Simple and efficient access to pyrazine-2,5- and -2,6-dicarbaldehydes

Efficient two-step synthesis of pyrazine-2,5- and -2,6-dicarbaldehydes is presented that consists of transformation of easily available corresponding dimethylpyrazines to distyryl derivatives and oxidation of the latter with the tandem system of osmium tetroxide/periodate ions. The proper choice of dehydration agent in the first reaction step and the good efficiency of the subsequent low-temperature oxidation are the key points of the developed protocol. Other examined synthesis routes were much less successful, but one of them leads to new powerful routes to methyl (5-hydroxymethyl)pyrazine-2-carboxylate and dimethyl 3,4-dihydropyrazine-2,6-dicarboxylate. Previously unknown characteristics of the title compounds are reported.