room temperature to 266 °C. 3.2. The cross-coupling reaction of iodobenzene with acrylic acid catalyzed by KGM–Pd 3.2.1. Effect of reaction conditions on the crosscoupling reaction of iodobenzene with acrylic acid In order to evaluate catalytic activity of KGM– Pd, the arylation reaction of iodobenzene (PhI) with
P. Liu et al. / Reactive & Functional Polymers 68 (2008) 384–388
387
Table 3 Heck reactions of aryl halide with olefins Entry
ArI (mmol)
Y (mmol)
Base (mmol)
Catalyst (g)
Temperature (°C)
Time (h)
Solvent (mL)
Yield (%)
1 2 3 4 5 6 7 8 9 10 11 12 13
C6H5I (2) C6H5I (2) C6H5I (2) C6H5I (10) C6H5I (10) 4-CH3C6H4I (2) 4-CH3OC6H4I (2) 4-CH3OCOC6H4I (2) 4-CH3C6H4I (2) 4-CH3OC6H4I (2) 4-CH3OCOC6H4I (2) 4-CH3C6H4I (2) 4-CH3OC6H4I (2)
COOBu-n (2.2) COOMe (2.2) COOEt (2.2) CONH2 (14) Ph (13) COOH (2.8) COOH (2.8) COOH (2.8) CONH2 (2.8) CONH2 (2.8) CONH2 (2.8) Ph (2.6) Ph (2.6)
Et3N(5) Et3N(5) Et3N(5) Et3N(25) Et3N(18) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5) Et3N(5)
0.05 0.05 0.05 0.05 0.10 0.025 0.025 0.05 0.05 0.05 0.05 0.05 0.05
100 100 100 100 120 100 100 100 120 120 120 120 120
1.5 1 1 2 12.5 10 10 6 3.5 5.5 1.5 12 12
DMF(4) DMF(4) DMF(4) DMF(2) DMF(6) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4) DMF(4)
99.0 90.8 93.0 85.5 95.6 82.8 87.8 92.7 85.8 88.8 92.9 87.9 88.2
a
a.u.
O1s
as follows: PhI:10 mmol, n(PhI):n(AA):n(Et3N) = 1: 1.4:2.5, catalyst 0.05 g, solvent DMF 6 mL and 100 °C for 1.5 h. Under the above conditions, the yield of cinnamate was 91.9%. 3.2.2. Catalyst recycling For the practical application in the Heck reaction, the lifetime of heterogeneous catalysts and
528
530
532
534
536
538
Binding energy (eV)
a
b
Pd3d
O1s
a.u.
a.u.
Pd(11)
528
530
532
534
536
Pd(0)
332
538
334
acrylic acid (AA) was studied. Effect of different reaction conditions (reaction temperature (entries 1–5), molar ratio of iodobenzene to acrylic acid (entries 3, 6–9), kinds and amount of base (entries 3, 10–16), solvent (entries 3, 17–19), amount of catalyst (entries 3, 20–22), and reaction time (entries 3, 23–25)) on the yield of cinnamate was investigated, the results are summarized in Table 1. The appropriate conditions for the reaction were established
338
340
342
344
346
b
Pd3d
a.u.
Fig. 1. O1s XPS spectra of (a) KGM and (b) KGM–Pd.
336
Binding eneryg (eV)
Binding energy (eV)
332
334
336
338
340
342
344
346
Binding energy (eV) Fig. 2. Pd3d XPS spectra of (a) fresh KGM–Pd and (b) the used KGM–Pd.
388
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4. Conclusions
Fig. 3. TG-DSC spectra of KGM–Pd catalyst.
For the first time, the palladium supported on KGM catalyst was developed which was successfully employed in the carbon–carbon bond formation to give good yields and selectivities only to the trans-products. Effect of different reaction conditions on the reaction of iodobenzene with acrylic acid was investigated. The catalyst was recycled up to five times without significant loss in the catalytic activity. For the arylation of conjugated alkenes with aryl halides, it offers practical advantages such as easy preparation, separation from the reaction mixture and reuse. References
their reusability are very important factors. After the completion of reaction, the catalyst was recovered by simple filtration and washed with solvent (DMF), and reused in next reaction of iodobenzene with acrylic acid. From Table 2, it can be seen that the catalyst was recycled up to five times without significant loss in the catalytic activity, and the yield of 89.3% in the 5th recycle was still achieved. Under the appropriate reaction conditions, when using PdCl2 (0.0010 g, the Pd amount is as same as 0.05 g of KGM–Pd) instead of KGM–Pd catalyst, the yield of cinnamate was only 79.1%, and the homogeneous PdCl2 catalysts cannot be recovered and reused.
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
3.3. The cross-coupling reaction of aryl halide with diverse olefins The cross-coupling reactions of various aryl iodides with diverse olefins were also investigated. The progresses of reaction were monitored by TLC. The results are summarized in Table 3. It shows that all of aryl iodides employed could be cross-coupled with olefins to give the desired trans-products in good yields, the trans-selectivity was always near quantitative and no cis-products were observed.
[12] [13] [14] [15] [16] [17] [18]
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