Metal-Catalysed Azidation of Organic Molecules

The azide moiety is a desirable functionality in organic molecules, useful in a variety of transformations such as olefin aziridination, C-H bond amination, isocyanate synthesis, the Staudinger reaction and the formation of azo compounds. To harness the versatility of the azide functionality fully it is important that these compounds be easy to prepare, in a clean and cost-effective manner. Conventional (non-catalysed) methods to synthesise azides generally require quite harsh reaction conditions that are often not tolerant of functional groups. In the last decade, several metal-catalysed azidations have been developed in attempts to circumvent this problem. These methods are generally faster, cleaner and more functional-group-tolerant than conventional methods to prepare azides, and can sometimes even be conveniently combined with one-pot follow-up transformations of the installed azide moiety. This review highlights metal-catalysed approaches to azide synthesis, with a focus on the substrate scopes and mechanisms, as well as on advantages and disadvantages of the methods. Overall, metal-catalysed azidation reactions provide shorter routes to a variety of potentially useful organic molecules containing the azide moiety.