Illustrated Glossary of Organic Chemistry

Birch reduction: A dissolving metal reduction reaction in which a benzene ring is reduced to a 1,4-diene with an alkali metal (lithium, sodium, or potassium; an electron source) in liquid ammonia in the presence of an alcohol (which serves as a proton source).

Birch reduction of methyl benzoate with lithium and tert-butanol in liquid ammonia produces methyl cyclohexa-2,5-diene-1-carboxylate, a 1,4-diene.