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Dipolar cycloaddition reactions (DCRs) are unique reactions when considering their versatility, their atom economy and the highly functionalized heterocyclic products they provide. The significant contributions by Rolf Huisgen has led to the description of a 1, 3-dipolar cycloaddition reaction, where a dipole (formally a zwitterionic molecule) adds to a dipolarophile (an alkene or alkyne) to form a five-membered heterocyclic ring. 1, 2 Two σ-bonds are formed in this concerted reaction where bond breaking and bond formation occurs simultaneously and in a stereospecific manner, which also can be described by frontier molecular orbital theory as the highest occupied molecular orbital of one component reacting with the lowest unoccupied molecular orbital of the other component. The field of dipolar cycloaddition reactions with azides in peptide chemistry has developed rapidly since Tornøe and Meldal first described the copper (I)-catalyzed cycloaddition between azides and peptide-linked terminal alkynes to exclusively form the 1, 4-substituted [1, 2, 3]-peptidotriazoles. 3 This reaction was later termed CuAAC (copper--catalyzed azide-alkyne cycloaddition) or simply the ‘click’reaction, and has been used extensively in all areas of chemistry, biology and material sciences due to its mild reaction conditions, high functional group tolerance, generally high yields and exclusive formation of 1, 4-substituted [1, 2, 3]-triazoles. The mechanistic aspects of the CuAAC leading to the 1, 4-substitution are complicated and have been discussed elsewhere. 4–6