A Highly Efficient Ruthenium(II) Catalyst with (1,2-Diarylvinyl

Jun 9, 2010 - Synopsis. Ruthenium(II) complexes with (1,2-diarylvinyl)phosphine ligands have been investigated as catalysts for the direct orthoarylat...
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Organometallics 2010, 29, 3222–3226 DOI: 10.1021/om100407q

A Highly Efficient Ruthenium(II) Catalyst with (1,2-Diarylvinyl)phosphine Ligands for Direct Ortho Arylation of 2-Arylpyridine with Aryl Chlorides Bingran Yu,† Xiaoyu Yan,‡ Song Wang,‡ Ning Tang,*,† and Chanjuan Xi*,‡,§ †

State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, People’s Republic of China, ‡Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China, and §State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, People’s Republic of China Received May 2, 2010

A series of (1,2-diarylvinyl)phosphine ligands were synthesized, and their ruthenium complexes have been prepared. The structure of [(1,2-diphenylvinyl)phosphine](η6-cymene)RuCl2 (C1) was confirmed by X-ray crystallography. Ruthenium (1,2-diarylvinyl)phosphine complexes are highly efficient catalysts for direct ortho arylation of 2-arylpyridine with a range of aryl chlorides (electronrich and electron-poor aromatic chlorides). Highly controllable formation of monoarylation and diarylation through functionalization of C-H bonds on the aromatic ring were achieved.

Introduction Transition-metal-catalyzed activation of aromatic C-H bond followed by new C-C bond formation is of considerable attraction in organic synthesis because it does not require prefunctionalization of the arene substrates by metalation or halogenation.1 Ortho arylation of sp2 C-H bonds involving subsequent regioselective formation of C-C bonds assisted by various functional groups under palladium, ruthenium, or rhodium catalysis have received *To whom correspondence should be addressed. E-mail: cjxi@ tsinghua.edu.cn (C. Xi). (1) For recent reviews, see: (a) Dyker, G. Angew. Chem., Int. Ed. 1999, 38, 1698. (b) Ritleng, V.; Sirlin, C.; Pfeffer, M. Chem. Rev. 2002, 102, 1731. (c) Dyker, G. Handbook of C-H Transformations; Wiley-VCH: Weinheim, Germany, 2005. (d) Alberico, D.; Scott, M. E.; Lautens, M. Chem. Rev. 2007, 107, 174. (e) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev. 2009, 110, 624. (f) Ackermann, L.; Vicente, R.; Kapdi, A. R. Angew. Chem., Int. Ed. 2009, 48, 9792. (g) Kakiuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345, 1077. (h) Thalji, R. K.; Ahrendt, K. A.; Bergmann, R. G.; Ellman, J. A. J. Org. Chem. 2005, 70, 6775. (i) Cai, G.; Fu, Y.; Li, Y.; Wan, X.; Shi, Z. J. Am. Chem. Soc. 2007, 129, 7666. (j) Ueura, K.; Satoh, T.; Miura, M. Org. Lett. 2007, 9, 1407. (2) (a) Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496. (b) Lafrance, M.; Gorelsky, S. I.; Fagnou, K. J. Am. Chem. Soc. 2007, 129, 14570. (c) Liegault, B.; Lapointe, D.; Caron, L.; Vlassova, A.; Fagnou, K. J. Org. Chem. 2009, 74, 1826. (d) Lafrance, M.; Rowley, C. N.; Woo, T. K.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 8754. (e) Gottumukkala, A. L.; Doucet, H. Eur. J. Inorg. Chem. 2007, 3626. (f) Chiong, H. A.; Pham, Q.-N.; Daugulis, O. J. Am. Chem. Soc. 2007, 129, 9879. (g) Ackermann, L. Org. Lett. 2005, 7, 3123. (h) Ackermann, L.; Althammer, A.; Born, R. Angew. Chem., Int. Ed. 2006, 45, 2619. (i) Oi, S.; Aizawa, E.; Ogino, Y.; Inoue, Y. J. Org. Chem. 2005, 70, 3113. (j) Oi, S.; Ogino, Y.; Fukita, S.; Inoue, Y. Org. Lett. 2002, 4, 1783. (k) Oi, S.; Sakai, K.; Inoue, Y. Org. Lett. 2005, 7, 4009. (l) Oi, S.; Tanaka, Y.; Inoue, Y. Organometallics 2006, 25, 4773. (m) Pozgan, € F..; Dixneuf, P. H. Adv. Synth. Catal. 2009, 351, 1737. (n) Ozdemir, I.; Demir, S.; G-etikaya, B.; Gourlaouen, C.; Maseras, F.; Bruneau, C.; Dixneuf, P. H. J. Am. Chem. Soc. 2008, 130, 1156. (o) Lewis, J. C.; Wu, J.; Bergman, R. G.; Ellman, J. A. Angew. Chem., Int. Ed. 2006, 45, 1589. (p) Wiedemann, S. H.; Lewis, J. C.; Ellman, J. A.; Bergman, R. G. J. Am. Chem. Soc. 2006, 128, 2452. (q) Kim, M.; Kwak, J.; Chang, S. Angew. Chem., Int. Ed. 2009, 48, 8935. pubs.acs.org/Organometallics

