Rediscovering Cyanogen Gas for Organic Synthesis: Formation of 2‑Cyanothiazole Derivatives

The expeditious synthesis of an API building block, 2-cyanothiazole, from cyanogen gas and a readily available dithiane is reported. A previously undisclosed partially saturated intermediate is formed, which can be further functionalized and isolated by the acylation of the hydroxy group. Dehydration using trimethylsilyl chloride furnished 2-cyanothiazole, which could be further converted to the corresponding amidine. The sequence provided a 55% yield over 4 steps. We envision that this work will spark further interest in cyanogen gas as a reactive and cost-effective synthetic reagent.