Synthesis and Properties of Backbone Silylated Imidazol-2-thiones

Imidazole-2-thiones have attracted considerable interest in the past as materials for potential applications in the pharmaceutical and chemical industries. Herein, the synthesis of a series of backbone silylated 1,3-dialkylimidazol-2-thiones is reported. The developed synthesis protocol involves the silylation of N,N-dimethylimidazol-2-thione 1 followed by the addition of organochlorosilanes R_nSiCl_4–n (R=Me, Ph; n=0–4) and enabled the synthesis of the C-silylated derivatives with monocyclic, silyl-bridged or fused tricyclic structures. Reactivity studies performed with N,N-dimethyl-4,5-bistrimethylsilylimidazole-2-thione as a model substance showed surprisingly stable silicon-vinyl bonds and reactivity patterns closely related to those observed for the unsilylated species 1. Combined UV-spectroscopic and computational studies revealed only minor impact of the silyl substituents on the electronic structure of the imidazol-2-thione ring.