Published on Web 06/09/2010

much attention.1,2 Arenes usually undergo chelation-assisted C-H functionalization with organic or organometallic coupling partners such as Ar-X (X = I, Br, Cl, OTs, OTf),2,3 organotin,4 organoboron,5 and arylzinc6 reagents, producing the cross-coupling products. Although a variety of coupling partner compounds have been successfully explored, the employment of less active aryl chlorides has met with limited success. Considering applications for industrial processes, the choice of aryl chloride is extremely significant because of its lower cost, better availability, and lower toxicity. Recently, there has been a noteworthy advance in the reaction of aryl chlorides using newly discovered ligands that sharply improve the effectiveness of the coupling reaction. For example, Bedford,7 Buchwald,8 Fagnou,9 and others10 have reported excellent procedures using palladium (3) (a) Kametani, Y.; Satoh, T.; Miura, M.; Nomura, M. Tetrahedron Lett. 2000, 41, 2655. (b) Oi, S.; Fukita, S.; Hirata, N.; Watanuki, N.; Miyano, S.; Inoue, Y. Org. Lett. 2001, 3, 2579. (c) Daugulis, O.; Zaitsev, V. G. Angew. Chem., Int. Ed. 2005, 44, 4046. (d) Larivee, A.; Mousseau, J. J.; Charette, A. B. J. Am. Chem. Soc. 2008, 130, 52. (e) Campeau, L.-C.; Schipper, D.; Fagnou, J. K. J. Am. Chem. Soc. 2008, 130, 3266. (4) (a) Oi, S.; Fukita, S.; Inoue, Y. Chem. Commun. 1998, 2439. (b) Peterson, A. A.; McNeill, K. Organometallics 2005, 25, 4938. (c) Ueura, K.; Satoh, T.; Miura, M. Org. Lett. 2005, 7, 2229. (5) (a) Kakiuchi, F.; Kan, S.; Igi, K.; Chatani, N.; Murai, S. J. Am. Chem. Soc. 2003, 125, 1698. (b) Chen, X.; Goodhue, C. E.; Yu, J.-Q. J. Am. Chem. Soc. 2006, 128, 12634. (c) Shi, Z.; Li, B.; Wan, X.; Cheng, J.; Fang, Z.; Cao, B.; Qin, C.; Wang, Y. Angew. Chem., Int. Ed. 2007, 46, 1. (d) Vogler, T.; Studer, A. Org. Lett. 2008, 10, 129. (e) Miyamura, S.; Tsurugi, H.; Satoh, T.; Miura, M. J. Organomet. Chem. 2008, 693, 2438. (f) Giri, R.; Maugel, N.; Li, J.-J.; Wang, D.-H.; Breazzano, S. P.; Saunders, L. B.; Yu, J.-Q. J. Am. Chem. Soc. 2007, 129, 3510. (6) Norinder, J.; Matsumoto, A.; Yoshikai, N.; Nakamura, E. J. Am. Chem. Soc. 2008, 130, 5858. (7) Bedford, R. B.; Cazin, C.S .J . Chem. Commun. 2002, 2310. (8) Hennessy, E.; Buchwald, S. L. J. Am. Chem. Soc. 2003, 125, 12084. (9) (a) Leblanc, M.; Fagnou, K. Org. Lett. 2005, 7, 2849. (b) Campeau, L.-C.; Parisien, M.; Leblanc, M.; Fagnou, K. J. Am. Chem. Soc. 2004, 126, 9186. (10) Miura, M.; Satoh, T. Top. Organomet. Chem. 2005, 14, 55. r 2010 American Chemical Society

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Scheme 1

complexes derived from tertiary phosphines, such as tBu3P, or 2-(di-tert-butylphosphino)biphenyl.11,12 Ackermann et al. developed a general method for ruthenium-catalyzed intermolecular arylation reactions using aryl chlorides,2h,i,13 in which secondary phosphine oxides14 were used as preligands. These ligands commonly are electron rich and sterically hindered. On the basis of the vinylphosphine structure, it was speculated that introduction of an aryl at the R-position might make the ligand more sterically hindered, and an aryl at the β-position might increase the electron density of the phosphorus atom through the vinyl moiety. However, these ligands have rarely been studied, although (2,2-diarylvinyl)phosphines15 and butadienylphosphines16 as ligands have been reported. For many years, we have been engaged in the study of zirconophosphination of alkynes.17 We disclosed a versatile and general method for the preparation of various alkenylphosphines, which have been widely employed in organic synthesis.18 Herein, we would like to report the synthesis and characterization of ruthenium complexes with (1,2-diarylalkenyl)phosphine and their catalytic activity in the arylation of 2-arylpyridine with aryl chlorides via C-H bond activation, although phosphine ligand free ruthenium complexes have been employed for direct arylations with aryl chlorides.2m,19

