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Synlett 2011(8): 1137-1142  
DOI: 10.1055/s-0030-1260534
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Efficient Iron/Copper Cocatalyzed N-Arylation of Arylamines with Bromoarenes

Xiaoyan Liu, Songlin Zhang*
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Dushu Lake Campus, Soochow University, Suzhou 215123, P. R. of China
Fax: +86(512)65880352; e-Mail: zhangsl@suda.edu.cn;
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Publication History

Received 18 January 2011
Publication Date:
18 April 2011 (online)

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Abstract

Fe(acac)3 and Cu(OAc)2×H2O were found to effectively promote the C-N cross-coupling reaction in the presence of K2CO3 as the base. A series of diaryl amine with different substituents can be synthesized in moderate to good yields. This efficient and economic method is attractive for applications on an industrial scale.

Key words

catalysis - iron - copper - diaryl amine

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General Procedure for the Synthesis of Diaryl Ethers
A Schlenk tube equipped with a magnetic stir bar was charged with p-toluidine (2a, 0.75 mmol, 80 mg), K2CO3 (138 mg, 1 mmol), Fe(acac)3 (34.4 mg, 20 mo%), and Cu(OAc)2˙H2O (20 mg, 20 mol%). Under a nitrogen atmosphere, bromobenzene (1a, 0.5 mmol, 78.0 mg) was added followed by dry DMF (0.8 mL). The reaction mixture was then heated in an oil bath of 135 ˚C. After being stirred at this temperature for 20 h, the mixture was cooled to r.t. and diluted with Et2O. The resulting suspension was directly filtered through a pad of Celite, the filtrate was concentrated, and the crude mixtures were purified by column chroma-tography on silica gel using PE-EtOAc solvent mixture as the eluent.
4-Methyl- N -phenylaniline (3a) ¹H NMR (400 MHz, CDCl3): δ = 7.22 (t, J = 7.7 Hz, 2 H), 7.07 (d, J = 8.3 Hz, 2 H), 6.94-7.00 (m, 4 H), 6.87 (t, J = 7.3 Hz, 1 H), 5.58 (br s, 1 H), 2.29 (s, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 144.35, 140.68, 131.34, 130.30, 129.75, 120.71, 119.31, 117.26, 21.15. HRMS (EI+): m/z calcd for C13H13N [M+]: 183.1048; found: 183.1051.
Ethyl 1- p -Tolyl-1 H -imidazole-4-carboxylate (Table 3, Entry 5)
¹H NMR (400 MHz, CDCl3): δ = 7.93 (s, 1 H), 7.82 (s, 1 H), 7.30 (s, 4 H), 4.41 (q, J = 7.1 Hz, 2 H), 2.42 (s, 3 H), 1.41 (t, J = 7.1 Hz, 3 H). ¹³C NMR (75 MHz, CDCl3): δ = 163.25, 138.99, 136.77, 135.30, 134.50, 131.02, 124.56, 122.02, 61.17, 21.481, 14.87. HRMS (EI+): m/z calcd for C13H14N2O2 [M+]: 230.1055; found: 230.1058.