Click Reactions: Azide‐Alkyne Cycloaddition

Abstract

The term “Click‐chemistry” is a general concept that describes reactions of enormous interest because of their unique characteristics for the synthetic chemistry. Many typical Click‐reactions –among them the Diels Alder reaction and 1,3‐dipolar cycloaddition reactions– have been known for a long time. The most famous amongst them is the copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) which opens up outstanding opportunities in various fields of science and technology. Since the development of the CuAAC by Meldal and Sharpless it gained enormous attention not only in the field of chemistry, but also in biology and materials sciences. In parallel to the development of new applications of the CuAAC, the need for further adaption of the original Click‐procedure e.g. for bioorthogonal approaches got obvious. Nowadays, the broader scope of the CuAAC‐reaction is often paid for with the abandoning of at least one of the mandatory Click requirements and the modified procedures do not stand the general criteria any more. This review will give an overview of the current progress of the famous CuAAC‐(Click)‐reaction, including postulated mechanisms and importance of additives. It will sum up the challenges that have been mastered under critical consideration of the fulfillment of the original Click‐criteria.