Validation of the Copper(I)-Catalyzed Azide−Alkyne Coupling in Ionic Liquids. Synthesis of a Triazole-Linked C-Disaccharide as a Case Study

Abstract

The first study of a copper(I)-catalyzed azide-alkyne click reaction in ionic liquids (ILs) is reported. The cycloaddition of a sugar azide with a sugar acetylene (CuI, i-Pr2EtN, 80 degrees C) was carried out in 10 ILs as well as in standard molecular solvents (toluene and DMF) to give the 1,4-disubstituted triazole-linked C-disaccharide. The highest yields (84 and 95%) were registered in Ammoeng 110 and [C(8)dabco][N(CN)(2)]. The latter solvent was recycled in four subsequent reactions without loss of the reaction efficiency. Reactions carried out in the absence of the Hünig's base afforded mixtures of 1,4- and 1,5-disubstituted triazole regioisomers.