The alkali metal reduction of pyrene structural and preparative aspects

Reduction of pyrene with alkali metals yields the corresponding dianion salts. The solvent, counterion and temperature must be carefully selected since side reactions such as protonation (e.g. in liquid ammonia) or cleavage of the etheral solvent occur readily. Moreover, the spectroscopic characterization of the dianion is complicated by rapid electron transfer processes. There is no experimental evidence for distorted dianion structures or for further reduction of pyrene toward a tetraanion. Knowledge of the ionic π-structures is essential for an understanding of reductive alkylation processes.