HETEROCYCLES

Short Paper | Special issue | Vol. 86, No. 1, 2012, pp. 713-718
Received, 30th May, 2012, Accepted, 18th July, 2012, Published online, 31st July, 2012.
DOI: 10.3987/COM-12-S(N)23

■ IMIDAZOLE AND IMIDAZOLINE DERIVATIVES AS N-DONOR LIGANDS FOR NICKEL-CATALYZED KUMADA-TAMAO-CORRIU COUPLING

Ryo Iwamoto and Masahiko Hayashi*

Department of Chemistry , Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

Imidazole and imidazoline (dihydroimidazole) derivatives can serve as simple and efficient ligands for the nickel-catalyzed Kumada-Tamao-Corriu coupling reaction. Among the imidazole and imidazoline derivatives in our investigations, the 2-phenyllimidazoline–nickel (II) chloride complex exhibited the highest catalytic activity.

In 1972, Kumada-Tamao and Corriu independly reported Ni-catalyzed cross coupling reaction between aryl halides and Grignard reagents. Kumada and Tamao used NiCl2(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane)1 and Corriu used Ni(acac)22 as a catalyst, respectively. After these two reports, several reactions using palladium catalysts combined with Grignard reagents or organolithium reagents were also explored.3 In most of these reactions, phosphine ligands4 have been employed, though recently, carbene type ligands have also been examined.5 On the other hand, we have interest in cross-coupling reactions catalyzed by nitrogen-based ligand metal complexes, because nitrogen-based ligands are generally easier to handle. For examples, we reported 2-phenylimidazole__PdCl2 and 2-phenylimidazoline__PdCl2 complex catalyzed Mizoroki-Heck and Suzuki-Miyaura coupling reactions.6 In these reactions, 2-phenylimidazoline__PdCl2 complex was found to exhibit higher reactivity than 2-phenylimidazole__PdCl2 complex. Furthermore, we also reported Ni and Cu-catalyzed Suzuki-Miyaura coupling reaction using 2-(4,5-dihydro-1H-imidazo-2-yl)phenol as a versatile phosphine-free ligand.7 Here, we will report Kumada-Tamao-Corriu coupling between substituted haloarenes and phenylmagnesium chloride catalyzed by NiCl2 and a nitrogeneous ligand system.8
We first examined the reaction of 4-bromotoluene (1) with phenylmagnesium chloride in the presence of 5 mol% of nickel precursors such as NiCl2 (51%), NiBr2 (18%), Ni(OAc)2.4H2O (41%), Ni(OH)2, (43%) and Ni(acac)2 (35%). Among the nickel precursors we examined, NiCl2 gave the best result (51% yield). After the choice of NiCl2 as a Ni precursor, we then examined the effect of addition of imidazole and imidazoline derivatives on reactivity. Phenylmagnesium chloride (1.2 eq) was used for 4-bromotoluene. It was clear that

4-bromotoluene. It was clear that addition of 2-phenylimidazoline (3 and 8) accelarated the reaction to give the cross coupling product 2 in 81% yield (entry 2). N-Methylated 2-phenyllimidazoline 4 remarkably retarded the reaction (entry 3). 2-Methylimidazoline (7) was not so effective compared with 2-phenylimidazoline (3). Remarkable rate enhancement was not observed in 2-phenylimidazole (5) and N-methylated one 6. The bidentated ligands (9__18) also did not exhibited ligand accelaration.
After confirmation that the combination of NiCl2 and 2-phenylimidazoline (3) was the best choice, we then examined the reaction of a variety of substituted haloarenes with phenylmagnesium chloride (1.2 eq). The results are shown in Table 2. The substituted haloarenes possessing both of electron withdrawing group and electron donating group worked as a substrate to give the desired coupling products in 60__88% yield, however, unfortunately, in all cases undesired homo-coupling products were obtained in 5__25% yield.

