Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

Fluorescent annulated imidazo[4,5-c]isoquinolines via a GBB-3CR/imidoylation sequence - DNA-interactions in pUC-19 gel electrophoresis mobility shift assay

Herein we report the development of a sequential synthesis route towards annulated imidazo[4,5-c]isoquinolines comprising a GBB-3CR, followed by an intramolecular imidoylative cyclisation. X-Ray crystallography revealed a flat 3D structure of the obtained polyheterocycles. Thus, we evaluated their interactions with double-stranded DNA by establishing a pUC-19 plasmid-based gel electrophoresis mobility shift assay, revealing a stabilising effect on ds-DNA against strand-break inducing conditions.

Application of heterocyclic aldehydes as components in Ugi-Smiles couplings

Efficient one-pot Ugi–Smiles couplings are reported for the use of furyl-substituted aldehyde components. In the presence of these heterocyclic aldehydes, reactions tolerated variations in amine components and led to either isolated N-arylamide Ugi–Smiles adducts or N-arylepoxyisoindolines, products of tandem Ugi–Smiles Diels–Alder cyclizations, in moderate yields. A thienyl-substituted aldehyde was also a competent component for Ugi–Smiles adduct formation.

Metal-mediated post-Ugi transformations for the construction of diverse heterocyclic scaffolds

The Ugi-4CR is by far one of the most successful multicomponent reactions leading to high structural diversity and molecular complexity. However, the reaction mostly affords a linear peptide backbone, enabling post-Ugi transformations as the only solution to rigidify the Ugi-adduct into more drug like species. Not surprisingly, the development of these transformations, leading to new structural frameworks, has expanded rapidly over the last few years. As expected, palladium-catalyzed reactions have received the foremost attention, yet other metals, particularly gold complexes, are fast catching up. This tutorial review outlines the developments achieved in the past decade, highlighting the modifications that are performed in a sequential or domino fashion with emphasis on major concepts, synthetic applications of the derived products as well as mechanistic aspects.