Reactions of pyrazinium salts with phenols:from σH-adducts to SN Hproducts and transformations into benzo[b]furans

The reaction of 5-(het)aryl-2,3-dicyano-1-ethylpyrazinium salts with phenol derivatives affords relatively stable dihydropyrazines, whereas the reactions of 6-(het)aryl-1,2,5-oxadiazolo[3,4-b]pyrazin-4-ium protic salts, depending on the phenol structure, result in products of nucleophilic substitution of hydrogen or open-chain transformation products: benzo[b]furan-substituted derivatives. The crystallographic data on the spatial structure of all types of the synthesized products were obtained.