Results and Discussion The ligands L were easily prepared in good yields by the reaction of (2-phosphinoethenyl)zirconocene chlorides17c with concentrated hydrochloric acid (12 M) in THF in the presence of 5 mol % of CuCl at 50 °C (Scheme 1). The ruthenium(II) complexes were obtained as red solids in high yield by the reaction of the (p-cymene)ruthenium (11) For recent use of palladium complexes generated from N-heterocyclic carbenes, see: Campeau, L.-C.; Thansandote, P.; Fagnou, K. Org. Lett. 2005, 7, 1857. (12) Terao, Y.; Wakui, H.; Nomoto, M.; Satoh, T.; Miura, M.; Nomura, M. J. Org. Chem. 2003, 68, 5236.  (13) (a) Ackermann, L.; Born, R.; Alvarez-Bercedo, P. Angew. Chem., Int. Ed. 2007, 46, 6364. (b) Ackermann, L.; Born, R.; Vicente, R. ChemSusChem 2009, 2, 546. (14) (a) Li, G. Y. Angew. Chem., Int. Ed. 2001, 40, 1513. (b) Ackermann, L.; Born, R. Angew. Chem., Int. Ed. 2005, 44, 2444. (15) Suzuki, K.; Hori, Y.; Nishikawa, T.; Kobayashi, T. Adv. Synth. Catal. 2007, 349, 2089. (16) Kaddouri, H.; Vicente, V.; Ouali, A.; Ouazzani, F.; Taillefer, M. Angew. Chem., Int. Ed. 2009, 48, 333. (17) (a) Yan, X.; Yu, B.; Wang, L.; Tang, N.; Xi, C. Organometallics 2009, 28, 6827. (b) Yan, X.; Xi, C. Organometallics 2008, 27, 152. (c) Xi, C.; Yan, X.; Lai, C. Organometallics 2007, 26, 1084. (d) Hao, P.; Zhang, S..; Yi, J.; Sun, W.-H. J. Mol. Catal. A: Chem. 2009, 302, 1. (18) (a) Gilheany, D. G.; Mitchell, C. M. In The Chemistry of Organophosphorus Compounds; Hartley, J. F. R., Ed.; Wiley: Chichester, U.K., 1990; Vol. 1, p 151. (b) Brunner, H.; Furst, J. Tetrahedron 1994, 50, 4293. (c) Braunstein, P. Chem. Rev. 2006, 106, 134. (d) Hansen, H. D.; Nelson, J. H. Organometallics 2000, 19, 4740. (e) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2005, 24, 2030. (f) Yan, X.; Liu, Y.; Xi, C. Appl. Organomet. Chem. 2008, 22, 341. (19) (a) Ackermann, L.; Vicente, R.; Althammer, A. Org. Lett. 2008, 10, 2299. (b) Ackermann, L.; Althammer, A.; Born, R. Synlett 2007, 2833. (c) Ackermann, L.; Althammer, A.; Born, R. Tetrahedron 2008, 64, 6115.

Figure 1. Molecular structure of complex C1. Thermal ellipsoids are shown at the 30% probability level; hydrogen atoms have been omitted for clarity. Scheme 2

