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 RnSiCl4–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. A systematic approach to C‐silylated imidazol‐2‐thiones with monocyclic, silyl‐bridged or fused tricyclic structures is reported. Reactivity studies of the resulting products show surprisingly stable silicon‐vinyl bonds. According to UV‐vis absorption spectroscopy and DFT calculations the impact of the silyl substituents on the electronic structure of the imidazol‐2‐thione ring is negligibly small.