Cobalt catalyzed alkenylation/annulation reactions of alkynes via C–H activation: A review

In the area of synthetic chemistry, there are various examples of inexpensive, highly abundant and less toxic transition-metal catalyzed inert C–H bond activation reactions. These reactions extended a productive test ground for the synthesis of biologically active heterocycles along with various beneficial structural motifs. Most of the C–H bond activation reactions deal with facile additions or functionalizations. In the last two decades, the less expensive and more abundant 3 d-transition metal cobalt has emerged as an effectual option for highly expensive noble metals of second and third-row. These alkenylation/annulation reactions provide highly important cyclic derivatives from easily accessible compounds in an expenditious and sustainable fashion. The aim of this review article is to highlight the power of cobalt metal catalyst in the C–H bond activation reactions involving alkyne species.