Metal Complexes versus Organocatalysts in Asymmetric 1,3-Dipolar Cycloadditions

In this review, a comparison between the Lewis acid catalysed and organocatalysed 1,3-dipolar cycloaddition is presented with special focus on the enantioselective synthesis of five-membered hetero- or carbocyclic systems, is described. These reactions exhibit very interesting features, but the most important one is the generation of up to four stereogenic centres in only one reaction step.