A simple and efficient reusable polystyrene-supported palladium catalyst for Hiyama cross-coupling

en *, 228 aryl lpho th d t the preparation of elaborated lication rganic alyzed with and pr lds.5,6 organometallic reagent by various cheap, non-toxic, and stable is the impossibility to reuse the expensive catalyst and, often, the difficulty to avoid the presence of small amounts of palladium in products andwaste. To the best of our knowledge, very few efficient reusable palladium catalytic systems have been reported for Hiyama couplings.16 For example, the use of palladium nano- particles, which can be recovered from the reaction mixture and directly reused has been described,17,18 but, their catalytic activity gradually decreased during the subsequent reuses.17a The group of Tsai has reported a reusable Pd(NH3)2/Cl2/cationic bipyridyl ligand a slightly lower Pd content (0.1%), the (diphenyl)- and (tert-butyl- palladium cata- the commercially rthy that 1a and moisture-stable. The reaction conditions were optimized using 4-iodotoluene and trimethoxyphenylsilane as model substrates in the presence of TBAF$3H2O and catalyst 1a or 1b (Table 1). Using catalyst 1a (0.1 mol % of supported palladium), the desired biaryl 2a was ob- tained in almost quantitative yields (entries 1, 3, 5 and 6). It is noteworthy that catalyst 1b turned out to be much less reactive (entries 2 and 4). Use of only 1 equiv of TBAF$3H2O or replacement of TBAF$3H2O by either CsF, Cs2CO3, NaOH or K3PO4$H2O (in con- ditions of entry 1) afforded 2a in only poor yields. Biaryl 2a was Contents lists available at he w. Tetrahedron 69 (2013) 264e267 * Corresponding authors. Tel.: þ33 (0)3 89 60 87 22; fax: þ33 (0)3 89 60 87 99; organosilicon reagents has suscited a huge interest.11 The Hiyama reaction is traditionally performed by coupling aryl halides with aryltrialkoxysilanes12 or sometimes arylsilanols13 in the presence of a base and a soluble palladium catalyst.14,15 The major inconvenient phenyl)-phosphinomethylpolystyrene-supported lysts 1a23 and 1bwere prepared in two steps from available Merrifield resin (Scheme 1). It is notewo 1b can be prepared on a 20 g scale and are air- and drawbacks is the high price of arylboronic acids or, in some cases, their difficulty of preparation. Other common methodologies used for the synthesis of biaryls imply palladium-catalyzed cross-cou- plings of aryl halides with organozinc,6b,7 organotin8 or organo- magnesium reagents.9,10 In the last decade, the replacement of the are also efficient for Hiyama reactions. 2. Results and discussion According to our previously published procedures,22a,b but with 1. Introduction Biaryls are key building blocks for molecules finding widespread app active compounds,1 agrochemicals,2 o organocatalysts.4 The palladium-cat coupling of aryl halides or sulfonates of the most powerful route to biaryls mild reaction conditions and high yie e-mail address: [email protected] (J.