Thus, by starting from commercially available 2amino-6-chloropyrazine, the target compound was obtained in 73% overall yield in five steps. This procedure allowed to up-scale the reaction sequence and the products were prepared on the gram -scale. First attemps to use trimethylsilyl-protected analogues as precursors or other sulfur sources for the ring closure reaction resulted in various complications such as thioethers as main or side products. For the synthesis of isomeric anti-dithienopyrazine 5 the same strategy was chosen and 2,5-dibromo-3,6-dichlorpyrazine 11, which is isomeric to halogenated pyrazine 7, was synthesized starting from 2-amino-6-chloropyrazine according to literature and patent procedures. Pd/Cu-catalyzed Sonogashira-type coupling of 11 with TIPS-acetylene 2 gave twofold ethynylated pyrazine 12 in 98% yield which was cyclized with KSAc in acetone (75% yield) and deprotected nearly quantitatively to targeted anti-dithienopyrazine 5 (Scheme 2). In this case, as well starting from the commer cially available 2-amino-6-chloropyrazine a lower overall yield of 41% was obtained due to the more tedious preparation of tetrahalogenated pyrazine 11.