Reductive Activation of Arenes: XVI. Anionic Products from Reduction of p-Tolunitrile with Sodium in Liquid Ammonia and Their Reaction with Butyl Bromide

Study of oxidation, protonation, and alkylation of the products obtained by one- and two-electron reduction of p-tolunitrile with sodium in liquid ammonia showed that these products are, respectively, p-tolunitrile radical anion and 1-cyano-4-methyl-2,5-cyclohexadienyl anion. The latter is formed by protonation of p-tolunitrile dianion with ammonia. The two-electron reduction involves protonation of p-tolunitrile dianion with initial p-tolunitrile, which gives rise to 4-cyanobenzyl anion. The yield of the latter depends on the order of mixing of the reactants. The anionic reduction products react with butyl bromide to afford products corresponding to ipso alkylation with respect to the cyano group, 4-butyltoluene and 3-butyl-3-cyano-6-methyl-1,4-cyclohexadiene, as well as the alkylation product at the benzylic position, 4-pentylbenzonitrile. The formation of 4-butyltoluene indicates the possibility for selective synthesis of p-alkyltoluenes by reductive alkylation of p-tolunitrile.