In our studies, the organocatalytic 1,3-dipolar cycloaddition between 2-nitrobenzofurans or 2-nitrobenzothiophene and N-2,2,2-trifluoroethyl-substituted isatin imines has been developed. The reaction has been realized by employing bifunctional organocatalysis, with the use of squaramide derivative being crucial for the stereochemical efficiency of the process. The usefulness of the cycloadducts obtained has been confirmed in selected transformations, including aromative and non-aromative removal of the nitro group.
In this paper, a new cycloaddition
between α,β-unsaturated aldehydes and coumalates realized
under dienamine activation has been described. The reaction proceeds
regioselectively with the distal double bond of the dienamine system
acting as electron-rich dienophile. It leads to the formation of biologically
relevant [2.2.2]-bicyclic lactones. Their functionalization potential
has been confirmed in selected, diastereoselective transformations.
The Front Cover shows the inverse‐electron‐demand hetero‐Diels‐Alder cycloaddition between azlactones and α,β‐unsaturated ketones derived from thioisatine. The metal gears shown in the picture directly refer to the aromatization process that constitutes the main driving force of the developed transformation. Artwork by Jan Bojanowski. More information can be found in the Communication by Ł. Albrecht et al.
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