dichloride dimer {[RuCl2(p-cymene)]2} with L in dichloromethane at room temperature (Scheme 2). Compounds C1-C3 have been fully characterized by spectroscopy and elemental analysis. Moreover, the structure of C1 was confirmed by X-ray crystallography (Figure 1). The alkenylphosphine coordinated to ruthenium in complex C1 displays a structure similar to those of [RuCl2(p-cymene)PPh3]20 and [RuCl2(p-cymene)PRPh2].21 Compounds C1-C3 were not sensitive to oxygen or moisture. The catalytic efficacy of the synthesized complexes C1-C3 was tested in the arylation of 2-arylpyridine with aryl chlorides via C-H bond activation (Table 1). 2-Phenylpyridine (1a; 0.5 mmol) was treated with an equimolar amount of chlorobenzene (2a; 0.5 mmol) in the presence of complex C1 (0.0125 mmol), and K2CO3 (1.0 mmol) in N-methylpyrrolidinone (NMP) at 120 °C for 24 h to yield the monophenylated product 3a in 87% yield with a small amount of the diphenylated product 4a (4% NMR yield) (entry 1). Under the same reaction conditions, the complexes C2 and C3 also showed high catalytic activity in the arylation of 2-arylpyridine with aryl chlorides (entries 2 and 3). [RuCl2(p-cymene)]2 or a mixture of [RuCl2(p-cymene)]2 and ligand L1 was examined in the reaction under the reaction conditions, in these cases, a moderate yield was observed with less (20) (a) Crochet, P.; Fernandez-Z umel, M. A.; Gimeno, J.; Scheele, M. Organometallics 2006, 25, 4846. (b) Mierde, H. V.; Ledoux, N.; Allaert, B.; Van Der Voort, P.; Drozdzak, R.; Vosb, D. D.; Verpoort, F. New J. Chem. 2007, 31, 1572. (c) Donovan, P. M.; Scott, L. T. J. Am. Chem. Soc. 2004, 126, 3108. (21) (a) Goux, J.; Le Gendre, P.; Richard, P.; Moı¨ se, C. J. Organomet. Chem. 2006, 691, 3239. (b) Goux, J.; Le Gendre, P.; Richard, P.; Moïse, C. J. Organomet. Chem. 2005, 690, 301. (c) Angurell, I.; Muller, G.; Rocamora, M.; Rossell, O.; Seco, M. Dalton Trans. 2004, 2450.

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Table 1. Directed Arylation of 2-Phenylpyridine with PhCl with Ru/(1,2-Diarylvinyl)phosphine Complexesa

entry

cat.

conversn (%)b

3a/4a ratio b

1 2 3 4c 5d 6 7e

C1 C2 C3 [RuCl2(p-cymene)]2 [RuCl2(p-cymene)]2 þ L1 RuCl2(p-cymene)PPh3 C1

96 91 89 82 79 87 66

96/4 91/9 88/12 78/22 82/18 85/15 91/9

Table 2. Ru/(1,2-Diphenyl)vinylphosphine-Catalyzed Ortho Arylation of 2-Phenylpyridine with Aryl Chlorides

a Reaction conditions: 2-phenylpyridine (77.5 mg, 0.5 mmol), chlorobenzene (56.0 mg, 0.5 mmol), K2CO3 (1 mmol), NMP (2.0 mL), cat. (0.0125 mmol). b Determined by 1H NMR using CH2Cl2 as internal standard; conversion of 2-phenylpyridine was obtained in proportion to the integral area of the CH2Cl2 signal. c Using 1.25 mol % [RuCl2( p-cymene)]2. d Using 1.25 mol % [RuCl2(p-cymene)]2 and 2.5 mol % L1. e The reaction conditions are similar to those indicated; the solvent was only replaced by toluene (2.0 mL).

selectivity in the controllable formation of monophenylated product (entries 4 and 5). For a comparison of catalytic activity, [RuCl2(p-cymene)PPh3] as a catalyst was examined under the same reaction conditions. Interestingly, PPh3 (in which the 1,2-diphenylvinyl moiety of C1 is replaced by a phenyl group) was found to be less efficient under the same conditions (entry 6). When the reaction was examined in toluene as solvent, the desired product was formed in 66% yield (entry 7). Catalysts C1-C3 were all effective for the phenylation of 2-phenylpyridine with chlorobenzene via C-H bond activation reactions; the use of C1 as a catalyst was studied further in the coupling of a number of aryl chlorides. Representative results are summarized in Table 2. Both electron-rich and electron-poor aryl chlorides could be successfully converted into the desirable products in excellent yields. When 2-phenylpyridine was treated with an equimolar amount of aryl chlorides, the monoarylated products 3a-h were afforded in 80-92% yields, and only small amounts of the diarylated products 4a-h were observed (entries 1-8). When 2-phenylpyridine was examined with 2.5 equiv of aryl chlorides, the diarylated products 4b,d,e,h were formed in excellent yields (entries 9-12). It is noteworthy that the catalytic system derived from the (1,2-diphenylvinyl)phosphine/ ruthenium(II) complex C1 enabled controllable formation of monoarylation and diarylation through functionalization of C-H bonds on the aromatic ring. The reaction of 2-o-tolylpyridine having only one ortho C-H bond on the phenyl ring with aryl chlorides 2 afforded the monophenylated product 5 in excellent yields. The results are summarized in Table 3. The reaction between biphenyl and chlorobenzene (2a), on the other hand, failed to occur under the reaction conditions, which suggested that the presence of the pyridyl group is necessary for the reaction to proceed. Although there is little experimental evidence at present to determine the exact reaction pathway for the direct cross-coupling process, the following two steps are believed to play some part in the catalytic pathway: (i) oxidative addition of the aryl chloride

a Reaction conditions: 2-phenylpyridine (0.5 mmol), aryl chloride (0.5 mmol), K2CO3 (1 mmol), NMP (2.0 mL), cat. C1 (8.4 mg, 0.0125 mmol). b) Reaction conditions: 2-phenylpyridine (0.5 mmol), aryl chloride (1.25 mmol), K2CO3 (2 mmol), NMP (2.0 mL), cat. C1 (8.4 mg, 0.0125 mmol). c) Determined by NMR. d) Isolated yield for major product.

