The Click Chemistry Approach Applied to Fluorine-18

New methods to introduce fluorine-18 into biomolecules are constantly of great interest. Particularly, the increasing number of complex structures poses a challenge to 18F-labelling chemistry. Indirect 18F-labelling procedures using prosthetic groups are commonly used for multifunctional biologically active compounds; however there is continuous demand for new and improved radiofluorination methods. The Cu(I)-catalysed variant of the Huisgen 1,3-dipolar cycloaddition of terminal alkynes and azides represents a most efficient and powerful reaction referred to as click chemistry. This reaction is highly specific and provides excellent yields under very mild conditions. This reaction ideally complies with the requirements of fluorine-18 labelling chemistry. Hence, it offers a convenient and efficient new 18F-fluorination method which is particularly suitable for prosthetic group labelling. The first few reports using the click approach in fluorine- 18 chemistry already demonstrated the particular feasibility of this approach. This review gives an overview of the Cu(I) 1,3-dipolar cycloaddition of terminal alkynes and azides and further describes the first applications of this click reaction in fluorine-18 labelling.