Vinyl carbanions. Part 3. The reaction of ββ-diphenylacrylonitrile derivatives with butyl-lithium

Abstract

ββ-Diphenylacrylonitrile (I) reacts with butyl-lithium in THF at –78° to give the derived vinyl carbanion Ph₂C–CN (Ia) in a rapidly established equilibrium. A competing nucleophilic addition of a butyl carbanion at the less hindered α-position, afforded the substituted olefins Ph₂CCHBu and Ph₂CC(Bu)CN, by elimination of either CN^– or H^–, respectively, from the intermediate carbanion. An addition product of butyl-lithium to (I) was not formed. Reactions of butyl-lithium with trans-α-cyanostilbene and with triphenylacrylonitrile were also carried out in THF at –78° in order to study the effect os structural variations on the site of the nucleophilic attack and on the type of products obtained.