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Synlett 2008(13): 2075-2077  
DOI: 10.1055/s-2008-1077952
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Aza-Henry Reaction of Ketoimines Catalyzed by Na2CO3: An Efficient Way to β-Nitroamines

Liwei Wanga, Cheng Tana, Xiaohua Liua, Xiaoming Feng*a,b
a Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P. R. of China
Fax: +86(28)85418249; e-Mail: xmfeng@scu.edu.cn;
b State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P. R. of China
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Publication History

Received 28 March 2008
Publication Date:
15 July 2008 (online)

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Abstract

A simple and efficient way to β-nitroamines via aza-Henry reaction of N-tosyl ketoimines and nitromethane has been developed. In the presence of only 5 mol% Na2CO3, most of the N-tosyl ketoimines can react to give products in good to excellent yields (up to 99%) in THF at room temperature.

Key words

aza-Henry reaction - inorganocatalyst - ketoimines - nitromethane - β-nitroamines

    References and Notes

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To demonstrate that the size of R is important in terms of the reactivity, some other examples, such as phenyl ethyl ketimine, phenyl cyclic ketoimine, etc., were examined, but no corresponding product was obtained. Meanwhile, some other nitroalkanes, such as nitroethane and nitropropane, were also examined; unfortunately, no corresponding product was obtained by the present method.

14

General Procedure for aza-Henry Reaction of Ketoimines
To a solution of 1a (0.2 mmol, 54.7 mg) with powdered Na2CO3 (5 mol%, 1.1 mg) suspended in THF (0.29 mL) was added MeNO2 (10 equiv, 0.11 mL) at r.t. and the mixture was kept stirring for 24 h. The crude product was purified by column chromatography on SiO2 (PE-EtOAc, 5:1) to give the corresponding product 2a. By the general procedure, compound 2a was obtained as a white solid in 86% isolated yield. ¹H NMR (400 MHz, CDCl3): δ = 1.69 (s, 3 H), 2.42 (s, 3 H), 4.81 (d, J = 12.8 Hz, 1 H), 4.94 (d, J = 12.8 Hz, 1 H), 5.93 (s, 1 H), 7.22-7.33 (m, 7 H), 7.63 (d, J = 8.4 Hz, 2 H). ¹³ C NMR (100 MHz, CDCl3): δ = 143.6, 139.7, 139.2, 129.6, 128.9, 128.4, 127.0, 125.3, 82.9, 60.1, 24.7, 21.5. ESI-HRMS: m/z calcd for C16H18N2NaO4S [M + Na]: 357.0879; found: 357.0882.