to the ruthenium complex, to afford an arylruthenium intermediate, and (ii) ortho ruthenation of the aromatic ring directed by coordination of the 2-phenylpyridine nitrogen to the ruthenium atom. Although phosphine ligand free ruthenium complexes have also been employed for direct arylations with aryl chlorides,2m,19 in our work, the electron richness of (1,2-diarylvinyl)phosphine might facilitate oxidative addition of the Ar-Cl bond to Ru(II) and the steric demand of (1,2-diarylvinyl)phosphine might favor ligand dissociation to afford an active ruthenium catalyst. In summary, the ruthenium/(1,2-diarylvinyl)phosphine complexes are highly efficient catalysts for direct ortho arylation of 2-arylpyridine with a range of electron-donating and electron-withdrawing aromatic chlorides. Moreover, the

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Table 3. Ru/(1,2-Diphenylvinyl)phosphine-Catalyzed Ortho Arylation of 2-o-Tolylpyridine with Aryl Chloridesa

a Reaction conditions: 2-o-tolylpyridine (0.5 mmol), aryl chloride (0.5 mmol), K2CO3 (1 mmol), NMP (2.0 mL), catalyst (8.4 mg, 0.0125 mmol). b) Isolated yield.

monoarylation and diarylation of 2-arylpyridine through functionalization of C-H bonds could be controllable under this catalytic system. Mechanistic studies as well as further applications of the present catalytic system are ongoing and will be reported in due course.

Experimental Section General Considerations. Unless otherwise noted, all operations were performed without taking precautions to exclude air and moisture. All solvents and chemicals were used as received without any further treatment, if not noted otherwise. 1H NMR and 13C NMR spectra were recorded on a JEOL 300 NMR spectrometer with tetramethylsilane (TMS) as an internal standard. 1H NMR yields, using CH2Cl2 or mesitylene as the internal standard, were obtained in proportion to the integral area of CH2Cl2 or mesitylene signal. 31P NMR spectra were recorded on a Bruker AC 200 NMR spectrometer at 81 MHz under 1H-decoupled conditions using 85% H3PO4 (δP 0 ppm) as an external standard. Elemental analyses were performed on a Flash EA 1112 instrument. Melting points were determined with a digital electrothermal apparatus without calibration. The IR spectra were obtained on a Perkin-Elmer FT-IR 2000 spectrophotometer by using KBr disks in the range of 4000-400 cm-1. GC analyses were preformed on a gas chromatograph equipped with a flame ionization detector using a capillary column (CBP1-M25-025). The GC yields were determined using suitable hydrocarbons as internal standards. Synthesis of Ligands L1-L3. Typical Procedure: Synthesis of Ligand L1. [2-(Dicyclopentadienylchlorozircono)-1,2-diphenylvinyl]diphenylphosphine (1.24 g, 2.0 mmol), CuCl (10.0 mg,

