Dilithiation of α,β-Disubstituted Activated Olefins: α,β-Dilithiocinnamonitrile

Article abstract of DOI:10.1021/jo00226a019

cis- and trans-cinnamonitrile were treated with an excess of LDA in an aprotic medium to give a high yield of one preferred isomer of PhC(Li)=C(CN)Li (C.N.-2Li).The chemistry and stereochemistry of its reactions with various electrophiles (MeOD, MeI, IBuI, RCHO, MeSSMe) was studied and discussed. α-Substituted and α,β-disubstituted derivatives of cis- and trans-cinnamonitrile were obtained.The reaction with MeOD resulted exclusively in a quantitative yield of trans-PhCD=CDCN.It is suggested that substitution at C^α takes place first to yield an equilibrium mixture of the corresponding β-lithiated intermediates: cis-PhC(Li)=C(E)CN and trans-PhC(Li)=C(CN)E.The type and structure of the products obtained in the reaction of this equilibrium mixture with electrophiles depends on factors affecting the nucleophilic reactivity and configurational stability of the C^β-Li bond of each of these two β-lithiated cinnamonitrile derivatives.