Propargyl Amines: Versatile Building Blocks in Post-Ugi Transformations.

The Ugi reaction, a multicomponent reaction, allows diversity-oriented synthesis Its importance is recognized by an exponential increase in the publications utilizing the post-Ugi transformations as a strategy to build complex molecules via simple and sustainable processes in the recent literature. A second concept, alkyne activation through metal-, acid-, iodine-catalysis and base-mediated transformations, also leads to wonderful molecules in short and efficient synthetic routes. Combination of these two approaches via application of an alkyne-containing component in the Ugi reaction brings the benefits of both protocols into one synthetic sequence. The propargyl amines come as an obvious choice in this context as they work wonderfully as an amine component in the Ugi reaction, while post-Ugi alkyne activation has the potential to generate biologically interesting carbo- and hetero-cyclic systems. Thus, one can compare the Ugi adduct with a pupa which has inherent property of metamorphosis into biologically interesting molecules. In this review, application of propargyl amines in the Ugi reaction is discussed with a focus on post-Ugi transformations.