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Paper | Regular issue | Vol 85, No. 2, 2012, pp.403-411
Published online, 28th December, 2011
DOI: 10.3987/COM-11-12407
A Facile Synthesis of 6-Substituted 7-Arylthieno[2,3-b]pyrazines from 2-Chloropyrazine

Kazuhiro Kobayashi* and Teruhiko Suzuki

*Division of Applied Chemistry, Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

A series of 6,7-disubstituted thieno[2,3-b]pyrazines were prepared by two- or three-pot reaction sequences starting from commercially available 2-chloropyrazine. The reaction of 2-chloro-3-lithiopyrazine with N,N-dimethylbenzamides gave directly aryl(3-chloropyrazin-2-yl)methanones, which were treated successively with sodium sulfide, BrCH2EWG (EWG = CN, CO2t-Bu, COAr), and sodium hydride to give the corresponding 6-substituted 7-arylthieno[2,3-b]pyrazines. Similarly, 6-substituted 7-heterarylthieno[2,3-b]pyrazines were prepared from (3-chloropyrazin-2-yl)heterarylmethanones, derived by the reaction of 2-chloro-3-lithiopyrazine with heteraromatic aldehydes followed by the PCC oxidation.