Highly Efficient Synthesis of Stereodefined Multisubstituted 1,4‐Dicyano‐ and 1‐Cyano‐1,3‐butadienes and Their Reactions with Organolithium Reagents

Stereodefined multisubstitut- ed 1-cyano- and 1,4-dicyano-1,3-buta- diene derivatives were obtained in ex- cellent yields of the isolated product from their corresponding monohalo- and dihalobutadienes and CuCN. This reaction proceeded with high stereose- lectivity and retention of the stereo- chemistry of the starting halobuta- dienes. A study of the utility of the thus-obtained 1-cyano- and 1,4-dicya- no-1,3-butadiene derivatives was dem- onstrated by their reactions with orga- nolithium reagents. 2H-Pyrrole or imi- nocyclopentadiene derivatives were formed in high yields from 1-cyano-4- halo-1,3-butadienes and organolithium reagents. When 1,4-dicyano-1,3-buta- dienes were treated with organolithium reagents followed by trapping with electrophiles, a tandem process took place to afford 2H-pyrrolyl nitriles in excellent yields. Reduction of 1,4-di- cyano-1,3-butadiene derivatives with LiAlH4 showed novel reaction patterns relative to normal nitriles.