In summary, NiCl2__2-phenylimidazoline (3) catalyst system worked efficiently in Kumada-Tamao-Corriu coupling to afford the cross-coupling products in good to high yield (60__88% yield), though homo-coupling products were also obtained in 5__25% yield.

EXPERIMENTAL
General: All reactions were performed under argon atmosphere using Schlenk tube techniques and freshly distilled solvents. 1H and 13C NMR spectra (400 and 100.6 MHz, respectively) were recorded on a JEOL JNM-LA 400 using Me4Si as the internal standard (0 ppm). The following abbreviations are used: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. Preparative column chromatography was carried out on Fuji Silysia BW-820MH or YMC*GEL Silica (6 nm I-40—63 um). Thin layer chromatography (TLC) was carried out on Merck 25 TLC aluminum sheets silica gel 60 F254. Gass chromatographic analysis was done using Hitach G-5000 (FID ditector) and NEUTRABOND-5 column (30 m × 0.25 mm I.D., 0.25 μm film).

General procedure for coupling reaction
A mixture of NiCl2 (2.6 mg, 0.02 mmol) and 2-phenylimidazoline (5.8 mg, 0.04 mmol) in THF (3.8 mL) was stirred at 50 °C for 1 h under an argon atmosphere. To this mixture was added haloarenes (2 mmol) and phenylmagnesium chloride (2 M in THF, 1.2 mL, 2.4 mmol), then it was stirred at 60 °C for 3 h. After allowing the reaction mixture to cool to room temperature, 1 M HCl was added , and products were extracted with diethyl ether. The combined organic layers were dried over anhydrous Na2SO4, filtered, and evaporated to afford the crude product. The distribution of the products was done by GC analysis. The condition was as follows; condition A: initial temp 100 °C, initial time 5 min, progress rate 10 °C /min, final temp 120 °C (tR of naphthalene as internal standard, 9.27 min); condition B: initial temp 100 °C, initial time 5 min, progress rate 5 °C /min, final temp 120 °C (tR of naphthalene as internal standard, 10.24 min).

4-Methylbiphenyl
GC (condition A): tR, 14.61 min; 1H NMR (400 MHz, CDCl3): δ 7.69–7.70 (d, 2H, J = 7.8 Hz), 7.60–7.62 (d, 2H, J = 8.4 Hz), 7.52–7.54 (t, J = 7.8 Hz, 2H, J = 7.8 Hz), 7.42–7.44 (t, 1H, J = 7.8 Hz), 7.35–7.36 (d, 2H, J = 7.8 Hz), 2.50 (s, 3H). 13C NMR (100.6 MHz, CDCl3): δ 141.3, 138.5, 137.1, 130.9, 129.6, 128.8, 127.2, 127.1, 21.2.

3-Methylbiphenyl
GC (condition A): tR, 14.44 min; 1H NMR (400 MHz, CDCl3): δ 2.38 (s, 3H), 7.17–7.30 (m, 9H). 13C NMR (100.6 MHz, CDCl3): δ 21.5, 125.5, 128.0, 128.3, 128.8, 129.6, 129.7, 135.6, 138.9.

2-Methylbiphenyl
GC (condition A): tR, 13.10 min; 1H NMR (400 MHz, CDCl3): δ 2.40 (s, 3 H), 7.18–7.39 (m, 9 H); 13C NMR (100.6 MHz, CDCl3) δ 21.5, 125.3, 127.6, 128.2, 128.4, 128.5, 129.3, 129.7, 133.7, 136.5, 137.2.

4-(Trifluoromethyl)biphenyl
GC (condition B): tR, 16.23 min; 1H NMR (400 MHz, CDCl3): δ 7.7 (bs, 4H), 7.61–7.62 (d, 2H, J = 7.8 Hz), 7.48–7.50 (t, 2H, J = 7.8 Hz), 7.4–7.44 (t, 1H, J = 7.8 Hz). 13C NMR (100.6 MHz, CDCl3): δ 144.9, 139.9, 135.8, 129.4, 128.3, 127.6, 127.4, 125.9, 125.8.

