Click Chemistry is a term that was introduced by K. B. Sharpless in 2001 to describe the reactions which can afford products in high yields with excellent selectivities by carbon-hetero bond forming reactions. Here, “Click” means joining of molecular pieces as easily as clicking together of two pieces of a seat belt buckle and “ in vivo ” means “within the living organisms”. Click chemistry has been broadly used for chemical reactions that have orthogonality, high yields, and fast kinetic second order reaction rate constants [ 1 , 2 ]. These kinds of orthogonal reactions are useful for organic synthesis containing multiple steps and various functional groups. Particularly, Organic chemists have attempted to remove the toxic copper catalyst from the representative click reaction, copper catalyzed [3 + 2] azide–alkyne cycloaddition (CuAAC). Their trials have resulted in ‘copper-free’ click chemistry which is highly attractive to biological or biomedical researchers [ 3 ]. To reduce...