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[摘要]：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, BrCH(2)EWG (EWG = CN, CO(2)t-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. |
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