Push–Pull Ynamines and Push–Pull Ynamides: Synthesis, Structure, Reactivity, and Application

Push–pull ynamines, whose triple bond carries a disubstituted amino group as electron‐donating group (EDG) and an electron‐withdrawing group (EWG), are characterized by a π ‐delocalization (push–pull effect) and a polarized triple bond. Push–pull ynamines exhibit the reactivity of both ynamines and EWG alkynes together with reactivities not exhibited by either class of alkyne. Their structure, in particular the push–pull effect, and high reactivity toward electrophiles, nucleophiles, and cycloaddition have been intensively studied. Push–pull oligoynamines, which carry two to four triple bonds and push–pull enynamines, which contain a double and a triple bond, are further push–pull ynamines whose synthesis, structure, and reactivity have attracted considerable interest. A second class of unique EDG‐EWG substituted alkynes are push–pull ynamides, whose triple bond holds an amido group as EDG and an EWG. Push–pull ynamides are more thermally stable but significantly less reactive than push–pull ynamines. The push–pull effect and the polarization of the triple bond are probably less pronounced in push–pull ynamides than in push–pull ynamines. Push–pull ynesulfonamides and push–pull ynecarbamates have been primarily studied in transition metal‐catalyzed reactions and cycloaddition. Keteniminium ions are key intermediates in the reaction of push–pull ynamines and push–pull ynamides with electrophiles. This review summarizes the chemistry of push–pull ynamines, push–pull ynamides, push–pull oligoynamines, push–pull oligoynamides, and push–pull enynamines, focusing on their synthesis, structure, reactivity, and synthetic application.