Synthesis of Polycyclic 3,3′-Biindoles via AgOTf-Catalyzed Nucleophilic Addition and Cycloisomerization

Brønsted Acid-Catalyzed Synthesis of 4-Functionalized Tetrahydrocarbazol-1-ones from 1,4-Dicarbonylindole Derivatives

A p-toluenesulfonic acid-catalyzed cascade reaction is reported for the synthesis of 4-functionalized tetrahydrocarbazolones via the reaction of 4-(indol-2-yl)-4-oxobutanal derivatives with a variety of nucleophiles in acetonitrile or hexafluoroisopropanol. After the initial intramolecular Friedel-Crafts hydroxyalkylation, the 3-indolylmethanol intermediate is subsequently activated and reacted with the external nucleophile. The reaction conditions are crucial to avoid alternative reaction pathways, allowing direct substitution reaction with thiols, (hetero)arenes, alkenes, or sulfinates. The procedure features high overall yields to access a diverse family of compounds bearing the tetrahydrocarbazole core.

Electrochemical Cyclization of Alkynyl Enaminones: Controllable Synthesis of Indeno[1,2-c]pyrroles or Indanones

We report an electrochemical intramolecular [3 + 2] cyclization of alkynyl enaminones in a user-friendly undivided cell under constant current conditions without an oxidant and catalyst, and indeno[1,2-c]pyrrole derivatives could be obtained in good to excellent yields. Notably, preliminary substituent-controlled selective transformation is also achieved under electrocatalysis alone, and indeno[1,2-c]pyrrole (R⁴ ≠ H) or indanone derivatives (R⁴ = H) could be prepared directly under electrocatalysis without adding a base and heating process.

Controllable methylenation with ethylene glycol as the methylene source: bridging enaminones and synthesis of tetrahydropyrimidines

Controllable methylenation using renewable ethylene glycol as the methylene source has been developed for the introduction of one or two methylene building blocks.