-M. Bech 0040-4020/$ e see front matter � 2012 Elsevier Ltd. http://dx.doi.org/10.1016/j.tet.2012.10.035 s as pharmaceutically materials for OLEDs3 or SuzukieMiyaura cross- arylboronic acids is one oceeds generally under However, one of its few catalytic system19while Sreedhar et al. have described very recently a magnetically recoverable and reusable Pd/Fe3O4 catalyst.20,21 We have recently reported a short preparation of highly efficient and reusable heterogeneous phosphinomethylpolystyrene-supported palladium catalysts for SuzukieMiyaura, MizorokieHeck, and Sonogashira cross-couplings.22 Herein,we show that these catalysts Green chemistry Polymers A simple and efficient reusable polystyr catalyst for Hiyama cross-coupling Carine Diebold, Antoine Derible, Jean-Michel Becht Universit�e de Haute Alsace, Institut de Science des Mat�eriaux de Mulhouse, LRC-CNRS 7 a r t i c l e i n f o Article history: Received 25 June 2012 Received in revised form 8 October 2012 Accepted 10 October 2012 Available online 16 October 2012 Keywords: Biaryls Heterogeneous catalysis a b s t r a c t An efficient synthesis of bi the presence of a dipheny cross-coupling proceeds in used at least four times an Tetra journal homepage: ww t). All rights reserved. e-supported palladium Claude Le Drian * , 15 rue Jean Starcky, F-68057 Mulhouse cedex, France s using a Hiyama reaction between aryl iodides and aryltrialkoxysilanes in sphinomethylpolystyrene-supported palladium catalyst is described. The e presence of only 0.1 mol % of supported palladium. The catalyst can be he palladium leaching is extremely low (ca. 1% of the initial amount). � 2012 Elsevier Ltd. All rights reserved. SciVerse ScienceDirect dron elsevier .com/locate/ tet obtained in 84% yield by reacting 4-bromotoluene instead of 4- leached from catalyst 1a. We determined also that 0.05% of the initial amount of palladium was found in the final product after usual work-up. It should be noted that this amount corresponds to a contamination of only 0.3 ppm of palladium in the final product. A hot filtration testwas carried out after 15min of reaction (according to Table 1, entry 1). The yield of 2a was then 54% and showed no increase even after heating at 100 �C for another 20 h. Therefore soluble palladium entities should not play any significant role in this reaction. It should be noted that catalyst 1awas not reusable if the reactionwas performed in THF, toluene/1,4-dioxane or toluene/ THF (according to Table 1, entries 3, 5, 6) or by replacing 4- iodotoluene with 4-bromotoluene in the presence of 0.5 mol % of supported palladium (conditions of Table 1, entry 1). To obtain information on the structure of this catalyst, Trans- mission Electron Microscopy (TEM) seems the method of choice. It turned out that some palladium aggregates were observed in the fresh catalyst 1a. Neither their size (up to ca. 1e5 nm) nor their abundance changed significantly after one use (Fig. 1). It should be noted that the nature of the support precluded the use of other, more powerful, methods of structural elucidation such as the Scanning Tunneling Microscopy (STM) that we had used to de- termine the shape of the palladium aggregates formed on Highly Ordered Pyrolytic Graphite (HOPG) surfaces.24 Cl 1) Li-PRPh, THF, rt, 72 h 2) Pd(PPh3)4, toluene, rt PRPh Pd 1a-b C. Diebold et al. / Tetrahedron 69 (2013) 264e267 265 Table 1 Optimization of the reaction conditions I Si(OMe)3 + TBAF.3H2O, Solvent 100 °C, 20 h Catalyst 1a or 1b 2a Entrya Catalyst Solventb Yieldc (%) 1 1a Toluene 99d (55)e 2 1b Toluene 35 1a: R = Ph (9.4 µmol Pd / g) Polystyrene-DVB copolymer 1b: R = tert-Bu (9.4 µmol Pd / g) Scheme 