1,2,3-Triazoles

This chapter is an update of the information regarding 1,2,3-triazoles and benzotriazoles published in previous CHEC editions. The discovery of the Cu(I)-catalyzed azide–alkyne cycloaddition by Meldal, Sharpless and Fokin 20 years ago revolutionized the chemistry of 1,2,3-triazoles. This reaction, together with other metal-catalyzed azide–alkyne cycloaddition reactions, offered chemists the power to synthesize regioselectively 1,4- or 1,5-disubstitued 1,2,3-triazoles in high yields under very mild conditions. At the same time, great developments were achieved on the strain-promoted azide − alkyne cycloaddition approach, a particularly important method for the synthesis of 1,2,3-triazoles for biological applications. These and other methods for the synthesis of 1,2,3-triazoles, the reactions of 1,2,3-triazoles and benzotriazoles, and also their applications, are reviewed in this chapter that is focused on works published between 2015–20.