Birch's reductive alkylation of biphenyl-4-carbonitrile (1) provides alkylated 1,4-dihydroderivatives of various structural types: 4-alkyl-4-phenylcyclohexa-2,5-dienone, 1,4-dialkyl-4-phenylcyclohexa-2,5-dienecarbonitrile (with the same or different alkyl fragments), and 4-(1-alkylcyclohexa-2,5-dienyl)benzonitrile. Each of these products become dominant depending on the nature of long-living anionic form generated from 1, namely, the stable product of two-electrons reduction – dianion (1²⁻); 1-alkyl-4-cyano-1-phenylcyclohexa-2,5-dien-4-yl anion (1-Alk₁^–), originated due to the alkylation of dianion 1²⁻ at the position 1 of biphenyl moiety; or 1-(4-cyanophenyl)cyclohexa-2,5-dien-1-yl anion (1-H_4’^–), being the product of dianion 1²⁻ protonation at position 4′ by protonating reagent (MeOH or NH₄Cl). The orientation of alkyl fragment incorporation into biphenyl-4-carbonitrile scaffold is in agreement with calculated electronic structure of the anionic species under investigation. The dominating type of their reactivity towards alkyl halides proved to be nucleophilic (S_N2 mechanism).

桦木对联苯-4-腈（1）的还原烷基化可提供各种结构类型的烷基化1,4-二氢衍生物：4-烷基-4-苯基环己-2,5-二烯酮，1,4-二烷基-4-苯基环己-2， 5-二烯腈（具有相同或不同的烷基片段）和4-（1-烷基环六-2,5-二烯基）苄腈。这些产物各自取决于1生成的长寿命阴离子形式的性质，即两电子还原的稳定产物–二价阴离子（1 ^2-）; 1-烷基-4-氰基-1-苯基环己-2,5-二烯-4-基阴离子（1-Alk ₁ ^–），是由于二价阴离子1 ²⁻的烷基化而产生的在联苯部分的1位; 或1-（4-氰基苯基）环己-2,5-二烯-1-基阴离子（1-H _4' ^- ），作为二价阴离子的产物1 ^2-第4位的质子化'由质子化试剂（MeOH或NH ₄ Cl）。烷基片段并入联苯-4-腈支架的取向与所研究的阴离子物质的计算电子结构一致。它们对烷基卤化物反应性的主导类型被证明是亲核（小号_Ñ 2机构）。