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0.10 mmol), 12 N HCl (200 μL), and THF (5 mL) were added to a Schlenk tube, and the mixture was stirred for 12 h at 50 °C. Removal of the solvent and further purification by column chromatography on silica gel (petroleum ether/EtOAc 15/1) gave L1 as a white solid in 87% isolated yield. 1H NMR (300 MHz, CDCl3, Me4Si): δ 6.57 (d, 3JPH = 9.2 Hz, 1H), 6.93-7.00 (m, 2H), 7.09-7.25 (m, 8H), 7.33-7.40 (m, 6H), 7.48-7.52 (m, 4H). 13C NMR (75 MHz, CDCl3, Me4Si): δ 127.1, 127.4, 128.1, 128.5, 128.6 (d, JPC = 5.0 Hz), 129.1, 129.3 (d, JPC = 6.5 Hz), 129.5, 134.4 (d, JPC = 19.4 Hz), 135.5 (d, JPC = 11.5 Hz), 137.0 (d, 2 JPC = 6.5 Hz), 138.2 (d, JPC = 18.6 Hz), 140.1 (d, JPC = 16.5 Hz), 141.6 (d, JPC = 18.6 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 9.1. Spectroscopic characterization data for compound L1 are consistent with the published data.17c Ligand L2. The product was obtained as a white solid in 80% isolated yield. 1H NMR (300 MHz, CDCl3, Me4Si): δ 2.24 (s, 6H), 6.57 (d, 3JPH = 9.3 Hz, 1H), 6.93-7.44 (m, aromatic, 20H). 13 C NMR (75 MHz, CDCl3, Me4Si): δ 21.3, 128.4, 128.5, 128.8, 129.0, 133.5 (d, JPC = 9.3 Hz), 134.2, 134.5, 138.8 (d, JPC = 12.9 Hz), 136.7, 137.2, 137.3, 137.9 (d, JPC = 17.9 Hz), 140.3 (d, JPC = 17.9 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 9.0. IR (KBr; cm-1): 3056, 3019, 1935, 1582, 1486, 1381, 1174, 915, 741, 692. Anal. Calcd for C28H25P: C, 85.69; H, 6.42. Found: C, 85.72; H, 6.64. Ligand L3. The product was obtained as a colorless liquid in 73% isolated yield. 1H NMR (300 MHz, CDCl3, Me4Si): δ 1.11 (m, 12H), 1.92 (m, 2H), 6.60 (s, 1H), 6.90-7.27 (m, 10H). 13C NMR (75 MHz, CDCl3, Me4Si): δ 19.8, 20.3, 23.1 (d, JPC = 14.3 Hz), 126.8, 127.2, 128.1, 128.4, 128.6, 128.9, 129.6, 130.4, 137.3 (JPC = 28.7 Hz), 139.3 (d, JPC = 29.4 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 21.4. IR (KBr; cm-1): 3056, 3020, 2944, 2861, 1953, 1887, 1592, 1487, 1442, 1150, 1074, 1022, 936, 866, 692. Anal. Calcd for C20H25P: C, 81.05; H, 8.50. Found: C, 81.26; H, 4.03. Synthesis of Complexes C1-C3. Typical Procedure: Synthesis of Complex C1. A solution of {[(η6-cymene)RuCl]2(μ-Cl)2} (31 mg, 0.05 mmol) and (E)-(1,2-diphenylvinyl)diphenylphosphine as ligand (0.10 mmol) was mixed in dichloromethane. The mixture was stirred at room temperature for 12 h, giving a red suspension. The reaction volume was reduced, and diethyl ether was added to the solution to obtain red solids, which were washed repeatedly with diethyl ether and dried under vacuum. A red powder was obtained in 91% yield. Mp: 187-190 °C. 1H NMR (300 MHz, CDCl3, Me4Si): δ 0.93 (d, 6H, JHH = 6.9 Hz), 1.84 (s, 3H), 2.662.71 (m, 1H), 5.07 (d, 2H, JHH = 5.5 Hz), 5.14 (d, 2H, JHH = 5.5 Hz), 6.46 (d, 2H, JHH =7.2 Hz), 6.88-7.86 (m, aromatic, 18H), 8.30 (d, 1H, JPH = 21.0 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 17.3, 21.6, 30.1, 86.0, 86.1, 90.7, 91.0, 94.8, 110.1, 126.8, 127.7, 127.9, 127.8, 128.0, 128.2, 130.2, 130.4, 130.5, 133.3, 133.8, 133.9, 135.9, 136.2, 137.5, 149.5 (d, JPC = 22.2 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 30.8. IR (KBr; cm-1): 3044, 2958, 1922, 1865, 2361, 1798, 1611, 1437, 1094, 695. Anal. Calcd for C36H35Cl2PRu 3 0.25CH2Cl2: C, 62.93; H, 5.17. Found: C, 62.32; H, 5.21. Complex C2. The product was obtained as a red powder in 92% isolated yield. Mp: 192-195 °C. 1H NMR (300 MHz, CDCl3, Me4Si): δ 0.94 (d, 6H, JHH = 6.9 Hz), 1.83 (s, 3H), 2.18 (s, 6H), 2.66-2.71 (m, 1H), 5.06 (d, 2H, JHH = 5.5 Hz), 5.11 (d, 2H, JHH = 5.5 Hz), 6.36 (d, 2H, JPH =7.6 Hz), 6.70-7.85 (m, aromatic, 16H), 8.19 (d, 1H, JPH = 21.3 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 17.3, 21.6, 30.1, 86.0, 86.1, 90.7, 94.8, 110.1, 126.8, 127.7, 127.9, 127.8, 128.0, 128.2, 130.2, 130.4, 130.5, 133.3, 133.8, 133.9, 135.9, 136.2, 137.5, 149.5 (d, JPC = 22.2 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 30.0. IR (KBr; cm-1): 2953, 2920, 2848, 2678, 1611, 1479, 1433, 1266, 1092, 945, 744, 731. Anal. Calcd for C38H39Cl2PRu: C, 65.33; H, 5.63. Found: C, 65.36; H, 5.74. Complex C3. The product was obtained as a red powder in 84% isolated yield. Mp: 185-190 °C. 1H NMR (300 MHz, CDCl3, Me4Si): δ 1.20-1.28 (m, 18H), 2.12 (s, 3H), 2.84-2.88