1. Preparation of catalysts 1a and 1b. iodotoluene with trimethoxyphenylsilane in conditions of entry 1, but this coupling required the use of 0.5 mol % of supported pal- ladium. The reaction between 4-chlorotoluene and trimethox- yphenylsilane was unsuccessful using either catalyst 1a or 1b. Commercially available Pd EnCat TPP30 or NP30 (in conditions of entry 1), afforded 2a in yields, respectively, of 87% and 91%, slightly lower than those obtained with 1a (entries 9 and 10). Finally, in- spired by a previous literature report,13 we tried the coupling of 4- iodotoluene with dimethylphenylsilanol in the presence of Cs2CO3 and 1a in toluene but only the starting materials could be found. The possibility to reuse catalyst 1a was then determined. It should be noted that 1a can be recovered in >95% yield after use (according to Table 1, entry 1). Using for each run the amount of catalyst recovered from the previous one, the reaction between 4- iodotoluene and trimethoxyphenylsilane can be performed at least four times with no significant decrease in the yield (Table 2). By completemineralization of the filtrate at the end of the reaction, we measured that only ca. 1% of the initial amount of palladium was The scope of the Hiyama cross-coupling was then evaluated by reacting various aryl iodides and aryltrialkoxysilanes in thepresence of catalyst 1a under the optimized reaction conditions (Table 3). Aryl iodides bearingelectron-donatingor electron-attracting groups 3 1a THF 98 (88)e 4 1b THF 5 5 1a Toluene/1,4-dioxane 50:50 99 (95)e 6 1a Toluene/THF 50:50 99 (98)e 7 1a Toluene/THF 25:75 90 8 1a Toluene/THF 75:25 79 9 Pd EnCat TPP30 Toluene 87 10 Pd EnCat NP30 Toluene 91 a Reactions performed with 4-iodotoluene (1.0 equiv), trimethoxyphenylsilane (2.0 equiv), and TBAF$3H2O (2.0 equiv) in the presence of 0.1 mol % of supported palladium. b Reactions performed in the presence of 1% of H2O. c Calculated yields by 1H NMR of the crude reaction mixture. d Using 1.0 equiv of trimethoxyphenylsilane instead of 2.0 equiv gave 2a in edr afforded the corresponding biaryls in 60e99% yields (entries 1e8). It is noteworthy that sterically hindered biaryls were also obtained in good yields by reacting 2-isopropyliodobenzene or 2,6- dimethyliodobenzene with trimethoxyphenylsilane (entries 4 and 5). Replacing trimethoxyphenylsilane by triethoxyphenylsilane gave the desired biaryl in 68% yield (entry 9). Finally, the couplings be- tween 4-iodotoluene and various trimethoxyarylsilanes bearing a methyl group were successful and afforded the corresponding biaryls, in 62e80% yield (entries 10e12). 3. Conclusion Hiyama couplings were performed in the presence of an easy to prepare and reusable palladium catalyst. The reactions were per- formed with only 0.1 mol % of supported palladium and the pal- ladium leaching was extremely low (ca. 1%). This work describes another example of the use of catalyst 1a for carbonecarbon bond forming reactions and constitutes, to the best of our knowledge, the first use of an efficient polystyrene-supported palladium catalyst in Hiyama reactions. 