4-Methoxybiphenyl
GC (condition A): tR, 17.15 min; 1H NMR (400 MHz, CDCl3): δ 7.54–7.58 (m, 4H), 7.42–7.46 (t, 2H, J = 7.8 Hz), 7.31–7.34 (t, 1H, J = 7.8 Hz), 6.99–7.01 (t, 2H, J = 9.0 Hz), 3.87 (s, 3H). 13C NMR (100.6 MHz, CDCl3): δ 159.3, 140.9, 133.9, 128.8, 128.3, 126.9, 126.8, 114.3, 55.5.

2,6-Dimethylbipheyl
GC (condition A): tR, 13.77 min; 1H NMR (400 MHz, CDCl3): δ 7.50–7.41 (m, 2H), 7.40–7.32 (m, 1H), 7.26–7.09 (m, 5H), 2.10 (s, 6H). 13C NMR (100.6 MHz, CDCl3): δ 141.8, 141.0, 136.0, 128.9, 128.4, 127.2, 127.0, 126.6, 20.8.

ACKNOWELEDGEMENTS
This work was supported by a Grant-in-Aid for Scientific Research on Innovative Areas, MEXT, Japan “Molecular Activation Directed toward Straightforward Synthesis” and No. B23350043 from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

References

1. K. Tamao, K. Sumitani, and M. Kumada, J. Am. Chem. Soc., 1972, 94, 4374. CrossRef
2. R. J. P Corriu and J. P. Massse, J. Chem. Soc., Chem. Commun., 1972, 144a. CrossRef
3. (a) M. Yamamura, I. Moritani, and S. Murahashi, J. Organomet. Chem., 1975, 91, C39; CrossRef (b) L. Cassar, J. Organomet. Chem., 1975, 93, 253; CrossRef (c) J. F. Fauvaque and A. Jutand, Bull. Soc. Chim. Fr., 1976, 765; (d) A. Sekiya and N. Ishikawa, J. Organomet. Chem., 1977, 125, 281; CrossRef (e) H. P. Dang and G. Linstrumelle, Tetrahedron Lett., 1978, 19, 191; CrossRef (f) T. Hayashi, M. Konishi, and M. Kumada, Tetrahedron Lett., 1979, 20, 1871.. CrossRef
4. (a) N. Yoshikai, H. Mashima, and E. Nakamura, J. Am. Chem. Soc., 2005, 127, 17978; CrossRef (b) R. Martin and S. L. Buchwald, J. Am. Chem. Soc., 2007, 129, 3844; CrossRef (c) C. Wolf and H. Xu, J. Org. Chem., 2008, 73, 162. CrossRef
5. (a) J. Huang and S. P. Nolan, J. Am. Chem. Soc., 1999, 121, 9889; CrossRef (b) K. Mitsudo, Y. Doi, S. Sakamoto, H. Murakami, H, Mandai, and S. Suga, Chem. Lett., 2011, 40, 936; CrossRef Z. Xi, B. Liu, and W. Chen, J. Org. Chem., 2008, 73, 3954. CrossRef
6. K. Kawamura, S. Haneda, Z. Gan, K. Eda, and M. Hayashi, Organometallics, 2008, 27, 3748; CrossRef See also for nitrogen-based ligands, (a) S. Haneda, Z. Gan, K. Eda, and M. Hayashi, Organometallics, 2007, 26, 6551; CrossRef (b) S. Haneda, C. Ueba, K. Eda, and M. Hayashi, Adv. Synth. Catal., 2007, 349, 833. CrossRef
7. S. Haneda, K. Sudo, and M. Hayashi, Heterocycles, 2012, 84, 569. CrossRef
8. For related report, N. Şahin, H. E. Moll, D. Sémeril, D. Matt, İ. Özdemir, C. Kaya, and L. Toupet, Polyhedron, 2011, 30, 2051. CrossRef