Reactions of 1,4-dilithiobutadienes with isothiocyanates: preparation of iminocyclopentadiene derivatives via cleavage of the CS double bond of a RNCS molecule

Reaction patterns of 1,4-dilithio-butadiene derivatives with isothiocyanates RNCS and isocyanates RNCO were investigated and synthetically useful preparative methods were developed. Isothiocyanates reacted with 1,4-dilithio-butadienes to afford iminocyclopentadiene derivatives in excellent isolated yields and high selectivity. When aromatic isothiocyanates were used, cleavage of the CS double bond of a RNCS molecule took place via a successive inter-intramolecular carbophilic addition. A number of products were obtained from the reaction of isocyanates with 1,4-dilithio-butadienes, probably due to the high reactivity of isocyanates towards 1,4-dilithio-butadienes.