Click chemistry: a fascinating method of connecting organic groups

Click chemistry, a modular synthetic strategy for synthesizing the assembly of novel molecular entities, has made a tremendous impact in the field of science since its debut. This powerful strategy relies mainly upon the construction of carbon–heteroatom bonds using spring-loaded reactants. Its growing number of applications are found in nearly all areas of modern chemistry ranging from drug discovery to materials science. This manuscript includes important aspects of the copper-catalyzed Huisgen cycloaddition reaction, which is considered a gold standard of click chemistry due to its biocompatibility and reliability, along with its applications in bioconjugation, drug delivery and polymer chemistry. A bird′s eye view of recent progress in developing the copper-free click chemistry protocols such as catalyst-free strain-promoted alkyne–azide cycloaddition (SPAAC) click chemistry has also been provided.