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Synlett 2011(4): 569-572  
DOI: 10.1055/s-0030-1259520
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Dehydrogenative Homocoupling Reaction for the Direct Synthesis of Hydrazines from N-Alkylanilines in Air

Xue-Ming Yana,c, Zhi-Ming Chena, Fei Yanga, Zhi-Zhen Huang*a,b
a College of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. of China
b Key Laboratory of Elemento-organic Chemistry, Nankai University, Tianjin 300071, P. R. of China
Fax: +86(025)83686231; e-Mail: huangzz@nju.edu.cn;
c College of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, P. R. of China
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Publication History

Received 1 December 2010
Publication Date:
27 January 2011 (online)

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Abstract

A copper-catalyzed N-N bond-forming reaction was performed by a dehydrogenative homocoupling of N-alkylanilines, affording N,N′-dialkyl-N,N′-diphenylhydrazines in 72-88% yields. This new strategy has the advantages of direct synthesis from N-alkylanilines, using air as the oxidant, convenient manipulations, mild reaction conditions and moderate to good yields. A possible mechanism by coordination and reductive elimination has been proposed.

Key words

homocoupling - oxidative dehydrogenation - copper catalyst - direct synthesis - hydrazine

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General Experimental Procedure: To a solution of N-alkylaniline 1 (0.107 g, 1.0 mmol) in DMF (2 mL) were added CuBr (0.029 g, 0.2 mmol), TMEDA (0.232 g, 2.0 mmol), CuO (0.016 g, 0.2 mmol), K2CO3 (0.276 g, 2.0 equiv) and 4 Å MS (0.1 g) successively, and the reaction mixture was stirred at 70 ˚C or 95 ˚C for 12-24 h in air. After the reaction was completed, the mixture was filtered, and the residue was washed with EtOAc (3 × 5 mL). Then, the combined filtrates were concentrated in vacuum, and the residue was purified by column chromatography (silica gel, PE-EtOAc as eluent) to afford the desired hydrazine 2.