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

ββ-Diphenylacrylonitrile (I) reacts with butyl-lithium in THF at -78° to give the derived vinyl carbanion Ph₂C=C̄-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 Ph₂C-CHBu and Ph₂C=C(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 of structural variations on the site of the nucleophilic attack and on the type of products obtained.