Annulation of 2‐Alkynylanilines: The Versatile Chemical Compounds

2‐Alkynylanilines as versatile building blocks have been widely applied for the construction of nitrogen atom‐containing heterocycles in organic synthesis. The focus of this review is on the application of 2‐alkynylaniline and its derivatives in the metal‐catalyzed or metal‐free synthesis of various heterocycles including indoles, oxindoles, indazoles, benzisoxazoles, quinolines, benzoxazines, benzothiazines, quinazolines, cinnolines, and seven‐ and eight‐membered heterocycles. 2‐Alkynylanilines, as versatile building blocks, have been widely applied for the construction of various nitrogen‐atom containing heterocycles including indoles, oxindoles, indazoles, benzisoxazoles, quinolines, benzoxazines, benzothiazines, quinazolines, cinnolines, and seven‐ and eight‐membered heterocycles. The used cyclization methods are catalyzed in the presence or absence of metal‐based catalysts