Room‐Temperature Synthesis of C2‐Unsubstituted 2‐Imino‐1,3,4‐oxadiazolines by Cyclization of N ‐Acyldiazenes With Trimethylsilyl Cyanide

Herein, a mild and efficient protocol for the construction of 2‐imino‐1,3,4‐oxadiazolines bearing a free N─H bond at the C2‐position has been established under ambient conditions. The cyclization reaction readily proceeds between readily available N ‐acyldiazenes and trimethylsilyl cyanide (TMSCN) with the promotion of tetramethylguanidine (TMG), furnishing a series of structurally diverse products in yields up to 72%. This approach features transition‐metal‐free conditions, operational simplicity, short reaction time (3–4 h), and gram‐scale scalability without obvious erosion of yield.