Redox reactions, reductions. It was the question if the dithienopyrazine system as aromatic system can be reduced or oxidized. Precedents in literature are scarce and for example related phenazine was reduced to corresponding 5,10-dihydrophenazine with sodium dithionite. The reduction obviously occurs at the central pyrazine ring, whereby the dihydrophenazine exhibits strong oxidation sensitivity. Furthermore, the reactive nitrogens in the pyrazine ring can be N-alkylated after in-situ reduction or acylated. Reductions of thiophene-fused pyrazines are not literature-known. Therefore, we wanted to investigate reduction possibilities of syn-dithienopyrazine 6. In this respect, reducing agents such as sodium dithionite or elemental sodium/alkylation agent did not lead to the corresponding dihydropyrazines and starting material was reisolated. Next, TIPS-protected syn-dithienopyrazine 10 and syndithienopyrazine 6 were subjected to reductive acylation conditions and heated under reflux with elemental zinc in acetic anhydride. N-diacylated syn-dihydrothienopyrazines 22 and 23 were isolated in quantitative and 93% yield, respectively. Acylated dihydrothienopyrazine 23 was furthermore brominated with NBS at room temperature under the exclusion of light leading to 2,6-dibromoderivative 24 in 53% yield (Scheme 6). The obtained substitution pattern was proven by NMR methods and showed that in contrast to the fused aromatic syn-dithienopyrazine 6, which was regioselectivly brominated at the -positions, dibromination of dihydrothienopyrazine 23 is -selective. Therefore, it can be regarded as nitrogenbridged aromatic thiophenes, which are typically substituted with electrophiles at the -position. This result is also rationalized by the fact that for the bromination of dihydrothienopyrazine 23 much smoother reaction conditions were necessary compared to those of dithienopyrazine 6.