Synthesis of functionalized benzimidazole–butyrolactone dyads

A two-step procedure transformation starting from the reaction of ortho-phenylenediamines on 2-acetylbutyrolactone 1 yielded (Z)-3-(1-aminoethylidene)butyrolactones 2, which were treated with either N,N-dimethylformamide dimethyl acetal, triphosgene, or carbon disulfide under different reaction conditions to produce a new series of benzimidazole–, benzimidazolone–, or benzimidazole-2-thione–butyrolactone dyads 3–5, respectively. The structures of compounds 2–5 were established by NMR and mass spectrometry. The isolation of important reaction intermediates as single-crystals allowed the determination of the (Z)-configuration in the resulting conjugate heterocyclic systems 3–5 by X-ray diffraction studies.