4. Experimental section 4.1. General remarks The reagents were obtained from commercial sources and were used without further purifications. Aryltrialkoxysilanes have been prepared from aryl bromides and tetramethoxysilanes following a literature report.25 Catalysts 1a22a and 1b22b have been previously prepared by our group. They are air- and moisture-stable and can be used and stored without particular precautions. The reaction mixtures were filtered on a polytetrafluoroethylene membrane (0.2 mm). 1H NMR spectra were recorded using a 400 MHz in- strument in CDCl3. Chemical shifts are reported in parts per million (d) downfield from TMS. Spin multiplicities are indicated by the following symbols: s (singlet), d (doublet), t (triplet), and m (mul- tiplet). The melting points or 1H NMR spectra of biaryls 2aek were in accordance with literature reports (see below). 4.2. General procedure for the syntheses of compounds 2aek Catalyst 1a22a (43 mg, 0.1 mol % of supported palladium) was added to a solution of aryl iodide (0.40 mmol, 1.0 equiv), aryl- trialkoxysilane (0.80 mmol, 2.0 equiv), TBAF$3H2O (252 mg, 0.8 mmol, 2.0 equiv) in amixture of toluene (5mL) and H2O (50 mL). The reaction mixture was heated at 100 �C for 20 h. After cooling to rt, 1a was filtered under vacuum on a 0.2 mm membrane. The catalyst was successively washed with toluene (10 mL) and Et2O (10 mL). The combined organic phases were washed with H2O (20 mL), dried with MgSO4, filtered, and concentrated under vacuum. The residue was purified by flash-chromatography on silica gel. Catalyst 1a was dried under vacuum and can directly be used for another Hiyama coupling. 4.2.1. 4-Methylbiphenyl (2a). Elution with Et2O/cyclohexane 1:99 afforded 66.5 mg (99% yield) of a white solid; mp 47e48 �C (lit. mp 47.7 �C).26 1H NMR (400 MHz, CDCl3) d (ppm): 2.41 (s, 3H), 7.26 (d, 3J(H,H)¼7.3 Hz, 2H), 7.35 (t, 3J(H,H)¼7.3 Hz, 1H), 7.44 (t, 3J(H,H)¼ 7.3 Hz, 2H), 7.50 (d, 3J(H,H)¼8.4 Hz, 2H), 7.59 (d, 3J(H,H)¼8.4 Hz, 2H). 13C NMR (100 MHz, CDCl3) d (ppm): 21.1, 126.9, 127.0, 128.7, 129.5, 137.0, 138.3, 141.1. 4.2.2. 3-Methylbiphenyl (2b). Elution with Et2O/cyclohexane 1:99 afforded 66.5 mg (99% yield) of an orange oil. 1H NMR C. Diebold et al. / Tetrah266 (400 MHz, CDCl3) d (ppm): 2.46 (s, 3H), 7.20 (m, 1H), 7.39 (m, 6H), 7.62 (d, 3J(H,H)¼7.3 Hz, 2H).27 13C NMR (100 MHz, CDCl3) d (ppm): 21.5, 124.2, 127.1, 127.2, 127.9, 128.0, 128.6, 128.7, 138.3, 141.2, 141.3. 4.2.3. 2-Methylbiphenyl (2c). Elution with Et2O/cyclohexane 1:99 afforded 57.9 mg (86% yield) of a yellowish oil. 1H NMR (400 MHz, CDCl3) d (ppm): 2.29 (s, 3H), 7.26 (m, 4H), 7.35 (m, 3H), 7.41 (m, 2H).28 13C NMR (100 MHz, CDCl3) d (ppm): 20.4, 125.7, 126.7, 127.2, 128.0, 129.2, 129.8, 130.2, 135.3, 141.9, 142.0. 4.2.4. 2-Isopropylbiphenyl (2d). ElutionwithEt2O/cyclohexane1:99 afforded 47.1 mg (60% yield) of a colorless oil. 1H NMR (400 MHz, CDCl3) d (ppm): 1.07 (d, 3J(H,H)¼6.9 Hz, 6H), 2.97 (hept, 3J(H,H)¼ 6.9 Hz,1H), 7.15 (m, 9H).29 13C NMR (100MHz, CDCl3) d (ppm): 24.3, 29.3, 125.3, 125.5, 126.7, 127.6, 127.9, 129.3, 141.0, 142.1, 146.3. 4.2.5. 2,6-Dimethylbiphenyl (2e). Elution with Et2O/cyclohexane 1:99 afforded 44.4 mg (61% yield) of a yellowish oil. 1H NMR (400 MHz, CDCl3) d (ppm): 1.93 (s, 6H), 7.05 (m, 5H), 7.25 (m, 3H).30 13C NMR (100 MHz, CDCl3) d (ppm): 20.8, 126.6, 127.0, 127.2, 128.4, 128.9, 136.0, 141.1, 141.8. 4.2.6. 