5. Modified reactions from Ugi and Passerini

Implicitly, the Ugi reaction represents couplings between isonitriles, aldehydes or ketones, primary amines and carboxylic acids. However, numerous studies have extended the synthetic scope of this coupling to significantly different partners. These extensions often lead to the implementation of new reaction mechanisms, particularly in the final stages of the reaction. While these efforts have mainly been devoted to Ugi-type couplings, the Passerini reaction has given rise to similar studies, albeit of less synthetic scope. We will first look at amine modifications in Ugi reactions, then move on to Ugi and Passerini couplings with different acid partners.