An efficient multigram-scale azide-alkyne coupling of cyclodextrin derivatives mono-6-azido-6-deoxy-β-cyclodextrin, mono-2-O-propargyl-β-cyclodextrin, and mono-2-O-propargyl-α-cyclodextrin with terminal alkynyl aryl ethers or azides, mediated by copper(I) is reported. This process uses a stoichiometric ratio of substrates and 5 mol% of the copper catalyst to give the products with full conversion; thus, no chromatographic purification is necessary. The yields of both α- and β-cyclodextrin derivatives are in the range of 80 to 99%.
Key words
cyclodextrins - azides - copper - cycloaddition - ligands