Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metallation of 2,3,5,6-tetraphenylpyrazine and the synthesis of 1,2-dihydro-1,4-diazine derivatives

Abstract

Treatment of 2,3,5,6-tetraphenylpyrazine (1) with sodium in tetrahydrofuran effected the formation of monomeric dianion 2. The chemical behaviour of this new disodium adduct was characterized by a variety of reagents. Generally, the protonation (water), alkylation (methyl iodide and benzyl chloride), and acylation (methyl and ethyl chloroformate) products were 1,2-dihydrotetraphenyldiazine derivatives. An annulation of the pyrazine ring system was accomplished by treating the dianion with polymethylene chlorides, Cl(CH2)(n)Cl, n = 2, 3, 4.