**8. Conclusion**

In summary, the ruthenium(II)-catalyzed activation of C-H bonds for the construction of C-C bond in organic synthetic methodologies have caused a revolution. The development of methodologies introducing multiple C-H/N-H activation is an emerging area of research and the oxidative alkyne annulation reactions allowing for the formation of C-C and C-N bonds in a single step. These approaches have already been competently used in the synthesis of several essential *N*-heterocycles from readily available reactants. The presence of nitrogen directing groups appears to be highly useful as starting materials for the direct access of various Nheterocycles in the field of ruthenium (II)-catalyzed C-H activation and oxidative alkyne annulations. Further, these reactions were also extended to other heteroatoms such as oxygen and sulfur directed groups for the straight forward synthesis of diverse oxygen and sulfur containing heterocyclic molecules. Therefor this methodology can definitely play a very useful part as an application in the field of natural products, biologically important molecules and heterocycles with potential application in the field of material science. Further developments in this area may open up broad opportunities for straightforward, efficient, and atom economical synthesis of various complex *N*-heterocyclic compounds from simple starting materials.
