Direct synthesis of benzo[a]carbazoles by palladium-catalyzed domino reactions: synthesis and photophysical properties of diverse benzo[a]carbazoles

Synthesis of Highly π-Extended Dihydrobenzo[a]indenocarbazole Scaffolds via Tandem Benzannulation and Friedel-Crafts Reaction of 2-Alkynylanilines and 2-Alkynylbenzaldehydes Promoted by Lewis Acid

A novel and efficient tandem protocol for the swift synthesis of dihydrobenzo[a]indenocarbazole frameworks from 2-alkynylanilines and 2-alkynylbenzaldehydes via BF3·OEt2-facilitated benzannulation and Friedel-Crafts reaction has been described. This innovative approach accommodates a wide array of functional groups, offering a myriad of diversified carbazole products. Later, postsynthetic modification leads to its C(sp3)-H hydroxylation. Furthermore, the photophysical properties of some selected synthesized moieties have been meticulously investigated, promising exciting avenues for further exploration.

Hauser-Kraus Annulation Initiated Multi-Cascade Reactions for Facile Access to Functionalized and Fused Oxazepines, Carbazoles and Phenanthridinediones

The Hauser-Kraus (H-K) annulation of N-unsubstituted 3-olefinic oxindoles with 3-nucleophilic phthalides triggers a cascade of ring expansion and ring contraction reactions through several regioselective steps in one pot. While oxazepines were isolated in the presence of stoichiometric amounts of base at room temperature, carbazoles and phenanthridinediones were the products in the presence of excess base and microwave irradiation. Mechanistic studies guided by stepwise reactions and control experiments revealed that the isolable oxazepine intermediate, formed via ring expansion of the H-K adduct, is the key precursor to carbazole and phenanthridinedione via decarboxylative regioselective cyclizations.

B(C6F5)3-Catalyzed [4 + 2] Cyclization Strategy: Synthesis and Photophysical Properties of 5H-Naphtho[2,3-c]carbazole-8,13-dione Derivatives

In this paper, a series of novel carbazolequinones were efficiently obtained by a B(C₆F₅)₃-catalyzed [4 + 2] cyclization reaction. This protocol not only had a simple operation, broad substrate range, and high atomic economy, but also had a low catalyst loading and avoided using metal catalysts. In addition, we constructed diverse new carbazole-fused compounds under different reduction conditions. The results of photophysical characterization showed that the structure of carbazole-fused derivatives had a significant impact on the fluorescence properties.