In the manuscript, the application of β,γ‐unsaturated ketones as precursors of electron‐rich dienophiles in the organocatalytic, aromative inverse‐electron‐demand hetero‐Diels‐Alder cycloaddition is described. The reaction leads to the formation of biologically relevant benzofuran derivatives bearing additional tetrahydropyridine ring. The reaction is fully site‐selective and occurs preferentially at the distal double bond of the dienolate intermediate. Given the absolute configuration assignment a step‐wise mechanism has been proposed and the formation of aromatic benzofuran ring indicated as the driving force of the cascade.magnified image

The great progress that took place in the field of higher‐order cycloadditions involving fulvene‐ and tropone‐derived systems in the last few years is astonishing. By application of organocatalytic activation modes, new higher‐order reactivities have been identified and described in the literature. These approaches take advantage of the high reliability of organocatalysis, at the same time expanding its potential and paving new directions for its further evolution. In this Minireview, the progress in the field of organocatalytic higher‐order cycloadditions involving fulvene‐ and tropone‐derived systems is summarized and insights into mechanistic aspects of the developed reactivities are provided. Furthermore, the discussion on the nomenclatural issues related to cycloaddition reactions has been conducted and solutions to clarify the picture proposed.

The first enantioselective higher-order cycloaddition involving a tropone derivative that acts as an electron-rich 8π-component is described.