Heterocycles are ring structures containing at least one heteroatom, such as N, O, and S, as a member of the ring in addition to carbon atoms [1, 2]. Heterocyclic compounds are at the forefront of almost every developing field, especially in the synthesis of biologically active molecules, pharmaceuticals, and a variety of industries. Many naturally occurring bioactive compounds possess heterocyclic skeletons as the main structural unit. All of the nucleic acids, hemoglobin, cellulose, majority of the drug molecules, hormones, vitamins, dyes and pigments, ligands in metal catalysis and many useful organic materials consist of heterocyclic skeletons. Heterocyclic compounds are regarded as very useful starting materials in a variety of industries such as plastics, cosmetics, agriculture, and other industries [3–7]. Over 95% of pharmaceuticals consist of at least one heterocyclic fragment. Among many others, N-based heterocycles are very common in vitamins, hormones, commercially available drug molecules, and many bioactive compounds that play vital roles in human and animal life
