Synthesis of Carbazoles and Dihydrocarbazoles by a Divergent Cascade Reaction of Donor–Acceptor Cyclopropanes

Abstract

An alkylation/olefination cascade of indolecarboxaldehydes and phosphonate-functionalized donor–acceptor cyclopropanes affords functionalized dihydrocarbazoles and cyclohepta[ cd ]indoles in formal (3 + 3) and (4 + 3) cycloadditions. A minor modification to the reaction conditions also allows access to the fully aromatic heterocyclic scaffolds by thermal loss of an electron-rich aryl moiety.

Recent synthetic strategies for the construction of functionalized carbazoles and their heterocyclic motifs enabled by Lewis acids

“…The obtained list of carbazole derivatives is cited in Scheme 39. 126 In 2002, Ila and co-workers developed SnCl 4 -induced domino carbocationic rearrangement for the synthesis of carbazole analogs 60 from N-protected indolyl cyclopropyl ketones 59 leading to the formation of 2,3-substituted cyclopentyl ring fused carbazoles (Scheme 40). 127 This typical annulation system allows us to form synthetically useful carbazole products with good yields.…”

Chemodivergence in Fluorine Source-Controlled Cascade Reaction of Aryne Precursors to Synthesize Pyrrolo[3,4-b]indoles and 3-Arylated Maleimides

“…Reaction strategies allowing chemodivergence represent one of the most cutting-edge developments in synthetic organic chemistry and pharmaceutical chemistry . A huge number of organic molecules with novel architectures were obtained from the same reactants by adjusting the reaction parameters .…”

Solvent Effects on the Photoinduced [6π]-Electrocyclization Reactions of Mono-, Di-, and Trisubstituted Arylamines: Photophysical, Preparative Photochemistry, and Mechanistic Investigations

“…Likewise, the preparation of carbazoles starting from diaryl amines was achieved successfully employing a Pd-catalyzed C–C bond formation route or oxidative Pt-catalyzed C–H activation . In addition, recent synthetic approaches toward the preparation of carbazoles have been investigated involving interesting strategies such as benzannulation reactions, intramolecular C–H aminations, metal-free processes, and diverted Bischler–Napieralski cascade reactions, among others . However, the thermal synthesis of carbazoles requires high reaction temperatures and long reaction times, and, in some cases, the reactions are carried out using expensive transition metal catalysts and selected phosphorous ligands as well as highly acidic conditions.…”