Interaction of alkali metals with unsaturated heterocyclic compounds. The reductive metalation of 1,4-diphenylphthalazine

1,4-Diphenylphthalazine ( 1 ) was reduced in tetrahydrofuran by sodium metal to a monomeric dianion 2 . Chemical reactions of this new dianion were examined with various reagents. Generally, the protonation, acylation and alkylation products were 1,2-dihydrophthalazine derivatives. An annulation of the phthalazine ring system was accomplished by treating the dianion with 1,3-dichloropropane or 1,4-dichlorobutane. With 1,2-dichloroethane however, only 1,4-diphenylnaphthalene was detected.