Nucleophilic substitution of 4H-imidazoles by thioles: New starting materials for tetraazafulvalenes and fused heterocycles

Different reactivities towards the 4H-imidazoles 1 depending on the nature of the sulfur containing nucleophile were observed. Whereas H2S and aromati c thioles led to 4,5-diamino-imidazoles in the course of a reduction proces s, treatment with aliphatic mercaptanes resulted in a substitution-reductio n-dimerization cascade which finally gave bis-imidazoles. Their oxidative m odification in presence of m-chloroperbenzoic acid then allowed new 1,3,5,7 -tetraazafulvalenes to be easily obtained. Treatment of the bis-imidazoles with acetylene dimethyldicarboxylate caused cleavage of the central bond, t hus leading to the formation of derivatives which are of interest for the t ransformation into fused heterocycles such as imidazo[4,5-b]azepines.