4-Methoxybiphenyl (2f). Elution with AcOEt/cyclohexane 2:98 afforded 65.6mg (89% yield) of awhite solid; mp 92e94 �C (lit. mp 91.1e92.3 �C).31 1H NMR (400MHz, CDCl3) d (ppm): 3.87 (s, 3H), 6.99 (d, 3J(H,H)¼8.8 Hz, 2H), 7.31 (t, 3J(H,H)¼7.3 Hz, 1H), 7.42 (m, 2H), 7.55 (m, 4H). 13C NMR (100 MHz, CDCl3) d (ppm): 55.3, 114.2, 126.6, 126.7, 128.1, 128.7, 133.7, 140.8, 159.1. 4.2.7. 4-Chlorobiphenyl (2g). Elution with AcOEt/cyclohexane 2:98 afforded 74.7 mg (99% yield) of a white solid; mp 78 �C (lit. mp 78.0e78.5 �C).27 1H NMR (400 MHz, CDCl3) d (ppm): 7.44 (m, 5H), 7.57 (m, 4H).28 13C NMR (100 MHz, CDCl3) d (ppm): 126.9, 127.6, 128.4, 128.8, 128.9, 133.3, 135.6, 140.0. 4.2.8. 1-(4-Biphenylyl)ethanone (2h). Elution with AcOEt/cyclo- hexane 10:90 afforded 62.0 mg (79% yield) of a white solid; mp 119e120 �C (lit. mp 118e120 �C).32 1H NMR (400 MHz, CDCl3) d (ppm): 2.66 (s, 3H), 7.45 (m, 3H), 7.64 (d, 3J(H,H)¼7.0 Hz, 2H), 7.69 (d, 3J(H,H)¼6.7 Hz, 2H), 8.05 (d, 3J(H,H)¼6.7 Hz, 2H). 13C NMR (100 MHz, CDCl3) d (ppm): 26.6, 127.1, 127.2, 128.2, 128.8, 128.9, 135.8, 139.8, 145.7, 197.7. 4.2.9. 4,40-Dimethylbiphenyl (2i). Elution with cyclohexane afforded 58.4mg(80%yield)of acolorlessoil.1HNMR(400MHz,CDCl3)d (ppm): 2.42 (s, 6H), 7.26 (d, 3J(H,H)¼8.1 Hz, 4H), 7.51 (d, 3J(H,H)¼8.1 Hz, 4H).33 13C NMR (100 MHz, CDCl3) d (ppm): 21.0, 126.8, 129.4, 136.7, 138.3. 4.2.10. 3,40-Dimethylbiphenyl (2j). Elution with cyclohexane affor- ded 51.7 mg (71% yield) of a colorless oil. 1H NMR (400 MHz, CDCl3) d (ppm): 2.55 (s, 3H), 2.57 (s, 3H), 7.29 (d, 3J(H,H)¼7.6Hz,1H), 7.39 (d, 3J(H,H)¼8.0Hz, 2H), 7.47 (t, 3J(H,H)¼7.6Hz,1H), 7.55 (m, 2H), 7.65 (d, 3J(H,H)¼8.0 Hz, 2H).34 13CNMR (100MHz, CDCl3) d (ppm): 21.0, 21.5, 124.1, 126.9, 127.6, 127.7, 128.6, 129.4, 136.8, 138.2, 138.4, 141.1. 4.2.11. 2,40-Dimethylbiphenyl (2k). Elution with cyclohexane affor- ded 45.2 mg (62% yield) of a colorless oil. 1H NMR (400MHz, CDCl3) d (ppm): 2.41 (s, 3H), 2.52 (s, 3H), 7.35 (m, 8H).35 13C NMR (100MHz, CDCl3) d (ppm): 20.5, 21.1, 125.7, 127.0,128.7,129.0,129.8, 130.2, 135.3, 136.3, 139.0, 141.9. 4.3. General procedure for hot filtration and determination of the palladium leached in the reaction medium during the Hiyama reaction on 69 (2013) 264e267 The reaction mixture was filtered at reaction temperature on a 0.2 mmmembrane and the catalyst washedwith AcOEt (3�10mL). For palladium determinations, the filtrates were combined and evaporated under reduced pressure. A mixture of concentrated H2SO4 (3 mL) and fuming HNO3 (2 mL) was added to the residue. This mixture was heated in a fume hood until disappearance of nitric fumes, complete evaporation of HNO3, and beginning of the refluxof the remaining H2SO4. After cooling to 100 �C, fuming HNO3 (2mL) was then added, themixturewas heated until evaporation of HNO3 and this process was repeated three times, the sample being 3. Moorthy, J. N.; Venkatakrishnan, P.; Huangb, D.-F.; Chow, T. J. Chem. Commun. 2008, 2146. 4. Spivey, A. C.; Fekner, T.; Spey, S. E. J. Org. Chem. 2000, 65, 3154. 5. Tsuji, J. Palladium Reagents and Catalysts: New Perspectives for the 21st Century; Wiley: New York, NY, 2004. 6. (a) Hassan, J.; S�evignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem. Rev. 2002, 102, 1359; (b) Wu, X. F.; Anbarasan, P.; Neumann, H.; Beller, M. Angew. Chem., Int. Ed. 2010, 49, 9047 and references therein. 7. Negishi, E.-i.; Hu, Q.; Huang, Z.; Qian, M.; Wang, G. Aldrichimica Acta 2005, 38, 71. 8. Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508. C. Diebold et al. / Tetrahedron 69 (2013) 264e267 267 heated in acids for globally 15 min. Most of the H2SO4 was then boiled off and after cooling a mixture of concentrated HCl (2 mL) and concentrated HNO3 (2 mL) was added and heated until evap- oration of the acids. The residue was then dissolved in H2O (25 mL) and the amount of palladium present in this mixture was then determined by complexation following a procedure described in the literature.36 4.4. General procedure for the determination of the palladium content of the catalyst Concentrated H2SO4 (3 mL) was added to a sample of the cata- lyst (20 mg). The mixture was brought to reflux in a fume hood. After cooling to 100 �C, fuming HNO3 (2 mL) was then added and the heating resumed until disappearance of nitric fumes, complete evaporation of HNO3, and beginning of the reflux of the remaining H2SO4. After cooling to 100 �C, fuming HNO3 (2 mL) was then added, the mixture was heated until evaporation of HNO3 and this process was repeated, the sample being heated in acids for globally 15 min. Most of the H2SO4 was then boiled off and after cooling a mixture of concentrated HCl (2 mL) and concentrated HNO3 (2 mL) was added and heated until evaporation of the acids. The residue was then dissolved in H2O (25 mL) and the amount of palladium present in this mixture was then determined by com- plexation following a procedure described in the literature.36 Three independent experiments were performed and the average value retained. Acknowledgements We are grateful to the Centre National de la Recherche Scientifique (CNRS) and the Region Alsace for a grant to C.D., to the Universit�e de Haute Alsace for a grant to A.D., to Dr. Didier Le Nou€en (EA 4566) for 1H NMR spectra, to Dr. Loïc Vidal (LRC-CNRS 7228) for TEM images, to Delphine Dru and Fanny Petitdemange for helpful technical assistance. Supplementary data Copies of 1H and 13C NMR spectra for products 2aek. Supplementary data associated with this article can be found in the online version, at http://dx.doi.org/10.1016/j.tet.2012.10.035. References and notes 1. Lloyd-Williams, P.; Giralt, E. Chem. Soc. Rev. 2001, 30, 145 and references therein. 2. Matheron, M. E.; Porchas, M. Plant Dis. 2004, 88, 665. 9. Knappke, C. E. I.; von Wangelin, A. J. Chem. Soc. Rev. 2011, 40, 4948. 10. Other powerful transition metal-catalyzed synthetic methods for the preparation of biaryls are available: (a) For Cu-catalyzed cross-coupling reactions see: Fanta, P. E. Synthesis 1974, 9; (b) For Ni-catalyzed cross-coupling reactions see: Lee, C.-C.; Ke, W.-C.; Chan, K.-T.; Lai, C.-L.; Hu, C. H.; Lee, M. M. Chem.dEur. J. 2007, 13, 582 and references therein (c) For CeH activation reactions see: Alberico, D.; Scott, M. E.; Lautens, M. Chem. Rev. 2007, 107, 174; (d) For decarboxylative palladium-catalyzed reactions see: Becht, J.-M.; Catala, C.; Le Drian, C.; Wagner, A. Org. Lett. 2007, 9, 1781. 11. (a) Gouda, K.-i.; Hagiwara, E.; Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1996, 61, 7232; (b) Hiyama, T. J. Organomet. Chem. 2002, 653, 58; (c) Denmark, S. E.; Sweis, R. F. Acc. Chem. Res. 2002, 35, 835; (d) DeShong, P.; Handy, C. J.; Mowery, M. E. Pure Appl. Chem. 2000, 72, 1655. 