Catalytic Hydrocyanation of Alkynes with HCN Surrogates: Advances and Challenges

Abstract Hydrocyanation of alkynes offers a straightforward and atom‐economical approach to the synthesis of valuable vinyl nitriles. However, classical implementations of this strategy rely on toxic and volatile hydrogen cyanide (HCN). Over the past decade, substantial efforts have been directed toward developing catalytic hydrocyanation protocols that employ HCN surrogates—compounds capable of delivering the cyano group in a safer and more practical manner. These surrogates range from still‐toxic but less volatile reagents (e.g., cyanohydrins, trimethylsilyl cyanide) to nontoxic alternatives such as organic nitriles and formamide. While HCN‐free hydrocyanation significantly improves safety and practicality, challenges remain—most notably, achieving precise control over the regio‐ and stereoselectivity of cyano group addition. This review summarizes key developments in the catalytic hydrocyanation of alkynes using HCN surrogates, highlighting both transition‐metal‐catalyzed and metal‐free strategies. Particular emphasis is given to selectivity control, with a systematic comparison of regio‐ and stereoselectivity outcomes across symmetrical, terminal, and internal alkynes. The recent advances reviewed here offer a comprehensive picture of the current state of alkyne hydrocyanation and point toward promising directions for developing practical, selective, and HCN‐free methodologies.