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Synlett 2008(20): 3163-3166  
DOI: 10.1055/s-0028-1087280
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

An Efficient Synthesis of Quinoxalines under Catalyst-Free and Microwave-Irradiation Conditions

Jian-Feng Zhou*a,b, Gui-Xia Gongb, Li-Tao Ana, Yu Liub, Feng-Xia Zhua, Yu-Lan Zhua, Shun-Jun Jib
a Department of Chemistry, Huaiyin Teachers College, Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, 223300 Huaian, P. R. of China
Fax: +86(517)84926385; e-Mail: jfzhou@hytc.edu.cn;
b School of Chemistry and Chemical Engineering, Key Laboratory of Organic Synthesis of Jiangsu Province, Suzhou University, 215123 Suzhou, P. R. of China
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Publication History

Received 12 August 2008
Publication Date:
26 November 2008 (online)

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Abstract

A series of quinoxaline derivatives was synthesized by the reaction of 3-(ω-bromoacetyl)coumarins with substituted 1,2-diaminobenzenes in the absence of a catalyst under microwave conditions. Reasonable yields of the products, environmentally benign and convenient workup are the advantages of this method.

Key words

quinoxaline - heterocycles - green chemistry - 3-(ω-bromoacetyl)coumarin - microwave irradiation

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Typical Procedure for the Synthesis of Quinoxaline 3a 3-(ω-Bromoacetyl)coumarin 1a (1 mmol) and 1,2-diaminobenzene 2a (1 mmol) were mixed in EtOH (2 mL) and sealed with a cap containing a septum. The loaded vial was then placed into the cavity of the microwave reactor and heated at 100 ˚C for 8 min (as indicated by TLC). After completion of the reaction, the reaction mixture was then allowed to cool to r.t., resulting in the precipitation of the solid product. The product was filtered off and dried. The crude product was subjected to 95% EtOH for recrystallization to afford the pure product; mp 198.8-199.0 ˚C. IR (KBr): 3062, 1718, 1610, 1565, 1200, 998, 756 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 7.41 (t, 1 H, J = 15.2Hz), 7.47 (d, 1 H, J = 8.4 Hz), 7.67 (t, 1 H, J = 15.6 Hz), 7.76 (d, 1 H, J = 7.2 Hz), 7.82-7.87 (m, 2 H), 8.17-8.23 (m, 2 H), 8.91 (s, 1 H), 9.86 (s, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 116.67, 119.36, 124.05, 124.89, 129.14, 129.29, 129.37, 130.31, 130.34, 132.96, 142.12, 142.17, 144.56, 145.34, 147.36, 154.46, 160.10. ESI-HRMS: m/z calcd for C17H11N2O2 [M + H]+: 275.0821; found: 275.0339.