12. (a) Gordillo, A.; de Jes�us, E.; L�opez-Mardomingo, C. Org. Lett. 2006, 8, 3517; (b) Srimani, D.; Sawoo, S.; Sarkar, A. Org. Lett. 2007, 9, 3639. 13. Denmark, S. E.; Baird, J. D. Chem.dEur. J. 2006, 12, 4954. 14. (a) For Hiyama reactions involving aryl mesylates instead of aryl halides see: So, C. M.; Lee, H. W.; Lau, C. P.; Kwong, F. Y. Org. Lett. 2009, 11, 317; (b) For Hiyama cross-couplings of alkyl halides and trialkoxysilanes see: Lee, J.-Y.; Fu, G. C. J. Am. Chem. Soc. 2003, 125, 5616. 15. For applications of Hiyama reactions in the synthesis of biologically active molecules see: (a) Seganish, W. M.; DeShong, P. Org. Lett. 2006, 8, 3951; (b) Montenegro, J.; Bergueiro, J.; Sa�a, C.; L�opez, S. Org. Lett. 2009, 11, 141. 16. For general reviews on reusable palladium catalysts and their use in organic synthesis see: (a) McNamara, C. A.; Dixon, M. J.; Bradley, M. Chem. Rev. 2002, 102, 3275; (b) Lu, J.; Toy, P. H. Chem. Rev. 2009, 109, 815; (c) Lamblin, M.; Nassar-Hardy, L.; Hierso, J.-C.; Fouquet, E.; Felpin, F.-X. Adv. Synth. Catal. 2010, 352, 33. 17. (a) Ranu, B. C.; Dey, R.; Chattopadhyay, K. Tetrahedron Lett. 2008, 49, 3430; (b) Shi, S.; Zhang, Y. J. Org. Chem. 2007, 72, 5927. 18. (a) Solvent-less and fluoride-free Hiyama couplings in the presence of reusable palladacycles have also been reported: Alacid, E.; N�ajera, C. Adv. Synth. Catal. 2006, 348, 945; (b) For Hiyama cross-couplings in the presence of a reusable organosilicon reagent see: Nakao, Y.; Imanaka, H.; Sahoo, A. K.; Yada, A.; Hiyama, T. J. Am. Chem. Soc. 2005, 127, 6952. 19. Chen, S.-N.; Wu, W.-Y.; Tsai, F.-Y. Tetrahedron 2008, 64, 8164. 20. Sreedhar, B.; Kumar, A. S.; Yada, D. Synlett 2011, 1081. 21. Hiyama reactions of aryl halides and aryltrialkoxysilanes in the presence of a reusable thiourea ligand have been described: Wu, Z.-s.; Yang, M.; Li, H.-l.; Qi, Y.-x Synthesis 2008, 9, 1415. 22. (a) Schweizer, S.; Becht, J.-M.; Le Drian, C. Adv. Synth. Catal. 2007, 349, 1150; (b) Schweizer, S.; Becht, J.-M.; Le Drian, C. Org. Lett. 2007, 9, 3777; (c) Schweizer, S.; Becht, J.-M.; Le Drian, C. Tetrahedron 2010, 66, 765; (d) Diebold, C.; Schweizer, S.; Becht, J.-M.; Le Drian, C. Org. Biomol. 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Rao, M. S. C.; Rao, G. S. K. Synthesis 1987, 231. 35. Moore, L. R.; Shaughnessy, K. H. Org. Lett. 2004, 6, 225. 36. Kasahara, I.; Tachi, I.; Tsuda, E.;Hata,N.; Taguchi, S.;Goto,K.Analyst1989,114,1479. A simple and efficient reusable polystyrene-supported palladium catalyst for Hiyama cross-coupling 1. Introduction 2. Results and discussion 3. Conclusion 4. Experimental section 4.1. General remarks 4.2. General procedure for the syntheses of compounds 2a–k 4.2.1. 4-Methylbiphenyl (2a) 4.2.2. 3-Methylbiphenyl (2b) 4.2.3. 2-Methylbiphenyl (2c) 4.2.4. 2-Isopropylbiphenyl (2d) 4.2.5. 2,6-Dimethylbiphenyl (2e) 4.2.6. 4-Methoxybiphenyl (2f) 4.2.7. 4-Chlorobiphenyl (2g) 4.2.8. 1-(4-Biphenylyl)ethanone (2h) 4.2.9. 4,4′-Dimethylbiphenyl (2i) 4.2.10. 3,4′-Dimethylbiphenyl (2j) 4.2.11. 2,4′-Dimethylbiphenyl (2k) 4.3. General procedure for hot filtration and determination of the palladium leached in the reaction medium during the Hiyama re ... 4.4. General procedure for the determination of the palladium content of the catalyst Acknowledgements Supplementary data References and notes