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(m, 3H), 5.53-5.56 (m, 4H), 6.60 (s, 1H), 6.95-7.40 (m, aromatic, 9H), 7.65 (d, 1H, JPH = 18.0 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 18.1, 20.0, 20.5, 22.5, 27.1, 27.4, 30.3, 85.0, 88.8, 95.6, 108.0, 126.9, 127.7, 127.9, 128.0, 128.1, 128.8 (d, JPC = 12.2 Hz), 129.5, 129.8, 130.1 135.6 (d, JPC = 14.3 Hz), 137.1, 137.9, 138.4 (d, JPC = 26.5 Hz), 143.3 (d, JPC = 14.3 Hz). 31P NMR (81 MHz, CDCl3, 85% H3PO4): δ 37.4. IR (KBr; cm-1): 2956, 2924, 2865, 2361, 1599, 1460, 1379, 1254, 1143, 696. Anal. Calcd for C30H39Cl2PRu 3 0.5CH2Cl2: C, 56.79; H, 6.25. Found: C, 56.74; H, 6.45. General Procedure for the Reaction of 2-Phenylpyridine with Aryl Chlorides. 2-Phenylpyridine (77.5 mg, 0.5 mmol), aryl chlorides (0.5 or 1.2 mmol), potassium carbonate (1 or 2 mmol), NMP (2 mL), and catalyst C1 (2.5 mol %, 8.4 mg) were placed in a screw-capped test tube. The mixture was stirred at 120 °C. After the reaction was complete, the mixture was quenched with water and extracted with ethyl ether. The organic layer was washed with brine, dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel using a mixture of petroleum ether and ethyl acetate. General Procedure for the Reaction of 2-(o-Tolyl)pyridine with Aryl Chlorides. 2-(o-Tolyl)pyridine (85.0 mg, 0.5 mmol), aryl chlorides (0.6 mmol), potassium carbonate (138.0 mg, 1 mmol), NMP (2 mL), and catalyst C1 (2.5 mol %, 8.4 mg) were placed in a screw-capped test tube. The mixture was stirred at 120 °C. After the reaction had completed, the mixture was quenched with water and extracted with ethyl ether. The organic layer was washed with brine, dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel using mixture of petroleum ether and ethyl acetate. 2-[2-(4-Methoxyphenyl)phenyl]pyridine (3b). 1H NMR (300 MHz, CDCl3, Me4Si): δ 3.76 (s, 3H), 6.75-7.72 (m, aromatic, 11H), 8.62 (d, 1H, JHH = 5.8 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 55.2, 113.6, 121.3, 125.4, 127.3, 128.6, 130.6, 130.89, 133.8, 135.3, 139.4, 140.3, 149.5, 158.6, 159.3. GC-MS (EI): m/z 261. 2-{2-[3-(Diethylamino)phenyl]phenyl}pyridine (3c). 1H NMR (300 MHz, CDCl3, Me4Si): δ 0.95 (t, 6H, JHH = 7.0 Hz), 3.15 (q, 4H, JHH = 7.0 Hz), 6.37-7.73 (m, aromatic, 11H), 8.63 (d, 1H, JHH = 5.7 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 12.5, 44.3, 110.6, 114.2, 116.9, 121.3, 125.5, 127.4, 128.4, 129.1, 130.4, 135.2, 139.4, 141.7, 142.2, 147.4, 149.4, 159.6. GC-MS (EI): m/z 302. 2-{2-[4-(Dimethylamino)phenyl]phenyl}pyridine (3d). 1H NMR (300 MHz, CDCl3, Me4Si): δ 2.93 (s, 6H), 6.51-7.68 (m, aromatic, 11H), 8.66 (d, 1H, JHH = 5.1 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 40.6, 112.2, 120.3, 123.6, 127.0, 128.1, 128.9, 129.9, 130.6, 135.0, 139.4, 141.9, 148.9, 149.4, 162.1. GC-MS (EI): m/z 274. 2-{2,6-Bis[3-(diethylamino)phenyl]phenyl}pyridine (4c). 1H NMR (300 MHz, CDCl3, Me4Si): δ 0.96 (t, 12H, JHH = 6.9 Hz), 3.15 (q, 8H, JHH = 6.9 Hz), 6.32-7.46 (m, aromatic, 14H), 8.63 (d, 1H, JHH = 5.7 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 12.5, 44.3, 110.6, 114.2, 117.6, 120.7, 126.2, 127.7, 128.5, 129.2, 134.7, 138.6, 142.6, 147.4, 148.5, 159.6. GC-MS (EI): m/z 449. 2-{2,6-Bis[4-(dimethylamino)phenyl]phenyl}pyridine (4d). 1H NMR (300 MHz, CDCl3, Me4Si): δ 2.87 (s, 12H), 6.51-7.68 (m, aromatic, 14H), 8.40 (d, 1H, JHH = 5.2 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 40.6, 112.2, 120.3, 123.6, 126.7, 127.3, 129.1, 129.4, 130.6, 135.1, 141.9, 148.6, 149.5, 160.0. GC-MS (EI): m/z 393. 2-(2,6-Di-o-tolylphenyl)pyridine (4g). 1H NMR (300 MHz, CDCl3, Me4Si): δ 2.02 (s, 3H), 2.10 (s, 3H), 6.32-7.46 (m, aromatic, 14H), 8.13 (d, 1H, JHH = 4.7 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 20.5, 120.7, 124.8, 125.5, 125.7, 126.8, 127.3, 129.1, 129.4, 130.3, 130.7, 134.3, 135.8, 136.0, 141.2, 141.4, 148.1, 149.5, 158.7. GC-MS (EI): m/z 335. 2-{6-Methyl-2-[3-(diethylamino)phenyl]phenyl}pyridine (5c). 1 H NMR (300 MHz, CDCl3, Me4Si): δ 0.96 (t, 6H, JHH = 6.7 Hz), 2.18 (s, 3H), 3.15 (q, 4H, JHH = 6.7 Hz), 6.37-7.73 (m,

