Metal-Ammonia Reduction: Effect of Methyl Substituents and a Question Concerning Protonation Sites in Dianions

Article abstract of DOI:10.1021/jo00321a012

The effect of substituents on Birch reductions and other metal-ammonia processes has received considerable attention.Since the intermediate(s) is negatively charged, activation and orientation effects have been dealt with in terms of electron donation or withdrawal of substituents.The methyl group displays somewhat irregular behavior in naphthalenes and biphenyls, and an explanation is offered in terms of methyl location on a charge-bearing or non-charge-bearing carbon in the intermediates.The observation is also made that protonation of dianions (produced by electron addition) always seems to lead to the most stable monoanion.Reasons for this are discussed.