Recent developments in cyclopropene chemistry.

The transformations of cyclopropenes have attracted the attention of organic chemists for decades. As readily accessible strained carbocycles, cyclopropenes show a diverse range of reactivities. This feature article focuses on the developments of cyclopropenes from 2016 until the end of 2019, including reactions through vinylmetal carbenes, reactions through metal complex insertion, addition reactions with 1,3-dipole, radical reactions of cyclopropenes, and reactions of highly reactive in situ generated cyclopropenes. In addition, several new synthetic methods and applications of cyclopropenes are also disclosed in this paper.