Yu et al. Table 4. Selected X-ray Crystallographic Data and Refinement Details for C1 empirical formula formula wt cryst color temp (K) cryst syst space group a (A˚) b (A˚) c (A˚) V (A˚3) Z Dcalcd (g cm-3) μ (mm-1) F(000) cryst size (mm) θ range (deg) limiting indices no. of rflns collected no. of unique rflns completeness (%) abs cor no. of params goodness of fit on F2 final R indices (I > 2σ(I)) R indices (all data) largest diff peak and hole (e A˚-3)

C36H35Cl2PRu 670.58 brown 173.15 triclinic P1 13.145(3) 15.043(3) 18.624(4) 3242.7(11) 4 1.374 0.721 1376 0.30  0.18  0.14 1.20-30.02 -18 e h e 18 -21 e k e 21 -26 e l e 26 51 508 18 849 99.4 (θ = 30.02°) empirical 812 1.519 R1 = 0.0726 wR2 = 0.2236 R1 = 0.0816 wR2 = 0.2372 2.415 and -3.698

aromatic, 10H), 8.68 (d, 1H, JHH = 5.2 Hz). 13C NMR (75 MHz, CDCl3, Me4Si): δ 12.5, 20.8, 44.3, 110.6, 114.2, 116.9, 121.3, 125.5, 127.4, 128.4, 129.1, 130.4, 135.2, 136.1, 139.4, 141.7, 142.2, 147.4, 149.4, 159.6. GC-MS (EI): m/z 316. The NMR data of 3a,3b 3e,22 3f,22 3g,23 3h,3b 4a,3b 4b,2h 4e,2h 4f,2h 4h,3b 5a,24 5b,19a 5f,19a 5g,4a and 5h3b have been reported in the literature, and our NMR data are consistent with the literature data. X-ray Crystallographic Studies. A single-crystal X-ray diffraction study of C1 was carried out on a Bruker SMART 1000 CCD diffractometer with graphite-monochromated Mo KR radiation (λ = 0.710 73 A˚). Cell parameters were obtained by global refinement of the positions of all collected reflections. Intensities were corrected for Lorentz and polarization effects and empirical absorption. The structures were solved by direct methods and refined by full-matrix least squares on F2. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. Structure solution and refinement were performed by using the SHELXL-97 package.25 Crystal data and processing parameters for C1 are summarized in Table 4.

Acknowledgment. This work has been supported by the National Natural Science Foundation of China (Grant Nos. 20972085, 20872076, and 20372041) and by the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200800030072). Supporting Information Available: A CIF file giving X-ray crystallographic data for complex C1. This material is available free of charge via the Internet at http://pubs.acs.org. (22) Shabashov, D.; Daugulis, O. Org. Lett. 2005, 7, 3657. (23) Yu, W.-Y.; Sit, W. N.; Zhou, Z. A.; Chan, S.-C. Org. Lett. 2009, 11, 3174. (24) Matsuura, Y.; Tamura, M.; Kochi, T.; Sato, M.; Chatani, N.; Kakiuchi, F. J. Am. Chem. Soc. 2007, 129, 9858. (25) Sheldrick, G. M. SHELXTL-97, Program for the Refinement of Crystal Structures; University of Gottingen, G€ottingen, Germany, 1997.