Gold‐Catalyzed Synthesis of Functionalized Pyridines by Using 2<i>H</i>‐Azirines as Synthetic Equivalents of Alkenyl Nitrenes

Abstract

Abstract 2 H ‐Azirines are easily synthesized from the corresponding ketones and, despite possessing a CN bond embedded in a strained three‐membered cycle, they are sufficiently stable to be isolated, stored, and manipulated. 2 H ‐Azirines can be regarded as valuable synthetic equivalents of alkenyl nitrenes, however, reactions capitalizing on the cyclic strain of the heterocyclic motif and involving the cleavage of the CN single bond remain surprisingly limited. A gold‐catalyzed reaction that allows the formation of polysubstituted functionalized pyridines from easily accessible 2‐propargyl 2H‐azirine derivatives was developed. This transformation, which corresponds to an unprecedented intramolecular transfer of an alkenyl nitrene to an alkyne, proceeds with low catalyst loading, is efficient, and exhibits a high functional‐group tolerance and a wide substrate scope.