AgN<sub>3</sub>-Catalyzed Hydroazidation of Terminal Alkynes and Mechanistic Studies
Shanshan Cao, Qinghe Ji, Huai Li, Maolin Pang, Haiyan Yuan, Jingping Zhang, Xihe Bi
Abstract
The hydroazidation of alkynes is the most straightforward way to access vinyl azides—versatile building blocks in organic synthesis. We previously realized such a fundamental reaction of terminal alkynes using Ag2CO3 as a catalyst. However, the high catalyst loading seriously limits its practicality, and moreover, the exact reaction mechanism remains unclear. Here, on the basis of X-ray diffraction studies on the conversion of silver salts, we report the identification of AgN3 as the real catalytic species in this reaction and developed a AgN3-catalyzed hydroazidation of terminal alkynes. AgN3 proved to be a highly robust catalyst, as the loading of AgN3 could be as low as 5 mol %, and such a small proportion of AgN3 is still highly efficient even at a 50 mmol reaction scale. Further, the combination of experimental investigations and theoretical calculations disclosed that the concerted addition mechanism via a six-membered transition state is more favored than the classical silver acetylide mechanism.